Pistons- Form follow function?
Thread Starter
Le Mans Master
Joined: Apr 2000
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From: B'Ville NY
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St. Jude Donor '05
Pistons- Form follow function?
I will be needing to have custom pistons made for my new engine that's in the works. I also will be ordering new heads.
So here's the question. I realize that by going with a smaller chamber in the head, it'll raise the compression, but what if yoiu went with a larger chamber and a small dome piston? Is there advantages to dome vs flat top pistons/ large vs small chamber heads?
I think I want to end up with around 11.0:1 compression. I understand that with aluminum heads & MFI I should have no problem with detentantion(sp?) with pumpgas (91 oct).
TIA :cheers:
So here's the question. I realize that by going with a smaller chamber in the head, it'll raise the compression, but what if yoiu went with a larger chamber and a small dome piston? Is there advantages to dome vs flat top pistons/ large vs small chamber heads?
I think I want to end up with around 11.0:1 compression. I understand that with aluminum heads & MFI I should have no problem with detentantion(sp?) with pumpgas (91 oct).
TIA :cheers:
Team Owner
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From: Reno Nevada
2024 C3 of the Year Finalist- Modified
Re: Pistons- Form follow function? (SmokedTires)
You have some real figuring to do. Your stroke isn't that uncommon. But if your specifying pistons you really need to have the block deck height. So they can make pistons near "Zero" You have to keep the quench right at .038 which would be a common Felpro compressed height. Your going to need to know your finished chamber cc because 64 cc heads Zero deck and blah ba blah.
Puts you right at 11.1. according to automath on smokemup! Right where you need to be with any kind of roller cam. You need to look at this site http://cochise.uia.net/pkelley2/
Don't even think about dome or big cc. 11.4 or less is good with a 3.75 stroke and anything over 284 advertised intake duration @ 232 degrees at .050 on 91 octane. Your 3.6ish stroke will even use less degree cam on 91
Puts you right at 11.1. according to automath on smokemup! Right where you need to be with any kind of roller cam. You need to look at this site http://cochise.uia.net/pkelley2/
Don't even think about dome or big cc. 11.4 or less is good with a 3.75 stroke and anything over 284 advertised intake duration @ 232 degrees at .050 on 91 octane. Your 3.6ish stroke will even use less degree cam on 91
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 7,562
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From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Re: Pistons- Form follow function? (gkull)
Thanks George. I'm looking at te Dart Little M block so I'll have an idea after the machinist preps the block. :)
Le Mans Master
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From: Park Ridge IL
Re: Pistons- Form follow function? (SmokedTires)
I ran 11.3 CR in my NA SBC 427 on 93 octane and never had a problem with detonation.
I believe you're better off with a "flat top" or even partially dished piston, and a small cylinder head combustion chamber. The idea is to maximize quench area to aid combustion efficiency and aid against detonation. Piston domes often interfere with the flame travel, hampering combustion efficiency, and potentially promoting detonation.
I believe you're better off with a "flat top" or even partially dished piston, and a small cylinder head combustion chamber. The idea is to maximize quench area to aid combustion efficiency and aid against detonation. Piston domes often interfere with the flame travel, hampering combustion efficiency, and potentially promoting detonation.
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Re: Pistons- Form follow function? (Monty)
Smoked tires: Wether or not 11 to 1 will be too much for 91 octane depends on a lot of variables. Monty's 11.3 on 93 was with a very well planned out motor and a very large duration cam, 255 + at .050 if I remember correctly. If you run a cam of 230 ish at .050 and 11 to 1 on 91 octane it will probably ping like crazy.
I ran a high lift short duration solid roller with aluminum heads 242 and 248 at .050 and it had slight detonation problems on 91 with a little over 10.25 to 1.
For the miniscul amount of power between 10.25 and 11 to 1 (approx 3%) (unless you don't mind a little octane boost) it is best to error on the safe side.
I ran a high lift short duration solid roller with aluminum heads 242 and 248 at .050 and it had slight detonation problems on 91 with a little over 10.25 to 1.
For the miniscul amount of power between 10.25 and 11 to 1 (approx 3%) (unless you don't mind a little octane boost) it is best to error on the safe side.
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 7,562
Likes: 9
From: B'Ville NY
Cruise-In III Veteran
St. Jude Donor '05
Re: Pistons- Form follow function? (69 N.O.X. RATT)
69NOX- Thanks fr the info. I ctually errored on the gas octane, I meant 93 octane since that is available at most stations :) . I currently run Sunoco 94 as much a possible.
I appriecate the info about the pinging though, thanks.
I appriecate the info about the pinging though, thanks.
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