Pontiac 400 motor timing

[Tommy C]

I recently bought a 1968 Firebird convertible. It came with a supposedly all rebuilt 400 motor that was done almost 20 years ago just never got put in the car. Since its been so long I've decided to freshen it up. I'm not too familiar with pontiac, I've usually done chevys.

But I noticed that my timing marks do not match up. The crank will be a 12 o'clock and the cam will be about a tooth off. At what looks like about 5 o'clock.

 The guy I bought the car from says they put a high performance cam in and that was all he knew about it. I took the cam out and since it has no numbers I can't identify it. So I'm at a lost as to why this motor would be set about 4° advanced unless there was a purpose behind it. Has anyone run into this problem before?

[TWO LANE BLACK TOP]

Does the bottom timing gear (crankshaft)  have 3 keyways in it.... 4 degrees retard..0 or straight up.....4 degrees advance..????? Or an offset key...???

if it does....Alot of builders like to use the 4 degree advance keyway...Or an offset key...Reason being that as the timing chain stretches and  wears over time it will wear toward the 0 or straight up position.....

Alot of newer street oriented  camshaft grinds will have the 4 degree advance ground into it already...to allow for the same thing without having to use offset keys....ETC. So you can just set it staight up...

Edited September 18, 2018 by TWO LANE BLACK TOP

[Tommy C]

There's only one key way on the crank.

 

[TWO LANE BLACK TOP]

is that key offset by any chance..?? Might have to pull the gear off to be 100% sure...

If not could be whoever did it wasn't paying attention or was incompetent. During the assembly phase 20 years ago.....

Either way the zero marks should be lined up......

Edited September 18, 2018 by TWO LANE BLACK TOP

[Tommy C]

I think it is offset but I will take the gear off to be sure. Thank you for your help.

[Frosty]

Check the timing chain. Is there slack in it? If there is slack, then it needs to be replaced as it could jump timing on its own.