In looking at aftermarket runners, I've noticed that both Edelbrock and TPIS specify that some of their runners are only for 89-92. I was wondering what the difference between the two styles of runners are.

Also, what is the difference between TPI systems from different years. I'm aware that in 89 or 90 they switched from MAF to SD, and I know in 89 they got rid of the 9th injector, but are there any other differences?

I'm especially concerned with casting differences. Are there any casting differences between the TPI years? When they eliminated the 9th start injector, did they plug the hole or make a new casting without the boss for it? Are the base, runners, and plenum the same for all years? What about the TB?

Any help on TPI differences between years is appreciated,

Jason

85-88 runners have a tube on the driver's side for the cold-start injector, going from the base to the plenum. 89-92 do not, there is no tube.

85-86 intake manifolds are identical. 87 they changed the intake bolt pattern, and its the same as 88. In 89, the removed the casting for the cold-start injector, so 89-92 is all the same.

85-88 plenums are all the same. There is a hole on the driver's side for the cold start injector, and in the front for the IAC passage. 89-92 has no cold start and the IAC routes thru the throttle body differently. But 90 they changed to MAP (speed density) and added an extra vacuum port and a hole for the MAP sensor bracket on the back passenger side. 90-92 plenums all have this.

85-88 throttle bodies are the same. 89-92 have a different IAC passage and a different throttle cable linkage. 85-91 all say TUNED PORT INJECTION on the throttle body top plate, while 92 is just a blank plate.


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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

that and the 92 runners were the vette style runners. meaning that they were not a smooth finish(85-90), but a rough cast finish. it mightve been like that in 91 also, i dont remember.

Thanks for the helps fellas, that about answers all my questions. One more thing though, if I have the 87 TPI setup and I'm going to use a 90 computer for SD purposes, can I plug the hole for the cold start injector?

Jason

yes you can plug the hole.i think Accell sells a kit for this.you probaly could find a couple plugs for the runners and fuel rail at a hardware store.

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1991 banditt2 #130 of 600
Project 350 TPI Banditt II
http://www.street-dawg-racing.cityslide.com
www.gcfba.com (Greater Cincinnati F-Body Association)
http://www.cincyspeed.com/

Only some of the 92 runners are from Corvettes, probably because GM was using up old stock.

If you have a complete 87 setup with the cold start injector, just leave it in, but dont connect the wire to it. It makes a cheap plug.

I was wondering what are the advantages of the sd system. Also, what are the differences in the way things are controled.

Thanks

Ben Brohez