[DiamondJim]

I have always heard that all things being equal(head flow/cam/etc) that cast iron heads will make more power than aluminum. As a percentage, any idea how much the difference is? Anyone ever see back to back dynos of heads with the same flows but one iron and one aluminum? What started me thinking about this is I woould like to get some Edelbrocks or KRE heads for another project, I also have some KRE race ported 6X-4's that flow 256/205. Opinions? Thanks -Jim

[WARPed]

There is no cast iron equivalent to any of the aluminum heads of today. The available aluminum heads are so superior to the iron heads that to do such a test would not be possible.

[myckee]

One of the magazines did a back to back comparo, on a chev I think, within the past couple of years, and the aluminum heads made slightly more power.

[DiamondJim]

Alex, I am not sure I would agree. My car with the ported 6X-s run very close to cars with box stock edelbrocks, (3800lbs/117mph), as a matter of fact I have outrun a few. At this point I don't want to spend money on something that would not really be an upgrade. What we really need is a modern fast burn type chamber, flowing 350 CFM and a reasonable price. Guess I am dreaming. -Jim

[Skip Fix]

Recent Chevy Hi Perf test of three DART 215cc heads on a 383. All same chamber size and same port size.One set iron designed with wet flow, one set aluminum, one set aluminum wet flow designed. The iron had the lowest HP! They all three had different power peaks. The aluminum wet flow design had the best peak , the highest average and the highest peak rpm.

So much for the superior iron advantage.

[1qikta]

Gotta keep some originality under the hood....I would much rather do work to iron heads and keep a factory appearance than go overboard with E heads
or KRE's.The look is almost BB Chevy.

Aluminum is expected to over achieve....Iron is not.


Sleeper?????

[Brian Baker]

Iron doesn't dissipate heat as quickly as aluminum. This is why all things "equal" (at least on paper), the iron will produce more power. It stands to reason the more heat retained in power production (and not wasted through transferring to the metal, and the coolant, and out the exhaust), the more efficient the engine will be. If someone ever figures out how to transfer 100% of the heat produced in combustion into power to the crankshaft, they'll have something, but it will never happen with internal combustion engines as we know them.

Iron heads will make good power, no question...but to compare an iron head that's had some porting done and flows 250-260 cfm (more for a round port) to a box stock Edelbrock is a bit "apples and oranges". Apply the same amount of porting to the Edelbrock head and you can get 325+ cfm before going to a wide port (the most flow I've seen from a non-wide-port E-head was in the 340-cfm range, but others may have seen more). Additionally, a box stock E-head purportedly flows 270-cfm (or thereabouts). For the same coin, you'll just be getting started with the E-head in terms of power producing capability whereas the ported iron head will be maxed out.

[potentpontiac]

Some good points Brian.My ra4's flow in the 295-300 range@28"at 650 lift.My E heads that I am working on flow 330@700 lift.Will be a good comparison to see if the E head out performs my steel heads.I think velocity may be the key here,with the bowl being much smaller with the iron head.Once I get finished with the new heads,will post some results,comparing the difference.

[DiamondJim]

Thanks Guys. Brian, the heat deal explanation really makes sense to me. Thanks. -Jim

[65nss4spdGTO]

I agree with Brian, I talked with Indy Cylinder head about this same issue. They feel some form of coating could help aluminum heads to retain the heat.

[White Warrior]

The other obvious issue is; Who needs the weight?

[Skip Fix]

I agree aluminum can disipate heat better,but guys, the Chevy test was similar flow heads, same motor different heads(all things equal Brian) and the cast iron lost-how can that be if it is really that much to affect HP? They were the same manufacturer so you wouldn't think advertising bias is in there.

Smokey Yunick used to used some kind of furnace coating in the BBC aluminum heads back in the day to help keep in the heat.Coatign the piston tops and chambers is soemthing some folks do to retain the heat.

I'm with you Dave I'm too old to lug cast iron heads or intakes around! I leave my weight lifting for the gym.

Grind the Edelbrock or Kaufman off and paint them and most folks wouldn't know they are aluminum.

[Brian Baker]

For my funny car engine (IA-2 block with E-heads), I had the pistons coated. Skirts for lubrication and tops for heat "reflection" back into the chamber.

[Dragncar]

D Jim,the High Port flows 330 out of the box and has a modern fast burn combustion chamber and is only 1500$ bare.Not a bad deal and it seems everyone that has them is happy.
On the back to back chevy test not enough info was given.What was the C/R of the heads and what was the octane fuel being used.
As far as weight what is the diff with Pontiac heads,40 pounds.It is not like it is 100 pounds like a bbc.

[Skip Fix]

Pontiac heads iron #16 62lbs. E head 36 lbs on my scale. More than a 10KG olympic weight!


Chevy test 10.3:1, 72cc chamber 384.6ci(4.04 bore,3.75 stroke) 91 unleaded. So enough there should have been possible heat issues. Don't know how that info makes much difference as it was a totally back to back short block/intake/carb/headers, if heat loss causes power loss the aluminum should be on the bottom not the iron.

[Brian Baker]

Skip...it does...aluminum dissipates heat much faster than iron. The reason the aluminum head came out on top in their test (or at least one of the reasons) could have been from better port and chamber design over the iron head. Did they list in the test which timing setting resulted in the most power for each combo, or did they test them both at the same total timing setting?

[Dragncar]

Exactly what I was after.At 10.3 to 1 an engine with iron heads will ping with 91 octane gas with any kind of timming to make power and the aluminum headed engine with everything the same will not.Thus it makes more power.Sounds like someone wants to sell more aluminum heads.
The heat loss helps the aluminum headed engine not detonate.
If everthing is the same the iron heads will make more power.Timming,octane,heat,cooling,commpression throws a monkey wrench in the middle of it.Also,there is more power in gas that is lower in octane not less.Regular has more BTUS in it than premium.The stuff in a gallon of gas that makes it higher octane and gives it the ability to have a higher flash point just takes up space and does not burn.

[DiamondJim]

Is KRE shipping the high ports now? Never really looked at them until just now. At 2400 bucks complete they look like the best deal on the market right now. I can dish the pistons on this next deal so the high ports may be the ticket. -Jim

[Brian Baker]

Originally Posted by DiamondJim

Is KRE shipping the high ports now? Never really looked at them until just now. At 2400 bucks complete they look like the best deal on the market right now. -Jim

Until you see their "no returns after 10 days" policy.

[Dragncar]

The High Ports can be used on a factory block and non offset roller lifters can be used unlike the Tigers.If you want to spend 1200$ on porting 370cfm is available in the standard pushrod location and 400cfm can be had if you want to go the wideport rout.Best bang for you Pontiac buck out there.Now if Edelbrock would just get smart and make a head with a modern chamber.