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Re: "hate this piston design"
[Re: slantzilla]
#3206298
01/19/24 06:18 PM
01/19/24 06:18 PM
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Joined: Jan 2003
Posts: 14,499
So. Burlington, Vt.
fast68plymouth
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 14,499
So. Burlington, Vt.
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What is the purpose of those grooves? Contact Reduction Grooves
These grooves are machined into the top ring land above the top ring to minimize contact drag when the piston rocks over upon reversal. They add minimal volume to the crevice volume, and they also help resist detonation by disrupting flame travel into the crevice volume where pressure spikes might unseat the ring.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
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Re: "hate this piston design"
[Re: AndyF]
#3206386
01/19/24 11:28 PM
01/19/24 11:28 PM
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Joined: Sep 2018
Posts: 166
West Palm Beach, Florida
Craig J
OP
member
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OP
member
Joined: Sep 2018
Posts: 166
West Palm Beach, Florida
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The grooves are a good idea, but it looks like the top groove was too high. Maybe a design error, maybe a machining error. I don't really know without seeing them. Sometimes pictures don't show everything. I believe the pistons I have are just an older version of this one from 440source. This discussion now has me a bit curious....I am certainly not a professional engine builder, and have never had an engine assembled in my garage on a dyno. Due to covid parts shortages I have a not very good combination in my car: 440 +0.032 (yes...32 over) with very old style L2295F30 TRW pistons, LY rods, 75 cc Performer RPM heads, a Hughes "real 6 pack" cam, performer 440 intake (fits under a flat e body hood) and iron hp manifolds. It has sky high cranking compression, but I think it would probably be safe on an engine dyno up to 6000 rpm with 112 octane fuel and conservative timing. If I can find a dyno around West Palm that would put up with my nonsense it would be amusing to make 3 pulls with this not so great ~12.1:1 440, then go home and put the same heads, intake, carb, exhaust manifolds, and cam onto this ~9.8:1 CR 493 with the 'hate' pistons and run it again on the same dyno to compare the results... does ~10% increase in displacement overcome ~20% lower static static compression ratio? 
Last edited by Craig J; 01/19/24 11:37 PM.
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Re: "hate this piston design"
[Re: Craig J]
#3206409
01/20/24 01:38 AM
01/20/24 01:38 AM
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Joined: Jan 2003
Posts: 20,179
Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,179
Park Forest, IL
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What is the purpose of those grooves? I have heard them referred to as anti-detonation grooves however, I do not know if that’s correct Thank you.
"Everybody funny, now you funny too."
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Re: "hate this piston design"
[Re: fast68plymouth]
#3206410
01/20/24 01:39 AM
01/20/24 01:39 AM
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Joined: Jan 2003
Posts: 20,179
Park Forest, IL
slantzilla
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 20,179
Park Forest, IL
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What is the purpose of those grooves? Contact Reduction Grooves
These grooves are machined into the top ring land above the top ring to minimize contact drag when the piston rocks over upon reversal. They add minimal volume to the crevice volume, and they also help resist detonation by disrupting flame travel into the crevice volume where pressure spikes might unseat the ring. Thank you too.
"Everybody funny, now you funny too."
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Re: "hate this piston design"
[Re: Craig J]
#3206444
01/20/24 10:00 AM
01/20/24 10:00 AM
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Joined: May 2005
Posts: 1,989
Apollo, PA.
B1MAXX
top fuel
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top fuel
Joined: May 2005
Posts: 1,989
Apollo, PA.
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The grooves are a good idea, but it looks like the top groove was too high. Maybe a design error, maybe a machining error. I don't really know without seeing them. Sometimes pictures don't show everything. I believe the pistons I have are just an older version of this one from 440source. This discussion now has me a bit curious....I am certainly not a professional engine builder, and have never had an engine assembled in my garage on a dyno. Due to covid parts shortages I have a not very good combination in my car: 440 +0.032 (yes...32 over) with very old style L2295F30 TRW pistons, LY rods, 75 cc Performer RPM heads, a Hughes "real 6 pack" cam, performer 440 intake (fits under a flat e body hood) and iron hp manifolds. It has sky high cranking compression, but I think it would probably be safe on an engine dyno up to 6000 rpm with 112 octane fuel and conservative timing. If I can find a dyno around West Palm that would put up with my nonsense it would be amusing to make 3 pulls with this not so great ~12.1:1 440, then go home and put the same heads, intake, carb, exhaust manifolds, and cam onto this ~9.8:1 CR 493 with the 'hate' pistons and run it again on the same dyno to compare the results... does ~10% increase in displacement overcome ~20% lower static static compression ratio? Cranking compression would probably still be up there with the same cam I bet.
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Re: "hate this piston design"
[Re: B1MAXX]
#3206730
01/21/24 04:21 AM
01/21/24 04:21 AM
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Joined: Sep 2014
Posts: 4,457
Washington
madscientist
master
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master
Joined: Sep 2014
Posts: 4,457
Washington
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I called Icon about these pistons several years ago. For use with open chamber heads you can run the pad proud of the deck. On closed chamber heads you run them to zero deck.
They reduced the outer band as a way to increase piston volume while keeping the dish reasonably shallow.
That’s all it is.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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