What to do with a C4 with a bad engine?

[Steve & his C4]

Hi everyone!
I'm new here. Hoping some of you could pass along some suggestions to me. I recently bought a 85 with a bad engine. Other than the engine, the car is in great shape. (Brand new interior too!)
Here's my predicament. There's obviously a bad piston in the original existing engine. The car is completely stock. Would it be best to tear down and rebuild what I have? Do I make it a 383? Do I abandone the tune port and install a carbureted,fresh 406 I have? (I've researched what I'd have to do to install the tune port) OR, do I pick up a wrecked Vette with a LS engine and trans and attempt a transplant? Not even sure if that last one would be an option.
Any input from you folks that have, I'm no doubt had more Corvette experience, would be greatly appreciated. Thank you in advance!

 

[Toms007]

Welcome aboard Steve. I think any one of those scenarios is an option. I'm sure all have been done in the past. I guess it all depends on which direction YOU want to go. I'd think that the ease of doing them is also the order which you listed them. Using the TPI, I believe, would be the easiest path. When you go to the carb version I think you have a lot of issues with the gauges and other computer things. Going to the LS, brings it's own set of issues. Hopefully, someone with actual experience doing these options will chime in here soon to shed some light into the matter.

 

[Steve & his C4]

I did list them in the order of simplicity and cost. I'm actually kinda surprised that finding a compatible short or long block for this car isn't so easy. I've yet to tear it down though so I'm not sure what I even have here. It most definitely doesn't sound good though. LOL

 

[Rob]

Welcome to the Corvette Action Center!

 

[LLC5]

I did list them in the order of simplicity and cost. I'm actually kinda surprised that finding a compatible short or long block for this car isn't so easy. I've yet to tear it down though so I'm not sure what I even have here. It most definitely doesn't sound good though. ������ LOL

It depends on what the vehicle is worth to you, and who is doing the work. It is very hard to find a reputable engine builder, so unless you know what you are doing and do the work yourself a quality long block is probably the way to go.

But, are you sure that a piston is bad or just guessing? Has the engine been torn down to verify the condition?

 

[Steve & his C4]

Thanks for the reply. I've been spinning wrenches for a little over 40 years, so I'd be doing all the work. I've rebuilt more sbc's than I can honestly remember. One problem I've encountered though is that due to a few machine shops around here closing, the one's that are still around are telling me that their at LEAST 2 months out. I haven't torn into the engine yet, but life's previous experiences has made me believe that something is definitely wrong with the number 2 piston. With valve covers being the only thing I've taken off so far, it's definitely just below the head. (The knock) I realise I need to pop that head off to know for sure, but I'm thinking wrist pin problem. Maybe even worse.
Thanks!

 

[LLC5]

Thanks for the reply. I've been spinning wrenches for a little over 40 years, so I'd be doing all the work. I've rebuilt more sbc's than I can honestly remember. One problem I've encountered though is that due to a few machine shops around here closing, the one's that are still around are telling me that their at LEAST 2 months out. I haven't torn into the engine yet, but life's previous experiences has made me believe that something is definitely wrong with the number 2 piston. With valve covers being the only thing I've taken off so far, it's definitely just below the head. (The knock) I realise I need to pop that head off to know for sure, but I'm thinking wrist pin problem. Maybe even worse.
Thanks!

As long as you know what you are doing and perform your own labor, then tearing it down and inspecting will be the best course of action to verify that the piston is bad, but I am not sure I would pay someone to tear it down only to find out major work is needed.

If you decide to repair it and the engine needs machine shop work, then it gets really tricky finding a quality machine shop to do the work. You might save a few dollars doing it this way, but a GM long block is competitively priced and is a good value with usually some sort of warranty. The LS engine would be a better and more efficient engine, but the nightmares involved in the conversion are expensive and frustrating.

 

[Steve & his C4]

Fortunately the machine shop I've been using, and have been extremely happy with, is still open. The bad part is that their swamped. Was told minimum of 2 months to machine a block. I'm assuming of course it's gonna need to be bored. Vette has 103k miles, so........ I know I need to get inside of it to see what's going on, but I'm guessing the worse. LOL (My luck!) I searched around a little bit for a short block, or even a long block, but for some reason, what I'm finding tells me it's not compatible with this application for some reason. Can't figure out why though. Even thought about a ZZ6 crate engine from GM, but for that kind of money I know of a wrecked 2006 ZO6 for sale. I know that's a huge undertaking but I would have the entire donar car. I'm leaning more and more towards a short block. If you (or anyone) might know of a good supplier of a compatible short block and could pass it on to me, that would be awesome and hugely appreciated.

 

[Steve & his C4]

One problem I've encountered in searching for a short block has been compression ratios. Stock, the L98 was at 9:1 with the stock 76cc heads. I'm finding short blocks that would actually have lower compression with these heads. If anything, I'd like to increase the compression a bit.
I'm definitely leaning towards a short block. That would get the car up and going (kinda chomping at the bit to drive it. LOL) and then I could take my time rebuilding the numbers matching block.
So, yes, if someone could point me in the right direction, that'd be GREAT!

 

[Vettehead Mikey]

I'd take it apart to see what's actually wrong before making any commitments.

 

[catbert]

I really like the 85 motor, and if you are a set of pistons short of a good one, I'd fix it. Tear it down, best case fix it, worse case replace it. But you'll know.

 

[jrose7004]

Upgrade to a LS7 and never look back!

 

[Wayback]

If you decide to yank the mill,the upper rear hood support up against the firewall can be removed by taken out the torx screws,gives ya better acess to the oil sender conections,ground wires & trans bolts etc.Cant remember if ya can just drop the pan ,ridge ream,pull out the piston.If your compresion is good on the other 7 i would go that route.