timing chain install

[black_81_vette]

Hello I have a cloyes doubble roller chain with the three different keyways for the crank gear.Wich keyway is for strieght up? theres a triangle a rectangle and a dot. Wich one do I use?

 

[SG4206]

It should be the dot. If you line up the "0" on the crank sprocket at 12:00 and the "0" on the cam gear at 6:00 ; you will be timed TDC on #6 cyclinder.

 

[Vette/Berlina-coupe]

-more info. please...

:eyerole-ok, but what applications are the other two keyway widgets for? -and should'nt that be TDC#1-cylinder (valves-closed/compression-stroke driver's-side front) instead of #6(3rd-back on Pass.side) for any SB-ChevyV8... ?? :confused
~Bob vH
-is that am or pm? :L

 

[SG4206]

4 degrees advanced and 4 degrees retarded,are the other marks.

You can put the dot on the cam gear at 12:00 and the dot on the crank at 12:00 ; that is TDC #1. This leaves a little more room for error ; like getting everything off 1 tooth.

 

[Pancho]

It should be the dot. If you line up the "0" on the crank sprocket at 12:00 and the "0" on the cam gear at 6:00 ; you will be timed TDC on #6 cyclinder.

Huh?
Lining up the marks (6:00 on cam, 12:00 on crank) is correct, but this is for #1 TDC, no ?

 

[JohnZ]

No, it's not. With the dots "dot-to-dot" (crank dot at 12 o'clock and cam dot at 6 o'clock), the engine is at #6 TDC; with both dots at 12 o'clock, it's at #1 TDC. The "dot-to-dot" alignment is preferred, as it's more accurate due to the proximity of the dots in that position and you're less likely to assemble it a tooth out of phase.

 

[SG4206]

Thank you John Z. Good word "proximity" , just what I wanted to say.

Doug

 

[Pancho]

OK, now I understand...

I guess since I always set it up 'dot to dot' I assumed that was TDC on #1, but never really paid attention to where the pistons were at the time.

A few weekends ago I changed the cam / lifters / pushrods and timing chain in my '79 L48 (one of the intake lobes was flat). Heads were also removed for guide work. Replaced the harmonic balancer as well (old one slipped). Now that it's all back together it runs great but my indicated timing is something like 30° advanced at idle (vac adv disconnected). I believe I have the correct balancer for my timing indicator... But now am wondering whether I could have the timing chain on one tooth off. (It runs great at both low and high RPMs, though).

/Pancho

 

[Jack]

OK, now I understand...

I guess since I always set it up 'dot to dot' I assumed that was TDC on #1, but never really paid attention to where the pistons were at the time.

A few weekends ago I changed the cam / lifters / pushrods and timing chain in my '79 L48 (one of the intake lobes was flat). Heads were also removed for guide work. Replaced the harmonic balancer as well (old one slipped). Now that it's all back together it runs great but my indicated timing is something like 30° advanced at idle (vac adv disconnected). I believe I have the correct balancer for my timing indicator... But now am wondering whether I could have the timing chain on one tooth off. (It runs great at both low and high RPMs, though).

/Pancho

30* ... hmmm ... simply a guess but maybe the new damper/balancer is designed for 1986 & up motor. '68 & back dampers had timing mark 2* to left of keyway centerline. '69 thru '85 dampers had timing mark 10* to left of keyway centerline. '86 thru about '91 or '92 dampers had timing mark 40* to left of keyway centerline. Or maybe the timing tab/indicator is wrong one or located improperly. Cam timing would be pretty far outa whack if you are one tooth off ... rough motor! Suggest back-check damper P/N & application ... also verify that mark is 0* when #1 piston at TDC.
JACK:gap

 

[grapeknutz]

4 degrees advanced and 4 degrees retarded,are the other marks.

You can put the dot on the cam gear at 12:00 and the dot on the crank at 12:00 ; that is TDC #1. This leaves a little more room for error ; like getting everything off 1 tooth.

Also you can drop the distributer in and it will be set for cyl #1

 

[Pancho]

Jack --

Thanks for the info on the balancers. I was aware there were differences but not how much!
The one I put on I didn't have a part number for, but it was one I had bought some time ago for the '76 (so same flavor, at least).
With the heads off I did verify 0° indicated with #1 at TDC, which is the aggrevating part. I painted a stripe across the hub/outer ring of the balancer to check in the future if it had slipped, but of course that's covered by pulleys now.

Thanks for the suggestions,
Pancho