Watterson02

I recently purchased a mystery forged bottom end with spun bearings. upon disassembly, we found Manley connecting rods and Wiseco 84mm 10.5:1 pistons. They were said to have been used with E85 + a fairly large ebay turbo. My question is, with spending the least amount of money, what is the best option for me moving forward with this motor? Here are some pictures of the pistons Piston 1 Piston 2 Piston 3 Piston 4] The plan for power/boost is 16-17psi, or really right before the 2560R runs out of boost. Not quite all it has got but about 90% of it. I've got this as my intercooler, so IATs shouldn't be outrageous but an upgrade is possible. I don't believe the cylinder walls were too bad, could be honed plus new piston rings I think. Could I just swap in the 84mm wiseco low compression pistons with new rings instead of these pistons, or would the tolerances be way off?

I've looked around and there are plenty of examples of people running these pistons with boost, but only with ethanol. Unfortunately, there is not any E85 near me. Which makes me ask, would this compression ratio be fine for use on 93 octane pump gas? Would those gas station octane boosters actually be of any use either? also we plan on tuning the ignition map using a Knockblock g4 my friend wants to go halfsies on, so I know it would run safely, but would it run significantly better with low compression pistons(enough to justify the extra $500+, when I don't care about 5-10hp difference, I'm in it for the reliability)? It's hard to tell if the pistons are worn or just dirty because my dumbass didn't wipe them off, but I'll get a machine shop's opinion on them once they're cleaned up to make sure they're physically okay for reuse. I'd just like to know if I can reuse these high-comp pistons and the bore, reuse the bore with new low-comp pistons, or am I gonna have to go all out and bore it out with new low-comp pistons? I'd like to go for supertech's 85mm piston because of their alloy's expansive properties, but if my block doesn't have enough material I can settle for the 84.5mm Wiseco pistons.

user 8202

I built mine with 84mm supertech pistons with an 8.8:1 compression ratio. I don't know that I would reuse yours bc 10.5 is really high. Ive really only heard of people going up to 9.5 tops on pump gas. Have you had the head checked? If tbe last owners shaved the head at all it would increase compression ratio even further. Definitely let your machine shop check the block and head out and do a rehone. As long as the cylinder walls weren't damaged all you need is a rehone and to get lower CR pistons. Have the machine shop check the ring gaps if you plan on reusing those.
I've only built my engine, but those pistons kinda look like they have alot of scoring on the side walls. Not sure if that's Normal or not.

patsmx5

iTrader: (16)

If you were going to run 6-8 psi on the 2560 I'd say sure. If you really want to run it at 90% of its max, I wouldn't do 10.5:1 without E85. You could, but the timing will have to be soft to keep it alive.

FWIW my next motor is getting 10.5:1 wiseco but I'm E85 only. If you decide to sell the used 10.5's cheap LMK.

technicalninja

Need to clean, measure, and inspect pistons/bores before anything else happens.
If the bores are re-usable I'd have it power honed by a machine shop and fit lower compression Wisecos.
No one can tell you if the tolerances are off until they measure them. A 84mm Wiseco piston should be exactly the same diameter regardless of compression ratio.
Sell Pat those...
Those pistons are best suited for high end builds with big turbos, giant intercoolers, and heavy fuel. You have none of that...
Those pistons would also be fine for a high output NA build on pump gas.

I'd be very interested in why the engine spun bearings.
There is always a root cause.
I'd find that before re-using anything.

Watterson02

pm'ing pat to sell them. Honestly, I'll probably use the stock pistons and my old motor (not the one I bought), since I'm only shooting for <300whp. I'll just steal the Manley rods + arp fasteners out of the purchased block. It would be cool to have the 1.9 liters of displacement, but the only noticeable difference would be on the low end from the increased torque/spool. The turbo would be the limiting factor in terms of HP anyways, regardless of displacement. The timing was always going to be soft, but I'd still like things to be somewhat efficient.

Whatever the cause of that motor spinning the bearing, if it were to be reused it will be completely machined/checked from the ground up and fitted with a boundary engineering oil pump, so there shouldn't be anything else possibly wrong with it, yeah? The same process would apply to the old motor. The reason for the old motor spinning a bearing was a wobbly harmonic damper, I'm 95% sure. That would also be addressed in the rebuilding process. Lastly, the head to be used is going to come from the original engine which is known to be unopened.

I'm in the same boat as Jmatt, as in I don't really know what kind of wear is normal or not, so I think it might be best just to start fresh with the stock block at the minimum. It's my first build I want the least amount of problems honestly more than I want to save a couple of dollars.

technicalninja

One fairly inexpensive suggestion is to ceramic coat the tops of the 99 pistons you have now and just re-use them
They will work far better with the 2560 than the Wisecos. Try to find NPR rings for them.

Bores should still be re-finished with a micrometer style fixed honing stone on a real honing machine
It will look like this.
Winona Van Norman/Serv-Equip Honing Machine PS1370 – MotorcycleLifts.com

These machines tend to reduce OOR (out of round), and taper.
This helps the new rings seat much better than a spring loaded or ball type hone.
It should cost 15-25 per hole, The machine shop should ask to see the rings, if they didn't I would be wary. Cast iron, plated, and chromed rings require different surface finishes and different stones.

Am I reading your last post correctly and both your original motor and the purchased basketcase have spun bearings?
So, you're "BearingsBane"? 😉

That 99 "un-opened" head is now 23 years old. This is the equivalent to using the lungs of an 89 year old man for a transplant...
The head should be re-done before you try to run boost on it. It might require little to no hard parts but both the springs and the valve stem seals should be automatically replaced.
New valve job should be completed and while that was apart I'd spend a little time cleaning up the transitions in the bowls at the seats. This is free power if you do it right (conservative with the grinding).

The pictures of your pistons show some skirt wear, It's a bit hard to judge being as dirty as they are but both Pat and I think they will be fine. He wants to use them and he's shooting for BIG numbers...