Can anyone tell me what the difference between the 305 LO3 TBI heads and the LB9 305 TPI heads. They have two different casting numbers and when I look them up all it comes back is that they were used from 87 - 95 305. The casting number for the TBI head is 10159551 and the LB9 head is 10159553.

 

I have looked into this in the past

do not use the tbi heads, unless your power band is under 4k

it has to do with the swirl port in the tbi heads that gives them good power of the hit but chokes the engine in the higher rpm range.

You will get some detailed reasons from some of the other members and that is going to help you or do a search like I did.

Bottom line- do not use Tbi heads

 

I did a swap from TBI to TPI on my 92 Camaro. I know the TBI motors had the peanut cam. I just wanted to know what made the heads different. I know the block and internals except for the cam was all the same.

 

swirl port intake chambers

 

Those numbers look like GM part numbers, not casting numbers.

Differences between the heads, along with head flow numbers, are shown here:
https://www.thirdgen.org/forums/tbi/...-headflow.html

 

OK thanks