Dusterfreak
Well-Known Member
Ok, simple question. Can I use 318 63cc edelbrock rpm heads on top of -68 340 shortblock that has original pistons?
Question about EDELBROCK RPM heads
- Thread starter Dusterfreak
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Which head exactly are you considering? The edelbrock #60779 has a "closed chamber" design. The 340 (68) has a piston that sticks above the deck surface by .018 thou. your head gasket choice may be a .039 thou thick (felpro 1008) choice. This is not enough clearance left between the top of the piston and the head. OR... Edelbrock #60179 has a recess of .060 for clearance built into the head (at 65cc chamber volume), so you can run pistons that stick out of the hole.
mechanicmark
Well-Known Member
Agree with Maxx1196
Dusterfreak
Well-Known Member
Thats what I thought, thanks.
DO NOT buy the 60179 head...
Buy the closed chamber model and put an appropriate head gasket on it to get your quench measurement.
Buy the closed chamber model and put an appropriate head gasket on it to get your quench measurement.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I agree with everybody
Just run the disc grinder over the .... no-no just kidding!
I ran .020 quench on my zero-deck 360 for at least one summer, with no problems.
That might indicate that the .039 FelPros could work. I say might cuz I am running Hypers at a very tight clearance, so very little piston rock. If you are running the stock forged slugs, with pretty loose clearance and worn holes, then YOU might not get away with it.
So measure your pop-up very carefully; and order custom gaskets.
Or cut the tops off the pistons.
But I wouldn't run the open chambers, there's just no quench available.
With .060 in the head, and even with the .020 thin gaskets, then, less the pop-up; you may get down to .062 quench, which they say is or may be, detonation prone, so better to run the .039 FellPros. And then you are up to .081, and probably out of detonation;but also too far out to reap any quench benefit.
I would use the 63cc heads and cut the pistons in a heartbeat.I would cut the quench pad area, down to 5 to 8 thou pop-up, and leave the rest of the pop-up alone. This might get you up to 10.3 Scr,with the .039 gasket, and with .031 to.034 quench,depending on the true pop-up.
The 65cc head might get you up to 10.6Scr, with no piston cutting, but with .081 or so quench.
So it really depends on your application, I guess...............either way will work for a weekend cruiser.
I know what I would. do
Just run the disc grinder over the .... no-no just kidding!
I ran .020 quench on my zero-deck 360 for at least one summer, with no problems.
That might indicate that the .039 FelPros could work. I say might cuz I am running Hypers at a very tight clearance, so very little piston rock. If you are running the stock forged slugs, with pretty loose clearance and worn holes, then YOU might not get away with it.
So measure your pop-up very carefully; and order custom gaskets.
Or cut the tops off the pistons.
But I wouldn't run the open chambers, there's just no quench available.
With .060 in the head, and even with the .020 thin gaskets, then, less the pop-up; you may get down to .062 quench, which they say is or may be, detonation prone, so better to run the .039 FellPros. And then you are up to .081, and probably out of detonation;but also too far out to reap any quench benefit.
I would use the 63cc heads and cut the pistons in a heartbeat.I would cut the quench pad area, down to 5 to 8 thou pop-up, and leave the rest of the pop-up alone. This might get you up to 10.3 Scr,with the .039 gasket, and with .031 to.034 quench,depending on the true pop-up.
The 65cc head might get you up to 10.6Scr, with no piston cutting, but with .081 or so quench.
So it really depends on your application, I guess...............either way will work for a weekend cruiser.
I know what I would. do
Last edited:
Marcohotrod
Well-Known Member
original 340 pistons are cast aluminum, measure deck height, then probably go with the .050" 8553pt fel pro and the closed chamber heads
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Are you sure they were cast?
I thought my 68s were forged......I guess my memory IS going!
I thought my 68s were forged......I guess my memory IS going!
Marcohotrod
Well-Known Member
positive all 340 pistons were cast aluminum. maybe the max wedges and hemi had forged
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Thx Marco;I'll try and remember that for next time. On thing I do remember, is that they were heavy!
Dusterfreak
Well-Known Member
Oh my, didnt know this was going to be this difficult 
Oh my, didnt know this was going to be this difficult
if it was easy we would all own chevies...lol
go with the close chamber head...but pick a head gasket to fit your needs....
Dusterfreak
Well-Known Member
Ok, so basicly with N/A engine best bang for the buck would be closed chamber heads with thicker gasket and possibly shaving the piston a bit?
But if I want put a vortech blower or a turbo on it some day? Will the closed chamber still work??
But if I want put a vortech blower or a turbo on it some day? Will the closed chamber still work??
moper
Well-Known Member
Yes. use the right parts, set the distance with the gasket.
Chances are it will "work". But will have too much static compression. If you want a boosted engine, build another one for boost. Otherwise build this one for boost and live with whatever it ends up with until you have the other parts.
ir3333
Well-Known Member
The answer to your question is "no"
Dusterfreak
Well-Known Member
Thank you!! This conversation makes me wonder, why do they even make open chamber heads 
Thank you!! This conversation makes me wonder, why do they even make open chamber heads
Because some knucklehead at edelbrock thought it would be a good idea to have more than one head... LOL
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