ok i had two fieros
i had a white 85 gt auto. yes i know they r slow. i was hit in the middle of a kit car. the frame was twisted. i hadnt order the kit yet so i was wondering if i could swap my v6 into my 87 coupe and retain the original coupes 5speed. i have started pulling the engine becouse i have lots of spare time until i go to europe. i kind wanna have it finished for this weekend. yes i do have two complete cars. only one with a good vin. any help on the swap

You will have to get a flywheel that matches the engine. The flywheel in your 87 is neutrally ballanced, which will frag the 85 V6 that needs to be externally ballanced.

ok so i need a fly wheel from a 85? any thing else

You will need an engine wiring harness from a V6. The wiring harness on your automatic V6 is different. As indicated by HellYes, you will need the flywheel, and a clutch and pressure plate for the 85 engine. You didn't indicate whether the 87 was a 4 or a 6. I'm not positive, but I don't think the 87 V6 was neutrally balanced. My belief was that only the 88's were. Maybe someone else here can clear that up.

If the 87 is a 4, I wouldn't use any of the flywheel, clutch or pressure plate. It's smaller. Though it will fit, it usually won't stand up to the rigors of the V6. If your 87 was a 4, you have an Isuzu tranny. You'll need to buy a clutch and pressure plate assembly for an 85 V6, without the throwout bearing, and get a separate throw out bearing for the 87 Isuzu. If the 87 was a V6, you can buy the complete assembly for an 87 V6.

sorry i didnt mention but yes it is a 4cyc. and i have the v6 harness which should be able to be spliced with the 4s.any other info?gear ratio good or bad?

You don't have to splice the harnesses. You say you have the V6 harness. Again, it must be for a V6 motor from a car with a manual transmission. The 85 V6 automatic engine wiring harness won't work. Don't ask me what the difference is, but our club mechanic has told me that, and I've read it here in this forum. When searching for an engine for my 3rd Fiero, a manual 4-speed, I was cautioned that if I couldn't find an engine from a manual, I'd have to purchase a separate wiring harness. Our mechanic routinely changes them, and he wouldn't if the didn't need to.

The gear ratio on the Isuzu is a little short in first gear. Good or bad? It's just a matter of personal taste. I have that setup in one of my cars and I have no problem with it. I have a V6 4-speed, a V6 with Isuzu and a V6 with Getrag and I like all of them.

ok but the ecm will still workor do i have to find one of those as well

I'm not sure about the 87 ECM, since it was a 4. Unless someone else can tell you otherwise, I'd spring for an ECM from a manual V6 85-87. I'm running the original 4-speed V6 ECM on the Isuzu/V6 setup. No problems. Some have said the 85-86 4-speed V6 ECM is the better of the bunch.

ok so the auto tranny ecm wont work

Right. If you plan to part out the other car, be sure to mark the ECM with the relevant info EI: 85 V6 automatic Fiero.

You might even try to run the transplanted engine on the 87 ECM to see if it gives any problems before buying one for a V6.

Sergio, I found this in another thread. Thought it might be of interest. This was a discussion of what ECM could be used. The thread is still current in the Technical Section if you want to read all of it. The subject was can an 85 V6 ECM run an 88 V6

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07-12-2005 07:38 PM

I used an auto in a 5spd, so I think you should be fine

ok i have taken all the info into consideration. i have ordered the cluthc fly wheel and pressure plate but, i am having problems finding electrical becouse gm has none in stock. i have heard that soem one will modify my harness just so i can runs the stock auto v6 ecm and harness.what else wont work

Not to add to the confusion, but the wiring harness from a V6 with automatic tranny can easily be made to work in your chassis. I have done it. You will need to lengthen the wires for the speed sensor & splice in a connector for the backup light switch. You will also have to splice the wires for the auto neutral safety switch and move one of the contacts in the C500 connector. I can give you the details if interested. It took me about 1/2 hour.

thanks can u please send me that so i can get the car on the road faster. did u use the stock auto ecm?

Since my project car is still in the works, this hasn't been "road-tested" yet but the engine starts & runs just fine & the clutch safety switch works. Don't know if the "shift" light on the dash is functional (I sure hope not)

Anyway...

Ok, here’s how you convert an automatic transmission harness over to a manual transmission application.

1.) Take the wiring bundle from the backside of the engine and strip back the insulation wrap to the alternator.

2.) You will need to cut the speed sensor connector off, leaving enough wire on the connector to splice on additional length. (I used the connector & wires from my old manual harness for this)

3.) Cut off the connector for the backup light switch from you old harness leaving as much wire as you can.

4.) Cut off the large connector that attached to the automatic transmission. You should be able to identify the backup light wires by color. Splice them to the pigtail on your connector. It’s best to solder all connections.

5.) Attach the speed sensor connector to the sensor and splice in longer wires to reach the wires in the harness.

6.) The heavy gage yellow & pink wires supply current to the starter solenoid. Splice these two wires together. You are bypassing your non-existent neutral interlock. The auto tranny uses a neutral safety switch in the transmission to prevent you from starting in gear. Your manual chassis has a safety switch at the clutch pedal instead.

7.) Insulate all connections with heat shrink tubing & re-install the wiring wrap.

ok thanks for the pics leave them up for a while so i cna save the stuff. but what ecm did u use?

I was putting my engine into a chassis that already had the correct manual transmission ECM. I have seen this ECM thing debated for a long time. I would try the ECM from your 85 V6 auto first & see what happens. If it doesn't work I would buy a proper one from somebody on the forum, a junkyard or call Bob Parker at Kick Hill Farm for a used one. I would not try to use your 4-cyl ECM as somebody else suggested.

Good luck to ya!

ok i finished the conversion. the engine runs and i havent seen any codes. i used the auto ecm and auto wire loom. but instead of conecting the yellow wire to the purple we omitted the yellow wire all together

i had to modify the brake booster and the entire cooling system. it did throw a code but it was becouse of the halfassesd brake booster set up which involved tape, at the time. i bought brass fittings and i have driven it and it goes much better than the duke and the auto tranny. but i cooked me altonator on the motor so i am trying to fit the 87 4cyc on their