Engine swap info needed

justacruzr2

justacruzr2

Apprentice
Jun 16, 2017
84
33
Midlothian, Illinois
Does anyone know if the instrument panel main wiring harness is the same between an 84 Grand Prix with a 305 and an 86 Grand Prix with a 231? I need to know because I'm going to swap the 84 305 into the 86. I'm sure the engine compartment wiring harness is different since the map/baro sensor on the 84 is a 3 wire sensor and is a 4 wire sensor on the 86. Any other things you guys have run across with this kind of swap please feel free to offer that advice also. Thanks.
 
buick7332

buick7332

Greasemonkey
Oct 21, 2014
233
63
N.E. Philadelphia area
Does anyone know if the instrument panel main wiring harness is the same between an 84 Grand Prix with a 305 and an 86 Grand Prix with a 231? I need to know because I'm going to swap the 84 305 into the 86. I'm sure the engine compartment wiring harness is different since the map/baro sensor on the 84 is a 3 wire sensor and is a 4 wire sensor on the 86. Any other things you guys have run across with this kind of swap please feel free to offer that advice also. Thanks.
I put a instrament cluster and gauges from a 79 into an 82 and everything worked out. Im sure you will have to change motor mounts.
 
pagrunt

pagrunt

Geezer
Sep 14, 2014
5,979
113
Elderton, Pa
The dash harness shouldn't be an issue with the sawp. Now the engine harness will need to be swapped out but the bulk head plugs should be pinned for the dash side bulk head connector for plug & play. Now if keeping it computer controlled, odds are the computer & computer itself will need to be swapped.
 
Bonnewagon

Bonnewagon

Geezer
Sep 18, 2009
7,383
113
Queens, NY
When I had a Chevy V-6 Malibu wagon I added a Pontiac V-8 and Monte SS gauge dash. LOTS of harness and dash wires had to be re-pinned to make it work. Now I have a Pontiac wagon that came with a Buick V-6. I swapped in a Pontiac V-8 and GP dash w/tach-gauges. All the wiring was there perfectly. Even the white tach wire is buried in the harness. Pontiac made it EZPZ.
 
justacruzr2

justacruzr2

Apprentice
Thread starter
Jun 16, 2017
84
33
Midlothian, Illinois
Thanks. I figured the computer would need to come along with the engine. I was hoping that I didn't need to tear the dash apart and change that harness too. Also hoping that the pinouts for the computer are the same between the two years. One last question. The 86 has speed control. I am not going to be using that. I think I read in a post here that all I need to do is exchange the speed control turn signal lever with a non-speed control lever and the extra wiring in the column will just go unused. Is that true? Thanks.
 
pagrunt

pagrunt

Geezer
Sep 14, 2014
5,979
113
Elderton, Pa
For pulling the computor harness just tear into the lower passenger kick panel for access to the hole, might have a little bit of a fight under the heater box but taking your time & not rushing will help. The cruise control lever swap is all you need other than pulling the related hardware & harness, pluging the hole in the firewall.
 
justacruzr2

justacruzr2

Apprentice
Thread starter
Jun 16, 2017
84
33
Midlothian, Illinois
For pulling the computor harness just tear into the lower passenger kick panel for access to the hole, might have a little bit of a fight under the heater box but taking your time & not rushing will help. The cruise control lever swap is all you need other than pulling the related hardware & harness, pluging the hole in the firewall.
OK. Thanks for that info.
 
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