307chevyengine

i have a 307 small block bord 30 over with 305 heads , a performer cam ,intake and 600 carb. it has low vac 6inchs ,ibelieve it to be the timing gear is off a tooth, can that be or can it be the stock 305 heads engine only comes 125 psi compression. NO vacleaks thanks

Those heads should be a good match,....sounds like the rings......how many miles on the build??

Run #1 cylinder up to TDC, verify with the plug removed, and see where your timing pointer is..... What do you have the timing set at?