Discussion Forum - Northstar Chevelle Club

jim larson · 2K+ Club

Did I make a mistake on re-installing Timing sprocket and Chain? And do these #'s on the cam tell anything?

John D · 2K+ Club

If you were doing a timing set "in the car" and wanting to get it running again a few hours later you'd be hosed... at least for a while until you got things back in time.

But,

Since the engine is out and apart you are in good shape. At this moment you are setting the timing baseline. Because nothing is "timed or synchronized" to eachother yet, as long as you've lined up the dots now (with the #1 piston at TDC) you're golden.

One extra labor thing to think about right now. At this stage of assembly you are in a perfect position to verify and mark your absolute/true TDC & "0" mark on your balancer and timing tab. If you don't mind a slightly long "hijack" here I'll explain.

Lost in the 60s · President

With the marks lined up, the piston will be at TDC but NOT necessarily on compression stroke. It could be exhaust. Years ago when I worked as a tech, MANY aftermarket sprockets were marked 180° off and I tore my hair out trying to get an engine to start on exhaust stroke. Once you have the chain on and I recommend a new double roller chain and sprocket set, look at the cam lobes for number 1 and see if they are both on the flat to know if you need to rotate the CRANK 1 revolution to drop the dizzy in.

I"m thinking the cam is a Cam Dynamics from the CD and the numbers represent the application.

jim larson · 2K+ Club

John D wrote:

If you were doing a timing set "in the car" and wanting to get it running again a few hours later you'd be hosed... at least for a while until you got things back in time.

But,

Since the engine is out and apart you are in good shape. At this moment you are setting the timing baseline. Because nothing is "timed or synchronized" to eachother yet, as long as you've lined up the dots now (with the #1 piston at TDC) you're golden.

One extra labor thing to think about right now. At this stage of assembly you are in a perfect position to verify and mark your absolute/true TDC & "0" mark on your balancer and timing tab. If you don't mind a slightly long "hijack" here I'll explain.

Go for it.

jim larson · 2K+ Club

Lost in the 60s wrote:

With the marks lined up, the piston will be at TDC but NOT necessarily on compression stroke. It could be exhaust. Years ago when I worked as a tech, MANY aftermarket sprockets were marked 180° off and I tore my hair out trying to get an engine to start on exhaust stroke. Once you have the chain on and I recommend a new double roller chain and sprocket set, look at the cam lobes for number 1 and see if they are both on the flat to know if you need to rotate the CRANK 1 revolution to drop the dizzy in.

I"m thinking the cam is a Cam Dynamics from the CD and the numbers represent the application.

Thanks Mitch, will check into the sprocket and chain set. Being inexperience, I am not sure what you mean by both lobes for #1 being on the flat. I think that would mean both lifters would be down rather than up?

How do I find out the information on the Cam so I can get the Dynamic CR?

Lost in the 60s · President

Cam Dynamics was bought by Crane a few years back. You may be able to get info by calling them.
866-388-5120

Dave Seitz · Mega Poster

Lost in the 60s wrote:

With the marks lined up, the piston will be at TDC but NOT necessarily on compression stroke. It could be exhaust. Years ago when I worked as a tech, MANY aftermarket sprockets were marked 180° off and I tore my hair out trying to get an engine to start on exhaust stroke. Once you have the chain on and I recommend a new double roller chain and sprocket set, look at the cam lobes for number 1 and see if they are both on the flat to know if you need to rotate the CRANK 1 revolution to drop the dizzy in.

I"m thinking the cam is a Cam Dynamics from the CD and the numbers represent the application.

I found that out the hard way my self, and the worst part was it was in a truck and fully assembled when I hit the key and went WTF! Yes that was a learning day with the engine and they said I didn't line the dots up correctly.

John D · 2K+ Club

Mitch is right - I was assuming all parts were correct, and forgot about checking the lobes.

Yes, the lifters for #1 cylinder should be down, or on the base circle of the cam when you are on compression #1.

Lost in the 60s · President

Dave Seitz wrote
I found that out the hard way my self, and the worst part was it was in a truck and fully assembled when I hit the key and went WTF! Yes that was a learning day with the engine and they said I didn't line the dots up correctly.

I used to do 1 timing chain job a week back when the plastic and aluminum cam gears went out. It was damn bewildering to never touch the dizzy but after you're done and it won't start to see the rotor pointing at the firewall with the timing marks lined up !!!!! I learned in a hurry to line the dots up with the cam dot at the TOP !

Chris R · 2K+ Club

Dont forget. If you have the dots lined up. You ARE on TDC. The dots only line up once for each stroke. A cam will rotate twice while the cranks rotates once for each stroke.

Lost in the 60s · President

Chris R wrote:

Dont forget. If you have the dots lined up. You ARE on TDC. The dots only line up once for each stroke. A cam will rotate twice while the cranks rotates once for each stroke.

You have that backwards, Chris....the CRANK rotates twice for every 1 revolution of the cam. The dots will line up twice during the cam rotation, both at the bottom and top and the piston will be at the TOP ( TDC) of it's travel with the dot in both positions. The piston doesn't care weather it's compression or exhaust. The cam position dictates which function it performs.

SteveS · Super Poster

The crank does rotate twice for every 1 cam rotation, but the dots only line up once per cycle. The crank will rotate once and the cam dot will be at 12:00 and on the second rotation it will be at 6:00. Its true you need to be on the correct cycle when you stick the distributor in, but if line the dots up, it will always be in the same place.

-- Edited by SteveS on Tuesday 4th of January 2011 11:16:31 AM

Chris R · 2K+ Club

Doh! I was in a hurry to get out the door this morning and did have it backwards now that I read it again. Meant to type it the other way around. I had forgotten the cam gets the larger gear even though its the smaller component.

-- Edited by Chris R on Tuesday 4th of January 2011 03:38:33 PM

Lost in the 60s · President

Gonna beat a dead horse. I removed the balancer and timing cover on my 93 Gen V today.
I removed the spark plugs and rotated the engine by hand to compression on #1. The timing marks lined up on the balancer and tab.

Pulled the chain cover to find the cam gear mark at the top, like I figured. When replacing a chain and sprocket, either align the marks as shown or rotate the mark to the top from the bottom BEFORE installing the distributor.

Didn't seem to matter to the builder where the dizzy went in as the rotor is pointing in a radom direction. I checked the cap and the wires were moved around the cap from normal position to allow it to run.

Strange front cover too. It has 2 timing tabs. Must be set-up for different applications... confuse

67ss · 1K+ Club

I only remember seeing a lower timng tab like that on vans and motorhomes. Since there was no way in heck you could usually see the top timing tab for setting timing.

Lost in the 60s · President

67ss wrote:

I only remember seeing a lower timng tab like that on vans and motorhomes. Since there was no way in heck you could usually see the top timing tab for setting timing.

I think we may have a winner. It IS a truck engine and with a balancer marked for that location, it would work. Makes sense to me, Chris.... smile