In preparation for pulling the body off the frame, I FINALLY took the time to upgrade the wheels on the rotisserie. I got the pneumatic tire set up from Craig aka Pushrod about 2 or 3 years ago. They roll really smooth right now. I hope they don't squish and roll hard once the weight of the body is on them. I will also be modifying the center brace arrangement. I am going with one on each side instead of a single in the middle. This will help stabilize it when rolling. I am going to fabricate a pinned holding system for the bars too, instead of the pinch bolt style that slips and lets the end T's separate.
New wheels
Bungy L-76 said
Nov 14, 2015
Do those air tires have a load rating on them? Might help you determine if they're going to "squish" if you're close to or over their weight limit. ???
Lost in the 60s said
Nov 14, 2015
Bungy L-76 wrote:
Do those air tires have a load rating on them? Might help you determine if they're going to "squish" if you're close to or over their weight limit. ???
Not in pounds, just load range B, whatever that is a for a 4" tire at 50 psi...
Load range B on a 12" trailer tire is 765 at 60 psi. I'm going with these being capable of at least 400 lbs each for a total capacity of 2400.
Lost in the 60s said
Nov 17, 2015
Today, John and I pulled apart the engine that will go back in the '66 after the chassis restoration. It was rebuilt in the late 70's with flat top pistons to lower the compression and a cam that was way too much for the pistons. It will get new pistons to get the compression to around 9-9.5 and a street friendly torque cam.
67ss said
Nov 18, 2015
Didn't you say this was a LS5 454 motor or something like that?
Lost in the 60s said
Nov 18, 2015
67ss wrote:
Didn't you say this was a LS5 454 motor or something like that?
Last pic...CRT...
How do I figure the comp ratio with 97.2 cc head and the flat top piston ? Bore is +.030
-- Edited by Lost in the 60s on Wednesday 18th of November 2015 08:23:49 AM
I use the calculator above though it needs a few more inputs to be accurate. Any part numbers on the pistons to try and figure out the valve relief volume? That has closed chambered head on it?
I use the calculator above though it needs a few more inputs to be accurate. Any part numbers on the pistons to try and figure out the valve relief volume? That has closed chambered head on it?
Getting way technical for me. I didn't see any part number on pistons and as they are already out, no way to measure deck height/volume. They were pretty much even with the deck. The block is original, uncut. I'll clean up a piston better today and look for more numbers. Valve relief is minimal. If necessary, I'll pop a piston back in.
Heads are closed but not original 290's. These are '65 206 heads.
67ss said
Nov 18, 2015
I can make assumptions on a few things to get you close. Typically most gm motors pistons are .025-.030 below deck. Gasket thickness and bore can be looked up on felpro's site. So trying to find a similar piston for valve reliefs is the only thing to figure out. Are the pistons typical 4 valve relief type I can't make it out in the picture?
67ss said
Nov 18, 2015
With a closed chamber head and flat top pistons you might be close to where you want to be. Just having the block zero decked could be enough to get what you want without buying new pistons.
Lost in the 60s said
Nov 18, 2015
67ss wrote:
With a closed chamber head and flat top pistons you might be close to where you want to be. Just having the block zero decked could be enough to get what you want without buying new pistons.
Block will never be decked in my possession... I don't want to lose the stampings. I actually tracked my old car down from them 10 years ago but couldn't afford the owners "asking" price to buy it back and return this engine to it's original body.
Let me run some numbers and see what I come up with. The machinist I use says he can deck the block without taking off the stamping. I asked him about it as the 327 for my chevelle is the correct 275 horse block and he said he can do it?
Let me run some numbers and see what I come up with. The machinist I use says he can deck the block without taking off the stamping. I asked him about it as the 327 for my chevelle is the correct 275 horse block and he said he can do it?
It wouldn't be worth the expense to me, Chris. Not for a couple points of compression on a street cruiser.
Couldn't I use a steel shim head gasket instead of a sandwich and get close to the same result ?
I appreciate you taking the time to work on this...
67ss said
Nov 18, 2015
So it comes in at 9.2. This is using a felpro 1037 gasket. Yes you could use a thinner gasket and maybe get it up a bit. If you did deck the block changing nothing else it comes out at 9.6. But I understand not wanting to to that but just wanted to give you a comparison.
ENTER YOUR DATA
CALCULATED DATA
Cylinder Head Volume (cc)
Cylinder Head Vol (cubic in.)
5.929
Piston Head Volume (cc)
Piston Head Vol (cubic in.)
0.122
Gasket Thickness (in.)
Swept Volume (cubic in.)
57.549
Gasket Bore (in.)
T.D.C. Volume (cubic in.)
6.996
Cylinder Bore Diameter (in.)
Gasket Volume (cubic in.)
0.585
Deck Clearance (in.) Note: Neg. number above deck, Pos. number below deck
Deck Volume (cubic in.)
0.360
Stroke (in.)
STATIC COMPRESSION RATIO
9.226
-- Edited by 67ss on Wednesday 18th of November 2015 02:05:17 PM
Lost in the 60s said
Nov 18, 2015
Is 9.6 going to make much of a difference in torque over 9.2 ? I could have the heads cut too. Since they aren't original, that wouldn't bother me. But is it really worth the expense for the .5 difference ?
Enganeer said
Nov 18, 2015
Are you trying for a good quench? Around.035" clearance?
Lost in the 60s said
Nov 18, 2015
I popped a piston back in and measured the clearance at .032.
Tim, the guy that built my 292 said he could take .015 off the heads for $80 and that would bring the static up a few points to around 9.5, which he likes with the flat tops. He has a Howard's hydraulic roller set up on his shelf that I can get for $700 that he has in his own car that makes gobs of torque.
As long as I don't need to buy piston's I'm giving serious thought to moving up to a roller cam.
67ss said
Nov 18, 2015
Hmm..are you sure about that measurement because I just realized the pin height on those pistons is different. It shows 1.627 and when I look up other 454 pistons is shows pin height of 1.645. I have seen this before on cheap rebuilder pistons they do that to lower compression even more. So I would expect your pistons to be about .043 or more in the hole which would bring the compression way down. Did you lay a flat edge across the opening and use a feeler gauge to check to the top of the piston?
There is one other thing we can do to be totally sure and that is to cc the whole volumn with the piston at TDC in the engine. I have a cc setup I can bring over and help you with it one night after work.
Lost in the 60s said
Nov 18, 2015
67ss wrote:
Hmm..are you sure about that measurement because I just realized the pin height on those pistons is different. It shows 1.627 and when I look up other 454 pistons is shows pin height of 1.645. I have seen this before on cheap rebuilder pistons they do that to lower compression even more. So I would expect your pistons to be about .043 or more in the hole which would bring the compression way down. Did you lay a flat edge across the opening and use a feeler gauge to check to the top of the piston?
There is one other thing we can do to be totally sure and that is to cc the whole volumn with the piston at TDC in the engine. I have a cc setup I can bring over and help you with it one night after work.
Yup, straight edge and feeler gauges. .035 won't fit, .032 does, .030 is slightly loose.
This engine was assembled in the late 70's, so anything modern is out the window...
67ss said
Nov 18, 2015
Guessing those Pistons being older they have a normal pin height. To answer your question is 9.2 to 9.6 going to make a big difference, no. But here are the two thoughts of why I would try and run the higher compression and why I would deck the block and not mill the heads. First decking the block is going to tighten the quench as John mentioned, this in turn makes the engine less prone to detonation to run higher compression. Second running most any aftermarket cam is going to give you some valve overlap, this is going to cause loss of cylinder pressure and or dynamic compression. So with the higher compression what you do lose won't be as bad which will give you better low end. Hoping this makes sense and is helping.
I know you are on a budget but it would also be a good idea to line hone the mains on a 40 year old block. Then everything will be nice and true.
Do you have the specs on that roller cam?
Derek69SS said
Nov 18, 2015
It has a legit LS5 "CRT" stamp.
Decking that block would destroy a LOT of value.
Lost in the 60s said
Nov 18, 2015
67ss wrote:
Guessing those Pistons being older they have a normal pin height. To answer your question is 9.2 to 9.6 going to make a big difference, no. But here are the two thoughts of why I would try and run the higher compression and why I would deck the block and not mill the heads. First decking the block is going to tighten the quench as John mentioned, this in turn makes the engine less prone to detonation to run higher compression. Second running most any aftermarket cam is going to give you some valve overlap, this is going to cause loss of cylinder pressure and or dynamic compression. So with the higher compression what you do lose won't be as bad which will give you better low end. Hoping this makes sense and is helping.
I know you are on a budget but it would also be a good idea to line hone the mains on a 40 year old block. Then everything will be nice and true.
Do you have the specs on that roller cam?
If John is suggesting a .035 clearance is a good quench then wouldn't the .032 I have be good ??
The block was checked in '78-79, when it was rebuilt with these pistons. The crank was polished and I believe the block was checked for main cap alignment or honed then. The only other thing they did was bore it the 30 thousands. There was very little use on it when it was removed from service in the mid 80's. It had sat in my former B-I-L's garage since then until I got it back about 8 years ago. This is the original engine from the '70 SS 454 Chevelle I bought in 1973. I know where the engine has been for 42 years... Not that it makes any difference to what we are doing right now, but I would sooner buy custom machined pistons than deck the block.
I didn't get a part number on the cam to look up the specs. You're saying less overlap will retain more of the compression. What is a good number for that...108, 110, 112. I get confused remembering if the lower number is the better.
67ss said
Nov 18, 2015
The quench is the headgasket plus distance of piston to top of block. So your quench area right now is .071. If block is zero deck then it is just the head gasket at .039.
Cam choice is going to be a combination of duration and lobe separation angle.
Did your machinist have any recomendations?
Enganeer said
Nov 18, 2015
What Chris said. A good quench distance can maximize the potential of the engine and provide more resistance to detonation even though you may increase the compression to get it.
Lost in the 60s said
Nov 19, 2015
I wasn't thinking about the gasket. I thought that .035 was just the piston to deck differential.
67ss said
Nov 19, 2015
What do you know about the 454 that is in the car right now? It is a newer 1 piece block I think you said, is it also a factory roller cam block, and a 4 bolt main?
SShink said
Nov 19, 2015
Here's some good reading on a basic 454 buildup from Super Chevy that sounds like it might be similar, other than they threw nitrous on it to get to 700HP!
I'd trust Chris P the engine whisperer before a magazine article... so take it for what it's worth.
Lost in the 60s said
Nov 19, 2015
67ss wrote:
What do you know about the 454 that is in the car right now? It is a newer 1 piece block I think you said, is it also a factory roller cam block, and a 4 bolt main?
It's a Gen V, so still flat tappet. It is a 1 piece seal and 4 bolt mains.
Lost in the 60s said
Nov 19, 2015
Back working on the rotisserie. I got square tubing from a local fabrication shop and cut it to make 2 cross ties to replace the single in the center.
Drilling a series of holes for adjustable length.
I will use 4, 1/2" hitch pins to secure the inner tube instead of the pinch bolt the center one has.
Tony Hoffer said
Nov 20, 2015
Lost in the 60s wrote:
67ss wrote:
Guessing those Pistons being older they have a normal pin height. To answer your question is 9.2 to 9.6 going to make a big difference, no. But here are the two thoughts of why I would try and run the higher compression and why I would deck the block and not mill the heads. First decking the block is going to tighten the quench as John mentioned, this in turn makes the engine less prone to detonation to run higher compression. Second running most any aftermarket cam is going to give you some valve overlap, this is going to cause loss of cylinder pressure and or dynamic compression. So with the higher compression what you do lose won't be as bad which will give you better low end. Hoping this makes sense and is helping.
I know you are on a budget but it would also be a good idea to line hone the mains on a 40 year old block. Then everything will be nice and true.
Do you have the specs on that roller cam?
If John is suggesting a .035 clearance is a good quench then wouldn't the .032 I have be good ??
The block was checked in '78-79, when it was rebuilt with these pistons. The crank was polished and I believe the block was checked for main cap alignment or honed then. The only other thing they did was bore it the 30 thousands. There was very little use on it when it was removed from service in the mid 80's. It had sat in my former B-I-L's garage since then until I got it back about 8 years ago. This is the original engine from the '70 SS 454 Chevelle I bought in 1973. I know where the engine has been for 42 years... Not that it makes any difference to what we are doing right now, but I would sooner buy custom machined pistons than deck the block.
I didn't get a part number on the cam to look up the specs. You're saying less overlap will retain more of the compression. What is a good number for that...108, 110, 112. I get confused remembering if the lower number is the better.
The tighter you go in LSA (lower number) the more overlap youll have... Overlap is also a function of duration as well..
Lost in the 60s said
Nov 20, 2015
I have a flat tappet cam I bought many years ago for this engine, but it may be too much overlap for the compression too. It's a Comp 280H. LSA is 110 with 280 degrees of duration. valve lift is .52. Their description is rough idle and 2-6k power range. Not really what I'm looking for anymore. I bought this along with an old Torker manifold that mounts the carb at an angle. Was looking for a "day 2" set up at that time.
Would that work with the pistons and deck clearance Chris ?
Not really in a position to funnel much for funds to the engine right now. I'm more concerned with the chassis and body restoration.
SShink said
Nov 20, 2015
Lost in the 60s wrote:
I have a flat tappet cam I bought many years ago for this engine, but it may be too much overlap for the compression too. It's a Comp 280H. LSA is 110 with 280 degrees of duration. valve lift is .52. Their description is rough idle and 2-6k power range. Not really what I'm looking for anymore. I bought this along with an old Torker manifold that mounts the carb at an angle. Was looking for a "day 2" set up at that time.
Would that work with the pistons and deck clearance Chris ?
Not really in a position to funnel much for funds to the engine right now. I'm more concerned with the chassis and body restoration.
Mitch, I had that 280H in the white w/black stripes '71 Chevelle a few years ago with a 396 and a Saginaw 4 speed. That was a great cam, and I really liked it. It had a nice lopey idle, but still had a lot of torque on the low end. At first the Chevelle had a TH350 with a 3K rpm stall in it, and it would squawk the tires leaving the light if the rpm got too high... then when I put in the Saginaw, I could overtorque the clutch pretty easy if I wanted to while it was in gear. It was a good cam for that motor.
Lost in the 60s said
Nov 20, 2015
That's good to hear, Stan...I like live reviews...
Bungy L-76 said
Nov 21, 2015
Sounds like Stan had good luck with that cam. My opinion is that cam is borderline for your combination and what you want out of the engine, but I think you can get away with it because your larger displacement engine will give you more low end torque. Another thing you could do is advance it 4 degrees to move the power band lower in the RPM range.
67ss said
Nov 21, 2015
280 is advertised duration, what is more important is duration at .050. I agree with Bungy that is borderline with the compression.
Do you have any issues with using the other 454 if we could make it work better?
Lost in the 60s said
Nov 21, 2015
OK, how about the XE268H ?? Seems to be more low compression friendly.
Probably not a good comparison... but I used that cam in the red '72 Chevelle 350 that I put 305 c.I. heads on to bump the compression, and it woke up the engine but it wasn't anything to write home about. Might be different used in a BBC. If I remember right... it was the Comp Cams version, and it did have a bit of a sewing machine sound to the valves because of the aggressive closing rates, which is common to a lot of their cams.
Again, I'll defer to Chris P.
67ss said
Nov 22, 2015
I like this one. I still think we should cc everything on your engine to be more accurate on the compression. I think it is less then what I calculated.
Stan, the small valves in the 305 heads were limiting your performance above 5k. Could be why you felt it woke up but didn't really perform to expectations.
I talked with Chris last night at bowling and I'm not looking for a screaming maximum performance engine right now. If a shorter duration cam will provide good street torque and keep the currently available compression in, that's all I am after. Comp specs the 268 torque range at 1600-5900. The cam that was in it was ridiculous for the compression. A complete refit can come at a later date. The engine is an afterthought that was evolving into threatening to eat the chassis restoration funds. I'd like to get the LS5 in the car this spring, but I need to stay focused on the chassis. Ideally, I'd like to eventually do a whole forged stroker kit and the pistons can be spec'd for a zero deck height at that time...
Lost in the 60s said
Nov 22, 2015
67ss wrote:
I like this one. I still think we should cc everything on your engine to be more accurate on the compression. I think it is less then what I calculated.
It still has plenty of lift but even less duration and overlap to prevent bleed off.
If you want to take the time to cc it first, that's OK with me.
Bungy L-76 said
Nov 22, 2015
IMO I'd go with the cam Chris picked out (#702) You don't want to go too small either and lose potential performance you could have got with a slightly bigger cam, if that bigger cam will work with your combo, which I think the 702 will. The cam you posted Mitch, (#701) has the same LSA of 112 as that of the 702. The duration @.050 being slightly less. If, however you cc everything and the comp comes out less then 9:1, then I'd probably go with the 701.
jim larson said
Dec 31, 2015
Interested in learning more about Static CR and Dynamic CR and how little changes make changes. I plugged in the numbers for my current engine, cam, and Fel-Pro gasket thickness of 0.39 and bore of 4.370, I came up with a Static of 9.289 and a Dynamic of 7.907. When I used a steel shim with thickness of 0.18 and bore of 4.370, the numbers were 9.736 and 8.279 respectively. With a copper gasket with thickness of .021 and diameter of 4.250 I got 9.694 and 8.244.
I read a couple of articles on Static vs Dynamic compression ration, which I don't quite understand; but it seemed to say that Dynamic is important when you are using 91 octane gas. Seems to say you would have a dynamic of 7.5-8.5.
-- Edited by jim larson on Thursday 31st of December 2015 08:46:48 AM
67ss said
Dec 31, 2015
The basic concept is you want to make your static compression high enough so that once you factor in the camshaft timing events it does not drop your dynamic compression so much the engine loses all its cylinder pressures. Example you don't want to have a motor with 8 to 1 static compression and then put a cam in with 230 + degrees duration as this will make the dynamic compression like 6 to 1 (just using an example did not calculate the actual). Motor now has no cylinder pressure and will be very lazy and could ping. In just the opposite fashion having 11 to 1 compression and putting in a stock cam with under 200 degrees duration with cause high dynamic compression, high cylinder pressures, and also pinging concerns depending on octane rating being used. You can also throw into the mix that when you supercharge or turbo charge in engine you typically drop your static compression because forcing air into the cylinder under pressure make it then act like it has a much higher static compression, dynamic compression is still in play here but just adds more complication.
Need to account for all these things to try and build a happy engine that runs on pump gas, makes good horsepower, and does not ping itself to death.
67ss said
Jan 13, 2016
Stopped by Mitch's house last night to CC his heads and top of piston to deck height volumn. Heads were supposed to be 97 CC chambers and they came out to about 120CC so not sure what is going on there. But case in point had we assumed they were 97 and put it together it would probably not have performed as expected.
Mitch here is a picture of the chamber on the 215 heads for the 396 I have. I think the chambers on your 206's looked a bit different, see what you think. I will CC one of them when I get a chance to see if it comes up as 101 CC that is stated on the internet.
By the pic, the pocket doesn't appear to be as deep as mine...
jim larson said
Jan 18, 2016
This is a photo from a pair of 206 heads I have that I am not going to use. Do yours look much different? I don't think these have been machined or worked on.
-- Edited by jim larson on Monday 18th of January 2016 03:43:13 PM
Bummer Jim had I known you had a set I would have had you bring one to the bowtie brunch and I could have CC it to compare to Mitch's.
jim larson said
Jan 18, 2016
A difference of 23 cc from standard to what you got at 120 on Mitch's head seem a lot. That a little more then a 1" cube of ice. When I cc'd my 207 heads they came out just a little over 98cc's according to the book they are suppose to 98.427 cc's. Something drastic must have been done to Mitch's heads. Could some of the liquid leaked down through a crack? His should look just about identical to the photo of my 206 head. Thats why I posted the photo. Unless something was wrong with the container you used to volume. I just used 25 and 10 cc syringes. Those kits designed for this task look to be the clear deal. I must have been off in space when you cc'd Mitch's head. I didn't realize what that head sitting on Mitch's frame was for.
-- Edited by jim larson on Monday 18th of January 2016 04:47:15 PM
67ss said
Jan 18, 2016
We did have leaks when I did it at Mitch's so that is why I wanted to do it again at Karl's. When I did it again after sealing the leaks they came out at 108cc. I did it twice and it came out the same both times. So maybe after a couple valve jobs the valves are in deeper or something.
Lost in the 60s said
Jan 18, 2016
I don't have a clue how much liquid 10cc's is but remember, I have those long spark plugs too. A correct thread length plug would take a little less liquid to fill...
In preparation for pulling the body off the frame, I FINALLY took the time to upgrade the wheels on the rotisserie. I got the pneumatic tire set up from Craig aka Pushrod about 2 or 3 years ago. They roll really smooth right now. I hope they don't squish and roll hard once the weight of the body is on them. I will also be modifying the center brace arrangement. I am going with one on each side instead of a single in the middle. This will help stabilize it when rolling. I am going to fabricate a pinned holding system for the bars too, instead of the pinch bolt style that slips and lets the end T's separate.
New wheels
Do those air tires have a load rating on them? Might help you determine if they're going to "squish" if you're close to or over their weight limit. ???
Not in pounds, just load range B, whatever that is a for a 4" tire at 50 psi...
Load range B on a 12" trailer tire is 765 at 60 psi. I'm going with these being capable of at least 400 lbs each for a total capacity of 2400.
Today, John and I pulled apart the engine that will go back in the '66 after the chassis restoration. It was rebuilt in the late 70's with flat top pistons to lower the compression and a cam that was way too much for the pistons. It will get new pistons to get the compression to around 9-9.5 and a street friendly torque cam.
Didn't you say this was a LS5 454 motor or something like that?
Last pic...CRT...
How do I figure the comp ratio with 97.2 cc head and the flat top piston ? Bore is +.030
-- Edited by Lost in the 60s on Wednesday 18th of November 2015 08:23:49 AM
https://www.uempistons.com/index.php?main_page=calculators&type=comp&zenid=3ae66e375eb987304caacc59ee0a75d5
I use the calculator above though it needs a few more inputs to be accurate. Any part numbers on the pistons to try and figure out the valve relief volume? That has closed chambered head on it?
Getting way technical for me. I didn't see any part number on pistons and as they are already out, no way to measure deck height/volume. They were pretty much even with the deck. The block is original, uncut. I'll clean up a piston better today and look for more numbers. Valve relief is minimal. If necessary, I'll pop a piston back in.
Heads are closed but not original 290's. These are '65 206 heads.
I can make assumptions on a few things to get you close. Typically most gm motors pistons are .025-.030 below deck. Gasket thickness and bore can be looked up on felpro's site. So trying to find a similar piston for valve reliefs is the only thing to figure out. Are the pistons typical 4 valve relief type I can't make it out in the picture?
With a closed chamber head and flat top pistons you might be close to where you want to be. Just having the block zero decked could be enough to get what you want without buying new pistons.
Block will never be decked in my possession...
I don't want to lose the stampings. I actually tracked my old car down from them 10 years ago but couldn't afford the owners "asking" price to buy it back and return this engine to it's original body.
OK, pics of the piston. Not much for identifiers.
Perfect is a silvolite 1448
https://www.uempistons.com/index.php?main_page=product_silvolite_info&cPath=6_25_27&products_id=1676
Let me run some numbers and see what I come up with. The machinist I use says he can deck the block without taking off the stamping. I asked him about it as the 327 for my chevelle is the correct 275 horse block and he said he can do it?
It wouldn't be worth the expense to me, Chris. Not for a couple points of compression on a street cruiser.
Couldn't I use a steel shim head gasket instead of a sandwich and get close to the same result ?
I appreciate you taking the time to work on this...
So it comes in at 9.2. This is using a felpro 1037 gasket. Yes you could use a thinner gasket and maybe get it up a bit. If you did deck the block changing nothing else it comes out at 9.6. But I understand not wanting to to that but just wanted to give you a comparison.
Note: Neg. number above deck, Pos. number below deck
9.226
-- Edited by 67ss on Wednesday 18th of November 2015 02:05:17 PM
Is 9.6 going to make much of a difference in torque over 9.2 ? I could have the heads cut too. Since they aren't original, that wouldn't bother me. But is it really worth the expense for the .5 difference ?
I popped a piston back in and measured the clearance at .032.
Tim, the guy that built my 292 said he could take .015 off the heads for $80 and that would bring the static up a few points to around 9.5, which he likes with the flat tops. He has a Howard's hydraulic roller set up on his shelf that I can get for $700 that he has in his own car that makes gobs of torque.
As long as I don't need to buy piston's I'm giving serious thought to moving up to a roller cam.
Hmm..are you sure about that measurement because I just realized the pin height on those pistons is different. It shows 1.627 and when I look up other 454 pistons is shows pin height of 1.645. I have seen this before on cheap rebuilder pistons they do that to lower compression even more. So I would expect your pistons to be about .043 or more in the hole which would bring the compression way down. Did you lay a flat edge across the opening and use a feeler gauge to check to the top of the piston?
There is one other thing we can do to be totally sure and that is to cc the whole volumn with the piston at TDC in the engine. I have a cc setup I can bring over and help you with it one night after work.
Yup, straight edge and feeler gauges. .035 won't fit, .032 does, .030 is slightly loose.
This engine was assembled in the late 70's, so anything modern is out the window...
Guessing those Pistons being older they have a normal pin height. To answer your question is 9.2 to 9.6 going to make a big difference, no. But here are the two thoughts of why I would try and run the higher compression and why I would deck the block and not mill the heads. First decking the block is going to tighten the quench as John mentioned, this in turn makes the engine less prone to detonation to run higher compression. Second running most any aftermarket cam is going to give you some valve overlap, this is going to cause loss of cylinder pressure and or dynamic compression. So with the higher compression what you do lose won't be as bad which will give you better low end. Hoping this makes sense and is helping.
I know you are on a budget but it would also be a good idea to line hone the mains on a 40 year old block. Then everything will be nice and true.
Do you have the specs on that roller cam?
Decking that block would destroy a LOT of value.
If John is suggesting a .035 clearance is a good quench then wouldn't the .032 I have be good ??
The block was checked in '78-79, when it was rebuilt with these pistons. The crank was polished and I believe the block was checked for main cap alignment or honed then. The only other thing they did was bore it the 30 thousands. There was very little use on it when it was removed from service in the mid 80's. It had sat in my former B-I-L's garage since then until I got it back about 8 years ago. This is the original engine from the '70 SS 454 Chevelle I bought in 1973. I know where the engine has been for 42 years...
Not that it makes any difference to what we are doing right now, but I would sooner buy custom machined pistons than deck the block.
I didn't get a part number on the cam to look up the specs. You're saying less overlap will retain more of the compression. What is a good number for that...108, 110, 112. I get confused remembering if the lower number is the better.
The quench is the headgasket plus distance of piston to top of block. So your quench area right now is .071. If block is zero deck then it is just the head gasket at .039.
Cam choice is going to be a combination of duration and lobe separation angle.
Did your machinist have any recomendations?
I wasn't thinking about the gasket. I thought that .035 was just the piston to deck differential.
What do you know about the 454 that is in the car right now? It is a newer 1 piece block I think you said, is it also a factory roller cam block, and a 4 bolt main?
Here's some good reading on a basic 454 buildup from Super Chevy that sounds like it might be similar, other than they threw nitrous on it to get to 700HP!
454 Super Chevy Link
I'd trust Chris P the engine whisperer before a magazine article... so take it for what it's worth.
It's a Gen V, so still flat tappet. It is a 1 piece seal and 4 bolt mains.
Back working on the rotisserie. I got square tubing from a local fabrication shop and cut it to make 2 cross ties to replace the single in the center.
Drilling a series of holes for adjustable length.
I will use 4, 1/2" hitch pins to secure the inner tube instead of the pinch bolt the center one has.
The tighter you go in LSA (lower number) the more overlap youll have... Overlap is also a function of duration as well..
I have a flat tappet cam I bought many years ago for this engine, but it may be too much overlap for the compression too. It's a Comp 280H. LSA is 110 with 280 degrees of duration. valve lift is .52. Their description is rough idle and 2-6k power range. Not really what I'm looking for anymore. I bought this along with an old Torker manifold that mounts the carb at an angle. Was looking for a "day 2" set up at that time.
Would that work with the pistons and deck clearance Chris ?
Not really in a position to funnel much for funds to the engine right now. I'm more concerned with the chassis and body restoration.
Mitch, I had that 280H in the white w/black stripes '71 Chevelle a few years ago with a 396 and a Saginaw 4 speed. That was a great cam, and I really liked it. It had a nice lopey idle, but still had a lot of torque on the low end. At first the Chevelle had a TH350 with a 3K rpm stall in it, and it would squawk the tires leaving the light if the rpm got too high... then when I put in the Saginaw, I could overtorque the clutch pretty easy if I wanted to while it was in gear. It was a good cam for that motor.
That's good to hear, Stan...I like live reviews...
Sounds like Stan had good luck with that cam. My opinion is that cam is borderline for your combination and what you want out of the engine, but I think you can get away with it because your larger displacement engine will give you more low end torque. Another thing you could do is advance it 4 degrees to move the power band lower in the RPM range.
280 is advertised duration, what is more important is duration at .050. I agree with Bungy that is borderline with the compression.
Do you have any issues with using the other 454 if we could make it work better?
OK, how about the XE268H ?? Seems to be more low compression friendly.
http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=395&sb=2
Probably not a good comparison... but I used that cam in the red '72 Chevelle 350 that I put 305 c.I. heads on to bump the compression, and it woke up the engine but it wasn't anything to write home about. Might be different used in a BBC. If I remember right... it was the Comp Cams version, and it did have a bit of a sewing machine sound to the valves because of the aggressive closing rates, which is common to a lot of their cams.
Again, I'll defer to Chris P.
I like this one. I still think we should cc everything on your engine to be more accurate on the compression. I think it is less then what I calculated.
https://www.lunatipower.com/Product.aspx?id=2150&gid=287
Stan, the small valves in the 305 heads were limiting your performance above 5k. Could be why you felt it woke up but didn't really perform to expectations.
I talked with Chris last night at bowling and I'm not looking for a screaming maximum performance engine right now. If a shorter duration cam will provide good street torque and keep the currently available compression in, that's all I am after. Comp specs the 268 torque range at 1600-5900. The cam that was in it was ridiculous for the compression. A complete refit can come at a later date. The engine is an afterthought that was evolving into threatening to eat the chassis restoration funds. I'd like to get the LS5 in the car this spring, but I need to stay focused on the chassis.
Ideally, I'd like to eventually do a whole forged stroker kit and the pistons can be spec'd for a zero deck height at that time...
There's this one too https://www.lunatipower.com/Product.aspx?id=2149
It still has plenty of lift but even less duration and overlap to prevent bleed off.
If you want to take the time to cc it first, that's OK with me.
IMO I'd go with the cam Chris picked out (#702) You don't want to go too small either and lose potential performance you could have got with a slightly bigger cam, if that bigger cam will work with your combo, which I think the 702 will. The cam you posted Mitch, (#701) has the same LSA of 112 as that of the 702. The duration @.050 being slightly less. If, however you cc everything and the comp comes out less then 9:1, then I'd probably go with the 701.
Interested in learning more about Static CR and Dynamic CR and how little changes make changes. I plugged in the numbers for my current engine, cam, and Fel-Pro gasket thickness of 0.39 and bore of 4.370, I came up with a Static of 9.289 and a Dynamic of 7.907. When I used a steel shim with thickness of 0.18 and bore of 4.370, the numbers were 9.736 and 8.279 respectively. With a copper gasket with thickness of .021 and diameter of 4.250 I got 9.694 and 8.244.
I read a couple of articles on Static vs Dynamic compression ration, which I don't quite understand; but it seemed to say that Dynamic is important when you are using 91 octane gas. Seems to say you would have a dynamic of 7.5-8.5.
This is the article I read. http://www.enginebasics.com/Advanced%20Engine%20Tuning/Static%20vs%20Dynamic.html
-- Edited by jim larson on Thursday 31st of December 2015 08:46:48 AM
The basic concept is you want to make your static compression high enough so that once you factor in the camshaft timing events it does not drop your dynamic compression so much the engine loses all its cylinder pressures. Example you don't want to have a motor with 8 to 1 static compression and then put a cam in with 230 + degrees duration as this will make the dynamic compression like 6 to 1 (just using an example did not calculate the actual). Motor now has no cylinder pressure and will be very lazy and could ping. In just the opposite fashion having 11 to 1 compression and putting in a stock cam with under 200 degrees duration with cause high dynamic compression, high cylinder pressures, and also pinging concerns depending on octane rating being used. You can also throw into the mix that when you supercharge or turbo charge in engine you typically drop your static compression because forcing air into the cylinder under pressure make it then act like it has a much higher static compression, dynamic compression is still in play here but just adds more complication.
Need to account for all these things to try and build a happy engine that runs on pump gas, makes good horsepower, and does not ping itself to death.
Stopped by Mitch's house last night to CC his heads and top of piston to deck height volumn. Heads were supposed to be 97 CC chambers and they came out to about 120CC so not sure what is going on there. But case in point had we assumed they were 97 and put it together it would probably not have performed as expected.
Mitch here is a picture of the chamber on the 215 heads for the 396 I have. I think the chambers on your 206's looked a bit different, see what you think. I will CC one of them when I get a chance to see if it comes up as 101 CC that is stated on the internet.
By the pic, the pocket doesn't appear to be as deep as mine...
This is a photo from a pair of 206 heads I have that I am not going to use. Do yours look much different? I don't think these have been machined or worked on.
-- Edited by jim larson on Monday 18th of January 2016 03:43:13 PM
Bummer Jim had I known you had a set I would have had you bring one to the bowtie brunch and I could have CC it to compare to Mitch's.
A difference of 23 cc from standard to what you got at 120 on Mitch's head seem a lot. That a little more then a 1" cube of ice. When I cc'd my 207 heads they came out just a little over 98cc's according to the book they are suppose to 98.427 cc's. Something drastic must have been done to Mitch's heads. Could some of the liquid leaked down through a crack? His should look just about identical to the photo of my 206 head. Thats why I posted the photo. Unless something was wrong with the container you used to volume. I just used 25 and 10 cc syringes. Those kits designed for this task look to be the clear deal. I must have been off in space when you cc'd Mitch's head. I didn't realize what that head sitting on Mitch's frame was for.
-- Edited by jim larson on Monday 18th of January 2016 04:47:15 PM
We did have leaks when I did it at Mitch's so that is why I wanted to do it again at Karl's. When I did it again after sealing the leaks they came out at 108cc. I did it twice and it came out the same both times. So maybe after a couple valve jobs the valves are in deeper or something.
I don't have a clue how much liquid 10cc's is but remember, I have those long spark plugs too. A correct thread length plug would take a little less liquid to fill...