Re: Striking out with Pistons
[Re: Hotlumpy]
#968725
04/07/11 08:51 PM
04/07/11 08:51 PM
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Joined: Oct 2007
Posts: 3,911
Oregon
hooziewhatsit
master
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master
Joined: Oct 2007
Posts: 3,911
Oregon
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It sounds like they're assUming a different head chamber size than what you used in your calculations.
If you ever find yourself in a fair fight, your tactics suck.
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Re: Striking out with Pistons
[Re: hooziewhatsit]
#968726
04/07/11 08:53 PM
04/07/11 08:53 PM
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Joined: Feb 2007
Posts: 612
Nampa, ID
None2Slow
mopar
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mopar
Joined: Feb 2007
Posts: 612
Nampa, ID
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Quote:
It sounds like they're assUming a different head chamber size than what you used in your calculations.
 that and assuming maybe a zero deck height. Combined, maybe 9.7.
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Re: Striking out with Pistons
[Re: None2Slow]
#968728
04/07/11 08:55 PM
04/07/11 08:55 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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I dunno what head your running, but original pass car 413's used a closed chamber head, maybe that is it.
You want more than the Sp unit you're probably looking at custom pistons.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: Striking out with Pistons
[Re: Hotlumpy]
#968729
04/08/11 01:18 AM
04/08/11 01:18 AM
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Joined: Jan 2003
Posts: 75,128
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,128
A Banana Republic near you.
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Quote:
So I have found out how to calculate compression ratios, and I can't find a flat top 413 piston with a higher compression distance than 2.019, that ends up at 8:96:1. Campbell Enterprises advertises the 238P sealed power pistons as 9:7:1, but with a 2.019 compression distance, it calcs out to 8:96:1. Talked to the Rep and he swears they are a 9:7:1 piston, but can't tell me how he arrived at this. Has anyone built a 413, and if so wherew do I find pistons that aren't the "Truck" spec? Am I the only idiot building a 413 that wants decent compression?
You will more than likely need a custom piston , Diamond can make one exactly like you need.
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Re: Striking out with Pistons
[Re: JohnRR]
#968730
04/08/11 02:20 AM
04/08/11 02:20 AM
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Joined: Jan 2007
Posts: 1,668
Mi,U.S.A.
mike s
top fuel
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top fuel
Joined: Jan 2007
Posts: 1,668
Mi,U.S.A.
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Diamond makes some really great pistons but the price for a custom piston is high(about $850.00 or so for the last set of 383 10-1 pistons I purchased).I have been talking to one of the piston manufacturers. 10 set minimum.Stock stroke 383,400 or 413.Forged flattop w/valve notches.I also will be speaking to another company who claims a smaller minimum, same type piston.Price either way should be very good at about $450.00 per set retail.Enough interest out there?
Last edited by mike s; 04/08/11 02:22 AM.
Leave the gun.......take the Cannoli's....Mike
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Re: Striking out with Pistons
[Re: Hotlumpy]
#968731
04/08/11 02:49 AM
04/08/11 02:49 AM
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Joined: May 2008
Posts: 5,399
Aurora, Colorado
451Mopar
master
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master
Joined: May 2008
Posts: 5,399
Aurora, Colorado
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The Sealed Power #238 piston is a flat top with no valve reliefs and a 2.00" compression distance.
That should place the piston at 0.082" below the deck at TDC.
With a 0.040' head gasket and 84cc heads, that's about 8.59:1 compression.
With 74cc chamber heads and 0.040" head gasket = 9.36:1
With 74cc heads and 0.020" head gasket = 9.79:1 compression.
This assumes the block height is 10.725", the rods are 6.768", and the crank is 3.75" stroke.
Besides custom pistons, the block or heads could be milled to increase compression, or the crank could be offset ground for some extra stroke.
Although custom pistons are expensive, they may be the best choice. The Sealed Power pistons are weaker cast pistons, and they are fairly expensive for a cast piston at about $60 each. Also, not having valve reliefs could be a problem if you do any of the options above that move the piston closer to the valves.
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Re: Striking out with Pistons
[Re: 451Mopar]
#968733
04/08/11 12:12 PM
04/08/11 12:12 PM
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Joined: Apr 2010
Posts: 166
California
Hotlumpy
OP
member
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OP
member
Joined: Apr 2010
Posts: 166
California
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Quote:
The Sealed Power #238 piston is a flat top with no valve reliefs and a 2.00" compression distance.
That should place the piston at 0.082" below the deck at TDC.
With a 0.040' head gasket and 84cc heads, that's about 8.59:1 compression.
With 74cc chamber heads and 0.040" head gasket = 9.36:1
With 74cc heads and 0.020" head gasket = 9.79:1 compression.
This assumes the block height is 10.725", the rods are 6.768", and the crank is 3.75" stroke.
Besides custom pistons, the block or heads could be milled to increase compression, or the crank could be offset ground for some extra stroke.
Although custom pistons are expensive, they may be the best choice. The Sealed Power pistons are weaker cast pistons, and they are fairly expensive for a cast piston at about $60 each. Also, not having valve reliefs could be a problem if you do any of the options above that move the piston closer to the valves.
Thank you for an answer that gives me some options, I think I am going to cc the heads to find out exactly where I am, and see about possibly milling them. I've seen .020 steel shim gaskets at summit, I thought those were used in conjunction with head gaskets, as "shims", can you run them alone?
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Re: Striking out with Pistons
[Re: Hotlumpy]
#968734
04/08/11 12:27 PM
04/08/11 12:27 PM
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Joined: Jan 2003
Posts: 75,128
A Banana Republic near you.
JohnRR
I Win
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I Win
Joined: Jan 2003
Posts: 75,128
A Banana Republic near you.
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Quote:
Quote:
The Sealed Power #238 piston is a flat top with no valve reliefs and a 2.00" compression distance.
That should place the piston at 0.082" below the deck at TDC.
With a 0.040' head gasket and 84cc heads, that's about 8.59:1 compression.
With 74cc chamber heads and 0.040" head gasket = 9.36:1
With 74cc heads and 0.020" head gasket = 9.79:1 compression.
This assumes the block height is 10.725", the rods are 6.768", and the crank is 3.75" stroke.
Besides custom pistons, the block or heads could be milled to increase compression, or the crank could be offset ground for some extra stroke.
Although custom pistons are expensive, they may be the best choice. The Sealed Power pistons are weaker cast pistons, and they are fairly expensive for a cast piston at about $60 each. Also, not having valve reliefs could be a problem if you do any of the options above that move the piston closer to the valves.
Thank you for an answer that gives me some options, I think I am going to cc the heads to find out exactly where I am, and see about possibly milling them. I've seen .020 steel shim gaskets at summit, I thought those were used in conjunction with head gaskets, as "shims", can you run them alone?
The original head gaskets from the factory were the thin .021ish steel gasket. There is a SHIM gasket , as long as you get the correct standard gasket you will be all set .
You really need to CC your heads FIRST and find out exactly what you have , there really isn't any accurate published data on head chambe cc , and DO NOT use NHRA specs as a guide , they aren't even remotely correct when it comes to the big block wedge mopar heads, max wedge maybe ??? , but everything else is smaller than actual. .
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Re: Striking out with Pistons
[Re: JohnRR]
#968735
04/08/11 12:32 PM
04/08/11 12:32 PM
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Anonymous
Unregistered
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Anonymous
Unregistered
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Use the .020 "steel shim" gasket as most places call them and use copper coat spray. Quote:
You really need to CC your heads FIRST and find out exactly what you have
I agree completely. Most 906/452 open chamber heads I've cc'd have combution chambers well over 90 cc's.
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