C4 TPI questions...
Thread Starter
Racer
Joined: Jul 2004
Posts: 276
Likes: 0
C4 TPI questions...
Hi all I have a 76 C3 with a stock engine that I want to put a C4 TPI setup on and lose the carb.
First off, yesterday I picked up what was supposed to be a TPI setup from a 86..however, after getting it home I noticed a tag on it that says 85.
Can you guys help me figure out which it is and does it matter? What are the differences?
Also, I cleaned up the runners and the plenum pretty good, and went to start working on the throttlebody, I tried to take off the water pass-thru and I ended up snapping the heads off of three of the bolts, the others barely came out.
I just read the excellent thread about the TB bypass, should I just go that route and not worry about it? Or should I scrap the TB?
Any help you could give would be great as I'm really new to this stuff.
I can post some part numbers tonight if it will help.
Oh, one more. Is the IAT on the water pass thru or on the bottom of the intake plenum? I thought the IAT was on the plenum, but the water pass-thru on the TB appears to have another sensor (not the TPS) that has a 4 wire connector....
Thanks!
First off, yesterday I picked up what was supposed to be a TPI setup from a 86..however, after getting it home I noticed a tag on it that says 85.
Can you guys help me figure out which it is and does it matter? What are the differences?
Also, I cleaned up the runners and the plenum pretty good, and went to start working on the throttlebody, I tried to take off the water pass-thru and I ended up snapping the heads off of three of the bolts, the others barely came out.
I just read the excellent thread about the TB bypass, should I just go that route and not worry about it? Or should I scrap the TB?
Any help you could give would be great as I'm really new to this stuff.
I can post some part numbers tonight if it will help.
Oh, one more. Is the IAT on the water pass thru or on the bottom of the intake plenum? I thought the IAT was on the plenum, but the water pass-thru on the TB appears to have another sensor (not the TPS) that has a 4 wire connector....
Thanks!
Racer
Joined: Apr 2003
Posts: 426
Likes: 0
From: Detroit MI
IAC on the bottom (idle air control). Can you get the rest of the screws out and replace them? You need that part on the throttle body and the aftermarket throttle bodies don't come with it. You reuse the one off your factory unit.
As for the year. Some major L98 differences would be al heads in late 86 and full roller block starting in 87.
As for the year. Some major L98 differences would be al heads in late 86 and full roller block starting in 87.
Thread Starter
Racer
Joined: Jul 2004
Posts: 276
Likes: 0
Thanks guys.
I know there are subtle differences between 85 & 86 (I think).
As for getting those 3 screws out, I'm not sure, I could probably drill them out.
If I plan on doing the bypass, does it matter? Could I just leave it like it is or even just cut it off the TB?
I know there are subtle differences between 85 & 86 (I think).
As for getting those 3 screws out, I'm not sure, I could probably drill them out.
If I plan on doing the bypass, does it matter? Could I just leave it like it is or even just cut it off the TB?
Instructor
Joined: Sep 2005
Posts: 107
Likes: 0
From: Arizona
A used TPI setup really deserves new sensors. The IAT sensor is below the plenum, coolant temp sensor is on the very front of the intake manifold, O2 sensor is on the drivers side aft manifold, knock sensor is on the rear of engine. Due to the replacement price, first clean off the mass air flow sensor GENTLY with electronic contact cleaner while out of the engine, then test the sensor.
Some easy-outs will remove those busted bolts, just take your time and they'll come out. I recommend doing the coolant bypass, heat soak is a nuisance on these cars. Also, remove your Idle air control valve (IAC) and clean it, it's passages, and the throttle body with THROTTLE BODY CLEANER, NOT carb cleaner. Do the same with the EGR valve on top of the intake manifold.
Replace ALL the gaskets while you're at it. The major differences between an '85 and '86 TPI was the computer PROM and the fuel pressure was 34-38 psi on the '85 and 38-42 psi on the '86+.
Contact me if you have any questions, and good luck.
Some easy-outs will remove those busted bolts, just take your time and they'll come out. I recommend doing the coolant bypass, heat soak is a nuisance on these cars. Also, remove your Idle air control valve (IAC) and clean it, it's passages, and the throttle body with THROTTLE BODY CLEANER, NOT carb cleaner. Do the same with the EGR valve on top of the intake manifold.
Replace ALL the gaskets while you're at it. The major differences between an '85 and '86 TPI was the computer PROM and the fuel pressure was 34-38 psi on the '85 and 38-42 psi on the '86+.
Contact me if you have any questions, and good luck.
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
I would suggest you find an ECU for a 1989... it's faster and more capible than the earlier units.
This would also eliminate the 9th injector.
I would also pick up a helm manual for the year you decide to go with, then you would know all about the injection system and how to debug it.
Another option is to get the book "Corvette Fuel Injection and Electronic Engine Management: 1981-2000", By Charles Probst. It's available from Robert Bentley publishing or Amazon.
This would also eliminate the 9th injector.
I would also pick up a helm manual for the year you decide to go with, then you would know all about the injection system and how to debug it.
Another option is to get the book "Corvette Fuel Injection and Electronic Engine Management: 1981-2000", By Charles Probst. It's available from Robert Bentley publishing or Amazon.
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Thread Starter
Racer
Joined: Jul 2004
Posts: 276
Likes: 0
Thanks on the book suggestion.
I'm not using a stock ECU or harness, going megasquirt:
www.megasquirt.info
I'm not using a stock ECU or harness, going megasquirt:
www.megasquirt.info
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
To do the TB Coolant bypass mod you just need to slip some large vacuum nipples over the coolant fitting on the lower front and on right side (below the TPS) of the TB.
The assembly under the TB needs to be in tact as that houses the IAC motor and air passages which control engine idle.
Also you may need different fuel lines as the TPI requires up to 60psi of fuel pressure, usually runs in the 30-50psi range.
The assembly under the TB needs to be in tact as that houses the IAC motor and air passages which control engine idle.
Also you may need different fuel lines as the TPI requires up to 60psi of fuel pressure, usually runs in the 30-50psi range.
Thread Starter
Racer
Joined: Jul 2004
Posts: 276
Likes: 0
Yeah, I know the fuel line thing is gonna be a pain, I'm thinking of using some of that braided SS line that Jegs/Summit sells.
Also, I still have to figure out the pump, internal/external, as well as how to mount it.
Alot of folks that have made the switch to EFI talk about putting baffles in their tanks to prevent air pickup due to fuel slosh.
Do the C4 tanks have baffles in them?
Also, I still have to figure out the pump, internal/external, as well as how to mount it.
Alot of folks that have made the switch to EFI talk about putting baffles in their tanks to prevent air pickup due to fuel slosh.
Do the C4 tanks have baffles in them?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by DonBecker
Hi all I have a 76 C3 with a stock engine that I want to put a C4 TPI setup on and lose the carb.
There are a few minor errors posted above. I'll see if I can't help straighten them out.
Originally Posted by jcsr72
...O2 sensor is on the drivers side aft manifold, knock sensor is on the rear of engine.
RACE ON!!!
Last edited by CFI-EFI; Sep 28, 2005 at 02:49 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by DonBecker
Hi all I have a 76 C3 with a stock engine that I want to put a C4 TPI setup on and lose the carb.
There are a few minor errors posted above. I'll see if I can't help straighten them out.
Originally Posted by jcsr72
...O2 sensor is on the drivers side aft manifold, knock sensor is on the rear of engine.
I had thought there were more. Good luck, and...
RACE ON!!!
