Question regarding Turbo vs NA internals

[Jacquiles]

I was wondering what the difference is between the 86 NA and 86 and later turbo (951) internals are.
From what I have read from other sources, the crankshafts are the same (forged), and the NA had cast rods, turbo had forged. But I'm not sure about the pistons. If someone could confirm this information for me i would greatly appreciate that.

I recently bought a 951 crankshaft and set of pistons w/ RARST connecting rods off ebay, the motor they came out of was described as not running, but that they appeared to be in good condition, matching the 120k miles on the odometer(according to seller). They looked great in the photos(maybe I'm just blind ) , but when i got the pistons/rods, 3 out of the 4 pistons had scratches/dents and are totally unusable, and one of the rods was bent. I'm not sure what happened, but I'm waiting on a response from the seller. Crankshaft appears ok, but I don't know if there is any damage I am unable to see with the naked eye. I am going to attempt to see if ebay will reimburse me for the pistons/rods through their money back guarantee, if the seller doesn't respond by this weekend.

My goal was to rebuild my NA motor with Turbo parts and put a turbo on(I already bought a k26/6 turbo), since the blocks are pretty much the same, and mine has threads at the OPR and sump for the turbo oil lines. I KNOW that turbocharging an NA is, according to most every article i have read, not worth it. "just buy a turbo model, or do a motor swap". But i enjoy tinkering and wanted to do it for fun. Or at least try.

I am super bummed that the pistons and rods appear to be a total bust and waste of $300, and apparently the 951 cranks are the same as the NA 944, so I likely didn't need to even buy the 951 crankshaft with the 951 rods/pistons. I only paid $89 for the crankshaft so its not a super big deal for that specifically. Both came from the same seller.

Again please let me know the details on the difference of the internals. And if anyone has some good 951 pistons/rods they are trying to get rid of let me know. Or if you want to try to talk some sense into me and tell me to leave my car alone, feel free i suppose.

I am located in Jackson TN.

Thank you.

Here is a link to the original listing for the pistons/rods: https://www.ebay.com/itm/306125375809?m ... media=COPY

Here are some photos of the damaged rod/pistons

[944m3]

There are a few threads out there that test the limits of NA internals. According to one post, you could live with 10psi on stock NA internals using E85 ensuring no knock. Meaning that if you have humble goals, you might get away with what you have.

To answer your question though, you are on track about the rods and pistons. But the biggest issue with the NA pistons is the compression ratio. You will need a standalone to get the right tune. It will be difficult to find a decent set of stock turbo pistons. Keep in mind that they are now approaching 40 years old. You’re better off buying Wossners and Molnar rods, about $1600 combined. You’ll need new bearings. This is all assuming your block and head are in good condition.

Tons of information out there as folks have tried this for the past 20+ years. Having owned an NA and rebuilt a 951, I would highly suggest just buying a 951 and tinker with that to improve it. Plenty you can do there. You will spend a lot of money and time getting an NA boosted and then you will learn that will need to upgrade the brakes and the suspension, and tons of other small things you will need for a turbo car. In the end you will have a Frankenstein that might or might not run well. But as it’s always said, with enough money and time you can make anything work.

[Jacquiles]

This is something I was thinking would be the case, especially after my issues with trying to buy used rods and pistons . I began looking at new rods and pistons, but was disappointed by the cost of new ones. I was already planning to have to put in a standalone ecu, as well as with upgrading brakes and suspension etc. so I’m not too worried about those.

I’d like to still keep myself open to this project, but unless I can get a good used set of rods and pistons, I’ll likely just keep things how they are.

I did read a post I believe you are referring to, one by Rogue Tuning where he boosted an NA on E85 at 17psi for about 9months before a pistons ringland cracked. I’ve considered doing this too, but I really prefer the idea of having a more reliable way to accomplish what I’m wanting to do, by replacing the rods and pistons

[944m3]

If you continue your search for pistons, don’t forget to check the tolerance group for your block and matching group on the pistons. You were probably already aware but thought I’d mention it.

Larts has a set of Rarst rods and pistons on eBay. He’s a very reputable seller. Might be worth checking out.

[michaelmount123]

I agree with 944m3; contact Lart.

BTW, don't just buy one rod. They need to be a matched set to avoid having to balance them. Get your $ back for them - too many scoundrels on Ebay.

The pistons can probably be used with some very careful deburring to address the damage in the ring grooves. They should also be soaked to remove the grunge and carbon so you can inspect them thoroughly.

Used complete 951 engines are often cheap. You'll get nickel/dimed to death with the small parts to convert a NA to work properly. Do the math and I think you'll find seeking a complete 951 will be the answer.

[Jacquiles]

If you continue your search for pistons, don’t forget to check the tolerance group for your block and matching group on the pistons. You were probably already aware but thought I’d mention it.

Larts has a set of Rarst rods and pistons on eBay. He’s a very reputable seller. Might be worth checking out.

Ok gotcha, I’ll check him out

The tolerance groups you are referring to, I’m not familiar with, but I was originally planning on comparing the tolerance between NA and Turbo pistons anyways so I probably would have gotten there eventually. I’m looking at buying two books, one covers the NA specs and tolerances, the other for the turbo models, and just cross referencing to make sure what I pistons I may use will work well with the tolerance of my block. I rebuilt the motor two summers ago, and I didn’t take any measurements when I had it apart. This time I was planning on buying some micrometers and such and actually seeing what’s going on.
Thank you for the advice

[Jacquiles]

I agree with 944m3; contact Lart.

BTW, don't just buy one rod. They need to be a matched set to avoid having to balance them. Get your $ back for them - too many scoundrels on Ebay.

The pistons can probably be used with some very careful deburring to address the damage in the ring grooves. They should also be soaked to remove the grunge and carbon so you can inspect them thoroughly.

Used complete 951 engines are often cheap. You'll get nickel/dimed to death with the small parts to convert a NA to work properly. Do the math and I think you'll find seeking a complete 951 will be the answer.

That’s good to know about matching rods, I thought that may have been the case but I wasn’t totally sure.

Im worried one of the pistons has too much damage, but I’ll take a closer look and re evaluate. I’d hate to cause damage to my block

You’re right though about trying to buy all the parts individually, it’s been adding up lol. I think I will do some more research and make sure what route I end up wanting to go. I’ll check out Lart.
Thank you for the tips

[Jacquiles]

The eBay seller got back with me, and accepted the return, and he is going to see if UPS will pay for it since it was damaged during shipping. He agreed that bending a rod during shipment seemed crazy, said it would take a lot of force to cause that. But he assured me they were in good shape before hand. I’m glad that was able to be resolved

[944m3]

I’m going to go out on a limb and say 0% chance the rod got bent during shipping….0% lol

[Jacquiles]

I’m going to go out on a limb and say 0% chance the rod got bent during shipping….0% lol

Haha yeahh I wasn’t too confident it was possible, but I didn’t want to say that to him lol