just bought a non running 86 iroc with a stock 305 tpi, bought a used 305 tpi out of a 91 iroc, the motor i bought also has the newer 700r4 transmission still attached ill also be swapping. is there anything i am going to have to modify (plugs, sensors, waterpump, etc) to complete this process? any input is greatly appreciated. thanks

 

Welcome aboard thirdgen.org.

First, why isn't the '86 running? Is the engine seized up? If not, replacing the engine may not help any.

Now, you have as different of configurations as you could possibly get (if the car was an '85, that would be as different as you could get). The transmission is fine, so don't worry about that.

But, as to the engines, accessories, and TPI, here are the differences:

Block & heads: '86 has perimeter bolt valve covers, 90 degree intake mount bolts, flat tappet cam. '91 has center bolt valve covers, center two intake mount bolts on each side are at 72 degrees, roller lifter cam. Not too big of a deal so far. The one thing they have in common is that both are one-piece rear main seal.

Accesories: '86 is V-belt & flat multi-groove mix. '91 is serpentine belt. Water pump is different, AC and alternator switch sides between the two, the connectors on the AC and alternator are different between the two years.

TPI: '86 is "MAF" (mass air flow), '91 is "SD" (speed density). About the only thing common between the two is the injectors.

So, what I would recommend (assuming the '86 engine itself is the reason it isn't running): Use the '91 "long block" and TPI base. Use the '86 accessories, TPI system (other than the base). You won't have to change any harness, computer, or have to drill anything out that way. Go ahead and use the '91 transmission as well.

 

first off thanks a lot for all the info and input, its greatly appreciated... the thing with the 86 is that the motor was completely rebuilt. however, whoever built it, did not properly line up the piston and piston rings and detroyed the bottom end. i was originally going to have it sent out and rebuilt, until i got my hands on this complete 91 motor and trans with 70k miles on them for only $200!!!! i couldnt pass it up... and figured i could get this bad boy up n running for way cheaper than rebuilding the old one...am i on the right track or am i crazy?? haha . Again all info and input is GREATLY appreciated. THANKS!!!

 

I assumed you got the TPI with the '91 engine, is that true?

If not, all is not lost. The '86 base can be mounted to the '91 heads with a little modification of the center two mount bolt holes.

 

yes did get the TPI with the 91, 91 motor is complete except for the alternator the preveious owner removed...there seems to be an extra plug on the head of the 86 that the 91 does not have. is that the MAF/SD difference you were talking about? and can that be bypassed?

 

Just a heads up also. Almost all wire color codes are different from 86 to 91. You will have to repin the c100 connector to use the 91 tpi setup. Like stated above, use the 91 longblock and swap the 86 tpi setup onto that engine. But do use the 91 700r4.

 

No, '86 MAF has a mass air flow sensor in the air inlet system, SD doesn't. Nothing to do with the heads.

Not sure what this plug could be you're talking about. Got a picture?

 

sorry..know its been forever....but just to make sure im understanding....i can use the 91 transmission, 91 block with the 86 tpi setup without any modifications? or if there are modifications needed wat exactly r they?