Big Block 454 Timing Question?

[savatreatabvr]

I checked the timing on my mid 70's C20 454 and the timing mark is way advanced to the point where it's almost not visible. The distributor is turned so far counter clockwise it comes close to hitting the intake manifold. The 454's runs best set at position, does that mean my timing chain has skipped a tooth or is it just worn out? If it has skipped a tooth can I pull the distributor and turn it back one gear tooth?

[willett]

Is it running alright?

Mine is at 14* I believe. I think that it is a few degrees past the timing gauge if I remember correctly. It's not abnormal

[savatreatabvr]

Originally Posted by willett

Is it running alright?

Mine is at 14* I believe. I think that it is a few degrees past the timing gauge if I remember correctly. It's not abnormal

I would say the timing mark is about 1 1/2" past the timing gauge. I've got good manifold vacuum at idle but when I retard the timing my vacuum goes down. Is that normal?

[monte0185]

did you pull the vacuum advance and plug it before you checked the timing?

[savatreatabvr]

Originally Posted by monte0185

did you pull the vacuum advance and plug it before you checked the timing?

That I did not do, I had my vacuum gauge tied into it with a "T" fitting! I will check it again and post the results!

[Junqueboi]

Your harmonic balancer may have "walked". I've had several do this: the rubber bond between the inner & outer ring deteriorates over time and the outer ring actually "walks". The one on my old '78 454 did this as did the one on my '86 350. The 350 was so far off the timing mark was probably 15 degrees OFF the edge of the timing tab.

You may as well check the advance mechanism in your distributor -- they'll seize up over time and cause issues also...although it won't affect the timing mark as much as what yours is doing.

FYI, two of my 454s had this issue also.

[bnoon]

Originally Posted by Junqueboi

Your harmonic balancer may have "walked".

THIS! ^^^ Gets my vote.

It happened so bad to one of my old Pontiac motors that it started a metal on metal sound that sounded like a rod knock. Engine wasn't smooth at all at that point. Couldn't set timing except to advance until it was hard to crank, then back off a couple of degrees. Replaced it with a used one for $5 and no more noise and engine was back in balance so it ran much smoother. The good part about stock mid 70's engines is that they are so low on compression that spark knock margin of error is rather large compared to a performance engine with higher compression.

[savatreatabvr]

Originally Posted by bnoon

THIS! ^^^ Gets my vote.

It happened so bad to one of my old Pontiac motors that it started a metal on metal sound that sounded like a rod knock. Engine wasn't smooth at all at that point. Couldn't set timing except to advance until it was hard to crank, then back off a couple of degrees. Replaced it with a used one for $5 and no more noise and engine was back in balance so it ran much smoother. The good part about stock mid 70's engines is that they are so low on compression that spark knock margin of error is rather large compared to a performance engine with higher compression.

I agree with the harmonic balancer being a problem, I replaced the harmonic balancer on my 1978 Dodge 440 moho and the difference was dramatic! Thank you for bringing that to my attention, I totally forgot about!

[billnorman]

Yeah it's normal to lose vacuum as you retard the timing. You need to take out all of your plugs and manually turn your engine both ways at #1 cylinder with a tool in the #1 spark plug hole to keep the piston from reaching TDC. I made one with a spark plug with a rod welded in it after breaking out the ceramic insulator which stops the piston. Mark the dampener to a reference point on the timing indicator where it stops turning CW, then turn it CCW until it stops. Mark it again, remove the tool. Half way between these 2 marks is true TDC. Use this reference to set your timing.
I must admit I never did this to a big block, but have with smaller motors.