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Tpi Question


Bill C

Is there a difference between a 305 TPI system and a 350 TPI system other than the computer? I have a chance to pick up one and I need to make sure that they are the same. I have an 85 TPI set up and I have no idea what this box of TPI parts came off of. Looks like the fuel rails, thermostat housing, EGR set up, runners, throttle body and electrical componets are all the same.

Is the manifold base, runners, fuel injectors and plenum really all the same? If they are different how do you tell which is which if the unit is off of the engine and in seperate parts??

I know that the fuel line location and hook ups on non- Vette applications are sometimes different.

Are there TPI set ups for other GM applications that will NOT work on a Vette. I know that there are EGR differences on some vette years.

Bill C


Well-known member
Jul 3, 2001
Auburndale, Florida
1969 Killer Shark

The injectors are different on 305 and 350 TPI units. I like you have a spare TPI manifold. I was able to get its origin from the fuel injector part number that traced it back to a 1988 350 Camaro.

You can check for several things. First, how about the center intake bolts? Do they indicate 85-87, or 88-91? Second question would be fuel lines. The F Body fuel lines don't run the same as the Vette. Yours go off the front of the intake and to the passenger side head. Next, look at the cold start (9th) injector. You have that on the 85 model, but that was a thing of the past by the late 80's. Due to the 9th/cold start injector, there will be a difference in the runners from year model to year model. The EGR intake of exhaust will move from the center of the intake manifold coming from the head to the rear next to the distributor hole on the aluminum headed L98 (all 86 convertibles, and then all L98 vettes 86 1/2 to 91). The camaro did not use that design as the cast iron heads allowed the EGR to stay in place.

However, regardless of 305 or 350 the size and shape of the intake manifold base, runners, top, and throttle body would all be the same. In fact, the "rumor" about the TPI history is that the TPI system was designed for the 305, and ended up getting put on the 350 eventhough it is undersized for the extra stroke and breathing capacity of the 350 engine.

I was going to mention to you that I have a spare TPI in your other thread about porting it out, and that it would be best to have a spare. However, mine is too new for your application and would not bolt straight on without mods.

Bill C

Thanks for the very informational reply.!!

My TPI expierence is only with Corvetts. The spare unit is off of an F body because the fuel lines are different. As soon as my new SLP runners arrive, I will start the porting and polishing job on the spare base. It has a 9th injector so its an early unit. I will see what the injectors tell me later. Right now the port job is on my mind.

Should I cut out the web portion of the plenun between the two side by side runners to match the SLP design OR leave the web in and just port them to acheive better air flow?


Bill C

Bill C

SOUNDS LIKE A PLAN TO ME!!!!!! Consider it G O N E!!!!!!!!!!!!!!

Bill C

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