Swapping an 86 5.0 into an 87 GT?

psycho78 · Mar 19, 2010

Okay, basically I am in the process of buying a project car: an 87 convertible GT but the problem is the engine is pretty shot. Rather than figuring out why its not cranking, Ive decided to just buy another engine and throw it in since the shop Im buying it from said they'd swap an engine for me for like $300-$350. Now, Ive found an 86 GT's 5.0 around here from a wrecked car that is a very good deal and I just wanted to know if that would work out ok in an 87? Would the fuel injector need to be swapped? Anything else that wouldnt work? Im not really technical on engines (which si why Im having them do it) but Im looking into getting this running easily and fairly cheap (poor college student lol). Any help or info would be appreciated!

347HO · Mar 19, 2010

I do know the 86' is speed density and the 87' is MAF.

psycho78 · Mar 19, 2010

Ok, I apologize in advance but what exactly does that mean? Is that a lot of extra work? What specifically would need to be done to swap the engines? Thanks again for the reply BTW

rd · Mar 19, 2010

Need more info on what is worn out with the existing engine.

If the engine is worn, yes, you can simply swap the long block assembly, and reconnect the 87 electronics and it should work. That would include using the mass air setup if the 87 has it.

Otherwise you would need to swap the 86 computer and engine harness into the 87, which is sort of an unnecessary step backwards.

Probably best to troubleshoot the 87 before pulling anything apart.

psycho78 · Mar 19, 2010

Well heres the thing: Im basically buying this 87 GT convertible that has a good auto trans and *supposedly* ran when it was parked 4 years ago, it was supposed to be a project. Well, the guy just went back to it to sell it since he doesnt have the time or money to do it so Im getting the car pretty cheap. It needs a lot of cosmetic parts on the interior etc but the body is pretty solid and looks nice. Well, when he just went back to it, it wouldnt crank. He said he tried changing starters, battery etc and just couldnt figure it out. Well, I can get a motor cheap and $350 is cheap to swap engines so I figured, rather than nickle and diming this thing to death, just spend the $500 for a different engine and be done with it. Now, if I went with an 87-93 GT 5.0 engine, then would it be a seemless swap? Im just trying to keep this thing low in cash and make it run lmao.

NIKwoaC · Mar 19, 2010

OK, first off, the 87 DOES NOT have mass air. It is a speed density car unless at some point it was converted. Mass air was not introduced until '88 in California and '89 in the rest of the states.

Second, the '86 longblock made significantly less power than the '87. The '86 also has pistons without valve reliefs, so upgrading cylinder heads, or even using the stock '87 heads, requires a little more planning and work.

Other than the performance issue, the '86 engine will drop right in. In fact, any 86-93 engine will drop in, providing you retain all the original electronics/EFI from the '87.

RatStang · Mar 19, 2010

NikwoaC said:
Second, the '86 longblock made significantly less power than the '87.

This portion is relative:

While the 86 made 25 less HP than the 87, it also had the widest torque range of any of the production 5oh Mustangs (save for maybe the Cobra). Although the 86 heads aren't really worth modifying, a switch over to an 87 intake will put that motor near, dead on, with an unmodded 87 in terms of HP; slightly lower in (in peak numbers) on torque; but with a much broader torque curve across the entire RPM range.

NIKwoaC · Mar 19, 2010

DontGivaRatz said:
This portion is relative:

While the 86 made 25 less HP than the 87, it also had the widest torque range of any of the production 5oh Mustangs (save for maybe the Cobra). Although the 86 heads aren't really worth modifying, a switch over to an 87 intake will put that motor near, dead on, with an unmodded 87 in terms of HP; slightly lower in (in peak numbers) on torque; but with a much broader torque curve across the entire RPM range.

Did you quote that from something, or are you just stating that? I do know that the '86 had a broad torque curve because of the "high swirl" shrouded valve heads, but these things run out of breath at anything much past 4800 rpm, regardless of intake. I'd like to see a dyno test based on your statement, otherwise, color me skeptical.

RatStang · Mar 19, 2010

It's fairly common knowledge for someone who owns an 86 and is looking for his/her initial upgrade. The intake is usually the first to go (being considerably cheaper than a set of heads for a hard-to-fit, set of pistons).

I'd love to be able to post up my before and after dyno sheet but it's been many, many moons since any portion of my drivetrain resemebled something from a production 86.

If you google HP or torque history for Mustang though, you should be able to find production numbers fairly easily. Everyone is aware that the 86 heads sucked. Fewer, (I suppose) realize that getting an 86 to equal up to an unmooded 87 was never really that difficult. Modding an 86 ($$/HP) alongside an 87 is much more difficult (if not impossible dollar for dollar).

That aside; I can tell you personally, that I never gotten walked by a near factory Fox all the way through 93 model year. Mods at the time included an 87+ upper and lower.... that was about it until I was able to swap heads and then went to a GT40 Upper/Lower.

The breathing past 4800 thing... well yeah... it was pretty crappy but the hit was a little higher than 4800 (not much but a little). I pretty much came down to driver though. If you allowed the car to get into that range where it was gasping for air, then you most certainly would be walked. From light to light though, that was rarely an issue. hehe

RatStang · Mar 19, 2010

Heya Nik... try this link: Ford Mustang (1986) with pictures and wallpapers

It kinda helps to illustrate my point. I'll post if I find something better.

NIKwoaC · Mar 19, 2010

Oh, believe me, I'm fully aware of the factory power numbers. One of my first mods was "upgrading" to a '87+ intake, too (now the car has an Explorer intake).

While I haven't dyno'd my car, I can tell you that with a host of bolt ons, street tires, and a very hot engine, my car ran low 14s last time I was at the track. I have reason to believe, that even with all my mods, the E6 heads are to blame, more so than the hot engine and street tires.

I guess all I'm trying to say is that if he is looking for a replacement engine, the '86 may not be his best bet.

RatStang · Mar 19, 2010

NikwoaC said:
Oh, believe me, I'm fully aware of the factory power numbers. One of my first mods was "upgrading" to a '87+ intake, too (now the car has an Explorer intake).

While I haven't dyno'd my car, I can tell you that with a host of bolt ons, street tires, and a very hot engine, my car ran low 14s last time I was at the track. I have reason to believe, that even with all my mods, the E6 heads are to blame, more so than the hot engine and street tires.

I guess all I'm trying to say is that if he is looking for a replacement engine, the '86 may not be his best bet.

As a replacement to get things going... I'd say he's good with that motor. As an engine to continue modifying for more power... I'm with ya. I'd choose the 87 block it's rotating assy over the 86 any day.

A thought occures to me at the same time. Drop that 86 into the car and drive it while tearing down that 87 motor for rebuilding as time and money permits.

psycho78 · Mar 19, 2010

Ok I am deciding between a 89 5.0 and an 86. Are they equally as easy on installing? If I go with the 86 will I need to swap the computer and/or 86 wiring harness? Im trying to make this as painless as possible... Will the 89 go in just as easy?

RatStang · Mar 19, 2010

The wiring harness from the 86 should be virtually identical to the one from the 87.

Mechanically, it doesn't really matter what engine you put in there (86 - 93). They all have the same accessories, belt setup, blah blah blah.

The speed density computer and harness should run with any of those motors so long as they retain the stock cam and injectors (read 19lb fuel injectors).

Should be direct swap.

psycho78 · Mar 19, 2010

Terrific, thanks guys! It sounds to me- tho this is all new to me - that the 89 5.0 would be more work than the 86, if the info about the Mass Air is correct (again, Im farrrrr from an expert here lol) Again, I appreciate the help guys!

RatStang · Mar 19, 2010

Not really any more work, one from the other. Just about the same. If you have an 89 donor car though... I'd also get the Harness, Throttle body, and computer from that car. You may not need it right now, but as you upgrade, you'll be glad that you have the A9 computer and harness.

Also... grab up the BAP/MAP sensor from whatever donor you get the motor and stuff from. It's always nice to have a spare.

psycho78 · Mar 19, 2010

hmm okay so its essentially the same thing? The reason I ask is because the shop guy (whos swapping it for me for a mere $350) said hes basically just doing that - swapping. he doesnt want to get into having to change things around at all so he said that as long as it goes right in hes got no problems. And by what ur saying, either will go right in, correct?

RatStang · Mar 19, 2010

Yep... either one will go in. There's not a lot of change between motors. Outwardly and physically, hardly any at all.

Any of the stock cams should be right at home with either the speed density or mass air systems (doesn't really matter).

Your original motor... the one you siad doesn't turn over. Have you tried rotating it by hand? Is it seized?

psycho78 · Mar 19, 2010

Well thats the thing, I havent tried cranking but he did and couldnt get it to crank, though he said it did run 4 years ago when he set it (its been sitting ever since). So I could go thru and try a dozen things or just swap out the motor (the 86 motor is $150 while the 89 is $350) so I figure paying $500-$700 for the motor + swap is better than buying half a dozen things, trying them and still with no guarantee. Plus, i could probably sell the 87 engine and make some of it back, even if its just a little.

RatStang · Mar 19, 2010

Personally, I think you're going about the whole thing the wrong way.

If that car has just been sitting, then it's unlikely (although no timpossible) that the motor itself is at fault. What's more likely is that old ass gass or a HOST of other things are wrong. Things that will STILL be wrong even if you swapped in a brand new crate motor!

I would urge you to find a mechanic buddy (or hire one if necessary) and take him with you to go look at this car. Explain the situation as best you can and let him take it from there.

The fact that it's "not cranking" alone, is definitely no reason to start swapping motors around.

Swapping an 86 5.0 into an 87 GT?

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