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Re: 440 Compression Ratio Advice
[Re: bobs66440]
#1150582
01/05/12 03:36 PM
01/05/12 03:36 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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after reviewing your cam selection i don't think you have a real compression ratio problem. that cam is basically the old crane power-max 278. it has 5 degrees of advance ground into it and closes the intake valve within a degree or two of a stock magnum cam. your compression ratio with those pistons, 88cc head and .020 shim gasket will be around 9:1. mill .030 off the heads and you have 9.5:1. this should get the cranking cylinder pressure to around 160-170psi. i have a 440 that uses more cam than what you have at 9.3:1 compression ratio (using quench dome pistons) and 160psi cranking pressure and what it does to the rear tires with a 3.23 gear should be considered an "act of violence". the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
Last edited by lewtot184; 01/05/12 03:37 PM.
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Re: 440 Compression Ratio Advice
[Re: lewtot184]
#1150583
01/05/12 04:07 PM
01/05/12 04:07 PM
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Joined: Jan 2003
Posts: 75,125
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,125
A Banana Republic near you.
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Quote:
the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.
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Re: 440 Compression Ratio Advice
[Re: JohnRR]
#1150585
01/05/12 04:43 PM
01/05/12 04:43 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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Quote:
Quote:
the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.
john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.
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Re: 440 Compression Ratio Advice
[Re: lewtot184]
#1150586
01/05/12 04:48 PM
01/05/12 04:48 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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Quote:
Quote:
Quote:
the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.
john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.
I would not even worry about "quench" on an engine like this
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Re: 440 Compression Ratio Advice
[Re: lewtot184]
#1150587
01/05/12 06:03 PM
01/05/12 06:03 PM
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Joined: Jan 2003
Posts: 75,125
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,125
A Banana Republic near you.
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Quote:
Quote:
Quote:
the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.
john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.
I'm not saying anything other than an 8.93 compression engine with no quench should be able to be tuned to run on 93 , if he is set on getting it up to 9.5 then that is a different story all together.
My experience with the big summit cam and open chamber 906's with no quench was ok with super as long as I had the vac advance disconnected , I never got the chance to do much as the motor expired before early after the spring driving season started .
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Re: 440 Compression Ratio Advice
[Re: JohnRR]
#1150588
01/05/12 07:26 PM
01/05/12 07:26 PM
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Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
bobs66440
OP
top fuel
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OP
top fuel
Joined: Mar 2010
Posts: 1,880
Out in Left Field, NY
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Quote:
Quote:
Quote:
Quote:
the real issue i see is not cam or compression ratio, but the big quench distance. that won't be pump gas friendly.
With his 906 at 88-90 cc he will be under 9.0 , 8.93 at 88cc , pump gas shouldn't be an issue.
john, i'm not so sure here. i've tried the big quench distance before and couldn't get it to work. hopefully you guys are sharper than me. good luck.
I'm not saying anything other than an 8.93 compression engine with no quench should be able to be tuned to run on 93 , if he is set on getting it up to 9.5 then that is a different story all together.
My experience with the big summit cam and open chamber 906's with no quench was ok with super as long as I had the vac advance disconnected , I never got the chance to do much as the motor expired before early after the spring driving season started .
I don't mean to seem ignorant, though I'm a little confused. So, what you are saying is my set up with the stealth heads, at around 9.5:1 compression, will not be able to run on pump gas?? Or are you talking about the 906 heads?? Sorry about the dumb questions, but I'm on a steep learning curve.
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Re: 440 Compression Ratio Advice
[Re: bobs66440]
#1150589
01/05/12 09:18 PM
01/05/12 09:18 PM
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Joined: Feb 2005
Posts: 4,324
Prospect, PA
BSB67
master
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master
Joined: Feb 2005
Posts: 4,324
Prospect, PA
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Quote:
Or are you talking about the 906 heads??
Yes, they are
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