A possible piston choice

[uscav_Scout]

So I have been beating my head against the wall all day trying to find a piston that fits in the jeep block, doesn't cost a shit load of money and works with 4.2 rods (if I didn't have them I would be going with the 4.0 and some custom pistons, but I bought them already so I am stuck with them... Unless someone wants to buy them???? (They are brand new), This is what I get for planning this engine build while I am still deployed to Afghanistan ).

Here are my goals:
Zero Deck Height
.043 quench
large bore .060 over is a minimum

As of now I am planning on doing this with a 4.2 rods and crank, unless someone wants to buy my brand new 4.2 rods I have been looking everywhere for pistons, from Jegs, to Summit, KB/SIlv, and even rockauto. They all make the process extremely difficult, for it is all organized by application, you can't just do a search by bore, compression distance, etc. Although on the summit site you can sort a particular bore of piston by Compression distance by tacking a little bit on url. For instance, http://www.summitracing.com/search/Part ... /3-955-in/, will show you all of the pistons that are of a 3.955 bore, now usually you'll have to pick a stroke before you can choose a compression distance (stroke is so application dependent that it is no help) but if you just tack on

?Ns=Compression-Distance-in|Asc

to the end of the URL so now it is http://www.summitracing.com/search/Part ... nce-in|Asc, it will sort all the pistons at that bore in ascending order.

But now on to my real question. I found some pistons. They are cheap (they are sealed power cast jobbers), 3.955 bore, and 1.640 compression distance, and I have never heard of anyone using them before, so I want to get everyones opinion before I drop some dough (although at this price I could buy thirty of them for what I paid for my header).

The Sealed Power 403CP/80. They are for a Chevy 250.

Bore size 3.8750"+.080
Ring grooves 5/64" 5/64" 3/16"
Compression distance 1.640"
Pin diameter .9275"
The dish is at a depth of .085", I couldn't find any info on volume. Plus I am gonna have to get it really dished anyways.
These things appear to be chamfered around their edge, I have no technical data on this (in terms of angle or depth, etc). I dont really know what the purpose of this would be, I could see it having some sort of dish effect on the SCR, but I also wonder if it would affect the quench negatively?

Now I am planning to use a 4.0 block, 4.2 crank and rods (unless some one wants to buy them )

Block Height = 9.450
Stroke = 3.411
Rod Length = 5.875
Compression Distance = 1.640

Therefore:
Deck Clearance = Block Height - (Stroke/2 + Rod Length + Compression Distance)
Deck Clearance = 9.450 - (3.411/2 + 5.875 + 1.640) = -.0125 or .0125" into gasket land, too low of a quench and the SCR would insane, not acceptable. So here is what I propose.

I figure I could just shave a .0125 off of the top of the piston, get rid of some of that chamfer, have a zero deck clearance and then dish them. Seems like alot of work, I know, and if someone knows of any cheap .060/.080 over pistons with a 1.625ish compression distance let me know, but part of me wants to be the guy that used chevy 2.5 pistons in his stroker. Let me know what you guys think.



. http://bpi.ebasicpower.com/mm5/merchant ... Code=ALL2I

[dwg86]

My opinion? It would probably cost too much in machine work to use in a jeep engine. So now you would have some very expensive CAST pistons in your engine. Not worth the money and time. Why not just use some sealed power hypereutectic 802's or 825's? They aren't that expensive...less than $30.00 a piece.

[gradon]

Taking .0125"off the pistons would be possible, but you'd basically have no dish left, so yeah the scr/dcr would be sky high. You'd also have to address getting the pin to fill the 4.2 rod. I'm with dwg on this--get the Sealed Power 802s or 825s in +.060 flavor or else pay the $500 for the Diamonds in +.080" as someone here has done(you'll be able to sell the 4.2 rods to someone).

[ccpanel]

My opinion? It would probably cost too much in machine work to use in a jeep engine. So now you would have some very expensive CAST pistons in your engine. Not worth the money and time. Why not just use some sealed power hypereutectic 802's or 825's? They aren't that expensive...less than $30.00 a piece.

I'm kinda in the same boat. i've done INSANE amounts of research to find out which piston to buy for my streeter stroker. my biggest issue is coming up with legible, verifiable CC numbers for piston dish. i have MULT conflicting reports.

I'm thinking the 802 as i REALLY want hyper pistons for a lot of reasons-closer tolerance to help eliminate piston slap(which broke the stock piston skirts in my 4.2), less expansion, better detonation flexibility-not that i intend to 'ping' but it may happen...

http://autos.groups.yahoo.com/group/str ... Rows&tbl=4 says 15.8cc

http://www.jeep4.0performance.4mg.com/tech_specs.html 15.1cc

and this guy http://www.colorado4x4.org/vbb/showthread.php?t=80410 says 15.2 but he also says the 677 is a hyper piston

then theres this site http://www.fourwheeler.com/techarticles ... atios.html that says they got a measured 18.8cc but say its listed at 17.5cc

I'm going INSANE!
Anybody have HARD measured numbers to back anything up? I'm going for zero ping daily driver and no-i refuse to do SBC. i want a stroker inliner.

[gradon]

Last May, the federal mogul tech dept. told me the 802s and 825s were 15.5cc. I'm using the 825cp30s. Go with the smallest case dish of 15.1cc and use that value in the calculations so that worst case, your dcr is less than what it is if it's actually 15.5cc.