Ported 452 or Edelbrock RPM

-
Miszny

Miszny

Well-Known Member
Joined
May 24, 2012
Messages
846
Reaction score
566
Location
Warsaw
Hi

Here is a dilemma I'm facing...
What I have on my 471 is a set of 452 heads mildly ported by Koffels.
Heads flow 277cfm @ .600" lift. They have 3 angle valve job and stainless valves 2.08" and 1.74" size.
They are shaved down to 85cc chambers.

What I have on my shelf is a set of Edelbrock RPM 6091 casting heads that had some bowl work. They are supposed to flow 301cfm @ .600" lift. They have 3 angle valve job, titanium exhaust and stainless intake valves 2.14" and 1.81" size.
They have 74cc chambers (measured after machining them with spark plug in)

I'm giving flow @ .600 because I have 618 net lift solid roller cam.

With my 452 heads I have exactly 10.1:1 compression (measured).
With Edelbrock I'm facing around 11.2:1 compression.

There are multiple advantages that I see with Edelbrocks like nicer chambers, less weight, some extra power.
Are there any things that could put me off going with aluminum heads? Any special parts I'm not aware off?
What would you do in my situation? Would you swap the 452s?

Thank for your opinions on this.
 
Install Edelbrocks and make sure you have fuel octane to run them.
 
crackedback said:
Install Edelbrocks and make sure you have fuel octane to run them.
Click to expand...
I run 98 or 100 octane only. I'm not that worried about pinging, just a bit unsure if I should put aluminium heads on... Simply not sure if potential gains are worth the effort thats all.
I was thinking to sell the Edelbrocks but winter is coming and suddenly there is time to work on the car again.
Frankly I was planning to redo whole cooling system for my trans and add engine oil cooler, just moved the heads this week and again started thinking what to do with them. What do I need for such swap?
I have 1009 felpro head gaskets, new set of arp head bolts for iron heads (will they fit)? Probably my pushrods for iron heads will be too short.
Did anybody did similar swap recently? Any tips?
 
Last edited:
Edelbrock 6091? This no known part number. Please confirm part number.
 
IQ52 said:
Edelbrock 6091? This no known part number. Please confirm part number.
Click to expand...
This is the casting number I see on the heads. They are 60919 heads that were bought as bare heads, milled down for smaller chambers and have nice set of valves and some cleanup and blending work done to them.

I was asking you about porting gains in summer time having these heads in mind actually.
 
Last edited:
So the big question here is what cc did the heads start out as. If they were the 84cc heads to begin with, they would have been milled at least .060" to get to 74cc. This will reduce your piston to valve clearance the same amount, at least .060".

The compression is probably not a problem as the combustion chamber shape will help and the cam is big enough to reduce the cylinder pressure to pump gas levels.

The RPM head should use the same ARP head bolts as the stock iron head.

The pushrods might work as the 452 heads must have been milled to get down to 84cc.

The compression bump and the head flow increase should make a noticeable difference. You can't race flowbenches so..........without a flow sheet from the same flowbench for both different heads it's hard to say for sure.

The rocker arms should switch right over but you may have to space the bolts to the rockers differently to center them back over the valves.
 
Miszny said:
This is the casting number I see on the heads. They are 60919 heads that were bought as bare heads, milled down for smaller chambers and have nice set of valves and some cleanup and blending work done to them.

I was asking you about porting gains in summer time having these heads in mind actually.
Click to expand...
There are lots of things to consider, valve to piston clearance changes for one, and what is the quench/squish distance now? By the sounds of it, You've got 10:1 flat-tops,
& they milled enough to compensate for the Fel-Pro head gaskets. That means no squish whatsoever, a closed chamber head could cause more trouble with the piston down
in the block that far, what type of Eddy chambers and how much was cut? If detonation doesn't rear it's ugly head, and the rockers/valvetrain is sorted out, You should see
a nice pick-up in grunt.
 
IQ52 said:
So the big question here is what cc did the heads start out as. If they were the 84cc heads to begin with, they would have been milled at least .060" to get to 74cc. This will reduce your piston to valve clearance the same amount, at least .060".

The compression is probably not a problem as the combustion chamber shape will help and the cam is big enough to reduce the cylinder pressure to pump gas levels.

The RPM head should use the same ARP head bolts as the stock iron head.

The pushrods might work as the 452 heads must have been milled to get down to 84cc.

The compression bump and the head flow increase should make a noticeable difference. You can't race flowbenches so..........without a flow sheet from the same flowbench for both different heads it's hard to say for sure.

The rocker arms should switch right over but you may have to space the bolts to the rockers differently to center them back over the valves.
Click to expand...

I have flat top pistons with pretty deep valve reliefs. I don't remember exactly, would need to check my notes but they were bit over 6cc volume I think. I have plenty of clearance now, I did some playdoh test and valves barely touched what I put on the piston. I will for sure test this before putting it all together. I am assuming 9.75cc for head gasket. Also there is 7cc between deck height and piston at tdc. So currently I am at almost 106cc chamber with 452s and it puts me at around 95cc with Edelbrocks.

I have plenty of shims and spacers for the rockers so no worries here. Hope pushrods wont stop me like with the cam swap.

I was thinking that perhaps I should sell the RPM heads and go TrickFlow 240 heads... this is why it took me so much time to think about installing them. Car is fun now, I'm just looking for some winter wrenching time well invested here thats all ;-)
 
Last edited:
Yeah, those are closed chambered, what is the piston flat to deck distance on Your slugs?
 
Make damn sure you send the Eddys to the machine shop to get checked our and worked over, because they will need it.
 
Killer6 said:
Yeah, those are closed chambered, what is the piston flat to deck distance on Your slugs?
Click to expand...
I don't remember but I measured it some time ago and my notes say it was just over 7cc capacity. I think minium safe distance is 0.035 and head gasket alone is 0.039 + I guess around 0.035 is the distance I have between piston and deck.
 
RustyRatRod said:
Make damn sure you send the Eddys to the machine shop to get checked our and worked over, because they will need it.
Click to expand...
They were checked, I did not get them new and they are already machined and ready for installation.
 
Miszny said:
I don't remember but I measured it some time ago and my notes say it was just over 7cc capacity. I think minium safe distance is 0.035 and head gasket alone is 0.039 + I guess around 0.035 is the distance I have between piston and deck.
Click to expand...
Well, it's a good thing You're running 98+ octane, 'cause .074" isn't a desirable distance to have in the quench/squish zone.
I would double/triple check that distance for sure.
 
Killer6 said:
Well, it's a good thing You're running 98+ octane, 'cause .074" isn't a desirable distance to have in the quench/squish zone.
I would double/triple check that distance for sure.
Click to expand...

Well I don't really see reaching 0.045" with current engine configuration. With thin head gasket I think reaching 0.055" can be a challenge. Also at 0.045" I am looking at 11.5:1 compression. I will measure it all but still it seems out of reach. Where I live the only options from pump are 95, 98 and 100 octane so this is not really a problem for me.
What is the thinnest head gasket I can get? 0.025"?
Can I use steel head gasket with aluminum heads? Like Mr Gasket 1135G?
 
Last edited:
Miszny said:
Well I don't really see reaching 0.045" with current engine configuration. With thin head gasket I think reaching 0.055" can be a challenge. Also at 0.045" I am looking at 11.5:1 compression. I will measure it all but still it seems out of reach. Where I live the only options from pump are 95, 98 and 100 octane so this is not really a problem for me.
What is the thinnest head gasket I can get? 0.025"?
Can I use steel head gasket with aluminum heads? Like Mr Gasket 1135G?
Click to expand...
I would search but recently, I think .029" is what is available, I still don't get why exactly Mopar ditched the .017" coated embossed shim gaskets. They worked perfectly
for a bunch of builds, but they're gone now, so the Mr. Gasket would be it. An MLS gasket would be best, but I think that is the .029" at best. I sprayed a copper coat on
the shim gaskets when I used them, I haven't used them on an Al head yet, but I would coat them for sure to help ease expansion movement. You may be able to run
that @.053" if those pistons are forged, they will expand more than cast slugs & close that up a bit more when things heat up. First You must have an EXACT measure
of the deck height, then proceed. If You can get an acceptable squish, I wouldn't worry if the squeeze creeps up a tad, the increase in burn rate should make it moot.
More importantly, enlighten Me on the rating method for octane there vs here in the States. Our RON+MON/2 ratings We're familiar with, not so much Your neck of the
woods!!
 
Is the price you spend on ported iron cheaper than new aluminum heads (plus machine shop inspection?) and what would be the flow comparison? If that could be known. And is the flow from the iron heads enough and/or worth it to you vs the cost of aluminum heads?

Hey do not find anything wrong with iron heads.
 
Killer6 said:
I would search but recently, I think .029" is what is available, I still don't get why exactly Mopar ditched the .017" coated embossed shim gaskets. They worked perfectly
for a bunch of builds, but they're gone now, so the Mr. Gasket would be it. An MLS gasket would be best, but I think that is the .029" at best. I sprayed a copper coat on
the shim gaskets when I used them, I haven't used them on an Al head yet, but I would coat them for sure to help ease expansion movement. You may be able to run
that @.053" if those pistons are forged, they will expand more than cast slugs & close that up a bit more when things heat up. First You must have an EXACT measure
of the deck height, then proceed. If You can get an acceptable squish, I wouldn't worry if the squeeze creeps up a tad, the increase in burn rate should make it moot.
More importantly, enlighten Me on the rating method for octane there vs here in the States. Our RON+MON/2 ratings We're familiar with, not so much Your neck of the
woods!!
Click to expand...

Actually in Europe its RON and in USA and Australia DON is used which is what you described.

I wanted to use the steel shim with permatex copper, if it fails to seal I will go with some MLS gasket which is like 4x the price. I have a fresh set of 1135G, I used these with my iron heads with perfect result. My concern was that perhaps embossed steel gasket will damage the heads.
 
rumblefish360 said:
Is the price you spend on ported iron cheaper than new aluminum heads (plus machine shop inspection?) and what would be the flow comparison? If that could be known. And is the flow from the iron heads enough and/or worth it to you vs the cost of aluminum heads?

Hey do not find anything wrong with iron heads.
Click to expand...

Thing is I already have both, I have flow numbers close to my cam max lift in my first post and its 277 iron and 301 alu @.600 lift. These are not the same flow bench numbers.
They are close but I simply have these alu heads and am tempted to try them out. Plenty of winter time ahead with some time to wrench on the car...
 
Miszny said:
My concern was that perhaps embossed steel gasket will damage the heads.
Click to expand...
Never happen.

Miszny said:
Thing is I already have both, I have flow numbers close to my cam max lift in my first post and its 277 iron and 301 alu @.600 lift. These are not the same flow bench numbers.
They are close but I simply have these alu heads and am tempted to try them out. Plenty of winter time ahead with some time to wrench on the car...
Click to expand...
Yes yes, I forgot. I was in on the thread at the beginning.
Well then, sounds like the next step is experimentation and fun.
 
In the end I installed the RPM heads, but let me be more specific:

I took the heads apart and discovered that all the valves were stainless, one of the exhaust valves was bent. (so much for heads ready for install and titanium valves advertised by seller)

I also discovered that Edelbrock only does 3 angle on seats, valves don't have 3 angle, so I had it done while I had it all apart and waited for a new valve.
These heads were machined down about 0.06" to have chambers at 75cc. This caused a bit of a problem with intake bolting down, but not too bad but I had no problem at atll with piston to valve clearance. Playdoh showed that there was a ton of room.

As for head gasket I decided to go with steel shim + permatex. I measured and it seems that with steel shim I am between 0.056 and 0.058 piston to head distance. Static compression is 11.3:1
Heads are on the engine, I did the psi check after install and found 185-190psi all around.
I used some online calculator to check DCR and it seems my cylinder pressure is in the right area and DCR at 9.03:1.

Did not start it yet but after putting spark plugs in I see that cranking seems like a bigger effort on the starter.

Here is my question: I talked to someone that suggested that I will have a problem with detonation because of poor quench (should be 0.035) and my cylinder pressure should be 200+ with aluminum heads...

On the other hand while browsing the internet I found a big block build with heads like mine, quench at 0.075, static compression at 10.7:1 and pump gas friendly...
What am I missing?

Should I use thicker head gaskets to bring the compression down to stay safe?
I have a set of 1009 Felpro just in case...

I use only 98-100 octane gas. The 98 here is 93 in USA, the 100 here is a racing gas, can not guess what is it in USA. I only remember 100 octane gas at Texaco in USA, here we have V-Power racing 100 at Shell.
 
Aluminum heads should/would require a "cylinder head manufacturers suggested choice of gasket", not the steel shim Mr G 1135G style choice. Those are meant for iron on iron.
100_1526-jpg.jpg
 
Max1196 said:
Aluminum heads should/would require a "cylinder head manufacturers suggested choice of gasket", not the steel shim Mr G 1135G style choice. Those are meant for iron on iron.View attachment 1715168516
Click to expand...

If they fail, fine I will use something else. In effort to be as close to optimum quench I decided to take a risk. I covered them with permatex copper to minimize different metal interaction effect.

My main question was if regardless of what material of gasket, perhaps trying to be as close to optimum quench as possible was not that good idea if the goal was not reached?
Perhaps putting my felpro 1009 and making it around 10.7:1 was a better idea afterall? Piston to head would be at around 0.077 then.
 
You must log in or register to reply here.
-

Back
Top