What and where to clean up Edelbrock RPM's?

[dano]

So I bought a set of RPM's for my 340. I have the stock above deck pistons (they are TRW Forged replacements) so I purchased the ones with the .060" cut chambers. I plan to measure all 8 pistons to find the highest ones and mill the heads to get .040 clearance with head gasket. I also plan to replace the spring to match my Lunati 60403, have a valve job done and everything checked out before I run them.

I've read these heads need cleaned up to flow better. I have ported heads before with good success, but always with someone familiar with the head to outline what needed done. This is a street engine so I'm not looking for a full port job, just clean up and minor correction if need be. My plan so far was gasket match, flash clean up and check the throats.

Any advice pertaining to cleaning up would be appreciated.

 

[crackedback]

IMO, send the open chamber heads back and get the 60779 closed chambered one. Use a .050-.070 head gasket to get your quench distance. You aren't going to get any quench with those open chambered heads and stock pistons.


Basic bowl clean up and a good valve job will help the ede heads.

 

[autoxcuda]

I don't think I'd say "need to be cleaned up for better flow". Almost any as cast head will flow more after they are cleaned up in the bowls and throats.

Just do a bowl to throat clean up while everthing is apart.

 

[dano]

IMO, send the open chamber heads back and get the 60779 closed chambered one. Use a .050-.070 head gasket to get your quench distance. You aren't going to get any quench with those open chambered heads and stock pistons.

It was my understanding the .060 ones are the same as the 60779, just clearanced for stock positive deck pistons? Wouldn't it be the same to deck the these down and get the same quench distance than it would be to add a thicker gasket? Unless their quench pad is different or angled like the stock open chambered heads.

 

[crackedback]

That's doing it the hard way.

I can make one left turn or make three right turns to get going the same direction. Similar situation here. Lots of extra work and cost IMO to use a poor chamber to start with.

Even with positive deck piston, I NEVER use those open chamber heads. In fact, every set I've ever possessed, the entire chamber gets milled off.

Lots of ways to skin a cat.

 

[dano]

Even with positive deck piston, I NEVER use those open chamber heads. In fact, every set I've ever possessed, the entire chamber gets milled off.

Lots of ways to skin a cat.

I'm trying to understand and wrap my mind around this, so please excuse the extra questions.

How would a quench pad recessed into a head and a theoretical .040" piston to pad clearance be worse or less ideal, than a head with its block to head mating surface be the quench pad and a theoretical .040" piston to pad clearance?

I'm not opposed to changing what I purchased, i just like to understand why. I do value the information and appreciate everyone's time.

 

[crackedback]

It's easier to deal with a flat machined surface. The heads will have some variations in depth from chamber to chamber, along with your piston deck height variations. Why not have one side be a variable at worst.

Some of the really thin head gaskets don't play well with ede heads.

Edelbrock didn't do the SB mopar would any favors with those open chamber heads, IMO.

.060 depth + .030 gasket - ~.015 deck height = .075, so you need to mill the heads .035-.040ish to have it fit in a sloppy open chamber. Less piston protrusion = more milling. So you are getting close to a flat surface anyways.

Much easier to know your piston deck height and choose a gasket to make it work. Even the felpro 8553 perma-torques sometimes work well with the above deck 340 pistons.

 

[dano]

It's easier to deal with a flat machined surface. The heads will have some variations in depth from chamber to chamber, along with your piston deck height variations. Why not have one side be a variable at worst.

Some of the really thin head gaskets don't play well with ede heads.

Edelbrock didn't do the SB mopar would any favors with those open chamber heads, IMO.

.060 depth + .030 gasket - ~.015 deck height = .075, so you need to mill the heads .035-.040ish to have it fit in a sloppy open chamber. Less piston protrusion = more milling. So you are getting close to a flat surface anyways.

Much easier to know your piston deck height and choose a gasket to make it work. Even the felpro 8553 perma-torques sometimes work well with the above deck 340 pistons.

Thanks for the explanation. I understand I may just end up with a .020-.015" recess in the head.

I'll see if I can change my order and go from there.

 

[autoxcuda]

Here are some before and the beginings of a cleanup and minor not aggressive port job.

 

[1972DusterPaul]

Edelbrock doesn't even like their own open chamber heads.

They used their 60779 heads on a 340 and took .035 off the pistons with their Power Package according to a Mopar Muscle article I read.

Paul

 

[dano]

Edelbrock doesn't even like their own open chamber heads.

They used their 60779 heads on a 340 and took .035 off the pistons with their Power Package according to a Mopar Muscle article I read.

Paul

Or is this a cart in front of the horse deal, did Edelbrock learn when they got their 340 that the 68-71's had positive deck pistons, so they created a head that was machined .060" based on the 60779?

 

[dano]

OK, So I got my order switched to the 60779.

And thanks for the pics Autoxcuda!

 

[flyfish]

Not sure if it is still a problem area, but when I got my Edelbrocks years ago (2001 I think) there was an issue with tight valve guides...might want to check to be safe.

 

[1972DusterPaul]

If you go to the Edelbrock website and to their Power Package page they have the 60779 listed for 340-360 engines...so you would think any new information would be updated there.

http://www.edelbrock.com/automotive_new/mc/power_package/rpm_power_packages.shtml

I hope to pick up my completed 340 tomorrow...the shop milled my pistons down for the 60779 heads...so hopefully I will be on the road in a couples weeks.

Paul

Or is this a cart in front of the horse deal, did Edelbrock learn when they got their 340 that the 68-71's had positive deck pistons, so they created a head that was machined .060" based on the 60779?