I believe the D-Max has aluminum heads and that's why it's so quiet.

Just throwing this out there, If you want more heat to stay in the head. Then why do so many guys run their water temps so cold?

You want as much heat to stay in the combustion chamber during the power cycle, which cools as the gases expand and the piston goes down, more heat and pressure at the beginning, more power.

After the power cycle, exhaust, and then compression, you want the combustion chamber cool enough that hot spots don't preingnite the compressing charge. Having the block cooler helps with this. There is a boundary layer at the surface of the metal, whether it is aluminum or iron that keeps the searing hot combustion gases from melting or burning away the metal. Aluminum passes more heat than iron as it is thermally more conductive and therefore is less likely to get those hot spots.

A bit of a segue, but would it be feasible to put a small blower like a B&M 250 on a 9.5:1, forged internals on a 502, and 91 octane pump gas? Would aluminum (Edelbrock Oval Performers) let you get away with that much CR under boost?

I ran Iron heads on my blower engines for years and it wasn't terrible. However the boost was low (6-7lbs).

Almost all Mercury's forced induction and high performance engines now have aluminum heads. I think the last time Mercury put an Iron head on a blower engine was the 800SC?

Not saying iron is bad... I kept mine for years because I was running in salt water. However, having switched over to aluminum and running them on a few other engines, I'm a believer.

I'm building a set of 509 MPI's and since the GM heads were junk, I started looking at replacement options and these came up in conversation. Thanks for the info, they seem like a viable option for the owner to consider.

Rumor has it, that EQ may be stopping the iron heads...so, if you are going to use a set, I wouldn't wait too long. Or atleast call EQ to see if this rumor is true or not.

I understand, and totally agree, thats why I run aluminum heads. I Also run my motors at a constant 140*. My question was for those who stated that they want to keep more heat in the head, by going with iron, or doing whatever to keep heat in. But yet run no water temps.

I spoke with Kevin there last week, he didnt mention anything like that. He actually said they are selling alot of them to marine and truck puller guys. At least the bbc heads that is. They have only had the bbc line since 2012, i know they have had the sbc stuff for some time now . Their main office is only a few minutes from my house. Ill have to doible check with him on that though

575sci had iron.

Im not suggesting iron is better, im just suggesting that sometimes we cant ignore whats worked in the past.

They have the CH454A head which is the heads i purchased. Those are the raised exhaust port, copies of the old RHS / Protoplines. They also have a CH502 head, which is meant to be a replacement for the stock GM /Merc head. That head is almost 50 bucks cheaper at around 385 dollars per casting bare.

One thing I noticed, was I had to run a richer AFR with a iron headed super charged engine. That is comparing same builds, whereas the only difference was iron eagles vs. brodix, everything else being identical.

Lets say your water jacket is at 200 degrees regardless of material type. The iron head will make more power because it will keep more heat in the chamber than the aluminum.

Now lets say you increase compression/boost etc. The aluminum head is still okay at 200, but the iron head needs to come down to 140 to avoid issues. Now you increase more, and the aluminum head needs to come down to 140 and the iron head either needs more octane or to be richened up to avoid issues. I think that is where aluminum starts to have an advantage and why cooling temps come down. Yes you start increasing heat transfer but you have to to allow the other big performance changes to occur safely.

They were also both low-boost engines with low compression ratios, that was sorta my point. It was old technology.

If I never moved to the northern Chesapeake and stayed up in NJ in salt water, I probably would have never switched over to aluminum.

But in the same regard, I would have never attempted to make the 965hp I have now with Iron heads.

Read info years ago were it would be better to have an aluminum block with iron heads by some experts.

When you swap the heads,are you doing other engine work as well. I'm really curious about the numbers if you are basically just changing heads, and retuning .From what I read of your stuff I'm assuming it will be run on a dyno. It would be cool if you could check at least on motor as it is now ,change heads and re dyno.....All in similar weather ,same dyno

How did you come to that conclusion? High EGT`s till you gave it more fuel? Just curious.

btw, I wish i could run higher engine temps temps... running no water temps is not by choice for me.



Why?

Wonder whats the most power one made reliably in a marine engine, with iron heads. I know a friend of a friend just bought a boat with some big Sterling blower motors. They have iron heads. Surely guys like Cheif, Zul, Sterling, and others must have built some big power saltwater ran engines with iron heads over the years.

First off THANK YOU to Joe Mild Thunder for sharing GREAT info like always, looking forward to hearing your positive results. There are a TON of members on here that could really appreaciate and benefit from the cost savings of these heads.

My factory sealed 800ish HP procharged 7psi iron head 500efi's are still going strong for the new owner after 300hrs pushing the Baja hard to 100mph.

The average powerboater with lower to mid hp levels would be fine with iron heads. I would rather see that then some of the other corners people cut, but hey they got fancy aluminum heads!

...

The price point of aluminum heads as well as the evolution of the metalurgy has evolved since the grumpy days.
Plus your likely to now be halfway there to the mls gasket territory that will help you with forced induction.i have seen properly cast aluminum alloy engines make 200 psi cranking compression and work perfectly (other than seeping oil) without head gaskets. The car guys are fighting to keep heat in for cold start emissions while still using alumimum eng components on todays engines.but i agree for bang for the buck aftermarket cast iron bbc offerings are where its at

I do it for the saftety factor. In my eyes, it's similar to why do folks run intercoolers or methanol injection on higher powered engines. The 800+/- hp level seems to be ok from what I've witnessed but beyond that I don't see engine builders using iron heads that often.

Heat in the combustion chamber makes power but heat soak in the head and everything bolted to it causes power loss and possible pre-ignition.

Heres a good read. In this test, between a dart aluminum, and dart iron, they found no difference

http://www.hotrod.com/how-to/engine/...er-heads-test/

Ive seen quite a few 900 plus hp iron headed blower engines come from aome pretty big name builders.

Some quotes from folks in the industry. There's plenty of debate to go around so make your own choices;

“Cast iron has been used for making cylinder heads since the early days of the internal combustion engine,” noted Jack McInnis of World Products, Louisville, Kentucky. “Its primary advantages relative to aluminum are lower cost and durability. Aluminum’s significant advantages are light weight and relative ease of repair by welding.”

“Thermal conductivity has been debated for many years,” said Kevin Feeney of RHS, Memphis, Tennessee. “Historically, an iron head was considered more durable, and able to make more power due to the fact that it would not dissipate the combustion heat as quickly. With everything else remaining equal, there exists some merit to this argument.”

"Mike Downs of Trick Flow Specialties, Tallmadge, Ohio, pointed out that the thermal conductivity of aluminum is “four or five times that of iron. This means an iron head will usually operate hotter. On the positive side, this means the fuel is pre-heated in the intake runner and easier to ignite in the cylinder. On the negative side, it means the preheated air/fuel mixture will expand, reducing the effective flow into the engine and increasing the risk of pre-ignition. A properly designed aluminum head will transfer heat more quickly to the coolant, leaving the intake runner cooler and therefore able to flow more air-fuel mixture into the cylinder. High-energy ignition systems easily compensate for the cooler intake charge and help achieve maximum fuel burn.”

“The greater thermal conductivity of aluminum is a great advantage,” agreed Chris Frank of Frankenstein Racing Heads, Joshua, Texas, “especially in power-adder applications. That ability to dissipate heat quickly allows for more aggressive tune-ups.”

“Aluminum heads dissipate heat quicker than cast iron,” echoed Torrance, California-based Edelbrock’s Smitty Smith. “This can be an advantage in elimination-style drag racing, keeping the head temperature consistent round after round.”

With aluminum, Tony Mamo of AFR (Air Flow Research), Valencia, California, concurred, “detonation is less likely in an engine on the ragged edge, as it won’t hold as much heat. But that also firms up the argument that a cast iron head on an engine without detonation issues would make more power for the very same reason!”

“You need to build more heat with aluminum to make the same power,” agreed Bill Mitchell Jr. of Bill Mitchell Products, Ronkonkoma, New York, “or compensate by coating the chambers to keep more heat in the cylinders.”

Source; http://www.performanceracing.com/mag..._aluminum.html

Hre's something I'd like to see. Test two identical 900 hp engines, one with Iron heads and one with Aluminum. Roots supercharged engines, making the same power and boost.

Make 5 mile WOT passes and see which melts down first.
1. Test 1: 93 octane
2. Test 2: 89 octane
3. Test 3: 87 octane

Another possible test:
1. Test 1: 93 ocatane 28* timing
2. Test 2: 93 Octane, 32* timing
3. Test 3: 93 octane, 34* timing
4. Test 4: 93 octane, 36* timing... 2 degree increments until one blows up.

I've seen quite a few 1500hp iron headed engines that would last as long as any aluminum headed engine.
Too much monkey see monkey do going on here. There is nothing about iron heads that will prevent them from making the same power and lasting as long - or longer- than any comparable aluminum head. A cylinder head being made of iron has nothing to do with it's reliability or ability to make power. Nothing. (I know you know that)

Thermal conductivity does not mean aluminum heads will make more power. Port and chamber design are what make power.
A running engine will reach a steady state temperature and I question whether an iron head will run "hotter" than an aluminum head.

Problem with this is the two heads would have to be identical.

Can you explain "heat soak"?

Like a chevelle running a 540, with a 6cyl radiator, autozone water pump, idking for 30 minutes on a 90 degree day with 220-230 deg water temps nearly melting the plastics off things under the hood.

For the record, I didn't debate what was said. To restate what I wrote, is that you don't see it often. If we did see iron being used all the time, there would be iron heads on all marine engines but that's simply not factual.

At the end of the day, do what works best for you.

I was not debating whether an aluminum head makes more power or not. It's a quote from an article and the reference link was included.

That is what I said (Identical). Same head design, different material. Now we're splitting hairs.

Agreed.
I certainly didnt buy iron heads hoping to make more power with thier heat retentitve attributes. I bought them because i simply wanted some heads that will last, because even in freshwater, aluminum corrodes. I also wanted a good head design, that flowed well, and a cost package, that would allow me to have a guy tailor them for my application.

As for power, i would rather make it with airflow, rather jacking the compression and boost up thinking its ok because you have "aluminum ". I dont think its nearly that cut and dry.

I find these threads amusing. Joe spends his free time HELPING others on this site. You guys think JOE doesn't already know MORE about this topic then what's been posted here before the thread started....LOL

This site is mainly used by BUDGET members. If not we all would have million dollar offshore boats.

We all can agree that with money no object aluminum would be our first choice. So would a brand new Mystic, Skater or MTI. Screw buying these used boats, they are junk!

I really don't understand how this topic is being ARGUED in such a negative way????

With no hard FACTS to prove that an engine properly designed around iron heads will be JUNK compared to its aluminum brother, just marketing brainwashing.

Come on guys (aluminum head koolaid drinker pretend Rich ballers who can afford the best of the best on every single part purchase) try to be a little more positive when participating on here. Do you want more GOOD threads to entertain us and learn or not?

I write this with a smile no hard feelings. It's all in good fun!

I was simply responding to the quote, not trying to be argumentative.

Whenever someone poses a different opinion on here, it seems the bandwagon jumps in and supports their friends. This started out as a mutual discussion until folks started to throw stones because they did not agree. I for one did not throw the first stone and simply stated my experience but was challenged. Apparently I was not able to respond to the challenge?

I do not make millions and and sure are not a "rich baller". In fact, it's quite the contrary. I work hard for what I own and build and maintain everything I have so it's clearly not about money. I'll just sit in the corner while the few folks who are allowed to speak can hear themselves and everyone listen.

I have been on this site for a very long time and have been helping folks out for a very long time. Apparently that seems to have gone by the wayside. Things sure have changed over here.

See ya'll later.

This stuff is just a hobby for me. A fun hobby.

I didnt NEED to buy new heads. I am always up for trying something new. Maybe it will work out, maybe it wont. What I am not interested in, is building the oso crate engine special. We have all been trained aluminum AFR heads are where its at, and nothing else compares to them, performance wise, price wise, and so on. Are they a great head, absolutely. But is it possible something else is as good, for similar or same cost ?

When its all said and done, i will probably have nearly as much into these EQ heads , as a set of off the shelf AFR 325s. The difference will be, my heads will have my spring choice, my retainers, locks, locators, a marine specific valve job, and some porting. I'm sure they will perform better than the darts I had when it was all said and done. I was actually surprised to see how poor the exhaust flow was on my particular darts. The exhaust flow on the 345 irons flowed much much better. Same bench, same fixture, same day. The intake port was nothing to write home about.

Its all good discussion. Nothing more , nothing less. Lots of good input here. Theres nothing wrong with disagreeing, and or explaining why we disagree. Its winter , what else we going to talk about lol :)

Your blowing this all out of proportion bud! It's all good. Everyone's opinion matters and I am glad this thread is actually going smoothly....

Please keep posting my comment was not directed towards you or just this thread.

Maybe you didn't catch the last sentence in my post :drink: