I have a 85 tpi motor complete w/ harness to relpace the lg4 setup.The problem is the 85 has a mechanical speedometer.My 87 formula has the electronic kind.I figure I can go two ways with this.First way would be to take the 85 tpi,harness,ecm install it all in place of the 87 harness+ecm.The only problems I would have is the vss and the harness that goes to the bulkhead connect in the firewall.My vss is currently sitting on the ecm bracket,as appose to the 85 vss on the back of the guages.I could splice the wires from there into the 85 harness if the 87 ecm does`nt control the signal from the tranny to the vss.Is the electronic speedo controlled by the ecm? Next thing is the harness on driver side that goes (if I remeber correctly)to the dist,alternator etc.I think that could be rewired at the firewall bulkhead.
My second idea is to get a harness,esc and prom chip out of a 87 tpi car.But it would be hard to find a harness or anything else in good shape though.My driveing factor is cost.I can`t afford a $275 aftermarket harness or $100 chip.I paid $400 for the tpi,motor,harness,ecm,alt,cruise control and emmisions equipment and more.It`s not that I`m a cheap *** but am more or less poor.I posted this on the tech board a while back and did`nt get much help.Thanks for any help!

 

You will need an external speed buffer that may be driven by your transmission mounted VSS, since the '85 ECM requires an input from a speed buffer (usually mounted to the cluster). You will need to get a speed buffer for an '84 - '86 Berlinetta from GM. The cluster mounted speed buffers will not work, as they are optically triggered. The Berlinetta speed buffer uses the transmission mounted two wire VSS as an input, and outputs a 4000 pulse per mile signal to the ECM and speedometer, and a 2000 pulse per mile signal to the cruise control.

Tim

 

After thinking about your post & reading it again, I understand that you already have the "yellow box" speed buffer - mounted on the ECM case. You may connect the output of that speed buffer to the VSS input on the '85 TPI ECM. You will have to cut the speed buffer out of your existing harness & solder it into the '85 TPI harness. There should already be a connection from the speed buffer to the speedometer & cruise control through the "ECM harness to chassis" connector, that you will be splicing into, as well, when installing the '85 TPI harness & ECM.

Tim

 

I'm usually helping every one with thier cars.It's a relief to get some help myself,thanks.I know this swap will work but am trying to map it out first.There is no reason to have no tcc lockup or a engine light on.I have a few other things to work out.One thing is the size of the gas tank sending unit.Would the in tank pump unit fit on my tank?The other thing is that driver side harness.It's either rewire the 85 one in or use the 87 acessories and brackets.I would love to make a tech article about it when I'm done,but my writing skills are bad.

 

So that's what that ugly yella thing is! And here all this time I thought it was the cruise control. So where IS the cruise control?

 

The cruise module is black, a bit larger than the speed buffer, & mounted near the ECM - more toward the drivers side, behind the passenger side kick panel.

Your '87 LG4 actually already has an in tank fuel pump - but it's a low pressure 3 psig pump, so you'll have to swap it out with a TPI pump - or get the BGN / TTA (Buick Grand National / Turbo TA) pump - it has a higher pressure & flow capability than the L98 / LB9 TPI pump & it is the same physical form factor as the LG4 & L98 pumps.

I just finished an LC1 (carbd V6) to LB9 (TPI 305) conversion on my '84 Berlinetta. Another thing to consider are the fuel lines. The LG4 lines don't have compression fittings at the end & are on the wrong side of the engine bay for TPI. You should be able to get a complete set - with the rear brake line, too, for cheap from a junk yard.

You will also need to add some fuses under the dash for the injectors.

Tim

 

I will get that turbo t/a pump when I beef the motor up.So I do have an in tank fuel pump.I have a salvage yard here in St.Louis thats cheap.The tpi pump would be $5.00 and the fuel lines are $3.99.I just got 92 rs ground effects brackets and all for $35.Those are going on my 87 camaro. I did figure out that the v6 mpfi fuel lines are the same.The thing I don't know is if the v6 pumps are the same.I did know about the fuses for the inj.Not sure about the fuel pump fuse.Thats about all I need to know and this swap will be easy.I was going to wait until the 85 engine gets rebuilt to swich to tpi.I could make the switch to tpi now.There has been two thing that has stopped me.First is the 87 engine was sounding bad.But after fixing alot of things it sounds stable.The other thing is my 87 has the heads w/ the different angle center intake bolt.Does the tpi intake bolt holes need elongated.And or can't a angled shim be used?I read about this before but forgot how it was done.If you (or anybody)can answer that then my formula will have TUNED PORT INJECTION.It would be a dream come true.I could have it in this weekend.I am very proud of my foumula.It already has 1 & 1/2 inch drop springs,KYB struts & shocks,energy suspension poly bushing everywhere.I have done all the work except the alignment and weld the flowmaster+tips.It actually looks nice too,for coming from the van nuys plant.Oh yeah my name is Tim too .

 

Sheeeeit - we have 3 Tims here

Tim

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TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's after installing Hooker LT Headers and reducing weight.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Thats a fast iroc-z,faster than a viper.I will be shooting for 12s with my formula.That all I'll need to smoke 99.9% of cars out my way.Really I'm just addicted to speed.What a great feeling in the gut!My car will not use power additives either.I'll be harder than that l98 to get to 12s though.But way cheaper than a supercharger.So can you lend a hand to the mod reqired for the 85 intake,Tim?

 

The '85 "perimeter bolt head" intake will bolt on the '87 "center bolt head" setup which has the "vertical" two middle intake bolts on either side, if you elongate the four intake manifold mounting holes, as you had mentioned. If you buy an aftermarket intake, the bolt holes are configured to work with either head type - there are two partial bolt mounting surfaces - one at each of the two different angles. Your '87 block is better than the '85 block, too, in that it has a factory roller cam, one piece rear main seal, & neoprene oil pan gasket & valve cover gaskets.

Tim

 

The only downside is I can't find a roller cam for under $240.The cam from a 350 roller will work for now(cam $9.99 salvage yard).Thing I'm not sure about is if the 85 tpi exhaust manifolds are better.
I did finish reading the tech article on prom burning.That will be my next step.I have seen some chips sell for $200 or more.For the same price I could burn as much as I want.Thanks alot for the help.

 

I wish i was a few hundred miles closed to that yard! They wouldn't happen to have an '89 305TPI/auto trans ECM, would they? If they do, there's a couple of us that want the chip out of one, ****** it up if you can!

 

Right now the only 305 tpi chip is for an 87 .Is this chip the same?I did pick it up though so if ya want it shoot me a price.

 

I know the feeling. That's why I use the "Not to Be confused . . ." line in my sig.

Jake - Not to be confused with my namesake.



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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9