I have a '85. I just bought an '86 engine...the complete package. Is it a direct replacement? Will my '85 ECM hookup and control everything on the '86 engine? Do I have to do any sensor changes?

Thanks,
Clint aka billybaloneey

 

When I bought my 86, the previous owner said he had replaced the 86 engine with a 87. Straight swap. I think the only difference is cast iron heads. But i could be wrong....

 

'85 is one year only ECM.
So long as you use all your original '85 wiring / sensors the ECM won't know the difference.

 

The only differences I can think of are:
1. the egr solenoid is on the right rear of the fuel injection plenum on an 85 and on the water neck on an 86
2. R.H. dipstick on the 86, L.H. on the 85
3. mas air burnoff on the 85 has a separate module, and the 86 is incorporated in the ecm and adds relays behind the battery
4. There is a heat baffle sticking out of the 85 R.H. exhaust manifold shrouding that is not there on the 86
5. The Egr valve temp sensor is on the intake manifold on the 85, and on the egr tube on the 86
6. The 85 has no precats on the Y pipe. 86. does
7.The 85 Catalytic converter hookup is different from an 86 to the rear Y pipe
8. The smog pump cat air pipe is 85 only and the 86 is the same till 89
9. The 85 smog pump is 85 only
10. 85 has a 2 piece rear seal, 86 has 1 piece. And a flat tappet cam on both.
11. 85 has forged pistons and 24# injectors. 86 are cast pistons and 22# injectors.
12. The 85 has 2 separate engine harnesses and a body harness, and the 86 has one harness, and incorporates the engine managemant, lights, heater, fan, etc. in that harness.
13. The 85 egr takes it's exhaust from the old heat riser passages in the middle of the head, and has no egr tube on the exhaust pipe like the 86. The alum. head 86 engine needs the egr tube since the alum heads do not have a heat riser passage. cast iron 86 heads are copies of the 85 head and can use the 85 egr setup.
14. The alternator on the 85 is 140 amp and the 86 is a 105 amp and are not interchangeable. Neither is the wire hookups.
15. The smog pump top alternator bracket is 85 only, and can't be used with the 86 alternator and smog pump bracket.
Other than that, they are the same.........

 

WOW 15 differences.

With all that being said, does all of that mean; if I pull my '85 engine as a complete package...leaving all of the existing '85 wiring & ECM untouched...can I drop in the '86 engine as a complete package and hook it up to the existing '85 wiring?

Or will I have a problem with item #'s: 3), 5), 6), 7), 12), 14).

Smog stuff I can bypass/remove a necessary, there is no inspection for that stuff where I live.

I have the '85 service manual and I'm watching an '86 manual on ebay. But it would be nice to know if it's going to be a simple one-for-one swap. If not, what parts, electrical connectors, modifications, etc, I'll have to start tracking down and preparing for.

Thanks,
Clint aka billybaloneey

 

You will never prepare for everything

You are as close as you need to be to a direct replacement. The 86' manual is a good idea for reference but as long as this is not you DD you will be better off getting it in and working from there. Unless you bought the 85' new you have no idea if sometheng was changed prior to your tear down.

 

well.........
i was just pointing out the differences.
If I were you , I'd pull the 85 engine out, and set them side by side.
take ten or more digital pics of each, and reassemble the 86 engine as an 85. You can use the 85 plenum on the 86, etc.
What you will have left over is a early smallblock with an 86 TPI setup and a modern smallblock in your car with items that fit your chassis.
A. I would use the 85 plenum and TPI, unless the 86 engine has aluminum heads.
#3 original mass air for the car would be fine.
#5. although, I would try to obtain an 88 and up r/h exhaust manifold and egr tube. it will make your valve adjustments a lot easier if you don't have to keep crimping the EGR tube back onto the exhaust manifold if you have to use the tube.
#6 I wouldn't use the precats, use your old front Y pipe.
#7 use your original exhaust end from end except the r.h. exhaust manifold and egr tube..
#12 use your original 85 wiring harnesses.
#14 use your original 85 smog pump, brackets and alternator, and keep the car original.
I guessI'm telling you to use the 86 long block, and swap all the 85 stuff over to the 86 engine.

 

You have given the OP great info here, I was in no way referring to your original post when I said that he can't prepare for everything

My point is that many people want step by step instructions and it doesn't work like that in the real world unless the car is new and untouched.

Great advice here