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Re: NORMAL COMPRESSION???
[Re: polyspheric]
#841591
10/30/10 12:36 PM
10/30/10 12:36 PM
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Joined: Feb 2005
Posts: 4,310
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,310
Prospect, PA
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Quote:
...out the exhaust valve" ???????
Which cam is that where the exhaust valve is open during the compression stroke?
I think you failed to understand my post. Obvously none, that's why there are the question marks. I'm quoting the other poster.
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Re: NORMAL COMPRESSION???
[Re: BSB67]
#841592
10/30/10 05:09 PM
10/30/10 05:09 PM
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Joined: Oct 2007
Posts: 4,206
New York
polyspheric
master
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master
Joined: Oct 2007
Posts: 4,206
New York
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You're right, sorry, yes I understood your comment to mean "Whaaaa?".
Was referring to prior comment.
Boffin Emeritus
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Re: NORMAL COMPRESSION???
[Re: polyspheric]
#841593
10/30/10 05:24 PM
10/30/10 05:24 PM
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Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
dusturbd340W5
master
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master
Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
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But, FWIW, the Calulater that Dodgem posted was Happy about by 20# PSI for my Combo. But with your engine specs, it was almost right on. mike  it's not even close for my motor and as stated my leak down is less than 3% so I know it is sealed up well I also know someone that there roundy round motor is well over 600hp and only 165 cranking compression.
70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake
best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4
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Re: NORMAL COMPRESSION???
[Re: dusturbd340W5]
#841594
10/30/10 05:34 PM
10/30/10 05:34 PM
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Joined: Jan 2003
Posts: 17,918
Akron, Ohio
ProSport
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 17,918
Akron, Ohio
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I run a big overlap pump gas cam, I get 150 cranking compression.  I put one gallon of 110 race gas in the tank when I race but don't need to. I've used lawn mower gas to drive to a local car show before, and still goes 9.80's. If I go E85 this winter, it will get a better cam for performance. 
1970 Challenger, all aluminum 528 Hemi, HDK suspension, Tremec 5 speed manual
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Re: NORMAL COMPRESSION???
[Re: Labratt]
#841595
10/30/10 05:44 PM
10/30/10 05:44 PM
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Joined: Apr 2006
Posts: 3,675
Akron, Ohio U.S.A.
roadhazard
master
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master
Joined: Apr 2006
Posts: 3,675
Akron, Ohio U.S.A.
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Quote:
BTW...how important is it to have the butterflies partially open,as Hardcore suggests? 
LABRATT, I feel it's very important. With the throttle closed can cause a restriction and produce lower than normal cranking compression readings 
My personal preferance is to set the carb @ WOT when testing. Usually I'll hold it open with a wire or use the return spring to hold it FWIW.
Don't forget to return the throttle closed before you start the motor again    
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Re: NORMAL COMPRESSION???
[Re: Dodgem]
#841597
10/30/10 08:52 PM
10/30/10 08:52 PM
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Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
dusturbd340W5
master
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master
Joined: Jan 2003
Posts: 4,616
Kissimmee Fl.
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yep carb wide open or removed and all 8 plugs removed and a battery charger hokked up and running is how I do it.
70 duster full chassis super pro 416 CNC Indybrock heads 727 w/brake
best so far 1.212 60 6.219 in 1/8 at 110.88 9.768 at 137.81 1/4
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Re: NORMAL COMPRESSION???
[Re: polyspheric]
#841598
10/30/10 09:05 PM
10/30/10 09:05 PM
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Joined: Dec 2008
Posts: 1,200
UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
Posts: 1,200
UK
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Quote:
large overlap cams bleeding compression
How exactly does this happen?
My thoughts exactly , overlap has no bearing on compression whatsoever.
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