No, I have a Gen V block. Pretty much any Mark IV 454 block would, since that's the only original part they use. Must say, I'd like to have one. Maybe I should send them my LS5 block...
jim larson said
Nov 2, 2011
Thought you would enjoy seeing how much the IV blocks can be built too. Do you have any numbers that your shooting for this winter?
Lost in the 60s said
Nov 2, 2011
jim larson wrote:
Thought you would enjoy seeing how much the IV blocks can be built too. Do you have any numbers that your shooting for this winter?
The engine is rated at 230 hp net. I would think with better heads, the cam that is in it or my 280H and the 750 Holley that I should be able to get the original 325hp rating out of it. I would most likely need to change pistons to get more and I'm not willing to spend the money on them. I would rather get my LS5 back in running condition. It used to put out 425hp.
jim larson said
Nov 2, 2011
that sounds like a good option
Bowtieman427 said
Nov 5, 2011
I am in planning stages D&D of a 489 close to the potential you have off ebay but using 049 heads and hyd roller cam (not solid roller) and 3x2 off Vette. Those are my limitters. The 049 are great heads and can be made to flow a takes ton of time and patients. The 3x2 dual plane intake and if I run manifolds it will limit me. I may bend and go headers or my dream of side pipes the way a Vette should be : ) I want the 489 to look completely original to my 427 3x2 Vette engine. Mitch I may have a set of heads for your LS5 they are original 290 Ovals with bigger I valves and have been clean up a bit in the bowls I have the flow data @ 25" not at 28". They flow pretty good and will make plenty of power. Have not run at all. Been sitting and waiting. I was going to run them in a future build but may not. If you need them to make your LS5 a LS5 again LMK. You may have to change the springs out to match whatever you want for a cam. I will in the future consider selling a set of '67 840 heads rec ports I have but they will not be cheap.
Lost in the 60s said
Nov 5, 2011
Jim, the 290's would be nice to go back to original. It has '65 vintage large valve ovals on it now. I don't remember the number. The engine may need a crank. It reportedly had a knock when i got it back and it doesn't seem to be a loose rocker like I was led to believe. I may pull it apart this winter to see what it needs to be run again. I know it needs pistons as the originals were removed and lower compression ones put in for my former B-I-L when he was 17. I'd like to bring it back to what it was when I had it and ran 13.10's in the original car.
Bowtieman427 said
Nov 5, 2011
Ok you want to make it a 454, LS5 ? Today you can make it better then it was in 1970. The 290 I have are the largest cast Oval intake 262cc close chamber about 100 or 100cc made 69-70 and that was it. They call them LS5 heads 290 casting for 1970 Corvette 454 390HP 3964290 Think they used them on others too. Personally if it needs a new crank and pistons I would consider a 489 or 496 build. They make good power and do not have to work to hard. There is alot to be said about a 4" stroke too like 460 -468 if you build to upper to take on more RPM it can be real fun. They will cost the same as far as getting new crank & pistons. 489 and 496 will not have to turn as hard to make power plus you would have streetable bottom end torque. You can go crazy too and make tons but it is not neccessary. If you do not find a good deal on a used 454 crank. Seems that i run into more people thinking there old truck 454 is a gold mine and they want more for a crank vs buying a new 4340 or a Scat 9000 which are $300 all day and can handle 700HP all day can even the Scat 9000 in internal balanced form. : )
The engine I have is a CRT code LS5 454 360 hp from a '70 Chevelle I bought from the original owner in 1973. He had replaced the heads with the '65 heads for more compression. I guess they have a smaller chamber. It is the same engine as the 390hp Corvette but GM didn't want to usurp the Corvettes hp supremacy.
I wouldn't mind getting correct heads for it and yes, if the crank is bad, I will go aftermarket and probably a stroker too.
Bowtieman427 said
Nov 6, 2011
WOW small world what are the odds of you having a '70 LS5 these are the correct heads. I am 99% sure they put these on all LS5 in 1970 & were only around for that year not sure I know for the Vette they were only used in 70 then I think they went to open chamber. I think these heads were only made between 69-70. I got them a while ago as they are suppose to have the best intake runner of any oval port closed chamber head. I dump $ into all check out valve job and new large intake valve and port/blend job and make the exhaust flow a lot better. They are done up ready to bolt in and go Full Solid roller springs got a sollid roller Comp cam 236i 242e @.050 around .646 lift LSA 110 intake 106 to match.
67ss said
Nov 6, 2011
Did you have hardened exhaust seats put in them when you had all the machine work done? Running those kinds of spring pressure for a solid roller cam they are going to take a beating.
jim larson said
Nov 6, 2011
My book says the 290 heads were use in 69 model year for chevy/ pass, chevelle camaro corvette and chevy II. It also says it was used in the 1970 model year;but doesn't indicate models. Also has 063 being used in 69 model year for same applications. Seems 063 discontinued and replaced by the 290's. Only about 2 cc's/ chamber larger than the 65-66 heads.
So which heads do you have Mitch, the 206's or the 702'S?
Lost in the 60s said
Nov 6, 2011
Bowtieman427 wrote:
WOW small world what are the odds of you having a '70 LS5 these are the correct heads. I am 99% sure they put these on all LS5 in 1970 & were only around for that year not sure I know for the Vette they were only used in 70 then I think they went to open chamber. I think these heads were only made between 69-70. I got them a while ago as they are suppose to have the best intake runner of any oval port closed chamber head. I dump $ into all check out valve job and new large intake valve and port/blend job and make the exhaust flow a lot better. They are done up ready to bolt in and go Full Solid roller springs got a sollid roller Comp cam 236i 242e @.050 around .646 lift LSA 110 intake 106 to match.
Way more cam than I want for the street and my days of solid lifters are past. The heads may be built beyond my needs too. I do see them at swap meets occasionally and have thought about getting some, but the heads on the engine are pretty good too. I'll have to find the number again and see what they are. The issue with rebuilding these old heads to work with today's fuel is by the time you're done, for a few bucks more I can get a decent set of aluminum heads with modern technology instead.
Lost in the 60s said
Nov 6, 2011
jim larson wrote:
My book says the 290 heads were use in 69 model year for chevy/ pass, chevelle camaro corvette and chevy II. It also says it was used in the 1970 model year;but doesn't indicate models. Also has 063 being used in 69 model year for same applications. Seems 063 discontinued and replaced by the 290's. Only about 2 cc's/ chamber larger than the 65-66 heads.
So which heads do you have Mitch, the 206's or the 702'S?
The 206 seems familiar. I'll have to look at them again. Are the valves bigger in the 206's too ?? It's been a LONG time since I knew all this and my memory isn't improving...
jim larson said
Nov 6, 2011
Orginally the valve size for the 206, 702, and the 290's were all 2.06/1.72
Have read about increasing this to 2.18/1.88; but I think there can be problems.
Some people recommend putting in SB valves to avoid the problems.
bwild70ss396 said
Nov 6, 2011
I had the 290 heads that came stock on my ss396 1970 El Camino. I had the bigger valves put in with the 2.18/1.88 with the hardened seats. They also had a pocket/ bowl port done. The cam I ran was a Comp xtreme energy 270 4x4 cam. The part number is 11-239-3 The specs are as follows, 270I, 278E, 226I & 234E@ .050, .544I & .564E, 1600 to 5800 rpm range, 111 lobe seperation with a 107 centerline. I liked the cam and it was nice for a 408 motor. I had 3:73 gears, 275/60/15 tires and back and a 2200 stall on a 400 turbo trans.
Not sure what you looking for, but thought I would share a combo I liked.
I am guessing it made around 400 to 410hp.
-- Edited by bwild70ss396 on Sunday 6th of November 2011 12:26:42 PM
Lost in the 60s said
Nov 6, 2011
bwild70ss396 wrote:
I had the 290 heads that came stock on my ss396 1970 El Camino. I had the bigger valves put in with the 2.18/1.88 with the hardened seats. They also had a pocket/ bowl port done. The cam I ran was a Comp xtreme energy 270 4x4 cam. The part number is 11-239-3 The specs are as follows, 270I, 278E, 226I & 234E@ .050, .544I & .564E, 1600 to 5800 rpm range, 111 lobe seperation with a 107 centerline. I liked the cam and it was nice for a 408 motor. I had 3:73 gears, 275/60/15 tires and back and a 2200 stall on a 400 turbo trans.
Not sure what you looking for, but thought I would share a combo I liked.
I am guessing it made around 400 to 410hp.
-- Edited by bwild70ss396 on Sunday 6th of November 2011 12:26:42 PM
Thanks for sharing that, Brad. It looks like a nice street cam. I put a .510 lift, 304 duration cam in the LS5 and it was too much but sounded really mean. When I sold the LS5, I bought a built LS6 and put the cam in it. It was very radical for the street in the 70's and wouldn't idle well below 1,200 rpm and was worhtless for power below 3,000. Between 3-6500 it was hang on and steer because there wasn't a street tire that would hold the power...
Bowtieman427 said
Nov 6, 2011
Never ran them. Change springs to what ever cam you want. Not sure I understand built beyond your needs? They have 2.19i 1.72e. Left e stock to avoid possible issues and at the time was on the fence on what to do with the e. No harden seats were installed and I am glad I did not install them. My Machinest was against it and I was weighing in the pros and cons. If I were to run them would change to modern harden 1.72 e valve . They were minor ported and blended to fix the possible others problems with the big e installed and to basically flow the e better : )
Many just like to throw big valves in and say wow I got these big valves in they flow great. NOT if you do not take to time to flow them to see if there are issues (shrowding is a biggy hear) you may have just made them worst.
The problems are with adding the bigger 2.19 /1.88 are 1) shrowding 2) the i and e run way to close. This is why I elected to keep the 1.72e and at the time put in the new style stainless i valve
Never heard of the SB valve thing plesae elaborate sounds interesting and impossible ??
Also 206 intake port is 225cc and the 290 port is 262cc intake. Have to remeber the 290 was designed for 454 and 206 or 65-67 were for 396. The 206 is NOT a "big oval" head it is actually pretty small I seen SBC heads bigger then 225cc i ports : ) The 290 head full casting number 3964290 is the LS5 head used in 1970 and others per my research. It is the corect head for a 1970 LS5. and also used on Corvette 390HP 454 in 1970 see data above. Years after that they took a HP loss which may have been more political then anything.
The cumbustion chamber size in 206 and 290 are very similar both are closed chambers heads as Jim stated above. I have no idea why someone would take off a 290 head and put on a 206 it is one big step in the wrong direction. Compression would be virtually the same with a loss in top end power especailly in a 454 do to the 206 having a small intake ports . Perhaps the LS5 Mitch has went through a bunch of iterations in its life. Maybe someone put harden seats ont he 290 and messed them up and had a set of 206s : )
I would advise against installing harden seats espcially with the new valve technology of today. Valves are typically hardened using the flame process right from the factory. Usually the old valves are as soft as the cast iron seat they seal against, grind them once and it gets even softer inside. If the valves are replaced with a modern equivalent you get a much harder valve face which makes a much better wearing pair with the soft seat, you don't get the seat material adhering to the valve face. Now if you grind a new valve your right back to square one. Besides valves are not that expensive anymore and regrinding them is almost half the price of a decent valve (sometimes equal?), I would just spend the extra money and put in new. Peace of mind for this critical component is cheap to me. It doesn't matter which part is hard, the valve or the seat. As long as you have a good wearing pair they will last, soft on soft will not last...long.
So when you compare the price and hazards or putting in hardened seats to replacing the valves and regrinding the soft seats. I've seen a lot of engineering data that debunks the old myth of seat erosion caused by lack of lead in the fuel, the data just does not support it particularly when you factor in modern valves materials. Actually putting seats in has many dangers especially with the thickness of castings and other risks, I have seen one set crack and read where many have cracks in heads due to improper installation of seats vs seat erosion issues. Plus installing harden seats really hurts flow. I think there is more risk of possible issues wtih installed harden seats over non harden seats especailly today. Future water leaks, cracks, & bad flow to name a few. We all have our opinions.
As far as the roller solution I would have concerns running 750-900 lift a tons of spring pressure with the springs to handle the high lift on there and .650 lift it is a non issue. If I was thinkign of running a bigger cam I would not use these heads. I had the cam ground to match the heads for a 454-468 solution about 5500-5700 HP Peak. There are new hyd roller cams today that are running 650 lift. but the total duration is way to big IMO for the street. Seen one that was 236i and 246e and with the 650 lift and the total duration was in the 300s. The solid roller I have total duration of 273i /279e and 236i/242e @ 0.050 .640 .646 lift which is not big by any means and makes one hell of a street cam and is not to big by any means if anything it is pretty small. If I was going Hyd Roller I would be looking at close to the same numbers @ 0.050" and maybe bigger total duraition and get the most lift I could.
Mitch here is a link to a post on Hotrodders forum on the 206 heads
I have the same cam and tire combo Brad ran. Accept I have an M21 instead of a 400 and the original 3:31 rearend. 400HP seemed about what I would have guessed as well. Feels about right in the seat of your pants.
jim larson said
Nov 6, 2011
Jim, They talked about using the SB valves in a BB on Team chevelle. It's been a while, so I don't remember where for sure. This was used when they were rebuilding 66 and 67 396 engines. I am not very knowledge in this area. But I specificly recall 2.15 SB valves. I will look to see if I can find the information
jim larson said
Nov 6, 2011
Jim, here is one of the threads. http://www.chevelles.com/forums/showthread.php?t=282341&highlight=valve. How do you get this underlined so a click takes you to the thread?
Lost in the 60s said
Nov 6, 2011
Seems strange that hardened seats aren't necessary with a harder valve. I thought that was the issue with the soft seats. The valve would beat it down to the head and then the seat would need to be replaced... I guess the boys with time and money are always coming up with something different. I know a guy on a GTO site that was advised to run solid roller lifters on a hydraulic roller cam and I thought it would pound the cam flat. He claims it runs great, doesn't click like on a solid cam and shows no wear yet...
jim larson said
Nov 6, 2011
Most all my responces on TC regarding hardened seats, was no for BB. The addative I use, Octane Supreme 130 has lead in it.
I have heard of circle track guys running solids on Hyd cams but never the Solid roller on Hyd roller cam. I would love to run a Hyd Roller on the Soid Roller cam I have 273i /279e and 236i/242e @ 0.050 .640 .646 lift. Becuase on a 454 this cam would seriously kick. Notice the total duration pretty close to what others posted ..... The 0.050" values are better and yes it actually has lift to let the head breath and flow filling the cylinders up.
Still think it is to big ????
The others are running "270I, 278E, 226I & 234E@ .050, .544I & .564E, 1600 to 5800 rpm range, 111 lobe seperation with a 107 centerline. I liked the cam and it was nice for a 408 motor. I had 3:73 gears, 275/60/15 tires and back and a 2200 stall on a 400 turbo trans."
Remember this is in a 408ci NOT a 454 or bigger in a 468 we are talking 60 more ci
Jim that link is really cool. I have learned somethnig new and with machining anything can be done. It is another way to get away from the unshrouding (which I can not spell) and getting in the bigger E valve if wanted or needed. Thanks for sharing that
recently I was researching to see what people do to old Cadillac 472 and 500 engines and it is pretty unreal. You can make some power from them that would make Cadillac collectors cry.
Here are some links on Harden seats enjoy : (like I said I am not a big fan and think a lot of it. Sometimes I think it is marketing to get you to spend money when you do not need to. Do not get me wrong they have there place and may be necessary if you have an issue but IMO if the seat is good why mess with it. In a factory setup or aftermarket the are part of the design. It jsut is not worth it to me for the other issue that can arrise form it. If you develope a crack or get a H2O leak over time the head is virtually junk. On the other hand if you sleep better for it by all means pay to have it done. )
http://www.ebay.com/itm/230694910554?item=230694910554&viewitem=&sspagename=ADME:B:SS:MOTORS:1123&vxp=mtr#ht_2989wt_1011
No, I have a Gen V block. Pretty much any Mark IV 454 block would, since that's the only original part they use. Must say, I'd like to have one. Maybe I should send them my LS5 block...
Mitch I may have a set of heads for your LS5 they are original 290 Ovals with bigger I valves and have been clean up a bit in the bowls I have the flow data @ 25" not at 28". They flow pretty good and will make plenty of power. Have not run at all. Been sitting and waiting. I was going to run them in a future build but may not. If you need them to make your LS5 a LS5 again LMK. You may have to change the springs out to match whatever you want for a cam.
I will in the future consider selling a set of '67 840 heads rec ports I have but they will not be cheap.
Jim, the 290's would be nice to go back to original. It has '65 vintage large valve ovals on it now. I don't remember the number. The engine may need a crank. It reportedly had a knock when i got it back and it doesn't seem to be a loose rocker like I was led to believe. I may pull it apart this winter to see what it needs to be run again. I know it needs pistons as the originals were removed and lower compression ones put in for my former B-I-L when he was 17. I'd like to bring it back to what it was when I had it and ran 13.10's in the original car.
Personally if it needs a new crank and pistons I would consider a 489 or 496 build. They make good power and do not have to work to hard. There is alot to be said about a 4" stroke too like 460 -468 if you build to upper to take on more RPM it can be real fun. They will cost the same as far as getting new crank & pistons. 489 and 496 will not have to turn as hard to make power plus you would have streetable bottom end torque. You can go crazy too and make tons but it is not neccessary. If you do not find a good deal on a used 454 crank. Seems that i run into more people thinking there old truck 454 is a gold mine and they want more for a crank vs buying a new 4340 or a Scat 9000 which are $300 all day and can handle 700HP all day can even the Scat 9000 in internal balanced form. : )
1970 Corvette Casting Numbers
Application Block Cylinder Head Intake Exhaust (left) Exhaust (right)
454 - 390 HP LS5 (early) 3963512 3964290 3955287 3969869 3880828
454 - 390 HP LS5 (late) 3963512 3964290 3969802 3969869 3880828
The engine I have is a CRT code LS5 454 360 hp from a '70 Chevelle I bought from the original owner in 1973. He had replaced the heads with the '65 heads for more compression. I guess they have a smaller chamber. It is the same engine as the 390hp Corvette but GM didn't want to usurp the Corvettes hp supremacy.
I wouldn't mind getting correct heads for it and yes, if the crank is bad, I will go aftermarket and probably a stroker too.
Did you have hardened exhaust seats put in them when you had all the machine work done? Running those kinds of spring pressure for a solid roller cam they are going to take a beating.
So which heads do you have Mitch, the 206's or the 702'S?
Have read about increasing this to 2.18/1.88; but I think there can be problems.
Some people recommend putting in SB valves to avoid the problems.
I had the 290 heads that came stock on my ss396 1970 El Camino. I had the bigger valves put in with the 2.18/1.88 with the hardened seats. They also had a pocket/ bowl port done. The cam I ran was a Comp xtreme energy 270 4x4 cam.
The part number is 11-239-3
The specs are as follows,
270I, 278E, 226I & 234E@ .050, .544I & .564E, 1600 to 5800 rpm range, 111 lobe seperation with a 107 centerline. I liked the cam and it was nice for a 408 motor. I had 3:73 gears, 275/60/15 tires and back and a 2200 stall on a 400 turbo trans.
Not sure what you looking for, but thought I would share a combo I liked.
I am guessing it made around 400 to 410hp.
-- Edited by bwild70ss396 on Sunday 6th of November 2011 12:26:42 PM
They have 2.19i 1.72e. Left e stock to avoid possible issues and at the time was on the fence on what to do with the e. No harden seats were installed and I am glad I did not install them. My Machinest was against it and I was weighing in the pros and cons. If I were to run them would change to modern harden 1.72 e valve . They were minor ported and blended to fix the possible others problems with the big e installed and to basically flow the e better : )
Many just like to throw big valves in and say wow I got these big valves in they flow great. NOT if you do not take to time to flow them to see if there are issues (shrowding is a biggy hear) you may have just made them worst.
The problems are with adding the bigger 2.19 /1.88 are
1) shrowding
2) the i and e run way to close. This is why I elected to keep the 1.72e and at the time put in the new style stainless i valve
Never heard of the SB valve thing plesae elaborate sounds interesting and impossible ??
Also 206 intake port is 225cc and the 290 port is 262cc intake. Have to remeber the 290 was designed for 454 and 206 or 65-67 were for 396. The 206 is NOT a "big oval" head it is actually pretty small I seen SBC heads bigger then 225cc i ports : ) The 290 head full casting number 3964290 is the LS5 head used in 1970 and others per my research. It is the corect head for a 1970 LS5. and also used on Corvette 390HP 454 in 1970 see data above. Years after that they took a HP loss which may have been more political then anything.
The cumbustion chamber size in 206 and 290 are very similar both are closed chambers heads as Jim stated above. I have no idea why someone would take off a 290 head and put on a 206 it is one big step in the wrong direction. Compression would be virtually the same with a loss in top end power especailly in a 454 do to the 206 having a small intake ports . Perhaps the LS5 Mitch has went through a bunch of iterations in its life. Maybe someone put harden seats ont he 290 and messed them up and had a set of 206s : )
I would advise against installing harden seats espcially with the new valve technology of today. Valves are typically hardened using the flame process right from the factory. Usually the old valves are as soft as the cast iron seat they seal against, grind them once and it gets even softer inside. If the valves are replaced with a modern equivalent you get a much harder valve face which makes a much better wearing pair with the soft seat, you don't get the seat material adhering to the valve face. Now if you grind a new valve your right back to square one. Besides valves are not that expensive anymore and regrinding them is almost half the price of a decent valve (sometimes equal?), I would just spend the extra money and put in new. Peace of mind for this critical component is cheap to me. It doesn't matter which part is hard, the valve or the seat. As long as you have a good wearing pair they will last, soft on soft will not last...long.
So when you compare the price and hazards or putting in hardened seats to replacing the valves and regrinding the soft seats. I've seen a lot of engineering data that debunks the old myth of seat erosion caused by lack of lead in the fuel, the data just does not support it particularly when you factor in modern valves materials. Actually putting seats in has many dangers especially with the thickness of castings and other risks, I have seen one set crack and read where many have cracks in heads due to improper installation of seats vs seat erosion issues. Plus installing harden seats really hurts flow. I think there is more risk of possible issues wtih installed harden seats over non harden seats especailly today. Future water leaks, cracks, & bad flow to name a few. We all have our opinions.
As far as the roller solution I would have concerns running 750-900 lift a tons of spring pressure with the springs to handle the high lift on there and .650 lift it is a non issue. If I was thinkign of running a bigger cam I would not use these heads. I had the cam ground to match the heads for a 454-468 solution about 5500-5700 HP Peak. There are new hyd roller cams today that are running 650 lift. but the total duration is way to big IMO for the street. Seen one that was 236i and 246e and with the 650 lift and the total duration was in the 300s. The solid roller I have total duration of 273i /279e and 236i/242e @ 0.050 .640 .646 lift which is not big by any means and makes one hell of a street cam and is not to big by any means if anything it is pretty small. If I was going Hyd Roller I would be looking at close to the same numbers @ 0.050" and maybe bigger total duraition and get the most lift I could.
Mitch here is a link to a post on Hotrodders forum on the 206 heads
http://www.hotrodders.com/forum/206-heads-135935.html
I have the same cam and tire combo Brad ran. Accept I have an M21 instead of a 400 and the original 3:31 rearend. 400HP seemed about what I would have guessed as well. Feels about right in the seat of your pants.
Seems strange that hardened seats aren't necessary with a harder valve. I thought that was the issue with the soft seats. The valve would beat it down to the head and then the seat would need to be replaced...
I guess the boys with time and money are always coming up with something different. I know a guy on a GTO site that was advised to run solid roller lifters on a hydraulic roller cam and I thought it would pound the cam flat. He claims it runs great, doesn't click like on a solid cam and shows no wear yet...
Still think it is to big ????
The others are running
"270I, 278E, 226I & 234E@ .050, .544I & .564E, 1600 to 5800 rpm range, 111 lobe seperation with a 107 centerline. I liked the cam and it was nice for a 408 motor. I had 3:73 gears, 275/60/15 tires and back and a 2200 stall on a 400 turbo trans."
Remember this is in a 408ci NOT a 454 or bigger in a 468 we are talking 60 more ci
Jim that link is really cool. I have learned somethnig new and with machining anything can be done. It is another way to get away from the unshrouding (which I can not spell) and getting in the bigger E valve if wanted or needed. Thanks for sharing that
recently I was researching to see what people do to old Cadillac 472 and 500 engines and it is pretty unreal. You can make some power from them that would make Cadillac collectors cry.
Here are some links on Harden seats enjoy : (like I said I am not a big fan and think a lot of it. Sometimes I think it is marketing to get you to spend money when you do not need to. Do not get me wrong they have there place and may be necessary if you have an issue but IMO if the seat is good why mess with it. In a factory setup or aftermarket the are part of the design. It jsut is not worth it to me for the other issue that can arrise form it. If you develope a crack or get a H2O leak over time the head is virtually junk. On the other hand if you sleep better for it by all means pay to have it done. )
http://www.chevelles.com/forums/showthread.php?t=145976
http://forums.hotrod.com/70/1267382/general-topics/hardened-seats-for-unleaded-gas-myth-or-truth/index.html
http://www.hotrodders.com/forum/hardened-valve-seats-4257.html
http://forums.corvetteforum.com/c1-and-c2-corvettes/2508760-hardened-valve-seats-yes-or-no.html