Intake bolt patterns
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Joined: Sep 2000
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From: The Top of Utah
Re: Intake bolt patterns (drumboytroy)
I'm not a TPI guy, but here is what I do know. The bolt patterns are the same. The manifolds will physically interchange. The iron headed '85 feeds EGR exhaust through the right side head to the EGR. The '89 get it's exhaust gasses from an external tube that runs from the right side exhaust manifold. The '85 has a cold start switch in the front of the intake manifold to activate the 9th injector for cold starts. I believe the '89 has neither the switch nor the 9th injector in the manifold. I am sure there are other differences in the TPI units, but I don't know how adapable they may be. They're both MAF systems. That ought to get you started.
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From: SE NY
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Re: Intake bolt patterns (drumboytroy)
The intake bolt angles varried on the F-body cars during the mid '80s but not on the Vette L98.
On the Vette TPI engines the major differences were in EGR routing and in the missing cold start injector access hole in the lower left runner. So to use an '89 intake base & runners on an '85 you would need to (1) install an EGR tube; (2) install an '89 ECM (possibly just a chip change??) for cold start control.
The EGR passages in the plenum varied over the years so the '89 plenum would be needed too.
Also the '85-'88 plenum had a triangular IAC passage while the '89 and up had no such passage. So you would also need an '89 TB.
Essentially it would take an entire '89 intake along with a little creative work to get it to work on an '85.
[Modified by 65Z01, 4:24 PM 5/24/2004]
On the Vette TPI engines the major differences were in EGR routing and in the missing cold start injector access hole in the lower left runner. So to use an '89 intake base & runners on an '85 you would need to (1) install an EGR tube; (2) install an '89 ECM (possibly just a chip change??) for cold start control.
The EGR passages in the plenum varied over the years so the '89 plenum would be needed too.
Also the '85-'88 plenum had a triangular IAC passage while the '89 and up had no such passage. So you would also need an '89 TB.
Essentially it would take an entire '89 intake along with a little creative work to get it to work on an '85.
[Modified by 65Z01, 4:24 PM 5/24/2004]
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From: Soddy Daisy TN
Engine change-out (drumboytroy)
Actually what I have done is I bought a 1989 Vette L98 with Edlebrock Performer Street Aluminum heads, Comp roller cam, roller lifters, ect....I have an 85 L98 in my car right now. What all do i need to change these engines out? The 89 has 56,000 miles compared to 115k on the 85. I wanted to take the 85, put it on a stand and build a 383 Stroker over time and drive the one I just bought until then. I know there are some differences the two. Do i need new wiring harness, computer, and so on? Or can I take my 85 intake and put it on the 89 and go for now? Any help would be appreciated. Thanks.Troy :)
[Modified by drumboytroy, 9:57 PM 5/24/2004]
[Modified by drumboytroy, 9:57 PM 5/24/2004]
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From: SE NY
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Re: Engine change-out (drumboytroy)
Even after you bore & stroke the '85 block you will need to go to some expense to install a roller cam, whereas the '89 came with the cam & heads.
Maybe it would be cost effective to build up the low mileage '89 block, unless there is a problem with the '85 not lasting long enough.
I think the '85 intake will bolt up to the '89 block but you will lose the EGR function as those heads don't have the internal passages. However you can have that function removed from the chip or fool the ECM to avoid a code.
Off hand I don't think you will need either a new wiring harness nor a new ECM as most of the I/F is the same, even the coolant fan control. The cold start injector runs from a temp sensor in the front of the intake base and it's own timer so that should not be a problem. I believe the fuel like hookup is the same too. If you have an aux fan on your '85 you will need to install the switch (or better a new switch) into the block of the '89 though.
Good luck and have fun with the project.
Maybe it would be cost effective to build up the low mileage '89 block, unless there is a problem with the '85 not lasting long enough.
I think the '85 intake will bolt up to the '89 block but you will lose the EGR function as those heads don't have the internal passages. However you can have that function removed from the chip or fool the ECM to avoid a code.
Off hand I don't think you will need either a new wiring harness nor a new ECM as most of the I/F is the same, even the coolant fan control. The cold start injector runs from a temp sensor in the front of the intake base and it's own timer so that should not be a problem. I believe the fuel like hookup is the same too. If you have an aux fan on your '85 you will need to install the switch (or better a new switch) into the block of the '89 though.
Good luck and have fun with the project.
