Timing Marks

[bruceb58]

Re: Timing Marks

Pulled engine, removed timing chain cover. Noticed that the locating pin on the cam was at 9 o'clock instead of three o'clock, with the engine at TDC on number one cylinder. Keep in mind, the engine ran great all season long.

The engine can be at TDC at either position since the crankshaft spins twice the RPM of the camshaft.

 

[MikDee]

Re: Timing Marks

The last time I put a (Summit brand) mild hydraulic cam in a 79'Camaro 350 Chevy, I lined up both timing gear marks next to each other, buttoned it up, put in the dizzy set for #1, and surprise, backfire??? (was #6 TDC!) pulled the dizzy, gave it 1/2 turn (180*) and it started right up!

I'm under the impression that, #1 TDC would be with the crank gear mark dead on top, And the timing gear mark dead on top (using an imaginary straight line intersecting through both) 180* apart!

Also, I'm betting that the big block Chevy is set up the same way.

Yeah, TDC comes up at the same time at #1, & #6, on the small block, & big block, V8 and #1, & #4, on the V6

 

[Maclin]

Re: Timing Marks

That is how it is on BB V8 MoPars, just had that come flooding back into my memory. When the cam timing gear marks are lined up (small gear with dot at the top and big gear with the dot on the bottom) then number 6 is at the top of the compression stroke ready to fire and #1 is at the top of the exhaust stroke.

 

[Zero Balance]

Re: Timing Marks

Well, after talking to the previous owner and verifying that the motor was rebuilt pretty standard he agreed that the balancer may need to be pulled and had a look see as he remembered it was used upon installation. Mind you this motor has only seen about 500 hours since the rebuild and most of that is trolling 800 to 1000 rpm. It's still daisy fresh.

I replaced the balancer, lined everything up and fired the engine. Upon timing it to 10 deg. (using advance light) the motor ran pretty well. I advanced it another degree or so to get it into that sweet spot I spoke of and she ran again like she used to. No more coughing or dying in neutral.

I still wonder what knocked the balancer out of sync though. besides old age.

 

[mkast]

Re: Timing Marks

I'm under the impression that, #1 TDC would be with the crank gear mark dead on top, And the timing gear mark dead on top (using an imaginary straight line intersecting through both) 180* apart!

Keep in mind that the cam and the timing chain have a locating dowel pin. That is whats going to dictate cam location in relation to the #1 piston.

 

[MikDee]

Re: Timing Marks

Keep in mind that the cam and the timing chain have a locating dowel pin. That is whats going to dictate cam location in relation to the #1 piston.

Irregardless, when the dots are lined up on the gears, thats gonna be top dead center, it could be #6, or #1. Then when the cam gear is turned 180* and the crank gear is on top, and the dots are lined up in a direct line it is TDC again #1, or #6, on a Chevy V6, or V8.
Don't remember the Ford or Mopar?

 

[bomar76]

Re: Timing Marks

Well, after talking to the previous owner and verifying that the motor was rebuilt pretty standard he agreed that the balancer may need to be pulled and had a look see as he remembered it was used upon installation. Mind you this motor has only seen about 500 hours since the rebuild and most of that is trolling 800 to 1000 rpm. It's still daisy fresh.

I replaced the balancer, lined everything up and fired the engine. Upon timing it to 10 deg. (using advance light) the motor ran pretty well. I advanced it another degree or so to get it into that sweet spot I spoke of and she ran again like she used to. No more coughing or dying in neutral.

I still wonder what knocked the balancer out of sync though. besides old age.

The rubber deteriorates.
Eventually the ring can fly off the hub...