compression question-.030 over 440
#2605937
01/13/19 04:01 PM
01/13/19 04:01 PM
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Joined: Sep 2003
Posts: 20,235 north of coder
moparx
OP
"Butt Crack Bob"
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OP
"Butt Crack Bob"
Joined: Sep 2003
Posts: 20,235
north of coder
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can an aluminum head [pocket ported eddy performer rpm] with an 11.0:1 CR be ran with 93 pump gas [with adding ?? amount of race gas or additive] in a 4000lb charger, MP590 cam, 3.91gear by backing timing down to around 18[or so] initial, 32-34 total, without detonation ? i know this is on the ragged edge, but just asking. how much will this affect performance ? a head gasket change can [i think] lower the CR to around 10.5:1 or so. other suggestions ? TIA
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Re: compression question-.030 over 440
[Re: dvw]
#2606064
01/13/19 07:25 PM
01/13/19 07:25 PM
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Joined: Sep 2003
Posts: 20,235 north of coder
moparx
OP
"Butt Crack Bob"
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OP
"Butt Crack Bob"
Joined: Sep 2003
Posts: 20,235
north of coder
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well guys, i screwed up. [well that's not a surprise ! ] it's 11.6. zero deck, flat tops, 79cc heads, .019 head gaskets. gotta change head gaskets. so guessing .040-.050 thick to lower it to around 10.5 or so ? next would be, how much torque will be lost ? sorry for the screwup on my end !
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Re: compression question-.030 over 440
[Re: dvw]
#2606068
01/13/19 07:31 PM
01/13/19 07:31 PM
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Joined: Feb 2005
Posts: 4,333 Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,333
Prospect, PA
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I'd bet that combo would come very close to running on Pump gas. We run 10.5-1 with a Mopar .557 cam, full timing. Doug Yup. I'm at 10.8 CR, pretty late intake closing, blows about 195 psi, and it works, but on the edge.
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Re: compression question-.030 over 440
[Re: BSB67]
#2606080
01/13/19 07:57 PM
01/13/19 07:57 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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If you are up & running (nice weather will be here before you know it) you might just proportion in a bigger % of race gas. On a side note wallace raceing & united machine have very user friendly CR calculators (& other services).
live every 24 hour block of time like it's your last day on earth
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Re: compression question-.030 over 440
[Re: moparx]
#2606082
01/13/19 08:01 PM
01/13/19 08:01 PM
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Joined: Mar 2006
Posts: 9,973 MI, usa
dvw
master
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master
Joined: Mar 2006
Posts: 9,973
MI, usa
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The combo I spoke of runs a 4.10, old Weiand 2x4, 2 600 Eddy's, untouched Eddy RPM heads, headers, and a decent converter in a 65 Belvedere, 3750lb race weight. Been 11.30's. Doug
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Re: compression question-.030 over 440
[Re: moparx]
#2606130
01/13/19 09:29 PM
01/13/19 09:29 PM
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Joined: Jun 2008
Posts: 3,916 usa
lewtot184
master
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master
Joined: Jun 2008
Posts: 3,916
usa
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well guys, i screwed up. [well that's not a surprise ! ] it's 11.6. zero deck, flat tops, 79cc heads, .019 head gaskets. gotta change head gaskets. so guessing .040-.050 thick to lower it to around 10.5 or so ? next would be, how much torque will be lost ? sorry for the screwup on my end ! 1cc will change static compression about 1/10th of a point, some slight variables. you'll still be 11:1 with gasket change. add in some carbon build-up and your back the 11.5+. that's internet/magazine pump gas doable; but not in the real world.
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Re: compression question-.030 over 440
[Re: lewtot184]
#2606161
01/13/19 10:08 PM
01/13/19 10:08 PM
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Joined: Jul 2004
Posts: 653 Fredericksburg Va
plycuda
mopar
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mopar
Joined: Jul 2004
Posts: 653
Fredericksburg Va
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well guys, i screwed up. [well that's not a surprise ! ] it's 11.6. zero deck, flat tops, 79cc heads, .019 head gaskets. gotta change head gaskets. so guessing .040-.050 thick to lower it to around 10.5 or so ? next would be, how much torque will be lost ? sorry for the screwup on my end ! 1cc will change static compression about 1/10th of a point, some slight variables. you'll still be 11:1 with gasket change. add in some carbon build-up and your back the 11.5+. that's internet/magazine pump gas doable; but not in the real world. so if you go to a .060 cometic summit sells. Its around 15cc compared to .019 4.5cc it would put you down 1 point to 10.5
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Re: compression question-.030 over 440
[Re: moparx]
#2606396
01/14/19 12:53 PM
01/14/19 12:53 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,531
So. Burlington, Vt.
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Not to mention what a “wonderful” street combo that would make...... 10.5cr, 590 cam, 4000lb car.
As far as getting the cr pump gas friendly and still have good quench....... the numbers work out fine for me:
914- swept 10- gasket(.040) 1- area above rings 6- typical valve pockets 79- chamber ———— 1010- total 96- total minus swept ———— 10.52:1- 1010/96
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: compression question-.030 over 440
[Re: moparx]
#2606432
01/14/19 01:51 PM
01/14/19 01:51 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,531
So. Burlington, Vt.
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I thought the “ “ were self explanatory.
It wouldn’t be my idea of a good combo, but I’m sure there are people running similar set ups that they’re happy with.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: compression question-.030 over 440
[Re: moparx]
#2607114
01/15/19 07:43 PM
01/15/19 07:43 PM
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Joined: Jan 2003
Posts: 24,562 Brookeville, Md
Mr.Yuck
Not enough dumb comments...yet
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Not enough dumb comments...yet
Joined: Jan 2003
Posts: 24,562
Brookeville, Md
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can an aluminum head [pocket ported eddy performer rpm] with an 11.0:1 CR be ran with 93 pump gas [with adding ?? amount of race gas or additive] in a 4000lb charger, MP590 cam, 3.91gear by backing timing down to around 18[or so] initial, 32-34 total, without detonation ? i know this is on the ragged edge, but just asking. how much will this affect performance ? a head gasket change can [i think] lower the CR to around 10.5:1 or so. other suggestions ? TIA I ran an 11.25:1 Stage VI headed (very worked) 440-6 on the street w/ 93 w/o issue. I did have a Meth/H2O injection kit for the track. Much cheaper than mixing gas. I had the timing at 37* all in at 2400. car was a 70 charger 3800+lbs 3800 stall 3.91's went 11.28@121
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