428 compression??
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Joined: Apr 2007
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From: Glenwood, IA
428 compression??
I have my engine at the machine shop and he wants to mill out new pistons to keep the compresson down to 9:1. I have always been told that 10:1 was fine for pump gas. At least using 91 octane. I want as much performance as I can get out of this thing. I am afraid that lowering it that low will hurt it alot. anybody have any facts regarding this?
Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
hey guys, trying to find out the compression ratio of my friends FE.
428, verified by stroke test. Bore is 4.16", which is, what, a .030" over 428 bore, right? Which makes it 434? Anyway, the pistons are flattops with very, very, minimal valve reliefs. He is using a std Fel-Pro blue head gasket. Eldelbrock aluminum heads with 72cc domes.
Thanks!
428, verified by stroke test. Bore is 4.16", which is, what, a .030" over 428 bore, right? Which makes it 434? Anyway, the pistons are flattops with very, very, minimal valve reliefs. He is using a std Fel-Pro blue head gasket. Eldelbrock aluminum heads with 72cc domes.
Thanks!
Tuned
Joined: Aug 2003
Posts: 286
Likes: 32
couple thoughts
I built my 428 for 9 to 1. I didn't want to ever worry about finding suitable gas and don't want to deal with detonation under load while towing. I went with forged pistons and cut a small dish in it to get the cr down. Most guys tell me I went a bit too low, but it works like a champ. I have no regrets.
It all depends on what you are building it for, your cam selection, etc.
Also, you should visit the fordfe.com web site. The guys over there recommend the Felpro 1020 head gasket specifically for aluminum heads. The Ford Motorsport headgasket is a FelPro 1020 (in fact it is printed right on it). It is available through Summit and costs about half what the FelPro is listed for.
It all depends on what you are building it for, your cam selection, etc.
Also, you should visit the fordfe.com web site. The guys over there recommend the Felpro 1020 head gasket specifically for aluminum heads. The Ford Motorsport headgasket is a FelPro 1020 (in fact it is printed right on it). It is available through Summit and costs about half what the FelPro is listed for.
Cargo Master
Joined: Jul 2003
Posts: 2,328
Likes: 14
From: Colorado
Thanks guys, I know everything that was just replied, except the ratios. That's not what I'm asking.
Can anyone verify the specific ratio with these 72cc domes and Fel Pro gasket combos?
The motor is what it is, he's not changing it, but the heads are going back on it in the next couple of weeks and I'm trying to find out if we should put thicker head gaskets on it to lower the compression a tad. I need numbers to decide if it would be worth it.
Thanks
Can anyone verify the specific ratio with these 72cc domes and Fel Pro gasket combos?
The motor is what it is, he's not changing it, but the heads are going back on it in the next couple of weeks and I'm trying to find out if we should put thicker head gaskets on it to lower the compression a tad. I need numbers to decide if it would be worth it.
Thanks
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Hotshot
Joined: May 2003
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From: south louisiana
I ran my 68 Merc's 390 (10.25 to 1) on 89 octane fuel with only a cam change. Crane 272* Energizer cam, stock C8AE-H heads, 12* initial ignition timing. No reason a 10-10.5 to 1 428 can't do it either.
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From: Colville, Washington
FWIW the 428 in my '66 is 10.04:1(measured it) 272 Energizer, Performer(not RPM, drat!!!), 750 Holley. I get pinging under load with regular(87) it is fine towing with premium(92).
How far down in the hole is the piston, it has a big effect on CR as well as quench.
How far down in the hole is the piston, it has a big effect on CR as well as quench.
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