I did a head and cam swap on my engine. Now I'm reading 40 degrees advance at idle. Before the swap, I was reading about 13 degrees advance. I've checked, re-checked and quadruple checked the timing marks on the cam and crank gears. Valve lash. Everything. Any ideas on why its running so much advance? The engine is a BB 454 Gen VI with aluminum heads, hydraulic roller cam, and carbed. HEI ignition. It was running perfect before the swap.

 

Did you change harmonic balancers? Some have the timing mark at 12 o'clock instead of 2 o'clock for TDC which can make the timing seem WAY advanced. That happened to me and it took me weeks to figure out what had happened.

 

It sounds to me like the distributor housing/cap needs a clockwise rotation as viewed from above it until that 40 degrees is reduced to 13 degrees or am I missing something?

 

When you swapped cams did you degree the cam or just install it straight up? Next question- are you 100% sure that the dots were lined up straight?

 

Does the engine start okay? Too much advance will generally make an engine start hard. Are you running the same dist? Did you change the vacumm advance from ported to manifold vacuum? Check out your advance weights and springs.

 

Did you just line marks up on the distributor and intake and now its 40 or will the motor only idle with 40? I'm kinda confused. Have you tried retiming the motor and setting it at 13?