ICON 9929 Piston Specs

[skinny z]

The compression height was just confirmed by Trevor from UEM Pistons.
1.550".
I've also asked about that same piston with a thinner ring pack. We'll see how that goes.
FTR, I've kind of zeroed in on that particular piston as it looks to be readily available. The rest that are listed in the typical mail order stuff are described as being "special ordered for you".

[rustbucket79]

Wiseco Pro Tru Street PTS503A4 looks like a 1.560” CH. perhaps your local machine shop is a dealer and can get you a good price on a set.They come with rings.

[skinny z]

Wiseco Pro Tru Street PTS503A4 looks like a 1.560” CH. perhaps your local machine shop is a dealer and can get you a good price on a set.They come with rings.

I'll look into that for sure.
Seems to me I've seen a couple of Wiseco boxes laying around his shop.
Thanks.

[rfoll]

I didn't see anything about the usage for the engine. You could always deck the engine while it is being bored to get where you want to be.

[skinny z]

Engine has been decked once before.
Now with the piston sitting .014" down with a 1.560" piston, my .026" Mahle head gaskets fit the bill perfectly.
I'd prefer not to trim the block again. My machinist offered the same solution.

Looks like that Wiseco piston has all the right dimensions. Plus a thinner ring pack than the Speed Pro I had previously or the ICON discussed here.

Now, I just need to find them. I trust the machine shop has a better handle on that than I do.

As for use, that's still somewhat undetermined other than it will definitely see the drag strip and a lot of highway miles. Still debating whether any open road racing will be part of the scene. I'm thinking that's becoming less and less likely.

[F-BIRD'88]

Can you not get the same pistons you had before?
Save you a lot of fuss for nothing.

[skinny z]

Speed Pro never came up in the conversation actually.
That said, looks like 40 over might be slim pickings for those too.
I've got the early uncoated version of the H631CP which is H631P. They have the thicker ring pack.
If I'm swapping pistons I might as well get something up to date. Wiseco are 1/16th.
I'm also liking the forging rather than the hypereutectic Speed Pro.

At this stage of the game, I'll let this play out and other than not wanting to deck the block again, I'll take whatever I can get.

[rfoll]

It's just a 350 block, $50 everywhere. Maybe start over with a fresh block.

[skinny z]

I could but that $50 sure gets inflated once you line bore, deck, bore, detail and all the rest.
This particular block had some serious attention paid to it when it was worked over 20 years ago. It's much more than a core. It should be a 40 over job and I'm out the door.
I wish it weren't so but savings are important.
But, the shop has plenty of cores to choose from too. If the crank had been toast, and by all accounts it's in fine shape, I'd scrap the whole project and jump into plan A. A fully forged 383 was the initial idea.
But a number of factors contributed to wanting to save a lot of the expense and I'm going for the easiest route back to the track.
The 355 becomes a 357.

[frnkeore]

Regarding your CR calculations, your off by a little.

None of the calculations, provided here, consider the position of the top ring. Most SBC range from .200 to .280, from the ring to the top of the pistons. In a 4.04 bore, the cc range will be .8 to 1.1cc.

If you look at Maxsoftware's input chart, though he didn't input any info for that, you will see the info needed. Piston top dia and piston top compression ring down boxes.

When I use the Kelly compression calculator, like your using, I just add about 1cc, when using it to figure DCR.

[skinny z]

I've always considered the crevice volume to be part of the calculation but I'll say the software posted by Larry is one of the few times, if not the only time, I've seen data entry for it.
I'm going to dig into it a little deeper now that the piston spec is confirmed. Or at least I hope the Wiseco are in stock.
Thanks.

[F-BIRD'88]

This free cr calc program has a optional for piston crevise volume..
http://www.maverickracing.co.uk/compratiosoft.htm

[F-BIRD'88]

But,,. realize that when the engine is at full operating temp and especially while under WOT the top of the piston gets hot and expands A LOT. The clearanxe then becomes tiny tiny essentually 0.

[frnkeore]

The clearance, at the top of the ring land area, on a 4.040 bore, is about .040. I don't think even 2618 can expand anywhere near that much, even under WOT.

You can calculate the expansion, if you know the expansion ratio of the material.

[rfoll]

This free cr calc program has a optional for piston crevise volume..
http://www.maverickracing.co.uk/compratiosoft.htm

The calculators are fine for doing the math, but unless you actually pour the chamber and the cylinder at tdc your compression calculation can easily be off by as much as 1/2 point. I bought a set of new Brodix heads a few years back and the advertised 64 cc chamber came out to 72 cc.