DCR calculating trouble

[Maddawg]

Ok me and my machince shop have a different opinion here on piston dish. He wants me to keep the stock dish on Speed pro STL-H825CP30 (.116 depth) don't know the cc volume. Planning on shaving deck to .0025 or closer. What ever I can do to keep @ 87 octane.I have a Elgin Pro stock cam (e-11122-p)280 int/exh & lobe 110 int/ 114exh. 258 rank & connecting rods, Victor head gasket, MLS style.038 - .042 thickness depending who & where it is mic'd. Please give a few suggestions.
2000 Grand Cherokee

[dwg86]

The only suggestion I can give is what I have read. I have read .040-.060 is best for quench. As for dishing the pistons? I don't know what to tell you. I had a set of silvolites dished. When the machine shop balanced them, they removed material from under the piston...right below the dish. So I don't know how thick my pistons are right now. I hope I don't blow a piston. (I guess I will find out) My deck is 0.00, and my static comperssion ratio is 9.24:1. Still don't know DCR

My next stroker will have KB944's.

[Maddawg]

Dishing my pistons 28 cc and .0025 deck hieght gives me these numbers on the Stroker CR caculator SCR9:1 DCR6.97:1 Quench .0465 . This is using .044 head gasket.

[Maddawg]

Ops sorry to many 11111111's Elgin Pro stock cam (e-1122-p)

[gradon]

Oleshot has dished the 802cp30s, which use metric(the 825cp30s are identical. but use standard rings). I used the 825cp30s and the dish is 15.5cc. I would hope a ~7:1 dcr would be fine on 87.

[nukfyrsq]

First build, haven't assembled mine yet, machine shop is dishing my pistons this coming week. Here's what my research has led me to for my plan utilizing this sites compression calculator. '92 block w/7120 head DIY P&P, SP677P stock dish, 258 crank & rods, Mopar head gasket .043, Comp cam 68-232-4. Plan to attempt to run on 89 octane, expect it will be 92. Here are the results after initial machining;
Head trued removed approx .010, combustion chambers - 57cc
Block trued removed approx .010, deck height remaining @ TDC - .040, bore volume - 24cc
Piston cc checked - 14cc
Insights, posts here and other site have scattered reports of pinging. My impression is these tend to fall into two general categories, large quench heights and/or high compression ratios, didn't take a genius to figure that out! Interesting to note is the factory quench is ~.0725. Read an article entitled Compression by Jim Hand http://www.boyleworks.com/ta400/psp/fea ... icles.html. Based on this article, which places significant emphasis on removing potential hot spots in the combustion chamber, and others it appears to me that tighter quench heights help to reduce 'pinging' at higher compression ratios. So I have chosen to try to get into the ideal quench height range of .040-.060 and run a SCR as close as possible to 9.5:1 and a DCR as close to possible of 8:1. I asked the machine shop to remove .030 from my block which would leave .010, this was intentional for possible future build/refinements. The tech that set up the machine did not allow for stone wear so I ended up with .015 remaining (removed .025). This resulted in a cylinder bore volume of 19cc. I have instructed the machine shop to dish my pistons to 21cc. Based on the calculator this is what I should end up with - SCR 9.55:1 DCR 8.06:1 (no advance or retard, yet) quench .0579.

[SilverXJ]

You might want to check with Comp Cams, but I think all of their Jeep cams has 4* advance built in. Which would put you around 8.24 SCR.

[gradon]

Also as Silver has discovered, the MP HG compresses to .044", unless, of course, you have an older one.

[nukfyrsq]

Thanks. Now I remeber someone had mentioned the 4* advance. I'll check w/comp to be sure, I had been planning on some advance anyway.

No, I do not have an older MP head gasket. I was going by the advertised spec that cam with the gasket through Summit. Thanks for the info.

[Maddawg]

This link to Fourwheeler is very informative http://www.fourwheeler.com/techarticles ... knock.html
I found it on Gradon's Stroker Project page viewtopic.php?f=8&t=147&start=30 .