Re: NORMAL COMPRESSION???
[Re: Labratt]
#841572
10/29/10 05:51 PM
10/29/10 05:51 PM
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Joined: Nov 2003
Posts: 6,293 Rock Springs
Bob_Coomer
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There might be, but hard to say when you have large overlap cams bleeding compression out the exh valve. When you test, make sure you run the test the same way. Like warm the engine up, and test with the carb at WOT. Make sure the battery doesnt run down so you have the same cranking power. This can effect the numbers, or if the engine cools etc. Look at each cylinder and they should be with in 5% of all others. I like my race engine in the 225-250 lbs + range. I healthy street engine should approach 200 psi. But many factors come in play here
[color:"red"]65 Hemi Belvedere coming soon [/color] [color:"#00FF00"]557" Indy engine 1.07 60ft 144mph in the 8th 2100 lbs package [/color]
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Re: NORMAL COMPRESSION???
[Re: Bob_Coomer]
#841576
10/29/10 07:24 PM
10/29/10 07:24 PM
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Joined: Jan 2003
Posts: 4,616 Kissimmee Fl.
dusturbd340W5
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my 14-1 small block stroker with a solid roller with 267/272 @ 50 only has 190# and the leakdown is less than 3% and it runs 6.32 at 109 in the 1/8 in a car that is 2975 lbs.
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: Bob_Coomer]
#841577
10/29/10 07:25 PM
10/29/10 07:25 PM
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Joined: Apr 2010
Posts: 1,049 ohio
all spooled up
super stock
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super stock
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ohio
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my small block 230-235 psi cam is solid roller 650 lift duration at .020 in 296 exh 303 @ .050 263 270 in at 106
Last edited by hookd; 10/29/10 08:53 PM.
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Re: NORMAL COMPRESSION???
[Re: all spooled up]
#841579
10/29/10 08:58 PM
10/29/10 08:58 PM
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Joined: Jan 2007
Posts: 3,695 nc
emarine01
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nc
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Quote:
my small block 230-235 psi cam is solid roller 650 lift duration at .020 in 296 exh 303 @ .050 263 270 in at 106
Whats the compression ratio?
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Re: NORMAL COMPRESSION???
[Re: emarine01]
#841580
10/29/10 09:02 PM
10/29/10 09:02 PM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
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Canton, Ohio
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Quote:
Quote:
my small block 230-235 psi cam is solid roller 650 lift duration at .020 in 296 exh 303 @ .050 263 270 in at 106
Whats the compression ratio?
Based on the PSI though, I will guess, 13.5 or more
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Re: NORMAL COMPRESSION???
[Re: Thumperdart]
#841581
10/29/10 09:25 PM
10/29/10 09:25 PM
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Joined: Dec 2007
Posts: 10,542 BROOK PARK, OH
WILD BILL
Senior Member of the Junior Dragster Club
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Senior Member of the Junior Dragster Club
Joined: Dec 2007
Posts: 10,542
BROOK PARK, OH
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Quote:
Guess our junk`s wore out.
No,
Just points to how inaccurate a compression test is at telling you anything.
About the only thing you can learn from one is if you took one and wrote it down when the engine was built and then compared it to when you think you may have a problem.
I prefer a leak down test myself.
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Re: NORMAL COMPRESSION???
[Re: Labratt]
#841585
10/30/10 01:37 AM
10/30/10 01:37 AM
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Joined: Jan 2003
Posts: 6,591 Canton, Ohio
Sport440
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Thats more like it. On one of your other threads you registered 185 PSI witch I felt was high for your combo. IMO with around 10.25 Comp and that 262* cam your 170-175 PSI is in the normal range for the combo. Maybe even a little high. 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
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Re: NORMAL COMPRESSION???
[Re: Bob_Coomer]
#841586
10/30/10 10:44 AM
10/30/10 10:44 AM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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New York
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large overlap cams bleeding compression
How exactly does this happen?
Boffin Emeritus
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Re: NORMAL COMPRESSION???
[Re: polyspheric]
#841587
10/30/10 10:56 AM
10/30/10 10:56 AM
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Joined: Feb 2005
Posts: 4,333 Prospect, PA
BSB67
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Prospect, PA
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Quote:
large overlap cams bleeding compression
How exactly does this happen?
...out the exhaust valve" ???????
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Re: NORMAL COMPRESSION???
[Re: Labratt]
#841588
10/30/10 11:07 AM
10/30/10 11:07 AM
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Joined: Feb 2005
Posts: 4,333 Prospect, PA
BSB67
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Quote:
I just checked a couple of cylinders for S&G's! One was 175psi..the other was 173 or so! Didn't know about holding the carb open,though! Thanks fella's! RandyB
If your doing it for S&G, and you like data, pick a cylinder, get a good consistant technique and baseline numbers, then change your intake lash plus 0.004" and minus 0.004". And then of course report back
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Re: NORMAL COMPRESSION???
[Re: BSB67]
#841590
10/30/10 12:24 PM
10/30/10 12:24 PM
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Joined: Oct 2007
Posts: 4,219 New York
polyspheric
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New York
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...out the exhaust valve" ???????
Which cam is that where the exhaust valve is open during the compression stroke?
Boffin Emeritus
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