Stockish 340 upgrades, cam needed

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Cudafever said:
Edit X head have a average cc combustion chamber of 74cc the SM heads have 64 so maybe only 10-15 cc dish would work just fine.
Click to expand...
I was thinking to mill the piston for zero deck and run a .039. 1008 head gasket. That will lighten the piston some. Lower the compression a hair also. Yes/no? Kim
 
The 7.5 cc volume in those pistons is not just the valve reliefs, but the bevel on the outside of the piston. When you remove the bevel, you can actually get a compression increase depending on how far the piston is out of the hole (like my buddy’s 340 with a .023 positive deck and a similar piston). So aside from milling the top, enlarging the valve relief to a common trough is an effective addition to lowering compression.
 
compression ratio is the volume above piston at tdc added to the value bellow or bdc or bottom dead center. then deviding the volume above to give you your compression ratio

So .039 and .038" is the same volume above the piston so compression will be the exact same thing.

I will explain better later
 
The CR certainly doesn’t seem to be an issue by my math......
I get 9.6:1 with the combo of parts being discussed here.

I’d like to see the math that’s showing 10.5:1
 
PRH said:
The CR certainly doesn’t seem to be an issue by my math......
I get 9.6:1 with the combo of parts being discussed here.

I’d like to see the math that’s showing 10.5:1
Click to expand...

Thanks PRH i was just about to run then numbers
 
I think we’re calling it 65cc.

Published spec for the piston valve pockets/chamfer is 7.5cc.

8553 gasket is 4.120 x .053

-.015 deck clearance

Don’t forget the area above the rings
 
Cudafever said:
compression ratio is the volume above piston at tdc added to the value bellow or bdc or bottom dead center. then deviding the volume above to give you your compression ratio

So .039 and .038" is the same volume above the piston so compression will be the exact same thing.

I will explain better later
Click to expand...
I get what ur saying about the quench being the same. I was just thinking about the .014 thicker gasket being more susceptible to failing. I am perfectly happy to use the thicker gasket with the piston above deck .015. So is there any theory that a thicker gasket will fail b4 a thinner 1? Or with a thinner gasket does the head get clamped to the block better cause of less gap. It would that even be a concern. I’m trying to learn. Kim
 
PRH said:
I think we’re calling it 65cc.

Published spec for the piston valve pockets/chamfer is 7.5cc. So what do u come up with? Thanks. Kim

8553 gasket is 4.120 x .053

-.015 deck clearance

Don’t forget the area above the rings
Click to expand...
. So compression will be just over 10-1? Kim
 
The guy doing the balancing recommended to shave the pistons as he says the 1008 gasket is better for an aluminum head. He said it’s a better gasket. He said u don’t want thick gaskets with an aluminum head.
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A complete waste of time and $$ for this type of build imo.
Zero extra hp.

It won’t be any worse, you’ll just be out more money.
 
LO23M8B said:
I think with the 3.23 gear and 10.5 comp. with alum. heads 224 @ 50 on a 112 centerline would work real well. The highest lift with 1.6 rockers or higher. Remember the alum. heads effectively reduce the comp. ratio. I would try to up the comp. ratio to 11.0 also. Just my 2 cents worth but copper pennies. The old 68 manual cam is a excellent choice always.
Click to expand...
ps That cam rumblefish recommen
rumblefish360 said:
Bullshit, bullshit, bullshit, bullshit.....
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bullshit what?
 
If it had anything to do with your cam choice part of my response didn't come thru is that I liked it. So what part of BULLSHIT is what!
 
The reasoning for me to have the piston milled was to lighten it cause their pretty dam heavy. But maybe it’s not enough difference to help efficiency anyways. Kim
 
The choice of metal for a cylinder head does not effectively lower the compression ratio in any way shape or form.
Put both, otherwise identical heads on an engine and do a rotating compression check in both will have the same psi. Aluminum has the effect of transferring hate quicker. And that is it. It does not lower the compression effectively ratio whatsoever.

This test has been done several times over. It’s in print several times over. This has been proven over and over again.
 
You can us a online calculator, but there are thing that you need to cc before you can get a accurate compression reading.
For example my 4.10 bore piston stuck up .017" above the block(so it take away from the top dead center reading because it removes head space) How Ever! because of the valve reliefs in the head was larger than the .017' pop up of the piston, it became a number that was add to the head volume. bore and stroke are set! the head volume make the compression ratio)
hope that wasn't confusing.

So here we go
head cc 70
head gasket cc 8
10.5: compression piston cc 7.35(in the hole even though it a pop up piston because of valve relief in piston)
above head total
85.35cc

Bore X Bore X Stroke X .7854 =43.70 X 16.387(convert to CC)=716.12 CC
Below head or bdc volume
716.12

716.12+85.35=801.47 cc Divided by 85.35=9.3903925
Aka my 10.5:1 piston equiled a actual compression ratio of 9.40:1
Compression Ratio = 9.40:1.

So let us you head cc on my .060" over bored 340 motor
65 head
8 head gasket
piston 7.35
total 80.35
80.35+716.12=796.47 divided by 80.35=9.9125078
New compression = 9.91:1

I used the felpro .040" thick head gasket , So your compression will be slightly lower........However, you decked and leveled your block, so it might be real close.
Edit: for math! Bore X Bore X Stroke X .7854= 43.70
 
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LO23M8B said:
Remember the alum. heads effectively reduce the comp. ratio
Click to expand...

@LO23M8B
I use to believe this as well, and all that has been said about it, made sence with the alu dissipating heat and all.
Go become a member of Motor Trend On Demand if you are not already. it like 3 buck a month!
Then watch this video from Engine Masters: They take and identical head that was available in alu and iron.
It was a vary well sorted out test. Worth the 3 buck membership and all the great other programs(I'm sounding like a salesman:BangHead::D)
https://www.motortrendondemand.com/detail/iron-vs-aluminum-heads-a-study-of-heat/0_623whon4/
 
My 340 seems to run pretty good with this little cam and 1.6's at 9.6:1:

upload_2020-4-11_10-53-40.png
 
[/QUOTE] That Howard’s cam GE posted is probably going to be as good as anything....... up to the point where the valvetrain gets unhappy.[/QUOTE]


I looked at that Howards cam for myself for a 318. I like it. It would work there too.
 
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