Originally Posted by SteveP

If that's you're experience, then I'm not going to try and talk you out of it. I'll simply pass along that I'm very familiar with the thermal properties of the various magnesium and aluminum alloys used to make cylinder heads and they do IN FACT, have nearly identical thermal properties. BTW, magnesium alloys can contain as much at 75-percent aluminum. Raw aluminum has better thermal properties than raw magnesium, but raw and 1000 series aluminum (actually better than raw Al) is butter soft and could never be used for a cylinder head. It's the kind of stuff you find inside air conditioning condensers and computer heatsinks, where they don't have to do anything but transfer heat. I have no intention of butting heads, so don't take this the wrong way, but there are thousands of reference books and website where you can look this stuff up, so I'm just passing along what I learned a long time ago.

Originally Posted by JAMMINKRAZY

The pro mod should preform like any of the speeds.

Originally Posted by Frank L

My speed broke in right about the 1 gallon mark. I heat cycled about 5 tanks through it using a modified johnnycoolguy.com method and then tuned on the track it was running consistent at about 230-245 and then all of a sudden after a 15 min main right about the gallon mark the temp dropped to 195 and it was running very rich. I re-tuned and it has been very consistent since then. I find that I tune very little on it from track to track. abut 2.5 gallons through it now and it has really come alive. Great little engine.

Originally Posted by JAMMINKRAZY

My experiences are that aluminum cools better. I know for a fact, that's why OS switched to aluminum. Atleast that's what they claimed when the AL head speed was first released. I also know that many guys were running standard v-spec heads on thier speeds before the Al head speed was out for just that reason. That was also GRP's reason for going to the big orange aluminum head over the mag ninja head they had developed for the ninja before they were producing thier engines under the GRP name. I don't know the properties of the metal. I just know what myself and others have experienced, which is that magnesium heads don't cool as well as aluminum heads do. Those are just my findings.

Originally Posted by WYLDTHING

With all due respect....I don't know that I can agree with that. If they performed like a Speed, then OS would just call it a blue-headed Speed and charge an extra $130 bucks for it.

The crank I seen the gentleman pull out of his Pro did not look my mag-head Speed crank, as far as the lightening and channeling goes, so I would really like to know what happened there. Did he got hosed?, or did the early versions of the Pro have the standard rod and different crank, or what? Very strange.....
I will see him this weekend, hopefully, and I'll talk to him about it. I'll see if he'll crack it open again we can look at it again a little closer. Maybe I'm just remembering wrong, but we talked about it that day when were comparing them, so.......

Heck, I don't know.....


Brad

Originally Posted by SteveP

It's hard to kill those urban legends, ain't it?!

I know the Gandinis, and the people at OS, Sirio, Novarossi, JP, RB and many other engine manufacturers fairly well, and the few of them where this has come up in discussion, they've said that they went to aluminum heads because mag doesn't cool any better, but it sure costs a heck of lot more. Plus, machining magnesium can be pretty dangerous. Desert rats who have witnessed the spectacle of a mag VW block burning will tell you. Magnesium burns at 4000°K and can't be extinguished. All things considered, the feedback from the manufacturers themselves, my own experience, the laws of physics and the entire metallurgical universe has a different opinion. I'm just saying.... I'm really just giving you a good-natured hard time at this point, so again, please take it for what it is... rubbin' is racin'!

Originally Posted by ezveedub

No matter what the properties are, the MAG didn't run hotter than the AL, so its strictly a cost factor a this point.

Originally Posted by WYLDTHING

That sounds good to me! I guess I'm hoping that it doesn't take two gallons...sort of. Part of me sys that if it takes two gallons for it to be completely broke in, then, in theory, the engine should last longer.

We'll see....I've heard about 99% good about these engines, so hopefully the one I am getting won't fall into the other 1%...lol.

I'm super excited, that's the ONE thing I do know for sure!

Originally Posted by JAMMINKRAZY

Pro mod v-spec does run like a speed. They are priced comparably to the old AL speeds. I also believe it is a Great Planes assembled product, not OS. Anyway, the parts should all be speed parts. That mixed with some standard v-spec parts, but as far as I know there are no new parts specifically for the pro mod.

We are talking about the same engine right?

http://www.towerhobbies.com/products.../osmg2067.html

Originally Posted by devilchrist

agreed, aluminum worlds selling for same price as the mag head just means higher profit margin.

magnesium is harder to work with and most costly than aluminum

Originally Posted by JAMMINKRAZY

Pro mod v-spec does run like a speed. They are priced comparably to the old AL speeds. I also believe it is a Great Planes assembled product, not OS. Anyway, the parts should all be speed parts. That mixed with some standard v-spec parts, but as far as I know there are no new parts specifically for the pro mod.

We are talking about the same engine right?

http://www.towerhobbies.com/products.../osmg2067.html