NoNonsensePete

So I have an 85 Corvette with the 4+3 Doug Nash Transmission.The timing chain snapped while I was sitting at a stop light and somehow bent 9 of the pushrods. With this much damage, I am planning on getting a donor L98 off of another early C4. If I buy one that was mated to an automatic, will there be any differences in the motors and how they mount or can I just swap them out?

This was the worst one!

Phobos84

I can't think of any major differences. The automatic car would have a bracket for the TV cable. And the electronics would have differences like the ECU but as to the motor itself there shouldn't be much. I'll throw this out there. I would pull the damaged motor and pull the heads just to see how bad the damage is. At this point why not? You might get lucky and the damage isn't as bad as you're fearing. You might just need a new set of pushrods and a valve of two. Or you might have a hole in a piston. But you don't know until you look.

WVZR-1

If you're intending to stay with your current 4+3 transmission and use your existing clutch I believe you need to make sure that the donor has a matching crankshaft flange bolt pattern so you can use the current flywheel. That pretty much limits you to another '85 I believe.

jazfe

The harmonic balancer might be different from an automatic car. I'm not sure about the chevy but this is true for other makes I've swapped in the past.

NoNonsensePete

Thanks for the tips! So as far as I understand, I would need to either have the same year engine with a manual transmission or mess around with the flywheel, ECU, and TV cable on an engine that went to an automatic (not 100% sure if that's all that needs to be swapped/purchased since I have never done something like this). I did some more digging on the forums and found a similar discussion: https://www.corvetteforum.com/forums...kick-down.html
So while it might be possible, it would be more than just a direct swap. Based on the part listings online, the harmonic balancer should be the same from 72 to 91. I'll pull the heads this weekend and see what the damage is.

NickPSI

You shouldn't have to do anything with the TV cable. What the above poster was referring to was both cars will have the bracket as they both used a TV cable. Should be a pretty direct swap. If anything youll need to transfer some bits from the old engine.

I agree with pulling the heads to see if its just top end work to get back on the road.

NoNonsensePete

Well, I just got the passenger side pulled. I have never dealt with this type of issue so I will probably need to look up how to diagnose what I have. Just checking, it is supposed to have coolant through one of the holes on the rear end of the block right? It spewed out as I was removing the last two bolts and got into the rear two cylinders.




If any obvious issues stick out to you guys from these photos then let me know.

Gale Banks 80'

Don.t be to concerned about the water just vacuum it out. Do an Oil Change before you start it again. Cant see much wrong in the photos I would just take the Heads to a machine shop and have them fresh'd up. Or now is your chance for Aluminum Heads. Wile this is being done change the Timing Chain.

tequilaboy

Piston to valve interference is what cause the pushrods to bend. Probably have a few bent valves as well. It appears that a couple of the exhaust valves are not seated normally.

NoNonsensePete

I see. Well this is coupled with a multitude of other issues: janky wiring with a few holes drilled into the car to route some silly subwoofer, cracked targa top, broken AC unit, deteriorating carpet on the doors, a smushed in front bumper that makes it hard to open the hood, and a handful of other things. At this point it may be more cost effective for me to purchase another one, Frankenstein together all the good parts, and sell off whatever is left. I have been doing some Facebook shopping for the past two weeks and a few listings have caught my eye. May have more money than sense, but I have grown tired of trying to fix this one. I'll post some more pictures if I come across anything interesting during the process.
Thanks again for all the quick and informative responses!

Gale Banks 80'

What You have there is a production engine that was mass produced. That is Casting Flash that could of been removed by hand when it was built but GM wasn't willing to spend the 5 minutes per engine because the other manufactures didn't do it and they were all competing with each other. By removing it you get two benefits the Oil will drain back to the Sump faster and You don't have the chance of the Flash breaking off and getting into the Bearings. So You could spend the 5 Minutes with a Die Grinder, but You have no way of containing the material removed and it will get into the Bearings doing exactly what You don't want. Best to leave it alone with the idea that it hasn't hurt anything so far and there are Millions of other engines out there with the same flaws. Now if you're going to tear the engine down to the bare block and rebuild it that's the time to spend cleaning this kind of stuff up. I will have to say that yours looks about as bad as I have seen.

NoNonsensePete

Yeah, I asked two of my friends about it and they told me it was the same thing. I decided to go back and re-edit my post to exclude that since I was no longer concerned with it, but I do appreciate the input!