Timing question - sorta ?
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Timing question - sorta ?
I have just replaced the rear main seal and oil pump on my 74 big block. Timing chain set and a comp 268 cam is next.
I have set the timing mark DEAD on the zero mark on the stock indicator tab. The rotor button IS pointing exactly at the #1 position in the distributor.
Should the #1 piston be perfectly at the TOP (dead center) of it's stroke?
(It's close, but...the piston is a "few" degrees" short of the TDC...with the timing mark on zero....that's why I am asking)
Thanks........Fred............
I have set the timing mark DEAD on the zero mark on the stock indicator tab. The rotor button IS pointing exactly at the #1 position in the distributor.
Should the #1 piston be perfectly at the TOP (dead center) of it's stroke?
(It's close, but...the piston is a "few" degrees" short of the TDC...with the timing mark on zero....that's why I am asking)
Thanks........Fred............
Last edited by fotyfobravo; Jan 26, 2007 at 11:21 PM.
Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
Likes: 3,865
From: Palm Springs, CA.
Hey Fred,
It "should" be at the top of it's stroke but a worn timing chain could cause the problem you're having. Easy way to check it:
Rotate the crank pulley about 15 or 20 degrees clockwise. Then, with the distributor cap off slowly rotate the crank pulley counterclockwise and see if the rotor moves as soon as you start to move the crank pulley. If it doesn't you have a pretty sloppy timing chain.
I have seen these with enough slop that you move the crank pulley quite a bit before the rotor starts to move. If you're going to replace the timing set soon, no problem.
Best,
Greg
It "should" be at the top of it's stroke but a worn timing chain could cause the problem you're having. Easy way to check it:
Rotate the crank pulley about 15 or 20 degrees clockwise. Then, with the distributor cap off slowly rotate the crank pulley counterclockwise and see if the rotor moves as soon as you start to move the crank pulley. If it doesn't you have a pretty sloppy timing chain.
I have seen these with enough slop that you move the crank pulley quite a bit before the rotor starts to move. If you're going to replace the timing set soon, no problem.
Best,
Greg
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
Hey Fred,
It "should" be at the top of it's stroke but a worn timing chain could cause the problem you're having. Easy way to check it:
Rotate the crank pulley about 15 or 20 degrees clockwise. Then, with the distributor cap off slowly rotate the crank pulley counterclockwise and see if the rotor moves as soon as you start to move the crank pulley. If it doesn't you have a pretty sloppy timing chain.
I have seen these with enough slop that you move the crank pulley quite a bit before the rotor starts to move. If you're going to replace the timing set soon, no problem.
Best,
Greg
It "should" be at the top of it's stroke but a worn timing chain could cause the problem you're having. Easy way to check it:
Rotate the crank pulley about 15 or 20 degrees clockwise. Then, with the distributor cap off slowly rotate the crank pulley counterclockwise and see if the rotor moves as soon as you start to move the crank pulley. If it doesn't you have a pretty sloppy timing chain.
I have seen these with enough slop that you move the crank pulley quite a bit before the rotor starts to move. If you're going to replace the timing set soon, no problem.
Best,
Greg
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
I have just replaced the rear main seal and oil pump on my 74 big block. Timing chain set and a comp 268 cam is next.
I have set the timing mark DEAD on the zero mark on the stock indicator tab. The rotor button IS pointing exactly at the #1 position in the distributor.
Should the #1 piston be perfectly at the TOP (dead center) of it's stroke?
(It's close, but...the piston is a "few" degrees" short of the TDC...with the timing mark on zero....that's why I am asking)
Thanks........Fred............
I have set the timing mark DEAD on the zero mark on the stock indicator tab. The rotor button IS pointing exactly at the #1 position in the distributor.
Should the #1 piston be perfectly at the TOP (dead center) of it's stroke?
(It's close, but...the piston is a "few" degrees" short of the TDC...with the timing mark on zero....that's why I am asking)
Thanks........Fred............
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Thanks for all the input. I have never replaced a cam before. I just wanted to see that I "understood" the basics of what I was starting. Sounds like a fresh timing chain/gears and a new balancer would be wise, while I'm there.
Last edited by fotyfobravo; Jan 27, 2007 at 09:35 PM.
Just another Corvette guy
Joined: Feb 1999
Posts: 8,518
Likes: 3,865
From: Palm Springs, CA.
Of course the piston should be at the top of its stroke with the balancer at zero.
The only reason it may not be is if the balancer has slipped on its rubber mounting.
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Melting Slicks
Joined: Dec 2000
Posts: 3,407
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From: Carmichael CA
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Would you believe this all started out as just a "good engine compartment clean up!"
Thanks for the help .... Fred
Le Mans Master
Joined: Dec 2006
Posts: 8,837
Likes: 1,028
YEP...just got into the chain...pretty slack. Probably about 6 degrees of dead turn turn between crank and cam movement. I will replace the cam...both gears...chain and the balancer.
Would you believe this all started out as just a "good engine compartment clean up!"
Thanks for the help .... Fred
Would you believe this all started out as just a "good engine compartment clean up!"
Thanks for the help .... Fred
Thread Starter
Drifting
Joined: May 2005
Posts: 1,909
Likes: 6
From: Lake Arrowhead - Georgia > 72 Base Coupe & 74 BB Roadster
Le Mans Master
Joined: Oct 2006
Posts: 7,123
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From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Check the position of the marks on the timing gears too. If #1 cylinder is in the firing position, the timing marks on the gears will be at 12 o'clock. Crank gear marks and Cam gear marks. Install them the same way. Personally, I like to be in the #6 position, I find it easier to see that the marks are lined up together in that position. It really makes NO difference, as long as you get them in line with each other.