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Iron heads, pump gas 93

Jeff_383

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I know its been asked before. But does 10.3 to 1 with closed chamber, flat tops, with a moderate cam size 247/255 110 constitute living on pump 93. Not a race car at all. B body with 3.xx gears and a 4 speed. Now its a 499, not a 440.
 
My opinion is better fuel equals better performance. I wouldn't try to run any less than 93 and that's questionable.
 
I think you are nearing the ragged edge, it will take a good tune, and maybe a little soft on total timing. You do have one advantage, you dont have to try on 91 octane 10% california cat pee.
I have a 10 1/2 iron head 440 with the .557 mopar solid, and i sweeten the cat pee a little with 100LL avgas.
 
I think you are nearing the ragged edge, it will take a good tune, and maybe a little soft on total timing. You do have one advantage, you dont have to try on 91 octane 10% california cat pee.
I have a 10 1/2 iron head 440 with the .557 mopar solid, and i sweeten the cat pee a little with 100LL avgas.
Wish I could get blue gas around me...
 
Anywhere under 12-1 compression is fine on pump gas
I have to disagree, no red X, just my opinion. I had a 68 RR Hemi 4-speed with 12:1 compression that would rattle like hell with anything less than 100 octane. Also my 68 Hemi Dart 12.5:1 has to have at least 110 octane and 115 is better. Just saying what's in my world.
 
I'm not wanting anything but pump premium for this. I might just wait and get some aluminum heads for this project. Although I do like the idea of the old iron heads, just for kicks. I don't need to win races, just cruising
 
What is pump premium in your area? If it's 93, tune it for it and go. The iron heads won't hurt you if tuned properly. Or use a thicker head gasket to get you closer to 10.0 compression.
 
Im running 10.3 with closed chambered heads and the .528 mechanical cam. No problems. Whats your quench?
 
Wish I could get blue gas around me...
Sshh, dont tell nobody. I bring it back from a tiny selfserve airport near home in az, when i go back to cali. The essentially race gas is about 40 cents more than pump 91 in ca. I bring back az diesel too.
 
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Thats what i was gonna ask!
Quench is kinda an enigma to me.

Pistons are flat top 6cc reliefs, chambers would be closed at 76cc, and pistons are .060 in the whole. With the .051 gaskets I came up with 10.38.
 
Quench is kinda an enigma to me.

Pistons are flat top 6cc reliefs, chambers would be closed at 76cc, and pistons are .060 in the whole. With the .051 gaskets I came up with 10.38.
Okay, that answers the question. With that deck height you essentially have no quench to lose, so if you want to lower the compression a bit with a thicker head gasket, you can. Quench wont be adversely affected.
Personally, i would shoot for 9 3/4-10 if you dont want to mix in a booster.
 
The 247/255 at .050 does not matter as much as the seat timing. The .050 isn't much help, cams can vary 20 degrees at the seat and have a similiar .050. You need to know when the intake valve is closed at .006. Also there are lots of details missing on the build. It has the potential to work, but could also be 1/2 point high.
 
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.040 as opposed to .060 makes it 10.7 or 11 with .051 or .039 gaskets. That's a bit high for a car that'll be lugging in summer heat
 
Is it built yet? The best way to get quench is get a flat top with a cup to lower the compression verse dropping the entire piston down the hole or by thicker gaskets.
 
Oh the shortblock is together. I'm looking to toss together some pieces I have laying around to make a new cruiser engine.
 
Did you measure the cc on the heads?
You can't just go by published numbers.
If they are really 76 then
I would look for 906 or 452 heads.
 
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