Re: Alum heads vs iron heads on street car
[Re: lewtot184]
#2746732
02/26/20 02:41 PM
02/26/20 02:41 PM
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Joined: May 2019
Posts: 722 Lake Villa Il
INTMD8
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As for the original post I think the hemi may lose a bit more thermally due to the massive chamber. I'm having trouble finding it now but thought I read about a test on an ss/ah Hemi cast iron vs aluminum heads with the same port program and aluminum was down 40hp. Could be wrong, that is just from memory, I'll keep looking for the info. EDIT- This is where I read that- https://board.moparts.org/ubbthread...55708/re-aluminum-heads.html#Post1355708
Last edited by INTMD8; 02/26/20 02:44 PM.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Alum heads vs iron heads on street car
[Re: polyspheric]
#2746738
02/26/20 02:57 PM
02/26/20 02:57 PM
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Joined: Oct 2004
Posts: 8,166 Left Coast
BobR
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One reason why they are more knock tolerant is... less power. The heat loss is power not reaching the crankshaft. This is why you do not remove carbon from the chamber and exhaust ports: it's a thermal barrier. Back to back tests done on BBC 50 years ago: iron wins. How does built up heat in the head get to the crankshaft? If both motors are maximized for their head material aluminum wins every time. NOBODY fast runs iron heads unless rules of their class dictate they must.
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Re: Alum heads vs iron heads on street car
[Re: BobR]
#2746744
02/26/20 03:15 PM
02/26/20 03:15 PM
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Joined: Jan 2010
Posts: 1,443 NW Chicago suburban area
Mopar Mitch
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I find this very interesting... I wanted to start with my cast iron heads... then later switch to aluminum in a about 2-years... but I was told that my pistons (-20 dish) dictated cast iron heads only because of the lower CR (~9.75:1). I've since installed the cast iron heads, and also cc'd chambers and cylinder... calculated the CR at 9.9:1
I'd still like to eventually swap to aluminum heads... per allowable racing class rules. Cast iron allows me to run in more classes and be more overall competitive, but giving up a little to the classes which allow aluminum heads.... weight is factor for me... more than engine power.
Mopar Mitch
"Road racers and autocrossers go in deeper and come out harder!"... and rain never stops us from having fun with our cars... in fact, it makes us better drivers!
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Re: Alum heads vs iron heads on street car
[Re: fast68plymouth]
#2746787
02/26/20 05:16 PM
02/26/20 05:16 PM
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Joined: Nov 2009
Posts: 3,082 St. Paul , Mn.
tubtar
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The notion that you “need” more compression with aluminum heads has been tested at least once with a SBC, where you can buy heads that are the same in iron or aluminum........ and the results are that the power was the same.
I don't know that anyone said aluminum heads " need " more compression. They ARE more tolerant of higher compression , and less likely to experience detonation. As far as over thinking , I guess most of my thoughts are in taking weight off the front of the car. Better handling is one claim , though few of us drive where that difference is really appreciable. But less weight is still less weight. I don't know that they are ever a bad idea , but that being said , I am looking at a set of J heads on my current project. There is a certain pleasure to underthinking.
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Re: Alum heads vs iron heads on street car
[Re: tubtar]
#2746802
02/26/20 05:54 PM
02/26/20 05:54 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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The internet wisdom premise is...... if you changed from iron to aluminum heads, all else being equal, you’d lose power...... because the aluminum absorbed some power away. And...... you’d have to up the CR for the aluminum headed combo to be equal to the iron head combo.
The test in the link I posted did what I feel is a pretty thorough test of that in a very “man on the street” type of build. The difference in power was with the margin of repeatability for the dyno.
That’s using heads that are as close as possible to being the same, other than the material they’re made from.
In the case of what most people here are doing......if they’re going from iron to aluminum....... you’re almost never comparing equal heads. In most cases, you’re replacing iron heads with better flowing aluminum heads(otherwise.....why are you changing the heads?).
It’s going to pretty hard to come up with some sort of “high performance” build combo where the better flowing aluminum heads get out powered by old iron heads.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Alum heads vs iron heads on street car
[Re: Neil]
#2746822
02/26/20 06:36 PM
02/26/20 06:36 PM
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Joined: Dec 2013
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GY3
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I don't know of any mopar heads that are available in both materials that are identical architecture wise.
DART sells sbc heads in both iron and aluminum, but not for Mopars. Going back to back with those heads on a dyno on the same shortblock would tell you. Were the old 440-C Indy heads the same as the 440-1?
'63 Dodge 330
11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs.
9.92 @ 135mph with a 350 shot of nitrous and 93 octane pump. 1.43 60 ft. 3,750 lbs.
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Re: Alum heads vs iron heads on street car
[Re: Neil]
#2746825
02/26/20 06:49 PM
02/26/20 06:49 PM
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Joined: May 2019
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INTMD8
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I don't know of any mopar heads that are available in both materials that are identical architecture wise.
Maybe the MP hemi heads?
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Alum heads vs iron heads on street car
[Re: INTMD8]
#2746827
02/26/20 06:53 PM
02/26/20 06:53 PM
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Joined: May 2003
Posts: 6,616 Downtown Roebuck Ont
Twostick
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I don't know of any mopar heads that are available in both materials that are identical architecture wise.
Maybe the MP hemi heads? Pretty sure those are Edelbrock castings with MP cast into them instead of Edelbrock. Kevin
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Re: Alum heads vs iron heads on street car
[Re: Twostick]
#2746831
02/26/20 07:10 PM
02/26/20 07:10 PM
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Joined: May 2019
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INTMD8
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Yes I thought Edelbrock made them but thought they were closer to the cast iron heads than their Victor heads, certainly could be mistaken on that but thought Victors had larger valves and ports.
69 Charger. 438ci Gen2 hemi. Flex fuel. Holley HP efi. 650rwhp @7250 510rwtq @5700
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Re: Alum heads vs iron heads on street car
[Re: INTMD8]
#2746851
02/26/20 08:04 PM
02/26/20 08:04 PM
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Joined: Mar 2010
Posts: 984 Tennessee
Hemi ragtop
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Yes I thought Edelbrock made them but thought they were closer to the cast iron heads than their Victor heads, certainly could be mistaken on that but thought Victors had larger valves and ports. Edelbrock says that Mopar would not allow any improvement.
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Re: Alum heads vs iron heads on street car
[Re: fastmark]
#2747036
02/27/20 12:21 PM
02/27/20 12:21 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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By the time I fix his 452 heads, I’m 70% there to 440 source alum heads. He is really tight on money. 70% of the way to the selling price? Or the price including shipping? Or the price, plus shipping, plus having them checked out?
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Alum heads vs iron heads on street car
[Re: 67Satty]
#2747081
02/27/20 01:58 PM
02/27/20 01:58 PM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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The 84cc E streets have straight plug holes.
If the OPs budget 383 uses angle plug friendly headers, the 75cc E streets would certainly go a long way to upping the compression.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Alum heads vs iron heads on street car
[Re: fast68plymouth]
#2747285
02/28/20 08:25 AM
02/28/20 08:25 AM
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Joined: Jan 2003
Posts: 6,569 Abilene, Texas
fastmark
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By the time I fix his 452 heads, I’m 70% there to 440 source alum heads. He is really tight on money. 70% of the way to the selling price? Or the price including shipping? Or the price, plus shipping, plus having them checked out? Well when you figure EVERYTHING, more like 50%. New bolts, better head gasket. He has cast iron manifolds and intake. I imagine I will end up with fixing the old 452. I can get him up to about 8.8 or 8.9 CR and use a smaller cam with about 218@.050 and survive. I may have to fly cut the pistons a little for clearance. Comp says their cam with a 110 centerline is ground with 4 degrees advance already. That’s as big as I dare get.
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Re: Alum heads vs iron heads on street car
[Re: fastmark]
#2747316
02/28/20 10:31 AM
02/28/20 10:31 AM
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Joined: Jan 2003
Posts: 14,531 So. Burlington, Vt.
fast68plymouth
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I highly doubt there would be any clearance issues with a Comp 268H cam.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
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Re: Alum heads vs iron heads on street car
[Re: fast68plymouth]
#2747339
02/28/20 11:46 AM
02/28/20 11:46 AM
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Joined: Dec 2003
Posts: 23,273 Here
jcc
If you can't dazzle em with diamonds..
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I got a similar dilemma with iron vs Alum heads.
I got a well built running mild built street 360 motor 9:1 mild cam Hyd cam with Hughes Stage 2 ported heads with SS valves. Its in a street cruiser.
I also got a spare set of built 305cfm Alum Hughes ported/coated heads sitting on the shelf.
Trying to figure out if its worth installing on a street motor, I like the weight weight loss, and not sure what I will ever do with them.
What to do?
" All sorts of things can happen when you are open to new Ideas" Inventor of Kevlar
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Re: Alum heads vs iron heads on street car
[Re: BobR]
#2747594
02/28/20 11:28 PM
02/28/20 11:28 PM
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Joined: Jan 2003
Posts: 27,421 Balt. Md
383man
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One reason why they are more knock tolerant is... less power. The heat loss is power not reaching the crankshaft. This is why you do not remove carbon from the chamber and exhaust ports: it's a thermal barrier. Back to back tests done on BBC 50 years ago: iron wins. How does built up heat in the head get to the crankshaft? If both motors are maximized for their head material aluminum wins every time. NOBODY fast runs iron heads unless rules of their class dictate they must. Course its not my statement but I think he means the iron heads wont disapate the heat as much as aluminum so the heat exspansion in the cyl will be more with iron heads since they hold more heat and can add to more power pushing on the piston which will go to the crank of course. Myself I agree with most that the difference is so minimal between iron and aluminum heads that many overthink it to much. As said most aluminum heads are newer and more modern with better combustion chambers and better flow then 50 year old iron heads. I have all the equipment to do the valve work on iron heads and set them up but to me its a no brainer in my street/strip car to go with the aluminum heads. And for the price of aluminum heads today most will spend as much paying someone to work iron heads for them anyway. And they do shave a little weight off the front end. Ron
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