I need help with understanding why my truck isn’t blowing tires off. I have a 1979 C10 chassis with a 47’ Chevy 3100 body. Truck has a 454 that was completely rebuilt , flat top pistons, large oval closed chamber heads (802’s) Fitech fuel injection, headers, flow masters, and TH400 transmission. Cam is Comp 11-205-3 (268h) with 3.73 gears and LSD.
The issue - truck runs smooth, but it has no bottom end grunt like it should. Feels like the clutch is partially engaged until it hits a certain RPM then it catches. If I try to power brake a burnout, it barely wants to break the tires loose. Much better without brake, just stomping the gas, but it shifts before it revs out and looses the power band.
should I be checking stall converter next ?

 

where is your timing set at? do you have your vacuum advance set to ported or vacuum?

 

I honestly have no idea what my timing is set at, the engine builder is out of town for the next four months and doesn’t answer his phone calls. The vacuum is hooked to a T in the manifold the other side of the T goes to the transmission modulator.According to my fitech I’m pulling 16 HG a vacuum

 

That would be my suggestion.

 

That would be my suggestion. Also as stated, vacuum should be ported off the intake, and not tee'd to the shift modulator. This however is minor, I'd look at the TC.

 

any thoughts on stall ? My cam states a 1500-5500 power band curve. Also, where can I hook up the modulator vacuum line so that I don’t tee it in with the vacuum advance on the HEI ?

 

I'd change the vacuum line of the carb somewhere. I don't think this is an engine issue, based on your post.

 

Also sometimes 1 wheel spins and sometimes both during burnouts.