cam/crank timing marks
Thread Starter
Racer
Joined: Apr 2007
Posts: 275
Likes: 1
From: Lafayette/marquez La/tx
cam/crank timing marks
i am in the process of changing my heads and cam. i have the 350/290hp crate motor. I turned the motor over till i felt compression on the #1 cylinder and lined up the timing mark on the tdc of the tab. Should be tdc? when i removed the timing cover the dots on the timing gears were on top of the cam gear and top of the crank gear. Which is correct for 1980 engines. I am assuming the 350/290 hp motor uses top and top marks. Anyone know for sure?
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
When you install the timing gears and chain, there are two ways and either one is fine. If you place the dots on the gears at the closest point- (CAM gear dot at 6:00 and CRANK gear dot at 12:00) then #6 cylinder will be close to TDC and you can use that to set your distributor.
If you like to put BOTH gears so the dots are at 12:00, again, acceptable, but use #1 cylinder when you set the distributor.
I like to put them at 12 and 6. Get them as close as possible to easily see alignment.
I'm also pretty sure there will be many more chime in with "no-no-no, do it this way" and that's fine. I like the KISS principle. Simple, easy, and works.
If you like to put BOTH gears so the dots are at 12:00, again, acceptable, but use #1 cylinder when you set the distributor.
I like to put them at 12 and 6. Get them as close as possible to easily see alignment.
I'm also pretty sure there will be many more chime in with "no-no-no, do it this way" and that's fine. I like the KISS principle. Simple, easy, and works.
Last edited by TimAT; Jan 6, 2013 at 03:02 PM.
Thread Starter
Racer
Joined: Apr 2007
Posts: 275
Likes: 1
From: Lafayette/marquez La/tx
I was going by memory. I thought if you put #1 cyl. at tdc on compression stroke then the timing marks would be at 6 and 12 oclock. Maybe i'm just confusing myself..... Ok i think i got it..... at 6 and 12 oclock it is on the compression stroke of #6 cylinder so i need to drop my dist in pointing to the #6 cyl. or spin it 180 deg at drop dist pointing at #1 cyl. Correct me if i'm wrong
Last edited by tgcattle; Jan 6, 2013 at 04:47 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,361
From: At my Bar drinking and wrenching in Lafayette Colorado
I turned the motor over till i felt compression on the #1 cylinder and lined up the timing mark on the tdc of the tab. when i removed the timing cover the dots on the timing gears were on top of the cam gear and top of the crank gear. Which is correct for 1980 engines. I am assuming the 350/290 hp motor uses top and top marks. Anyone know for sure?
Of course, you can put both dots together and simply install your distributor with the #6 in the firing position - no problem.
Lars
Burning Brakes
Joined: Sep 2012
Posts: 818
Likes: 0
From: coon rapids mn
you are on #1 compression stroke if all the rocker arms on #1 and #8 are both be closed .if all the rocker arms on #6 and #5 are closed and the balancer mark is ligned up with the pointer ,you are on #6.in the old days it was dot to dot for the timing chain gear alignment .
Drifting
Joined: Mar 2011
Posts: 1,886
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you are on #1 compression stroke if all the rocker arms on #1 and #8 are both be closed .if all the rocker arms on #6 and #5 are closed and the balancer mark is ligned up with the pointer ,you are on #6.in the old days it was dot to dot for the timing chain gear alignment .
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Tech Contributor
Joined: Aug 1999
Posts: 14,370
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From: At my Bar drinking and wrenching in Lafayette Colorado
GM engines have never been dot-to-dot for TDC #1 compression stroke - it's always exhaust stroke. Chilton's and all the manuals show the timing gear alignment as dot-to-dot for easy visual reference, but that's not the compression stroke. Never has been.
Lars
Lars
Instructor
Joined: Aug 2012
Posts: 162
Likes: 5
From: Visalia CA
In order for the camshaft to be installed correctly, you should use a degree wheel. Find true TDC and degree the cam. A couple degrees out one way or the other can really change the way the engine make power.
Glen
Glen