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Re: Is 120 psi just too darn low?
[Re: RapidRobert]
#1023142
06/29/11 11:12 PM
06/29/11 11:12 PM
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Joined: Apr 2008
Posts: 212
Mid Michigan
Coronet-R/T-Rag
OP
enthusiast
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OP
enthusiast
Joined: Apr 2008
Posts: 212
Mid Michigan
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Quote:
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How much power do you think I would gain with another 30 pounds of cylinder pressure???????
Not sure but 120 is way too low & w alum heads you'd want more than 150. I would suggest a leakdown & check sealing/get a baseline & go from there
I'm sure the blow by isn't helping but the pistons are flat top .30 over with no valve reliefs so I'm guessing about 80 thous in the hole? I've got another short block that's 30 over with trw sick pack pistons. Would those give me more cylinder pressure?
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Re: Is 120 psi just too darn low?
[Re: Coronet-R/T-Rag]
#1023143
06/29/11 11:20 PM
06/29/11 11:20 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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You'd lose a slight bit from the 6 pack valve reliefs as opposed to flat tops w no reliefs but what's imp is the deck height on the six pack pistons. If it's alot close(er) to zero deck you may b in real good shape & even if not it'd b a fresh shortblock. Plug it all into KB's calculator. You want a SCR in the 10's
Last edited by RapidRobert; 06/30/11 12:22 AM.
live every 24 hour block of time like it's your last day on earth
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Re: Is 120 psi just too darn low?
[Re: Coronet-R/T-Rag]
#1023144
06/30/11 08:03 AM
06/30/11 08:03 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
Quote:
How much power do you think I would gain with another 30 pounds of cylinder pressure???????
Not sure but 120 is way too low & w alum heads you'd want more than 150. I would suggest a leakdown & check sealing/get a baseline & go from there
I'm sure the blow by isn't helping but the pistons are flat top .30 over with no valve reliefs so I'm guessing about 80 thous in the hole? I've got another short block that's 30 over with trw sick pack pistons. Would those give me more cylinder pressure?
Yes they will give plenty more compression, they will only be around .028 in the hole.
I did the same thing years ago took out some flat tops that were around .80" in the hole and put some sealed power "6pak" pistons that were about .028" down. You will be around 10-1, perfect.
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Re: Is 120 psi just too darn low?
[Re: Baxter61]
#1023147
06/30/11 01:16 PM
06/30/11 01:16 PM
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Joined: Apr 2008
Posts: 212
Mid Michigan
Coronet-R/T-Rag
OP
enthusiast
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OP
enthusiast
Joined: Apr 2008
Posts: 212
Mid Michigan
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Quote:
where is the cam degreed in at (if at all)? how are you doing the cranking test? with all plugs in or out? carb wired open or resting like at idle?
Cam was just set up dot to dot so not at all. Cranking test was warm with a couple plugs out. Carb resting at idle.
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Re: Is 120 psi just too darn low?
[Re: Coronet-R/T-Rag]
#1023148
06/30/11 01:48 PM
06/30/11 01:48 PM
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Joined: Nov 2004
Posts: 2,495
Oregon City, OR
Baxter61
top fuel
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top fuel
Joined: Nov 2004
Posts: 2,495
Oregon City, OR
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I would degree the cam first before spending money on other things. yea, your 440 isnt ideal with lower compression but that cam should still get you 150 psi cranking which from my amatuer tests is a minimum. As a side note but related, me and a buddy put a .509 in a 10:1 440 by "lining up the dots" put it on the dyno and it put down a whopping 296 hp and same tq and couldnt get the a/f ratio over 11:1 with a 750 carb and 67/68 jets. later did a cranking comp test and came up with 115, put some 915's to replace the 906's and got it up around 140 or 150, still way low. later pulled the motor out and checked the degree of the cam (borrowed tools from buddy) and found it was 14 degrees retarded even though the dots were perfectly lined up! I felt about 14 degrees retarded after that and I bought my own degree tools and have degreed every cam, including stock type cams/motors, since that point. sorry for getting long-winded. 
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Re: Is 120 psi just too darn low?
[Re: Coronet-R/T-Rag]
#1023149
06/30/11 02:46 PM
06/30/11 02:46 PM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Quote:
where is the cam degreed in at (if at all)? how are you doing the cranking test? with all plugs in or out? carb wired open or resting like at idle?
Cam was just set up dot to dot so not at all. Cranking test was warm with a couple plugs out. Carb resting at idle.
pull all the plugs, pull the coil wire and wire the carb wot. then do your compression test. yes degreeing the cam is important.
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Re: Is 120 psi just too darn low?
[Re: Challenger 1]
#1023150
06/30/11 07:03 PM
06/30/11 07:03 PM
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Joined: Jun 2011
Posts: 129
London Ontario Canada Eh
Dono
member
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member
Joined: Jun 2011
Posts: 129
London Ontario Canada Eh
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Quote:
Quote:
Quote:
where is the cam degreed in at (if at all)? how are you doing the cranking test? with all plugs in or out? carb wired open or resting like at idle?
Cam was just set up dot to dot so not at all. Cranking test was warm with a couple plugs out. Carb resting at idle.
pull all the all plugs, pull the coil wire and wire the carb wot. then do your compression test. yes degreeing the cam is important.
Cam over lap as well. When spinning higher RPM the compression can be much higher than at cranking. I am betting the cam timing and over lap is to much for that motor.
Don.
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