Why am I drawn to the aluminum??

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Idaho

Idaho

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I've been planning a junkyard 5.9 Magnum in my 69 Dart, with plans to use the RHS heads from IMM.

I'm close to ordering heads and find that for whatever reason, I'm wanting the Edelbrock Performer RPMs.

One reason that makes some sense is weight reduction. I've added about 50 lb with Caddy CTS seats and can balance that out with the lighter heads. Really not that big a deal but not insignificant. Maybe it's just that aluminum is sexy :D

With the same parts, I think performance will be a wash. I'm planning an an air gap, 750 DP, and "a cam".
Power to the ground via 833 OD 4 spd with 8.8 410 gears, 27" rear tire - 285 40 18.

Trying to choose a cam hurts my brain. Brian at IMM had suggested a Thumpr. I don't want to get into a debate with the Thumpr haters but I think it would be a good match with either head.

Cost will be close enough between the two to be a non issue. I'll need rockers and pushrods either way. I found a local head shop that will go through the Eddies for a reasonable fee.

I had thought I'd need a piston change to make enough compression for the Eddies. Doing further research I think not. This is likely the key factor in my decision. Here's why I think I don't have to change them.

http://www.hotrod.com/techarticles/engine/hrdp_0804_small_block_mopar_engine/viewall.html

The Eddies made excellent power with stock pistons. However they do not give the details on compression ratios and I would not want to put all my faith in one article.

So I did what I could to gather more info. Here's what I came up with using my Mopar Engines reference, Google and the Summit compression calculator.

Some info was hard to track down. Stock piston dish volume and how far down in the bore they sit are not in the reference. Below deck height is listed anywhere from zero deck to .070 on forums. .050 is the most common spec given. I found nothing for dish volume.

Working backwards using .050 below deck, a factory .048 gasket, 62 cc chamber and factory 9.1 CR gives a 9 cc piston dish volume.

Eddie heads are 58 cc. Using a .028 gasket and 9 cc DV gets compression up to 9.87. A .010 head shave puts it up to 10.

Eddie states the head is good for up to .580 lift but warns that stock pistons may not have clearance depending on the cam. They specify a .042 gasket. The Thumpr cam has a modest .513 lift so some room to play with.

My gut says the Eddies could work out fine but I know I could be way off base with my calculations.

So like O'Reilly says, "tell me where I'm going wrong here".
 
If you think the eddie held will perform with Brians head the way you pull them out of the box, you're in for a rude awakening...

Compression on aluminum MAY be able to be bumped up, NOT always. There have been test that show there is no true compression advantage with aluminum.

50# isn't gonna do squat on a street driven car.

Unless you port the eddies, they won't run with an RHS head like what Brian does.
 
johnparts said:
You can also run higher compression on the aluminum heads because of lower heat soak issues.
Click to expand...

The common knowledge that's out there says you HAVE to run higher by 1 to 1.5 points to make the same power. That's why I've fussed with the calculations.

However... there is this - which flies in the face of that idea.


http://www.carcraft.com/techarticle...luminum_cylinder_heads_test/dyno_results.html

Very interesting to me in this test - the engine made more power at lower temp with either aluminum or iron heads. How does that jive with the idea that heat = power and heat loss by aluminum heads requires more compression to compensate?
 
I think the best approach is to pull a head and see where the pistons are. I'd take aluminumover any iron any day. And the RHS heads are heavier than the factory heads but a bit. You're doing your homework - s otake some measurements to get tit right. And yes - I'm a Thumper hater...lol.
 
crackedback said:
If you think the eddie held will perform with Brians head the way you pull them out of the box, you're in for a rude awakening...

Compression on aluminum MAY be able to be bumped up, NOT always. There have been test that show there is no true compression advantage with aluminum.

50# isn't gonna do squat on a street driven car.

Unless you port the eddies, they won't run with an RHS head like what Brian does.
Click to expand...

Interesting. The flow numbers for the two heads are close.
 
Have my heads off,my 00 Magnum.If you want ,I can verify piston to deck. All original. The Edelbrocks out of the box,won't even come remotely close to Brian's RHS ,prepped. Could have him prep,some Eddys,as well. The thumper,is a neat grind.Just follow ,Brian's degreeing instructions.
 
moper said:
I think the best approach is to pull a head and see where the pistons are. I'd take aluminumover any iron any day. And the RHS heads are heavier than the factory heads but a bit. You're doing your homework - s otake some measurements to get tit right. And yes - I'm a Thumper hater...lol.
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You are so right. I will be yanking a head off shortly. I had thought of that but got caught up in calculations :sad7:
 
Abodybomber said:
Have my heads off,my 00 Magnum.If you want ,I can verify piston to deck. All original. The Edelbrocks out of the box,won't even come remotely close to Brian's RHS ,prepped. Could have him prep,some Eddys,as well. The thumper,is a neat grind.Just follow ,Brian's degreeing instructions.
Click to expand...

Abodybomber Lmao! 4 posts,all at the same time!
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LOL I can't keep up! I didn't know Brian would prep Eddies. I do like the idea of his help in setup. Why the RHS advantage when the flows are close?
That would be awesome if you could take a measurement.
 
Trust me,Eddys DON'T flow that number,out of the box.I spent 40+ hours ,on a set porting.Sold them to someone here.Flowed 280 -ish, at a local reputable shop. Out of the box,maybe 230,235. Mind you,Brian gets,270 with RHS's.
 
Idaho said:
Interesting. The flow numbers for the two heads are close.
Click to expand...

15+ cfm at 400, and 20+ at 200-300 is not close. I know that a OOTB ede does not flow what they edelbrock says on Brians bench. The difference is and could be larger. Better springs and valves on the RHS stuff too.

With a thumpr you'll be accessing about 400 lift and the fill rates at the lower points will help tq. That alone could be 30hp, more likely, closer to 20hp.

The only time I would take an aluminum head over an iron head is if it performed the same or very close to iron counterpart. Not the case here. Take a well ported iron W2 or a box stock ede head? No comparison.

Plus, you aren't dealing with a compression limitation issue here.
 
Abodybomber said:
Trust me,Eddys DON'T flow that number,out of the box.I spent 40+ hours ,on a set porting.Sold them to someone here.Flowed 280 -ish, at a local reputable shop. Out of the box,maybe 230,235. Mind you,Brian gets,270 with RHS's.
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I see... Is that 270 with or without porting?
15+ cfm at 400, and 20+ at 200-300 is not close. I know that a OOTB ede does not flow what they edelbrock says on Brians bench. The difference is and could be larger. Better springs and valves on the RHS stuff too.

With a thumpr you'll be accessing about 400 lift and the fill rates at the lower points will help tq. That alone could be 30hp, more likely, closer to 20hp.

The only time I would take an aluminum head over an iron head is if it performed the same or very close to iron counterpart. Not the case here.

Plus, you aren't dealing with a compression limitation issue here.
Click to expand...

I do know there's at least two guys on here posting impressive times at the track with stock bottom 5.9s and RHS or EQs. I tend to trust that more than an article showing high numbers. (A nod to your sig).

Thanks this is all helpful.
 
crackedback said:
The only time I would take an aluminum head over an iron head is if it performed the same or very close to iron counterpart. Not the case here. Take a well ported iron W2 or a box stock ede head? No comparison.
Click to expand...

Of course not, one is ported and one is OTB.....not really an apples-apples comparison is it? :coffee2:

Some of these head discussions are very interesting......until the poo poo flinging starts.....
 
Yes,no porting. Brian,got this RHS head dialed. No porting,sweet Ferrea stainless valves,a real valve job. You looking at roughly, 1000-1500 on top of the Edelbrock's price. Valve job,porting are not cheap.
 
inkjunkie said:
Of course not, one is ported and one is OTB.....not really an apples-apples comparison is it? :coffee2:

Some of these head discussions are very interesting......until the poo poo flinging starts.....
Click to expand...

Well one is Iron and the other is alum, according to some, you take alum every time. :) It's a generalization which will find you seeing tail lights.

moper said:
I'd take aluminumover any iron any day.
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:happy1: :D. This is good stuff. Since i never opened up a Magnum, i'm curious about the piston deck height........050" is deeper then i expected?
 
Abodybomber said:
Yes,no porting. Brian,got this RHS head dialed. No porting,sweet Ferrea stainless valves,a real valve job. You looking at roughly, 1000-1500 on top of the Edelbrock's price. Valve job,porting are not cheap.
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Eddies for roller cam run $830 or so at Summit so $1660.

Brians unported setup is a bit less IIRC so not sure why you're saying 1000 - 1500 extra?

Edit: Brians are $1469 per set, less than I was thinking so maybe a bargain in comparison.
 
Just an FYI.

You know how much more HP it takes to move a 3250# car to 12.00/112 that originally weighed in at 3200#.

FIVE hp... that's IT!

I'll take the weight penalty for an extra 15+ hp. Remember kids, as Barbie says, Math is HARD! :)
 
Brian's RHS head's are some Bad Mo Fo's and for the $$ can not be beat. You want to dump another 1000-1500 into the Eddy's after you buy them for $1500.00 $1700.00 then they will start to contend with the Brian's RHS Head.
 
Abodybomber said:
Trust me,Eddys DON'T flow that number,out of the box.I spent 40+ hours ,on a set porting.Sold them to someone here.Flowed 280 -ish, at a local reputable shop. Out of the box,maybe 230,235. Mind you,Brian gets,270 with RHS's.
Click to expand...

You got to remember Brian's gets those numbers and the heads are NOT Ported.
 
Idaho,Edelbrocks,are corn cobs,out of the box.The extra hours ,to do a valve job ,and port add up.Like I posted earlier,30 to 40 hours personally porting a set of Edelbrocks. With their valve job,flowed 280,on the intake port. Hours spent porting- equals hourly rate.A good porting job alone,starts at 500 minimum .Worked at a head porting shop,for 3 or 4 years.Brian's RHS heads,are a steal.
 
It's all cool,Ink.The pics,of your stuff ,rocks.I just want someone,to avoid, what I had to go through. Just making ,a truthful statement,of time spent fixing silliness.
 
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