I thought it was an interesting discussion. I only offered some input based on thermodynamics/heat transfer as I have engineering background there (not a professional by any means).

As a side note, I'm currently building a pair of engines, and have gone with Dart 308 iron eagles. The biggest reasons I went iron are 1: Corrosion and 2: Cost.

Had I gone with aluminum, the only changes would be a smaller intake runner (not many options with iron) and probably a little more static compression.

What did i miss ? Whos throwing stones or arguing ? Sure we are debating each others thoughts, but nothing wrong with that.

The main purpose of my post, was more to see if anyone has any hard data, to back up the theory of aluminum dissipating the heat, and its effect . I certainly have heard this theory for many years, its not a new one. Ive seen it mostly promoted by those selling aluminum heads.

I guess at what power level , is this even a concern ? I would love to see an Na 572 or 540 build with the Engine Quest 320 heads, or those 330 cnc oron eagles

Funny, I didn't see any negativity worth noting.
Some differing opinions, but that's what forums are for.
Maybe try not to be so sensation to posters who offer opinions contrary to those you hold in high regard.

I hear ya on corrosion and cost issues. The first thing that I ask people when they ask me what is best to use, we have a lot of discussion about maintenance and upkeep of steel vs aluminum heads. On the set of engines I'm building right now for a friend, I determined that an iron head was probably better for him for cost reasons and his regular boating habits.

I think things like Fourier's Law are very interesting topics when it comes to engines. I'm not an engineer but I do work with engineers for a living.

Some posts were modified after posting but that's ok... moving on!

On a side note, I just got done with a mild (450 ish hp) 446 for my Mopar. We used iron HP Mopar castings that are widely considered "old school" and outdated. With a good bit of port and bowl work, meticulous setup and a good valve job, we achieved a good result.

If I believed that the only way to go was to buy some "bolt on" aluminum heads, I'd be a grand lighter and no further ahead.

Honest question

What is, or is there, a realistic max power level for a properly built Marine engine with Iron heads?

Or should it be at what power level is the cost savings not worth it anymore?

LOTS of good info on this thread for and against IRON heads!

My first thought here (and very simple thinking) is once you reach max cubic inches, max boost for max octane all at max compression for iron heads, you could go a little further with aluminum heads on the boost/compression talking gasoline.

The other issue is most ultimate max performance heads will be aluminum with no iron counter part.

And what is the number for say a 632 inch running 112 octane? 2000 horse?

In my experience with boats it was right around the 800-850hp mark. In my own engines and others that I've worked on over the years I would notice signs of heat on the deck between cylinders and on head gaskets between cylinders. Once I switched over to aluminum I saw those tell tale signs go away. I also noticed, with blower engines, valve sealing (valve sealing with the seat) to degrade faster, especially on the exhaust side with steel heads. On the flip side, I've seen aluminum head surfaces wear faster. And, just because they're aluminum doesn't mean they don't corrode. I had to have my hard anodized AFR's worked on around the water passages after 3 seasons. They never leaked but when I did my builds last year I had to have them fixed. Suffice to say, now my engines get fresh water flushed regardless of how much salt (lack there of) is in the water I boat in.

My thoughts exactly

There's so many variables, there really can't be a hard number in my opinion. In an offshore marine application you have almost unlimited cooling capacity, so I can't really see an edge there for or against, as long as your combination and tune up is good. It's true the alu head may give you a little extra safety factor (much like forged pistons) if your tune up is off, or your combo really needs a bit more octane. Chamber softening, polishing, etc, on an iron head can help mitigate pre-ignition as well. I have some iron headed boosted stuff in the 1000-1100hp range that has run for years with no issues, and am currently doing a pair of 540's with iron RHS 320's with 4.0 whipples, and a 540 3.3whip with the eq320's. Also some marine race stuff that requires a 23 degree iron head and makes 1.8hp per cube. I don't tune it any different because of the head material; chamber and piston design have far more influence.

I think the main advantages of aluminum heads, as has been previously stated is : Wider selection of port sizes and shapes, weight, and repairability after catastrophic chit. If you can find an iron head that fits your engine design criteria, and the durability and corrosion resistance is a benefit, then I wouldn't let a theoretical hp limit enter the decision process

Conventional head I'd say it's equivalent to aluminum. The material of the cylinder head is not it's limiting factor. The availability of a comparable head to it's aluminum counterpart is going to be the limiting factor. Since we're talking predominantly about BB Chevy, the RHS 360 can be ported and valved to make stupid power on a really big engine. Same with the 345 Iron Eagle. Engine builders and cyl heard porters will have their preferences. Like I said before, there are racing sanctions who's rules dictate iron-only and there is NO shortage of power in those classes. I have a customer/friend who has a 509ci BB Ford in a truck pull class that demands iron heads. He runs the IDT head and the engine turns 9800 rpm and makes over 2hp/ci with a 4150 carb n/a. That head would be right at home in any other application; blown, bigger cubes, marine, off road, whatever. It's basically a copy of the A460 head only made of iron. There are comparable BB Chev builds with iron heads too. Unfortunately RHS quit making that head.

Do you have an A/F ratio or BSFC range that you like to tune for (blown)?

Using bsfc numbers as a tuning method would scare me.

power-adder and aggressive tune-ups? :cartman:

"I took my silverado to the dealer and they gave it an aggressive tune-up because it had a power adder K&N filter..."

Was getting some PM's about the EQ heads. Heres a couple pics of them as requested

Spec sheet

Those look like very nice castings.

Mild do you think the hard anodized will hold up in salt?

Does hard anodizing work on cast iron ? If so, best hard anodizing I've seen was how Canfield used to do there aluminum heads. They would hard anodize everything but spark plug threads/seat , valve seat, and accessory bolt holes. Yes, the deck suface was anodized too. Since anodizing makes normal grounding points dead, run a negative battery cable to both heads. Again, with accessory holes and spark plug threads/seats bare, your ignition system will work as desgined. Coolant temp sensor will have to be grounded externally (easy - just ground the body of it) and if you have electric choke, the ground wire will have to go to one of your new ground points. Oh, get the intake manifold hard anodized too - especially if aluminum.

I also think incorporating a sacrificial anode can be beneficial to aluminum heads, even in fresh water.

I was thinking about camshafts, the overlap effects on chamber temperatures today.

I know some guys are all about aluminum heads, cold water temperatures, and intercoolers, to help reduce detonation, and its true. But I think everyone overlooks the impact a camshaft design has on combustion temperatures. Theres still plenty of engines out there with aluminum heads and superchargers, burning pistons, blowing head gaskets, and tuliping valves. While the Iron vs aluminum debate is certainly worth talking about, I also think there are other things to consider when building a detonation free supercharged engine. Everyone wants a cam that simply will "make power". I want a cam that makes power, doesn't beat up my valvetrain, and possibly can help cool down my cylinders. I can care less about mpg in my application.

Back when the "EGR" valve was introduced, its goal was to reduce combustion chamber temperatures. What it did, was pretty much take the burnt exhaust gas, and recirculate it back into the engine at certain engine loads. It basically was diluting the intake charge, with gas that can't be burnt again, as its not really combustable any longer. Modern engines, can achieve this, through VVT, or variable valve timing. By being able to manipulate when the valve opens and closes, it can lower combustion chamber temperatures.

So, when not using a EGR valve, or not having VVT, the basic camshaft design, can have an impact on the combustion chamber temperatures. Heres a good read on the EGR effects.

http://www.aa1car.com/library/egr.htm

Heres a list of BDS blowers cams they use. All 110 LSA cams. Check out the footnote at the bottom saying **For use with alcohol avail in 112-114 LSA

http://www.blowerdriveservice.com/blower-cam-specs.html

I think Harold Brookshire may have been onto something with this statement

Blown engines are quite different from unblown ones; clean air and fuel starts entering the combustion chamber as soon as the intake valve cracks off the seat, generally around .001" of valve lift. Unblown engines don't start putting clean air and fuel into an engine until a little while AFTER TFC. Before TDC, the piston is moving upwards and pushing the exhaust gases out the exhaust port, there is no air/fuel intake until after TFC and the piston starting down on the intake stroke.
This is just for blown gas engine, as blown alcohol engines require different cams, as do turbo-charged engines.
Because gas burns HOT, pumping a lot of fuel into the combustion chamber causes a very hot cylinder head, and detonation problems. The more racier blown gas cams are on 108-110 LSA, and use the intake overlap to COOL the combustion chamber down. Needless to say, they don't make that good of a gas mileage. They also have all of the normal actions of tighter LSAs, plus a lot of torque. Tight LSAs don't make good street engines, too snappy.
Wider LSAs make flatter torque curves and deliver better mileage, particularly at lower boosts---6-8 lbs. The blower will add lots of power.
When you get up in real racing blown gas engines, 36 lbs of boost lets you accomplish with 116 LSAs what you used to do at 110 with 8 lbs of boost.
I generally go with wide LSAs on the street with low(6-8 lbs) boost, moving to tighter LSAs (108-110) with higher boosts and racing use, then back to very wide LSAs with very high (24-39 lbs) boosts.
I also tend to pay lots of attention to those who make this their field of expertise.

UDHarold

ARP headbolts rot fast too, right, when they go in water jackets ??? Talking salt water here still.

Heck, when I rebuilt my engines a few years ago, that NEVER seen salt, all my ARP head studs were junk. Thats in freshwater! :picard1:

The GM one's are plated/coated but I don't think they offer the 4 bolts that need to be longer on most aftmkt heads exhaust holes.

I've found liberally coating the end of the bolt with sealer helps with corrosion

Speaking of and I'm not sure if anyone else has noticed this but what I've noticed over the years is that studded Gen IV engines would corrode the studs faster than their head bolted counterparts in salt water. Because of it, once Cometic head gaskets got popular I would run those engines with head bolts instead of studs (blown and un-blown).

Anything with an aftermarket block or Gen V/VI that is blown, I run studs since the bolt boss' are blind.

Too small a camshaft for an engine will also affect this. Sometimes folks say, "it's a blower engine, no need to put a big cam in it." Which might be true but putting a small cam in it can be detrimental. Some 15+ years ago I learned that lesson the hard way when I allowed someone to choose a small cam for me. The "right" cam made over 100hp more but made the engines more reliable.

An engine needs the right size cam depending on what's right for the whole combination. I've learned enough over the years to get myself a "ball park" cam but I've come to rely on various industry experts to help me in my selections.

From MT's post

"Back when the "EGR" valve was introduced, its goal was to reduce combustion chamber temperatures. What it did, was pretty much take the burnt exhaust gas, and recirculate it back into the engine at certain engine loads. It basically was diluting the intake charge, with gas that can't be burnt again, as its not really combustable any longer. Modern engines, can achieve this, through VVT, or variable valve timing. By being able to manipulate when the valve opens and closes, it can lower combustion chamber temperatures.

So, when not using a EGR valve, or not having VVT, the basic camshaft design, can have an impact on the combustion chamber temperatures. Heres a good read on the EGR effects. "



My 06 Cummins uses the camshaft to accomplish EGR during the combustion cycle. It's more prevalent than we might think.

Can anyone recommend where to get some accurate flow numbers on the EQ-CH454A heads?

I have stock 500 efi's in my boat and a guy I know told me at a poker run that the iron heads where holding me back. Is this true that on stock power I would be able to get a little more from the motors by making the switch?

its not so much iron vs alum in your case unless your upping the compression too.. what it comes down to is that you have a GM rectangle port head, with head technology straight out of the 1960s. You could bolt on a decent set of modern aftermarket iron heads and see a nice gain. There are head comparisons out there...do a little searching, from the stock rectangles to good aftermarket can be a significant difference.

I had a set flowed last month. As they were out of the box. They are being slightly ported/cleaned up as we speak. They were flowed on a 4.500 bore fixture.

I can't wait to see the before & after results of these!

The man asked for some numbers...you come back with "I got some numbers last month" but you dont post no numbers.. Your like Eddie Murphy and the ice cream truck...

"You got no ice cream you got no ice cream, you got no ice cream/ You on the welfare, you on the welfare/ And you daddy's an alcoholic/ Want some?/ Psych!"

Your lucky he dont send his Aunt Bunny to go all goony goo goo on your azz throwin shoes and sh!t......



. https://www.youtube.com/watch?v=0bXpQVJwlsY

I`m just gonna get it out of the way ... Mild your flow bench is happy and the correction factor is way off.
ok post away.

Gimme Fuel, here is the info you requested.

The 308 Darts, had some work done to them. Performance valve job, little chamber cleanup/polish, some bowl/throat work. They were my old heads. For the flow test on the EQ heads, we used my old valves, just for a comparison of the heads. The valves themselves, kind of suck. There was no back cut on the intake valve, and the exhaust valve, was a manley nail head valve. The EQ heads will have custom valve jobs, chamber porting/bowl work, 30 deg back cut on the intake valves, and new ferrea tulip exhaust valves. The EQ head was literally pulled out of the box, and went to the flow bench. All three of these heads were flowed on the same bench, same 4.500 bore fixture. No pipe on the exhaust.

It will be interesting to see how the EQ heads respond with some hand work. From all the head guys I've spoke with regarding this particular head, is that they respond very well to porting. Several guys now have CNC programs for them. They are very popular with the truck puller guys.

Those turned out very very close to the Dart 308 albeit a slightly larger runner. Looks like some great flow for the money. I had a set of Dart 308 on my first 540 MPI build. Those things made some serious torque. I'm very interested to see how they do with good valves and a bit of massaging. Those look to be a heck of a big improvement over GM rectangle ports for not a whole lot more than refurbishing a set.

actually, my 308's were what they originally were stamped, but after some work, they actually measured 319cc and 315cc on the intake ports, prior to testing them.

I'm sure with better valves, the flow numbers on both would be up a bit. At 425 per casting bare, you can't beat it with a stick. The castings are excellent quality as well.

I know of a recent build that used them. Very light cleanup, 2.30 valve installed. 540ci, whipple, low rpm deal. made 900hp with 8lbs boost, at 5500rpm. A little more cam and rpm, 1,000hp was on the table.

Great now my secret flow numbers are out there for everyone to see.. don`t you know you`re supposed to keep that stuff off the internet!? What if someone benefits from all your hard work or trial and error??
- end sarcam-


:rolleyes: