Choosing a T.P.I Unit

When it comes time to find a T.P.I Injection for your engine, there are several difference’s that you should be aware of. In the following story we will give you the information that you need to let you find the system that you need for you engine.

All GM Units are basically the same from 85 to 92. A few things have changed over the years but 305 units are basically the same as the 350 except for the injectors. Corvette units are the same unit as a Camaro/IROC, or T/A except the fuel rails come out on the passenger side and all Camaro fuel rails come out on the Drivers side.

All Corvette's from 85 to 91, had early head bolt pattern,85-86 IROC, T/A had the early head bolt pattern and were only 305’s. The 87 to 92 IROC, T/A had the late cast iron head bolt pattern were the two center bolts are straight up and down, but the two center bolt holes can be modified to fit the early head bolt pattern. In the years between 87 to 92 GM Produced the IROC and the T/A with both the 305 and the 350 but the Corvette’s all had the 350 injection. The 85 IROC, T/A and Corvette's all used a mass air flow with a 1227870 Computer. 86-89 IROC, T/A and Corvette's all used a 1227165 Computer with mass air flow. All 85-88 used a ninth injector for cold start. 89 was the only year that GM used the mass air flow computer and fired all eight injectors for cold start. 90-92 IROC T/A used the 1227730 Computer and fires all eight injectors for cold start, the 90-91 Corvette used the 1227727 Computer which was designed to use under the hood and is a heat resistant and water proof computer and used all eight injectors for cold start. All 90 -92 IROC T/A, 90-91 Corvette's were speed density and used a map sensor and not mass air flow. The older units can be converted to speed density by changing the harness and computer which is more desirable in a street rod application.

Most people have heard the story that mass air flow is more desirable when changing the cam or making engine modifaction, that used to be true before we had the knowledge of programming the computer chip.

(A) 85-86 IROC, T/A, Vette Bosch Pintle injector With a plastic tip

(B) 87-88 IROC, T/A, Vette Bosch Pintle injector With a aluminum tip

(C) 89-92 Camaro, IROC, T/A 89-91 Corvette Multi-Tech (Rodchester) injector. Street & Performance can clean and match your injectors and provide with O-Ring, Tips and performance screens

(A) and (B) Notice that the two center bolts are at the same position as the end bolts and will fit all early heads bolt pattern.

(A) 85-88 Intake (B) 89-92 Intake

Note: (A) Intake has a coolant temp(a) and a cold start sensor (b) for the ninth injector.

(B) only has the coolant temp sensor (a) for cold start and coolant temp for the

computer

When converting to the newer speed density computers the (b) ninth injector sensor can be eliminated and you can install your temp sending unit for gages (VDO), (Dakota Digital), ect.

87-91 Corvette Intake for Aluminum Heads

Which can also be used on early cast iron heads. (a) The Heat riser tube port that brings exhaust from the header to the intake for the EGR which is used with the aluminum heads and full emission, (e) is the port for the EGR valve. Street & Performance supplies block offs with gaskets and bolt to block off (a) and (e) when used in NON EMISSION vehicles. (b) is the water cross over port that let’s coolant come for the back of the heads and goes back into the coolant system. (c) These intake gaskets have a metal insert with a small coolant hole to allow a measured amount of coolant to pass thru to the intake. (g) This gasket is used on all other TPI intakes except Corvette.

Three styles of Injection Intake Manifold

(A) Was used on 87- 91 Corvette's with aluminum heads and a heat riser tube off of the passenger side header and has a water cross over at the back of the intake to releave hot spots on the back of the heads simular to the later LT-1 engines.

(B) Was used on 85-86 IROC, T/A, and Corvette's with cast iron early heads with outside valve cover bolt holes

Not Pictured: S&P and GM has new TPI intake to adapt a TPI to Vortec and Fast Burn style heads