Am I making a mistake?

[TN Mopar]

The recent post on aluminum heads has me a little bit worried
I am fixing to order some 75cc Edelbrock RPM heads for my engine and am glad this came up before I ordered them

Question is 75cc 0r 80cc heads

I had planned the 75cc which would give me 10.5:1 compression (.027 gasket)
is that too much? and should I go for the 80cc at 10:1
Engine is a 030 440 with speed pro L2355s which are .029 in the hole & the 509 292 Purple shaft cam
Currently I have a 906 88cc head on it with an .020 steel shim gasket & 9.5:1 compression
but no quench due to the open chamber
The closed chamber aluminum heads will give me .056 quench with an .027 gasket
Not good quench but better than none

So is 10.5:1 compression for premium pump gas too much with .056 Quench?

Thank you
I don't want to spend my money and get more problems or little to no improvement

 

[66Satellite47]

IMHO, a true 10.5 CR with the EDE RPM's will work fine on 93 pump premium. My 500" 10.5 EDE RPM 88cc true flat top single valve relief piston motor worked just fine, no detonation, stayed cool. Having said that I'd still probably go with the 75 cc style. Good luck

 

[67Satty]

.029" in the hole with 2355 pistons doesn't seem right to me. Is that what you actually measured? I've never seen anyone say those pistons ended up that far down with their 440 build. I measured mine when I swapped from open chamber 452s to close chamber 84cc Edelbrock E Streets and the farthest any of my pistons were down was .010".

And if your pistons are really .029" down in the whole and you use a .027" gasket wouldn't that give you .046" quench?

 

[TN Mopar]

I measured but I have made mistakes however they are in the hole

And I add 029 & 027 and get 056
am I missing something

I know you cant tell from a picture but here is one from when we assembled the engine

 

[PRHeads]

There’s more to it than just the CR and quench.

There’s also the cam, vehicle weight, gearing, stall speed, exhaust system, etc.

Edit...... I see you have the 509 cam.
If you have an appropriate converter, gearing, and headers for that cam.....you “should” be good.

75cc E Streets have angle plugs, 84cc version has straight plugs.

 

[TN Mopar]

There’s more to it than just the CR and quench.

There’s also the cam, vehicle weight, gearing, stall speed, exhaust system, etc.

Edit...... I see you have the 509 cam.
If you have an appropriate converter, gearing, and headers for that cam.....you “should” be good.

75cc E Streets have angle plugs, 84cc version has straight plugs.

3800# car
3.91 Gear
2800 stall convertor (needs bigger)
will get new exhaust after the new heads going to 3" from 2 1/2"

Do you know if the angled plugs will work with a set of Hooker Super Comps?

 

[cryplydog]

I like the 75cc heads. You could easily go with a thicker head gasket.

 

[67Satty]

I measured but I have made mistakes however they are in the hole

And I add 029 & 027 and get 056
am I missing something

I know you cant tell from a picture but here is one from when we assembled the engine

View attachment 916022

Ooops, my bad.

 

[IQ52]

3800# car
3.91 Gear
2800 stall convertor (needs bigger)
will get new exhaust after the new heads going to 3" from 2 1/2"

Do you know if the angled plugs will work with a set of Hooker Super Comps?

I've run Hooker Super Comps on Edelbrock RPM heads with the angled plugs during dyno runs on Comp Cams dyno.

 

[PRHeads]

The 2” super Comps work fine with the angled plugs.

I have heard the 1-7/8” super comps are problematic with angle plugs.

The “Competition” series headers, also 1-7/8”...... no issues on the drivers side, a little dinging is req’d on the passenger side...... but it’s not a big deal.

Not sure at all on the 1-3/4” super comps.

 

[road chicken]

Your head gasket bore diameter can effect the ratio as well. They aren't all equal. What composite gasket did you find in .027?

 

[TN Mopar]

Your head gasket bore diameter can effect the ratio as well. They aren't all equal. What composite gasket did you find in .027?

Cometic MLS 4.38 bore
Engine is 4.35 (0.030 0ver 440)

 

[TN Mopar]

The 2” super Comps work fine with the angled plugs.

I have heard the 1-7/8” super comps are problematic with angle plugs.

The “Competition” series headers, also 1-7/8”...... no issues on the drivers side, a little dinging is req’d on the passenger side...... but it’s not a big deal.

Not sure at all on the 1-3/4” super comps.

FYI the 1-3/4" super comps will not work with angled plugs
So the headers I have wont work
It's okay though because I really wanted the 2" tubes anyway
I have been looking at the Doug's headers and like everything I have read so far

I will list the headers I have on craigslist and hope to move them

 

[road chicken]

That's what suspected. Please comment back on how they seal. I was under the impression they had to have a specific finish on the head and the block for them to seal properly.