Re: High compression in a big inch street motor
[Re: rickseeman]
#2835341
10/20/20 10:44 PM
10/20/20 10:44 PM
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Joined: Jan 2008
Posts: 35 Livonia,MI
1968fury
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Look into piston coating,cylinder head chamber and valve coatings, wide lsa cams to reduce cylinder pressure. Fuel injection setups that retard the timing if need be when it starts to detonate. $$$$$$ is it going to be worth it on a street car probably not.
71 scamp 340 509 cam 456 gear,68 fury1 318 3spd on the tree,50 merc flathead 3x2 3spd w/overdrive
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Re: High compression in a big inch street motor
[Re: 1968fury]
#2835632
10/21/20 01:34 PM
10/21/20 01:34 PM
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Joined: Feb 2013
Posts: 154 Canada
cuda499
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Ive ran 12:1 on pump gas without any issues.... But pump gas varies from state to state, your camshaft will play a large roll in bleeding off some of the cylinder pressure... I usually use pumping compression for a good indication for pump gas. Ive seen multiple engines make a 1000 hp on pump gas naturally aspirated. Both were close to 600 inches.
Last edited by cuda499; 10/21/20 02:06 PM.
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Re: High compression in a big inch street motor
[Re: quickd100]
#2836069
10/22/20 12:39 PM
10/22/20 12:39 PM
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Joined: Jul 2004
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Thumperdart
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I have a customer with a Pettis 572 w/11.7 compression races on 94 pump and makes close to 1000hp based on it's 8.84 et at 151 mph at 3450 lbs with a pretty big 800 lift cam. so the RIGHT combo of parts can obviously work and his plugs look great so far......
72 Dart 470 n/a BB stroker street car `THUMPER`...Check me out on FB Dominic Thumper for videos and lots of carb pics......760-900-3895.....
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Re: High compression in a big inch street motor
[Re: rickseeman]
#2836095
10/22/20 01:44 PM
10/22/20 01:44 PM
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JERICOGTX
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I think you can run as high of a compression as you want with pump gas if you weren't ever going to get on it. Some of the big hitters on Drag Week run 15:1 compression, but they run race gas on the street all week. Curt Johnson is a prime example of this, and his 632 CI engine with LOTS of compression, runs race gas all week. He told us if he tries to run any type of pump gas through it, it will wash the rings out right away. He changes oil every day as well.
69 GTX
68 Road Runner
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Re: High compression in a big inch street motor
[Re: JERICOGTX]
#2836110
10/22/20 02:08 PM
10/22/20 02:08 PM
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Posts: 13,376 Marion, South Carolina [><]
an8sec70cuda
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I think you can run as high of a compression as you want with pump gas if you weren't ever going to get on it. Some of the big hitters on Drag Week run 15:1 compression, but they run race gas on the street all week. Curt Johnson is a prime example of this, and his 632 CI engine with LOTS of compression, runs race gas all week. He told us if he tries to run any type of pump gas through it, it will wash the rings out right away. He changes oil every day as well. Wow, I can't imagine what it costs him to do Drag Week! That's ridiculous.
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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Re: High compression in a big inch street motor
[Re: an8sec70cuda]
#2836137
10/22/20 03:07 PM
10/22/20 03:07 PM
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JERICOGTX
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I think you can run as high of a compression as you want with pump gas if you weren't ever going to get on it. Some of the big hitters on Drag Week run 15:1 compression, but they run race gas on the street all week. Curt Johnson is a prime example of this, and his 632 CI engine with LOTS of compression, runs race gas all week. He told us if he tries to run any type of pump gas through it, it will wash the rings out right away. He changes oil every day as well. Wow, I can't imagine what it costs him to do Drag Week! That's ridiculous. LOTS!!! We figured it out, to around 3K for fuel alone. But he has won his class 7, or 8 times. He has the formula figured out. He one year built a Pump gas engine, to minimize maintenance. Won his class yet again. He got bored, and the next year he had a 15:1+ engine again. He told me they put a 3-4K chip on the high side of the MSD for street driving. Didn't leave any room for goofing off, and was easier on the valvetrain. If anyone ever gets a chance to talk with Curt, do it. You will not be disappointed.
69 GTX
68 Road Runner
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Re: High compression in a big inch street motor
[Re: quickd100]
#2836155
10/22/20 03:46 PM
10/22/20 03:46 PM
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Blusmbl
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For what it's worth, my advice.....keep the compression on the low side. You will never hear the detonation before it breaks stuff. x2. Modern stuff does more than just retard timing to keep the engine from pinging, most of the engines that have high cylinder pressures (either high comp NA stuff or boosted applications) will limit engine load to keep them out of detonation. I don't know of any mass produced OEM car engine that is much past 12:1 NA. On a high output motor it isn't worth the risk.
'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
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Re: High compression in a big inch street motor
[Re: Blusmbl]
#2870603
01/07/21 06:57 PM
01/07/21 06:57 PM
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572charger
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my hemi was 12.2 to 1 comp ran on pumpgas always 93 octane at 30 degrees of timming it ran 9.60s at 140+ mph i eaven sprayed it into the 8s on pumpgas and 22 degrees of timming
606 hemi pump gas best 9.60 at 142mph on motor 05 hemi daytona 1500 go-mango 4wd quadcab 2007 hotrod mag pump gas drags runner up, roadkill nights dodge big tire winner 2018 2019 back to back
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Re: High compression in a big inch street motor
[Re: polyspheric]
#2870851
01/08/21 07:31 AM
01/08/21 07:31 AM
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quickd100
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W/r/t "big cam bleeding off cylinder pressure" It does reduce CCP... all the way up to 3,000 RPM (more or less, depending on too many variables to list, but stops well before the torque peak). After that, it increases cylinder pressure - that what it's for. It doesn't always need 5 seconds to "build heat", the piston damage can occur in 1 second. How True! Unless you have an unlimited supply of 'good' fuel to ALWAYS use you are playing with dynamite. You will never hear it detonate, the damage can occur in a blink of an eye. A big inch street motor with a sane compression ratio will make way more torque than you can stick to the ground. My 605 makes 750+ ftlbs at 3500 rpm.
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Re: High compression in a big inch street motor
[Re: quickd100]
#2870868
01/08/21 08:40 AM
01/08/21 08:40 AM
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Joined: Jan 2003
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B3422W5
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For what it's worth, my advice.....keep the compression on the low side. You will never hear the detonation before it breaks stuff. You also may not be able to always access the fuel your motor needs to stay happy. On a big stroker it will make WAY more power than you can safely use on the street, you'll never notice the difference in a point or two in compression. My old truck tries to kill me on a regular basis just gently rolling into the throttle. Compression will make a big difference in power and torque, at the track and in the street. I live in Michigan so have only driven my cars in the summer, but, if given the chance, i much prefer running race gas. Its easy to get, consistent compared to pump swill with who knows what in it.iItsvnever hard to access I drive a few hundreds of miles on the street every summer, typically not thousands of miles, so at 7 bucks a gallon the cost to run race gas isn't that big of deal.i figure if i cant afford to put fuel in it, i am probably involved in a hobby i cant afford. I have had several engines where i raised compression and saw it immediately at the track. My project over the winter here will yet again. Going from a 360 to a 418, Changing nothing other than the cubes and compression, little bit of head work. Heads will be way to small for 418 inches. But going from 10 to 1 to 12.5 to 1 compression. I am expecting big gains for primarily that reason. Figure the compression alone is probably 40-45 horsepower. Same cam, headers, carb, etc, etc
Last edited by B3422W5; 01/08/21 10:09 AM.
69 Dart GTS A4 Silver All steel, flat factory hood, 3360race weight 418 BPE factory replacement headed stroker, 565 lift solid cam Best so far, 10.40 @127 1/4 1.41 best 60 foot 6.60 at 103.90 1/8
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Re: High compression in a big inch street motor
[Re: 73DAD]
#2870926
01/08/21 10:20 AM
01/08/21 10:20 AM
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Joined: Jan 2012
Posts: 2,658 Stuttgart, Arkansas
rickseeman
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Can Hemi's get away with more compression than a Wedge? That's my understanding
2011 Drag Pak Challenger
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Re: High compression in a big inch street motor
[Re: rickseeman]
#2870972
01/08/21 11:08 AM
01/08/21 11:08 AM
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Posts: 1,145 Arizona, USA
gsmopar
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605 Hemi, 11:1, no signs of detonation on the plugs or audible pinging on 92 octane and 32 degrees of timing. IMG_8495 by Greg Ault, on Flickr
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Re: High compression in a big inch street motor
[Re: 73DAD]
#2871024
01/08/21 12:10 PM
01/08/21 12:10 PM
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Joined: May 2004
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Dragula
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Can Hemi's get away with more compression than a Wedge? Yes...Typically 12:1 is no issue on pump gas....I am at 11.6:1 on my big Hemi...No issues with that.
Last edited by Dragula; 01/08/21 12:29 PM.
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Re: High compression in a big inch street motor
[Re: polyspheric]
#2871058
01/08/21 12:51 PM
01/08/21 12:51 PM
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Hemi_Joel
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W/r/t "big cam bleeding off cylinder pressure" It does reduce CCP... all the way up to 3,000 RPM (more or less, depending on too many variables to list, but stops well before the torque peak). After that, it increases cylinder pressure - that what it's for. It doesn't always need 5 seconds to "build heat", the piston damage can occur in 1 second. Dead on. I've driven high compression motors on the street using not enough octane, with the plan being to stay out of the throttle. The question is do you have enough a self-discipline when an impromptu challenge arises? I don't. It's like being alone in a motel room with a lingerie clad super model and agreeing not to look at her.
[img]http://i.imgur.com/boeexFms.jpg[/img]31 Plymouth Coupe, 392 Hemi, T56 magnum RS23J71 RS27J77 RP23J71 RO23J71 WM21J8A I don't regret the things I've done. I only regret the things I didn't do. "Wise men talk because they have something to say; fools because they have to say something. ~ Plato"
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Re: High compression in a big inch street motor
[Re: gsmopar]
#2871377
01/08/21 09:51 PM
01/08/21 09:51 PM
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Joined: Jan 2004
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cudaman1969
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605 Hemi, 11:1, no signs of detonation on the plugs or audible pinging on 92 octane and 32 degrees of timing. IMG_8495 by Greg Ault, on Flickr What is your piston comp height? I have ta buy some pistons for my 572 Hemi (7.1 rod)
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Re: High compression in a big inch street motor
[Re: Hemi_Joel]
#2871399
01/08/21 11:07 PM
01/08/21 11:07 PM
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Joined: May 2004
Posts: 12,397 Taxes & Virus's R-US, NY
Dragula
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W/r/t "big cam bleeding off cylinder pressure" It does reduce CCP... all the way up to 3,000 RPM (more or less, depending on too many variables to list, but stops well before the torque peak). After that, it increases cylinder pressure - that what it's for. It doesn't always need 5 seconds to "build heat", the piston damage can occur in 1 second. Dead on. I've driven high compression motors on the street using not enough octane, with the plan being to stay out of the throttle. The question is do you have enough a self-discipline when an impromptu challenge arises? I don't. It's like being alone in a motel room with a lingerie clad super model and agreeing not to look at her. Well I said earlier 12:1 Hemi on pump gas is no issue, save one, ever driven a +800hp on the street? And if there was a super model in the hotel room with me, in lingerie, I was only looking to make sure it was all female..I am on a budget after spending all that money on a Hemi...
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