The more I learn about my car, the more I enjoy it and have better knowledge to proceed with upkeep and upgrades. I'm now wondering what specific smallblock I have and, does it really matter?

I bought the car in January of this year and noticed immediately that it was badged a TPI car, but had a carb. The owner at the time said that when he did the rebuild of the motor, he converted it from TPI to carb.

So, knowing that, what block do I really have? Wasn't the LG4 the carbed model and the LB9 the TPI? Does the block itself really matter when the top end has been swapped out for a different system? I have spent all of this time thinking and quoting that I had the LG4, but if I actually have the LB9 I would like to be accurate when I talk about it. Would there be an important difference bewteen the actual blocks of these two engines?

 

different heads and cam
I belive thats it

 

The blocks are the same for the 305's. If it dosen't matter the previous owner was full of crap what about what he told you.

Stock on 1986 Z28
LG4 305 Carb 165HP/250TQ
LB9 305 TPI 190HP/285TQ
So draw your own conclusions and check the VIN for the orginal engine (eigthn digit (F) for a TPI if it isn't its LG4

 

If the 8th digit of your vin is "F" then it was a TPI car to begin with, if it was an "H", then it was the LG4.

On my 86 Trans Am LG4, I installed an Edelbrock 1406 and Edelbrock 7101 Intake and the car ran a best of 14.94@93mph with only those mods.
The best my 88 Formula runs is 15.2 @ 92mph with all the mods (except the headers) that are in my sig.

I did decide to convert my 86 Trans Am to a TPI with a new cam and using the 87 TPI heads and intake with a modified harness and 90-92 Speed Density computer,

 

Checked the VIN and it's an H coded engine. So.... it's always been a carbed model then. Interesting.

Nice Zepher! Good to know that those almost identical mods to mine produced those numbers.

I've been really happy with the performance. I don't go to the track and spend a lot of time in traffic, so I just like to peel 'em every now and then as well as dust a ricer or two. For that, it's great.