Max compression?
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Senior User
Joined: Sep 2002
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From: mt. shasta california
Max compression?
Is there a maximum compression allowed on iron heads on a 460? I have a 77 460 and the pistons are 9.7:1, someone said that I needed aluminum heads to run that kind of compression, but I thought it sounded hokey so I thought that I would ask.
thx
erk
thx
erk
Senior User
Joined: Jan 2003
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Max compression?
The compression that you want to run is controlled by the quality/octane of fuel you will be feeding the motor. 9.7:1 maybe a little high for 87 octane, but not 93. As to what an iron head can take for compression 12:1 isn't a problem. I ran iron heads at 14:1, but O ringed the block on that motor, and used 118 octane fuel. As for the aluminum head, they say you can go 1 point higher in compression, so if 9:1 works with 87 octane with a iron head, then 10:1 would be okay with the aluminum head. FYI, every point of compression you increase your spark plugs should be 1 range colder.
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Senior User
Joined: Sep 2002
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From: mt. shasta california
Max compression?
Thanks a bunch, the guy told me that I would have to run aviation fuel! I knew I would have to run higher octane fuel but not like that. He was kind of a jerk anyway.
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Joined: Mar 2002
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From: Sapulpa
Max compression?
9.7:1 is a little high for todays cars, but not that high. 35 years go that was low compression! Alot of performance cars run more then that, and use premium fuel. Use high octane and watch your timing/advance curve. As for the iron heads, my 429 has D0VE-A heads which are iron, and had 11.5:1 compression. Granted we had leaded fuel then, but it held up to 70k miles and no wear inside. Someone read too many magazines that would lead you to think you need t orun octane boost and titanium rods and alloy heads, etc to make it hold up. Read thru this forum, all sorts of guys are running that much or more compression. The pistons I plan to order should drop my ratio to around 9.7to 10.0:1.
Postmaster
Joined: Aug 2001
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From: Nevada
Max compression?
There are a lot of different factors involved when determining what c/r can be used with pump gas. Quench is always the primary criterion. With zero deck, a long duration cam, clean combustion chambers and a reasonable ignition advance curve, many people are running 11.1:1 with iron heads. You shouldn't have any problem with 9.6:1 unless the piston is way down in the cylinder.
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Joined: Apr 2001
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From: texarkana, tx
Max compression?
erikl85 -
Just my 2 cents worth; I've run 12.5 with a 5:33 rear and floating pins with iron heads (daily driver from Smyrna to Altanta) without any problem - but when I did, I was able to get HIGH octane fuel.... and I think gas at that time was about 50 cents a gallon....
Just my 2 cents worth; I've run 12.5 with a 5:33 rear and floating pins with iron heads (daily driver from Smyrna to Altanta) without any problem - but when I did, I was able to get HIGH octane fuel.... and I think gas at that time was about 50 cents a gallon....
