Another Edelbrock RPM head question!

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v8fish

v8fish

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Ok so I found a deal on a set of new in the box RPM aluminum heads (Closed chamber). I have a mild 360 with flat top pistons and hydraulic cam. Im not looking for a race motor or maximum flow but I've read many postings about improvements to be had with porting/polishing of these heads. I can see immediately that they can use some runner smoothing/blending to improve effieciency. So again Im not looking for max flow numbers just gonna clean them up a little. I messed around a little back in the day with iron heads and used a carbide burr for shaping and sanding rolls for smoothing. I am thinking I can do what I want with sanding rolls on these heads. But I've never worked on aluminum heads. I will also be disassembling them to check things such as guide clearance valve job and shavings as reported by many. Am I on the right track or what have I missed?
 
I would do some calculating to figure out your compression ratio it maybe high with those heads .
 
I am not sure what you will gain worthwhile with porting for a mild cam engine. These flow so much more than stock heads out of the box. I'd put the effort into getting someone with a Serdi machine to clean/open them up right below the valve seats and call it good.

Yes, on looking at the CR for sure. What pistons and cam do you have?
 
Nobody tries to port with a sanding roll so I think what you are trying to do will be just fine. Blend the sharp corners where the machining meets the as cast port, check clearances and the valve job. Clean 'em up and assemble them. It should make a difference to a completely stock engine.
 
nm9stheham said:
I am not sure what you will gain worthwhile with porting for a mild cam engine. These flow so much more than stock heads out of the box. I'd put the effort into getting someone with a Serdi machine to clean/open them up right below the valve seats and call it good.

Yes, on looking at the CR for sure. What pistons and cam do you have?
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Im not trying to "port" them just clean up the machined to cast transitions and maybe some minor smoothing to rough cast runners.
 
nm9stheham said:
I am not sure what you will gain worthwhile with porting for a mild cam engine. These flow so much more than stock heads out of the box. I'd put the effort into getting someone with a Serdi machine to clean/open them up right below the valve seats and call it good.

Yes, on looking at the CR for sure. What pistons and cam do you have?
Click to expand...

I didn't build the engine so I don't know for sure what pistons were used. Runs fime on 93 pump gas with no ping/detonation. Has a racer Brown .510 hydraulic cam. Again I'm not looking for porting or max flow just want to clean up the transition from machined to cast surfaces and maybe smoothe the rough cast runners a bit. Everythung I read says aluminum heads want more compression so I don't anticipate any trouble with the closed chamber heads.
 
v8fish said:
I didn't build the engine so I don't know for sure what pistons were used. Runs fime on 93 pump gas with no ping/detonation. Has a racer Brown .510 hydraulic cam. Again I'm not looking for porting or max flow just want to clean up the transition from machined to cast surfaces and maybe smoothe the rough cast runners a bit. Everythung I read says aluminum heads want more compression so I don't anticipate any trouble with the closed chamber heads.
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Well everything you've read about aluminum heads wanting more compression just might be bologna. Old mechanics tales. But I'm tired of fighting that battle. What is your present cranking compression?
 
v8fish said:
I didn't build the engine so I don't know for sure what pistons were used. Runs fime on 93 pump gas with no ping/detonation. Has a racer Brown .510 hydraulic cam. Again I'm not looking for porting or max flow just want to clean up the transition from machined to cast surfaces and maybe smoothe the rough cast runners a bit. Everythung I read says aluminum heads want more compression so I don't anticipate any trouble with the closed chamber heads.
Click to expand...
OK on just a clean up. Got it.

The concern over the compression is very real. The fact that you are presently OK with 93 octane with the current open chamber heads does not mean at all that you will be OK with these closed chamber heads. You will be lowering the chamber volume by about 10 cc's. As an example, your SCR could go from 9.4 to 10.4, and it could be very touchy for avoiding detonation, unless the cam is moderately large and you are a good tuner. So you can't just blithely conclude you will be OK based on the present heads' performance.

Don't take this as a criticism at all; you are looking at a great set of heads. We just want to help steer you away from very possible trouble.

Just to help move this along, do you have the PN on that .510" lift Racer Brown cam? Or the cranking pressure as suggested?
 
nm9stheham said:
OK on just a clean up. Got it.

The concern over the compression is very real. The fact that you are presently OK with 93 octane with the current open chamber heads does not mean at all that you will be OK with these closed chamber heads. You will be lowering the chamber volume by about 10 cc's. As an example, your SCR could go from 9.4 to 10.4, and it could be very touchy for avoiding detonation, unless the cam is moderately large and you are a good tuner. So you can't just blithely conclude you will be OK based on the present heads' performance.

Don't take this as a criticism at all; you are looking at a great set of heads. We just want to help steer you away from very possible trouble.

Just to help move this along, do you have the PN on that .510" lift Racer Brown cam? Or the cranking pressure as suggested?
Click to expand...

I do not have the cam specifics other than the previous owner states it was a .510 lift hyfraulic from Racer Brown. I can get the cranking pressure with the existing heads as it is still assembled,but don't currently have it.
 
Probably the SSH44, 292 advertised, 242@ .050, .510 lobe lift @ 1.5:1, LSA?
 
OK, if that is the cam advertised duration, and if the pistons are flat topped, then is not likely going to be any issue. That level of cam duration is gonna keep DCR down below 8. But the deveil is still in the details. I'd expect the the engine presently show weakish torque at very low RPM's with open chamber heads.
 
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