I have my '87 N/A and well she has a blown rear rotor best I can tell. Such is the condition I got her in. I knew didn't run when I bought it. Am starting to work towards getting her running. Body is fairly solid "minor" rust on edge rear fender well and couple dings, but that aside solid ride apart from nonrunning engine.

Thus my question. What ya'll think would be the best approach to getting her running?

Was debating:

1. Possible donor engine
2. Seeing about getting it rebuilt
3. Buying a rebuilt
4. JDM import engine
...also open to ideas I may not have mentioned.

thanks in advance

 

Buy a donor on the cheap for now. That's the fastest way to get it going.

Then, take your engine, tear it down, piece out what you need to rebuild it, then take a weekend to swap it in. Sell the cheap donor engine for as much as you bought it for. That way you get an engine in fast, can still drive the car, and you can build a good engine the right way which will last you years and thousands of miles.

 

How much would you say is reasonable for a donor?

 

$300-600 for a stock engine, $600-800+ for a used rebuilt engine

Rotary >Pistons

 

Yes rotary greater than pistons :P

Seems I may have found an S5 the has lowish compression and an S4 that is supposed to be running fine for basically the same price. And suggestion there? Was leaning toward the S5 and doing some work on it before putting in (assuming fits all the same in '87). thought about taking both.

 

Well don't install a low compression engine in it. That's just asking for trouble.

 

yea for sure. He says it just has worn seals. Was thinking just rebuild the damn thing since it's already out. At least do seals and basic maintenance anyways.

 

If the engine is already out, it shouldn't take you too long to rebuild her. Besides, it will give you some peace of mind since you'll be able to inspect the internals before reassembling.

 

In response to the blown s5 vs good s4 engine...

My opinion? First off, don't use an S5 engine (even a good one) unless you're also using an S5 transmission, ecu, injection, driveshaft, etc. It's a superior (lightened rotors, higher compression) design, but as with bolt-on turbos and turbo swaps, you're inviting tragedy by mixing high-power engine with stock driveshaft, differential, suspension, and transmission. Also, while an S5 might have higher performance on paper, an S4's heavier engine has better inertia, so you trade a slightly slower pedal response (note that you're still driving a naturally aspirated 13b, so your pedal response is still lightning quick) for better high-end torque. On the downside, you're looking at a 7k redline with an S4 vs 8k with an S5. Unless you're doing some pro circuit drift championships though, I don't think you need to be too worried about it. Besides, you'd have to get an S5 tachometer in order to safely exercise the S5's full powerband. Just stick with the S4 engine.

 

^ What?

The S4 and S5 transmissions are almost identical, and offer no advantages over the other. The only thing I could find on the S5 is that the 5th gear ratio on those that came with limited slip differentials was changed from .697 to .756.

You can use all the S4 manifolds on the engine as well. It will run off S4 electronics and everything, the ONLY difference it will have is that it's got a slightly higher compression ratio, from 9.4:1 to 9.7:1.

Bolting the S5 engine in an S4 car is nothing to be afraid of, and it would probably offer slightly better power and throttle response with the lightened rotating assembly and higher compression ratios.

But like I said, if the S5 engine's already got low compression, then why buy and install it? Grab the S4 keg and swap it in. Then you have plenty of time of how you're going to either build a nice NA engine, turbo engine, whatever.

 

maybe. in the SAE paper for the S5's they mention the cast combustion pocket rotors (88 and older) have a variation in compression ratio of .3. so its 9.4:1 +/- .3.

the machined combustion recess has a variation of .003. the 9.7 ratio is chosen as its just the higher end of the tolerance from the old rotors, 9.4 + .3 = 9.7.

what does this mean? nothing! the S5 block is just a better built S4 block. the rotors are a little lighter, the flywheel is a little lighter, the rotors are more consistent across all the faces, other than that its the same thing

 

Truth. That's the difference between the cast S4 and machined S5 rotor pockets. It's still acknowledged that the S5 should have higher compression ratios than the S4, as the tolerance was +/-0.3, so it could also have 9.1:1 as well.

I think we're splitting hairs at this point. The point was that yes, you can swap in an S5 block in an S4 without having to change the rest of the drivetrain to S5.

 

What I would do is get the S4 donor engine because it'll all go back in just fine and rebuild the blown one to the way you like or turn it as a core for an S5 to swap out later. That's if you're really wanting it to run in like now kinda situation.