alum heads

reidp wrote: Hey, while were talking corrosion, can anyone tell us why raw water cooled marine engines always came from the factory with a 140-143 degree T-stat while fresh water engines used a 160-180 degree? I had no clue but heard from the knowledgable fossils at Holman Moody and it all clicked. For the record and as a clue, they suggested using a higher degree if you always run fresh water only in a RW cooled engine.

got me a little confused raw and fresh seem the same to me. Are you talking about a closed cooling system vs a fresh/raw open system? My take would be the thermal sock, like you don't put cold water in a over heated motor, that pop you hear is the block cracking.

reid you added to your posting.

Mine are actually 1969 302 D0OE heads that have been reworked for 1/2" head bolts, 1.94/1.60 valves and the exhaust bowls cleaned up to flow better, machined for screw in studs and have .600" lift springs, scorpion roller rockers and guide plates as well

I'm not sold on the anodizing as a solution; one scratch and you have all the electrolysis concentrated on one spot, not good. Fresh water ie closed cooling is the solution. Big temp swings are eliminated by the ma$$ of the heat exchanger and coolant, and corrosion is in check by the gylcol and additives.

Tim,

I thought the ZR6 had Alum heads, my thought was in regards to Alum head on a cast block, PCM uses closed cooling in that situation, is it to eliminate extreme temp varience from Raw water cooling or for some other reason(s)?

quinner wrote: Tim, I thought the ZR6 had Alum heads, my thought was in regards to Alum head on a cast block, PCM uses closed cooling in that situation, is it to eliminate extreme temp varience from Raw water cooling or for some other reason(s)?

Gotcha. I would like to hear from someone at PCM as to why they went with closed cooling on the ZR6. I a$$ume its due solely to the aluminum heads, but Id like to hear their take as to what the the biggest factor was. Corrosion may have been a bigger issue since some people run in salt, but thats just speculation.

backfoot100 wrote: Didn't the very first generation Corvette engines in boats cause problems? I think that was in the mid-90's. I keep thinking the LS1 but that could be the second generation Corvette motor in a boat.

Youre right- the LT1 was the first generation Corvette motor used in boats. I believe it was a Mastercraft exlusive. It was first used on the 25th Anniversary Prostar 190 in 1993, and then flowed to the rest of their lineup in 1994. I am not sure if the LT1 has aluminum heads, though I have heard that before. It is a RWC motor, though. Its widely considered a great performing, reliable motor in the MC community. Personally, I have 4 friends with early LT1's (1993 25th 190, 1994 190, 1995 190 and 1996 190), and none have had any major problems.

closed cooling means higher engine temp, better combustion, better performance and No issues with thermal expansion rates caused by AL on steel.

And the exhaust manifolds are still raw water cooled and not in series with the closed loop cooling system.

Sorry about the previous post, I have to try and figure out how you guys do the cut and paste thing from one post to another and put in a box. That last one didn't work out as good.

reidp's link

Well I can't show you how to do it, because it'll just make whatever you do a link. Refer to the top thread in General Discussion, Keith tells you how to do this.

I am sold on sticking with cast next year.

bkhallpa$$ wrote: To quote a previous post, click the quote icon on the upper right corner of the post you want to quote. You can now remove any text that you don't want to repeat. Do not remove the words in [] at the beginning and at the end of the quoted material. To set up a hot link to another post, website, etc, Click the 4th icon from the left in the post reply section "Add Hyperlink." An instruction box will appear. Type in what you want the hotlink called, and hit return. Antother box will pop up. Type in or copy and paste the URL of the material you want to link to, and again, hit return. BKH

79nautique wrote: closed cooling means higher engine temp, better combustion, better performance and No issues with thermal expansion rates caused by AL on steel.

BKH and Hollywood, thanks for the posting info. This is awesome!

ReidP, thanks for the link to understand FWC and RWC. Makes complete sense now. It makes more sense as to why a AL head engine needs the FWC system to properly function and the different T-stat temps for each type of cooling setup.

Now, "Riddle me this Batman....." I was under the impression that a AL head dissipates heat more efficiently than an iron head, causing lower combustion chamber temps which in turn helps to eliminate detonation. This allows you to run somewhat higher CR's than an equivalent iron head engine which in turn improves HP (not to mention the weight savings). If this is true, why doesn't running a cooler T-stat (like 140-143) make an iron head engine more efficient and produce the same results? I know in a car, running a 180 vs. a 195 T-stat can improve performance in some instances. Or is this the old addage that "if some is good, more isn't necessarily better" apply here.

Hey Eddie; I am tryin' to learn this stuff too.Reids Link

I will be amazed if this works

john

We can use my boat as a test, everybody pitch in, and I will buy these heads, install them on my boat, and then I will let you know how they work...ok..ok.. it was worth a try, but I do like these heads!


MY DREAM HEADS

i's ben oute celerbating jbare's birfday, so if dis dont make cents just jbere with me.

To attempt to answer backfoot, dissipating heat is not necessarily good for making HP. If you have two identical by-design heads, one in alum and one iron, the IRON theoretically makes MORE horsepower because they said it. I found this quote:

Aluminum vs. Cast Iron Heads - Many people don't pay attention to the compression ratio when going from cast iron to aluminum heads. Fact is that if everything was equal the cast iron head will make more power than an aluminum head. This is because the cast iron head doesn't absorb heat from the combustion process as fast at the aluminum head. Therefore more heat is available to push the piston down. The way to get back the lost horsepower is to up the compression on the aluminum head. Typically you can run about a half to full point more compression with an aluminum head over the cast iron.

I ran a yahoo query "Cast iron or aluminum, which makes more horsepower?" That's where i found the above and lots more interesting stuff. I've always understood that you needed heat to make horsepower, however too much causes detonation. The quote above may not be the best and a bit confusing in terms of the word absorb, so please read more with a query if interested.

I don't know if this totally answers backfoot's question about lower T-stat temps. The lower alum head temps help deton but loose HP, so the alum head's lower temp is a short coming vs iron, but is compensated for by higher allowable comp with same gas octane. So you don't want the cooler 140 T-stat temp with iron as you WANT that heat if your octane can stand it.

backfoot, we'll solve this and numerous other world issues as we toss back a few while watching MM install jbear's intake.