I know this question probably gets asked a lot, but assuming I had a complete L98 out of a 91 Z28 with wiring harness and computer, would there be any problems with putting this into an 86 TA? Would this be a problem when it comes to the tranny or the gauge cluster?

 

What does your '86 have in it now? That will probably define most of the issues that would come up.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R4. 2.93 limited slip. 2-1/2" cat-back, ZZ3 intake, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LG4 CC system w/'87 LB9 block, ZZ3 cam, ported World 305 heads, Hooker 2055 headers, 3" Catco cat & 3" catback, restalled TC, Spohn SFCs).
57 Bel Air, my 1st car. '66 396, 9.7 CR forged TRWs, Weiand Action+, Holley 750VS w/4150 conversion, GK 270 cam, Magnum rockers, Jacobs Omnipack, 1-3/4" Hedders & 3" Warlocks, TH400 w/TCI Sat Night Special conv & Trans-Scat shift kit, MegaShifter, 3.08 8.2" 10-bolt w/Powertrax, AMSOIL syn lubes bumper-to-bumper. Idles smooth @ 600 RPM in D. Best 15.02/95.06 @ 5800' Bandimere (corrected 13.93/102.4 @ sea level).

 

I apologize, I guess I should've mentioned the the 86 TA has a 305 with TPI.

 

If you want to avoid all issues, you could put the '86 TPI on the '91 engine, using the base and injectors from the L98. I'm not clear enough on what vehicles had digital dash, VSS on the tranny, VATS, etc., to go beyond that. Perhaps someone else can chime in.

 

No cluster problems as you should have mech speedo.
No trans problems new computer should control that as well.

You will need to address the VSS. Painless makes an inline four pulse VSS that will work with your system. I stock this VSS. As an alternative to that it is posible to rewire the new harness to feed the computer the 2 pulse signal. This will require a PROM change. If you burn your own PROM you may be able to take advantage of this.

If I can do anything else for you or you need more info you can contact me at hotpowerandperf@hotmail.com.

John

Heart of Texas Power and Performance

 

Actually his speedo is electric, operates off the VSS on the tranny.

If you have the complete 91 engine and harness, I'd use that and take the related 86 wiring out. A wiring diagram would be a good idea, but at the most you would have to repin the IP harness that connects to the underdash wiring, but I dont think its different. Keep the engine harness that runs to the driver side and its related sensors, like the oil pressure sender and the temp sender and stuff like that just to avoid incompatability problems. If you use the 86 exhaust manifolds, you will find out like I did that they dont work real well with the centerbolt covers and also the stock heat shields dont fit right either. I think the exhaust ports on the newer engines are in a slightly different location. The only issue with the 91 computer would be the VATS that your car doesnt have, so you can either get the vats box and key and cylinder, or have someone turn it off on the prom which is relatively easy given the equipment. I wouldnt use the 86 stuff just for the fact that it sucks, let alone you are going to a 350 from a 305 and the timing curves are entirely different.

Should be a fairly easy swap really.

 

Thanks for all the great information guys! The car is actually my cousin's car. For who knows what reason, he decided to go ahead and rebuild the 305 instead of buying the 91 350, but this will definately be great stuff to know for future reference.

 

Actaully, I think Hot may be correct about the different VSS as SD cars use a MAG type which gives 4,000 pulses/mile while the MAF cars use the 2,000 pulse/mile type. I have had a number of e-mails from guys with older electronic speedos that converted to SD and they had a problem with the VSS and the older electronic speeds.

Since you will have to address the VATS issue as Madmax said and the simplest method is to just "turn it off" in the eprom, you could just change the "switch" for the different VSS type to turn off "MAG type".

Just make sure to use the proper knock sensor that should be in the SD L98.

Alternatively, you could look at running the 89 350 Memcal if you wish to retain MAF. Just swap the knock sensor from your 305 to the SD L98.

You have a couple of options. But I would agree with Madmax and not retain the 86 type MAF/Memcal. Go 89 if you want MAF or fully convert to SD. Going with the 89 MAF type setup would avoid having to change the wiring.

 

Glenn, wouldnt it just be a matter of changing the VSS on the trans or the box inside the car? And another question, have any idea what the pulse is on a G-body car? I know that someone once posted it and I searched and cannot find the post... Grrrr...
I still have not sorted my VSS issues out, its not reading right at all and the torque converter is subsequently not locking up like it should. May be time for a SD swap if the pulses match up LOL

 

From guys that have e-mailed me about a similar problem (ie. converting from MAF to SD with electronic speedos), the simplest solution seems to be retain the older VSS and change the switch in the eprom "off" on "MAG type VSS".

I am not hot on G-bodies. What intake and ECM are you running? The toughest ECM is the "compu-carb" due to the very limited information on them.

Though I like SD and find it easier to tune the VE Tables than recalibrating the 6 MAF Scalar Tables (long story as to my trials and tribulations with helping a buddy with a potent 383 Mouse running MAF...we are trying to see how far we can go with the MAF system); I don't recommend swapping unless you are planning on making big power.

 

It had a LG4 with whatever ecm that is, that stuff is long gone. I have a 7165 in there now with a modified 89 bin file, but thats not the problem with the VSS, it read fine and the torque converter worked fine until we had the speedo modified, and now its fubar. When I originally swapped in the 7165 and wiring, I just hooked up the signal lead for the VSS off a small green box thats just sorta hanging off the back of the speedo on the G-body, it really looks like some sort of optical pickup with 3 wires, so I traced down the appropriate wire and prayed it was going to report to the ecm correctly. During my initial scan tool tests the speed the ecm was reporting matched the speedo fine, now its off by a factor of about 2. I remember the post I was looking for was by 88SS6speed, he had problems during the swap... I know now , he is running SD and had to fix that problem because the G-body was a 2000 pulse and he said F-bods were 4000 (SD anyway).

I think what the ecm is getting now must be half the signal it used to, so... the SD ecm would just make matters worse. Darn. I really dont wanna get a conversion box... Guess I gotta find out where that stuff is hiding at in the bin.

Thanks anyway Glenn, I think I solved my own problem

 

I will look a little more into the 6E hac to see if there is some "magical constant" like there is on SD.

SD has a means of also adjusting the "pulses/mile", but it is only for the MAG type.

I sent an e-mail to Ashley (and cc'd yourself) to see if Ashley can give you some insight to the VSS and speedo. I am SURE with a solution can be found.

 

Thanks Glenn.