Re: Which head for my 340 stoker?
[Re: rumundo]
#2387503
10/14/17 10:39 PM
10/14/17 10:39 PM
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Joined: Jan 2003
Posts: 27,471 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,471
So Cal
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Why would you pick pistons without knowing what head cc you were going to run??
I think 9.5 DCR will be too much for 93 octane.
91 seems to need very low 8 or very high 7's DCR.
Youre gonna be stuck with an open X head just for compression reasons. I see your calca all use .051 head gaskets. Sound like your realizing the corner you've painted yourself in.
Last edited by autoxcuda; 10/14/17 10:49 PM.
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Re: Which head for my 340 stoker?
[Re: rumundo]
#2387514
10/14/17 10:52 PM
10/14/17 10:52 PM
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Joined: Jan 2003
Posts: 27,471 So Cal
autoxcuda
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 27,471
So Cal
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This is your cam:
Advertised Duration (Int/Exh): 268/276 Duration @ .050 (Int/Exh): 226/234 Gross Valve Lift (Int/Exh): .494/.513 LSA/ICL: 110/106 Valve Lash (Int/Exh): Hyd/Hyd RPM Range: 1800-6200
You'd need a ton more cam to bleed off 11:1 compression. Start asking your machine shop about flycutting your piston tops if you what to run those smaller cc edelbrock heads.
IMHO you are stuck with an open chamber head with 72+ cc's. I think that will be X, J, or W-2.
X heads by your calcs give you 10.2:1. That might work with 93 octane. But you'll have no quench and cast iron heads that tend to promote pinging vs closed chamber alum.
Last edited by autoxcuda; 10/14/17 11:28 PM.
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Re: Which head for my 340 stoker?
[Re: rumundo]
#2387683
10/15/17 12:09 PM
10/15/17 12:09 PM
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Joined: Nov 2003
Posts: 36,041 Lincoln Nebraska
RapidRobert
Circle Track
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Circle Track
Joined: Nov 2003
Posts: 36,041
Lincoln Nebraska
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I'm assuming running 93 octane is set in stone. What Cab said I would CC/measure everything to see exactly where you are at for SCR but IMNHO it is way too high from what you posted. Cometic makes thicker gaskets. I would not go with a wilder cam to lower the DCR, keep the cam that suits your driveing style. For manifolds the best are early 340 HP ones & magnums, '92/early 93 ex manifolds which have ~2&5/16 outlets. Holler how it turns out. I would stay with the iron heads (for now).
live every 24 hour block of time like it's your last day on earth
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Re: Which head for my 340 stoker?
[Re: rumundo]
#2387740
10/15/17 02:09 PM
10/15/17 02:09 PM
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Joined: Aug 2005
Posts: 6,008 Salem
Grizzly
Moparts Proctologist
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Moparts Proctologist
Joined: Aug 2005
Posts: 6,008
Salem
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Go with the Edelbrock package you want, go thinner on the head gasket to get quench back, run it until it pings, then back your timing off 2 degrees.
Mo' Farts
Moderated by "tbagger".
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Re: Which head for my 340 stoker?
[Re: rumundo]
#2387872
10/15/17 09:37 PM
10/15/17 09:37 PM
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Joined: May 2003
Posts: 6,566 Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,566
Downtown Roebuck Ont
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What about the Eddy Magnum head? If it has the fast burn chamber it might help with you DCR problem. They take a lot less timing to make power and less timing is usually less prone to detonation. Whether that's enough to overcome its even smaller chamber volume . Kevin
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Re: Which head for my 340 stoker?
[Re: Twostick]
#2388350
10/16/17 08:10 PM
10/16/17 08:10 PM
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Joined: Jan 2003
Posts: 16,376
dogdays
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,376
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You're kind of in a pickle. Using the engine size, a zero deck piston, 5cc in the valve pocket and 64cc head, you're right at 12:1.
First of all don't buy the Edelbrock 340 heads. They were made for guys who already had new or nearly new 340 pistons that come out of the bore. By carving out the material where the piston would collide, they eliminate the opportunity to get squish.
For a 30 over 4" stroke 340, to get to 10.5:1 you need 90cc above the piston. Assuming your new head is 64cc, the head gasket is 10cc, there's 5cc in the valve pocket, you need about 11cc more volume. This comes out of the piston top closest to the spark plug. That's with piston at zero deck.
To get to 10.5:1 without machining the piston, it needs to be down in the hole 0.046".
Regarding heads, the consensus opinion for the best flow out of either an X or J head, stock, is 220cfm. The max flow out of a Edelbrock LA head is 251 cfm. Using this as an example you are looking at as much as a 65hp increase.
A 3" diameter circle 0.090" deep is about 10.5cc.
Clear as mud, right? Rats! I just found out that while I was calculating a 64cc chamber, the LA head is 63cc.
R.
The Magnum heads are only 58cc and would need to have an inverted dome machined into them that matches the chamber's shape. Just slapping them on with a 10cc gasket, piston at zero deck, and 5cc valve pockets you'd see 12.7:1 compression.
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Re: Which head for my 340 stoker?
[Re: dogdays]
#2390111
10/20/17 12:18 AM
10/20/17 12:18 AM
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Joined: Jan 2006
Posts: 132 Kingman, Az
Scojodak
member
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member
Joined: Jan 2006
Posts: 132
Kingman, Az
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To get to 10.5:1 without machining the piston, it needs to be down in the hole 0.046". While not desired, couldn't he bleed off some compression with the cam ABDC spec?
Dakota for life!
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