Setting timing gears
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Joined: Jul 2007
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Setting timing gears
Hi everyone
I am rebuilding my 87 vette. I am starting with a fresh machined
block, scat rods and forged pistons with a comp cam,duration 262/264
.450/480 lift. I purchased the edlebrock true-rolling timing chain. On
every small block chevy that I have rebuilt (and that's not too many)
when you set the timing gears for TDC for cylinder number one on the
compression stroke, the dot on the cam gear and the dot on the crank
gear are both almost touching and lined up. The tooth for each gear
are on the inside. I was looking at a chilton manual and it says something completely different. That for cylinder number 1 at compression stroke the dot for one gear is say at 6 o'clock, while the
dot for the other gear is on the other side of the gear. In other words they are not almost touching in my case, but are completely opposite.
Can anyone clear this up for me, thanks.
I am rebuilding my 87 vette. I am starting with a fresh machined
block, scat rods and forged pistons with a comp cam,duration 262/264
.450/480 lift. I purchased the edlebrock true-rolling timing chain. On
every small block chevy that I have rebuilt (and that's not too many)
when you set the timing gears for TDC for cylinder number one on the
compression stroke, the dot on the cam gear and the dot on the crank
gear are both almost touching and lined up. The tooth for each gear
are on the inside. I was looking at a chilton manual and it says something completely different. That for cylinder number 1 at compression stroke the dot for one gear is say at 6 o'clock, while the
dot for the other gear is on the other side of the gear. In other words they are not almost touching in my case, but are completely opposite.
Can anyone clear this up for me, thanks.
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
If that's what Chilton's says it's wrong.
If it's the same timing set I used in November to assemble mine, make sure to read the instructions carefully - you don't want to have to tear it down to re-do it if it won't start!
If it's the same timing set I used in November to assemble mine, make sure to read the instructions carefully - you don't want to have to tear it down to re-do it if it won't start!
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Manual is correct. Crank dot and cam dot are both on top at # 1 TDC. They line up together and meet when # 6 is a TDC.
In other words, both dot marks are straight up (very top) when #1 is TDC. They meet when #6 is TDC.
So #1 TDC= Cam and crank dot at 12 o'clock. #6 TDC = cam dot at 6 o'clock and crank dot at 12 o'clock which is where they meet or mesh point in which you are thinking this is what # 1 TDC should be.
But if you do it your way it still is the same because the cam gear rotates once for each two times the crank rotates so it is the same any way.
Rotate it so both marks are at 12 o'clock before you button up the timing chain cover to make dropping the distributor in easier and being on # 1 TDC for aligning you rotor.
In other words, both dot marks are straight up (very top) when #1 is TDC. They meet when #6 is TDC.
So #1 TDC= Cam and crank dot at 12 o'clock. #6 TDC = cam dot at 6 o'clock and crank dot at 12 o'clock which is where they meet or mesh point in which you are thinking this is what # 1 TDC should be.
But if you do it your way it still is the same because the cam gear rotates once for each two times the crank rotates so it is the same any way.
Rotate it so both marks are at 12 o'clock before you button up the timing chain cover to make dropping the distributor in easier and being on # 1 TDC for aligning you rotor.
Last edited by TommyFox; Apr 7, 2013 at 11:33 PM.
Melting Slicks
Joined: Jun 2011
Posts: 2,383
Likes: 385
From: Leland , North Carolina
Hope I did not confuse you but many install it where gear dot marks meet which is ok but forget to turn the engine to what your manual says for # 1 TDC and when they drop in the dizzy they point the rotor at # 1 not realizing the are actually at # 6 TDC and 180 degrees out and the back fire begins
You had no trouble before because you probably turned the engine over by hand watching for both # 1 valves to be closed and checked for position of the # 1 piston.
You had no trouble before because you probably turned the engine over by hand watching for both # 1 valves to be closed and checked for position of the # 1 piston.
Safety Car
Joined: Jan 2004
Posts: 3,556
Likes: 13
Makes no difference for setting the cam timing.
Only relevance is for TDC on #1 when dropping the dist in which you can easily find by other means even after the engine has been buttoned up
