Using 351W Forged Piston
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Junior User
Joined: Mar 2004
Posts: 70
Likes: 1
From: Long Beach, CA
Using 351W Forged Piston
Howdy. I've been crunching some numbers recently and came across this piston on Summit's site.
http://www.summitracing.com/parts/sl...view/make/ford
I understand that I would need to use the earlier rod to have the right pin diameter or re-bush later rods. Fine there. The compression distance is also very close to the 300's. Fine there too. Then I used Summit's compression calculator with the felpro gasket compressed thickness of .035 and a zero deck with both 68cc (240 head) and 76cc (300 head) chambers. I was surprised to come up with about 9.3 and 8.5 to 1 compression ratios respectively. Anyone object to the accuracy of my findings? If this is so, I think there should finally be a piston sticky. There's so much talk about 351, 352, and 390 pistons with so many combinations, but I haven't really seen a nice guide through this mess. Anyone interested in helping me tackle this?
http://www.summitracing.com/parts/sl...view/make/ford
I understand that I would need to use the earlier rod to have the right pin diameter or re-bush later rods. Fine there. The compression distance is also very close to the 300's. Fine there too. Then I used Summit's compression calculator with the felpro gasket compressed thickness of .035 and a zero deck with both 68cc (240 head) and 76cc (300 head) chambers. I was surprised to come up with about 9.3 and 8.5 to 1 compression ratios respectively. Anyone object to the accuracy of my findings? If this is so, I think there should finally be a piston sticky. There's so much talk about 351, 352, and 390 pistons with so many combinations, but I haven't really seen a nice guide through this mess. Anyone interested in helping me tackle this?
Thread Starter
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Junior User
Joined: Mar 2004
Posts: 70
Likes: 1
From: Long Beach, CA
You are correct. I made a mistake and used the incorrect stroke. I'm thinking that a little unshrouding and cleanup of the 76cc head will yield at least a couple more cc's bringing it down to about 9.3.
Postmaster
Joined: Nov 2012
Posts: 2,806
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From: Langley, BC
Why zero deck and then later make the combustion chamber larger? With that setup, you have a 0.028" deck clearance. If you're zero decking to get better quench, you should use a Fel-Pro 1024 head gasket, which not only is a better overall gasket but has a compressed thickness of 0.039", a lot closer to the ideal 0.040" quench distance. This will also give you a slightly smaller combustion ratio.
Question. Why do you want that piston? The Probe P2446F with a 15.9cc dish might be a better choice. I'm using the Probe 11938 in mine with a 20.1cc dish, but it belongs to the SRS series which is more expensive.
Question. Why do you want that piston? The Probe P2446F with a 15.9cc dish might be a better choice. I'm using the Probe 11938 in mine with a 20.1cc dish, but it belongs to the SRS series which is more expensive.
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Junior User
Joined: Mar 2004
Posts: 70
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From: Long Beach, CA
I was concerned with the broad dish area of the probe adversely affecting quench. If you look at the Speed Pro, it has a smaller, but deeper dish area. I'm guessing that would create a smaller burn distance lending to less possibility of detonation?
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Junior User
Joined: Mar 2004
Posts: 70
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From: Long Beach, CA
What piston did you use in your build?
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Postmaster
Joined: Nov 2012
Posts: 2,806
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From: Langley, BC
I'm using 240 rods in mine. The 11938's compression height is 1.175", which is too small for the longer 300 rods.
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Thread Starter
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Junior User
Joined: Mar 2004
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From: Long Beach, CA
So what kind of deck height did you end up with using that setup?
Postmaster
Joined: Nov 2012
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From: Langley, BC
Thread Starter
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Junior User
Joined: Mar 2004
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From: Long Beach, CA
Thanks for the details. I get it now. There really needs to be a solid piston sticky because there are way too many threads about 390 or 352 pistons. This is a simple, straight forward way to use a forged piston with a ton of off-the-shelf choices to be had. My goal ultimate goal is boost, but I'll cross that road when I get there.
Elder User
Joined: Nov 2010
Posts: 573
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From: San Jose Ca.
Hey Bigfootsurfin, Take a look at Trozei's thread. He and I actually discussed just what you are lookin to do. I am useing the TRW L2446F-30. The only difference over stock 300 pistons is that they are .012" taller compression height.
https://www.ford-trucks.com/forums/1...ine-build.html
https://www.ford-trucks.com/forums/1...ine-build.html
Posting Guru
Joined: Jun 2012
Posts: 1,061
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From: Mims, FL
Thanks for the details. I get it now. There really needs to be a solid piston sticky because there are way too many threads about 390 or 352 pistons. This is a simple, straight forward way to use a forged piston with a ton of off-the-shelf choices to be had. My goal ultimate goal is boost, but I'll cross that road when I get there.
Question: why are you using a forged piston? Hypereutectic are cheaper and good quality if not using forced induction.
Postmaster
Joined: Mar 2005
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From: Earth
Sorry, got all caught up in deer season and didn't check back. I used these:
http://www.summitracing.com/parts/ue...-060/overview/
http://www.summitracing.com/parts/ue...-060/overview/