Tdc

1970camaronut

Veteran Member
Jul 25, 2010
125
Hey guys,

Looked at some old threads on this but still need assistance.

-Engine is turning over but not starting.
-Wanted to make sure distributor wires were on cap correct. So pulled #1 plug and had wife turn it over until I felt the compression in #1 cylinder with finger.
- The line on the harmonic balancer was at 9:00PM and the rotor was pointing at #6 terminal and not #1.

Question: Could I have felt the exhaust compression instead of intake compression and still need to have the engine turned over or does distributor need to be taken out?

Thanks
 

Gary S

Administrator
Lifetime Gold Member
Apr 14, 1999
24,514
Bismarck, North Dakota
The exhaust valve doesn't cause compression. When you check for the compression stroke, you need to make sure you have completed the trip of the piston to TDC. The beginning of feeling compression is not TDC yet.
 

Gary S

Administrator
Lifetime Gold Member
Apr 14, 1999
24,514
Bismarck, North Dakota
Did you turn it far enough so the piston reached the top of the stroke? The piston will create pressure during the entire compression stroke, not just at TDC. To time the engine, you need to be exactly at TDC, not 30 or 40 degrees before TDC.
You probably need to insert a stick or some other measuring device into the plug hole and watch it as the piston rises to find the exact top.
 

jb451

Veteran Member
Jan 17, 2011
861
Mesquite, Texas
Are you just trying to troubleshoot an existing problem or did you install something like a distributor where you have to find TDC? I had the same problem when i installed my dizzy the first time.... But gary is right, just stick a coat hanger in the and when the piston touches it, you'll know you're at TDC!
 

COPO

Veteran Member
Lifetime Gold Member
Sep 15, 1999
21,698
Ontario, Canada
You should wait until you hear the sound of your finger getting air pissed by it, then the balancer line will be approx at the 11am location, then slowly rotate the engine. If you have a manual trans, you can rock the car back and forth to move the balancer. Push more at the front of the car to turn the balancer towards the drivers side fender and pull on the bumper if you went past the timing gauge mark and want to go back to the timing gauge mark. I use this method when I set my solid lifters. I use a remote starter to get close to where I want then do the push/pull method to get it dead on.
 
Last edited:

1970camaronut

Veteran Member
Jul 25, 2010
125
COPO said:
You should wait until you hear the sound of your finger getting ass pissed by it, then the balancer line will be approx at the 11am location, then slowly rotate the engine. If you have a manual trans, you can rock the car back and forth to move the balancer. Push more at the front of the car to turn the balancer towards the drivers side fender and pull on the bumper if you went past the timing gauge mark and want to go back to the timing gauge mark. I use this method when I set my solid lifters. I use a remote starter to get close to where I want then do the push/pull method to get it dead on.

I did bump ignition to TDC but the rotor was not pointing to the #1. It was at 1:00 oclock
 

jb451

Veteran Member
Jan 17, 2011
861
Mesquite, Texas
1970camaronut said:
I did bump ignition to TDC but the rotor was not pointing to the #1. It was at 1:00 oclock

Have you checked your order of your plug wires? as long as it was at TDC when the distributor was stabbed in, you can just set your #1 plug wire to wherever your rotor is. Then just follow the firing order on the cap. Thats what i did at least.
 

1970camaronut

Veteran Member
Jul 25, 2010
125
pulled the dist and reset with rotor pointing at #1. Runs better.

The spark plug was in it was the smaller one and not the one with the gasket. I bought and installed the tapered type spark plug.

These heads are from 1969 however. Will the car run better with the gasket type plug or does it really matter. The guy at bennett auto said I am losing some compression with the tapered spark plug in there.

Thanks for your advise.
 




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