Re: high compression, NA street combos-pump 93
[Re: moparx]
#2639454
04/01/19 12:45 AM
04/01/19 12:45 AM
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Joined: Jul 2006
Posts: 4,319 Puyallup, WA
StealthWedge67
master
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master
Joined: Jul 2006
Posts: 4,319
Puyallup, WA
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I run non-oxygenated 93 octane pump gas. Combo is a 400 based 452” 3.75 stroke at 10.65:1. Heads are 84cc Source Stealths that have been milled & cc’d at 82cc. Flat-top Iconn pistons are at zero-deck. Cam is a flat-tappet solid, 252* (.050) & .573 lift. (Currently at .610 lift with 1.6 rockers.), on a 109* c/l. I’ve been beating on this low-budget home-built combo for 9 years now, and still finding more in it. A new best was just found this past weekend.
LemonWedge - Street heavy / Strip ready - 11.07 @ 120
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Re: high compression, NA street combos-pump 93
[Re: moparx]
#2639644
04/01/19 12:45 PM
04/01/19 12:45 PM
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Joined: Jan 2003
Posts: 15,439 Val-haul-ass... eventually
BradH
Taking time off to work on my car
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Taking time off to work on my car
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
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what would be a "minimum" overlap, or duration at 50, when approaching 11 : 1 static compression ?
It's not that simple: chamber design, piston top design, quench height, camshaft seat duration, LSA... not even all of the variables that can factor into this. Also, some people say the overlap influences cranking pressure, I've always understood it to be a result of the intake valve closing point. A lot of overlap does impact the ability of the engine to have more complete combustion at lower RPMs That's not cylinder pressure; it's dilution of the air/fuel mixture with residual exhaust gasses. And, there's been a running debate (about which I've presented my position in the past) of whether the engine build should target cylinder pressure based upon using a "higher" CR and crutching it with a longer-than-normal-duration cam, or targeting a more "typical" CR for the fuel to be used and spec'ing the cam to be aligned with that CR. I've been through that last topic enough that it's now included in my no-no discussion categories, along with politics, religion, and choice of engine oil.
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Re: high compression, NA street combos-pump 93
[Re: BradH]
#2639820
04/01/19 07:23 PM
04/01/19 07:23 PM
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Joined: Jan 2007
Posts: 7,664 IN
ahy
master
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master
Joined: Jan 2007
Posts: 7,664
IN
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400 based 496, pocket ported Ed heads, 243@.050 mechanical flat tappet cam, 10.2 CR. EFI. Zero deck and .042 quench with "D" dish piston. Truly "street driven" including summer trip from IL to CA and back in 9 days. Desert temps at sea level to freezing over 7500'. I ran the Silver State route backwards. Did fine. Also run hard for extended laps on a road course. With this combo, I would not want more compression for extended street or extended road course driving.
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Re: high compression, NA street combos-pump 93
[Re: 451Mopar]
#2640036
04/02/19 08:10 AM
04/02/19 08:10 AM
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Joined: Nov 2006
Posts: 1,074 Manitoba Canada
67autocross
super stock
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super stock
Joined: Nov 2006
Posts: 1,074
Manitoba Canada
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There is a guy on forabodies only that has a 360 with aluminum heads with I think 11.3ish compression and he claims it has 1000s of miles on 87 octane,,, he posts quite a bit about calculating DCR along with how gear ratios should be considered etc.
A new iron curtain drawn across the 49th parallel
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Re: high compression, NA street combos-pump 93
[Re: moparx]
#2640041
04/02/19 08:18 AM
04/02/19 08:18 AM
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Joined: Jan 2003
Posts: 13,402 Marion, South Carolina [><]
an8sec70cuda
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 13,402
Marion, South Carolina [><]
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Hemis are more tolerant to detonation than a wedge supposedly. My hemi is 11:1 and runs great on pump 93 (9.50s at 140 mph). Never tried any less octane. It slows down a tenth and about 1.5 mph on 112 race fuel, but it goes a whole lot faster when I turn the nitrous on.
CHIP '70 hemicuda, 575" Hemi, 727, Dana 60 '69 road runner, 440-6, 18 spline 4 speed, Dana 60 '71 Demon, 340, low gear 904, 8.75 '73 Chrysler New Yorker, 440, 727, 8.75 '90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt '06 GMC 2500HD LBZ Duramax
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