Im looking at a set of eddy rpm's for my 440 and would like around 10-1 comp, max 10.5. I have L2355 pistons and was wondering what kind of compression I would have with either the 75cc or the 84cc rpm's. Was told today that edelbrock don't have any idea when the 75cc castings will be in stock so I could be limited to the 84cc head. Any idea what comp I would have with either of these two heads. Also what is the difference between the RPM's and the E-street 75cc head. Is the casting and finish the same, are the valve springs different. Thanks

Should be just about 10 to 1. Is the block decked? I'm building an engine with 2355s and pistons will be .024 in hole iirc. That's block un decked. 80cc 440source heads. I came up with 10.24 to 1. But if I deck for 0 deck it will be about 10.5.

As a rule of thumb, that piston at 0 deck height, with a 79 cc chamber and a .017 head gasket will get you right at 11:1, so you can calculate from there...

If you've got 91 octane pump swill available in your area, I'd run AT LEAST 11:1, with aluminum heads, JMHO...

With my block decked .010 and .040 over 2355s I calculated 10.5:1 for 80cc Stealths and 10.2:1 for 84cc RPMs.

# of Cyl. 8 COMPETITION WEDGE
Bore 4.3500
Stroke 3.7500
Rod Len. 6.760
Gskt Bore 4.410
Comp. Gskt .0390
Block Deck Ht. 10.7200
Top ring down 0.280
Chamb. Vol. 75.0
Dome (-) Dish (+)5.30
Piston / deck 0.019

Total volume 1009.37
Cylinder volume 913.28
Clearance volume96.09
Gasket volume 9.76
Top ring volume 1.40
Deck volume 4.63
Piston top land 4.305
1/2 Stroke 1.875
Comp. Ht. 2.066
Cubic Inches 445.85
Compression ratio 10.50

Changed thew deck height on this one to match their listefd 2.061 C/H.




# of Cyl. 8 TODD @ COMP. WEDGE
Bore 4.3500
Stroke 3.7500
Rod Len. 6.760
Gskt Bore 4.410
Comp. Gskt .0390
Block Deck Ht. 10.7150
Top ring down 0.280
Chamb. Vol. 84.0
Dome (-) Dish (+)5.30
Piston / deck 0.019

Total volume 1018.37
Cylinder volume 913.28
Clearance volume105.09
Gasket volume 9.76
Top ring volume 1.40
Deck volume 4.63
Piston top land 4.305
1/2 Stroke 1.875
Comp. Ht. 2.061
Cubic Inches 445.85
Compression ratio 9.69

I like this engine compression calculator.


http://www.csgnetwork.com/compcalc.html

You should be able to run that combo on unleaded Premium until the cows come home.

Whatever you do, do NOT buy the 88cc Edelbrocks! If you do, all squish goes out the window.

R.

Thanks for all the replys guys. I was ready to buy the 75cc head but was told they aren't available at the moment so I will buy the 84cc head. Are the springs and retainers that are supplied with the rpm's any good, will be running a flat tappet hyd cam.

did they say when 75cc eddies would be available? I would guess they will be a hot seller just because of so many 440s having such low compression.

I sent a note to my Edelbrock rep today, so lets see what they have to say. Its very hard to pin them down regardless of what you hear.

No they didn't say when they would be available so it could months

They're still vaporware. They've shown up in catalogs for well over a year and haven't been available ever, IIRC. And at first the price war ridiculously low too!
R.