Specific Question - ARP Head Studs on 2.7 Magnesium case - Insane?

[Henry Schmidt]

Originally Posted by Lapkritis

.....edit..... I suspect the issue of detonation that Henry mentions as unsolved may not be from the head alone and is possibly from the cylinder that is much hotter than the head in his experiments. ....edit.....

This conclusion is completely backward and we proved it.

The cylinders are designed to pull heat from the heads not the inverse. The cooling fan is there to cool the cylinders and heads. What really happens is no matter what cylinder you use, if the head temp gets to hot, detonation become an issue. The goal is to control the heat. If the cylinders don't pull heat away from the heads they will heat up.

In the 90s I built a 2.2 liter E engine, with 2.4 T cylinders and E pistons. The engine was installed in a 914-6 (mine) and driven on a daily basis. It was actually used as a shop vehicle. Those who were around back then may remember it. Anyway, the engine ran great until it got hot. Then it was prone to detonation. It was like a switch. No detonation then it would ping. We check all the tuning parameters including fuel mixtures with no anomalies. We could control the detonation by retarding the timing but that offered unsatisfactory performance as well as lazy acceleration. We installed a Bug Pack head temp sensor (sensor under the spark plug) and discovered high head temps.
I took the engine apart, installed E cylinders and no other modifications then drove it again. Low and behold, no more detonation. I'm a poker player so trip to Vegas are a regular occurrence and the best test for detonation is the long uphill out of Baker on a 100 degree day. Biral cylinders, no detonation, steel cylinder almost undriveable under these conditions.

One quick question about the finned valve covers: What happens to the cooling when the car operated at low or no speed (like traffic or stop lights)? With the heater boxes directly under the valve covers, won't the radiant heat from the heater boxes superheat the finned valve covers?

[HawgRyder]

I like the idea of the fins to help with heat dissapation.
I agree with the idea of shorter fins...perhaps anodized black...and oriented so they take full advantage of air flow.
WE used something like that on several VW engines for desert racing...made out of billets of aluminum (t6061)...and milled to the correct size etc.
We also anodized them.
Don't know if they were great or just good...the cars finished the race...the engines were still running...so who knows?
I noticed your have grooves in them for seals...good idea.
Just a thought...if anodizing helps...what is the best color?
Mother Nature seems to prefer dark green (plants)...we use black...just brain on over drive.
Bob

[Walt Fricke]

Something along these lines?

"In the early 1950s, Porsche had been working with US company Fletcher Aviation to develop and test a jet cooling system for Porsche’s new 1952 356 cabriolet. The jet cooling was an interesting scheme that saved the power required to drive a cooling fan."

I couldn't quickly find a photo of what I recall seeing. We racers (sometimes) don't care about no stinkin noise.

[Lapkritis]

Just watched the Bruins win - what a game. Unbelievable comeback.

Originally Posted by Henry Schmidt

One quick question about the finned valve covers: What happens to the cooling when the car operated at low or no speed (like traffic or stop lights)? With the heater boxes directly under the valve covers, won't the radiant heat from the heater boxes superheat the finned valve covers?

Heater boxes and headers are ceramic coated and the header pipes will also be wrapped with the good stuff over the coat. Should be better than stock under the same conditions as ambient air temp will always be less than the temperature of the sink. The wrap and coats should make for the largest possible delta under those conditions.

[Lapkritis]

Originally Posted by HawgRyder

I like the idea of the fins to help with heat dissapation.
I agree with the idea of shorter fins...perhaps anodized black...and oriented so they take full advantage of air flow.
WE used something like that on several VW engines for desert racing...made out of billets of aluminum (t6061)...and milled to the correct size etc.
We also anodized them.
Don't know if they were great or just good...the cars finished the race...the engines were still running...so who knows?
I noticed your have grooves in them for seals...good idea.
Just a thought...if anodizing helps...what is the best color?
Mother Nature seems to prefer dark green (plants)...we use black...just brain on over drive.
Bob

Good guess there Bob. They have been treated with Military Spec MIL-A-8625(latest version), Type III, Class 2 black; this is the hard anodize.

[Walt Fricke]

Cooling the heads seems like it is the key. The current water cooled 911 motors pull 11:1 CR with a single plug. Somewhere (Anderson?) I've seen it asserted that when Porsche tried 4 valve heads on air cooled 911 motors they had heat problems. Which they solved for the 962s and such with water cooled heads.

Hard to say how much more heat can be carried away from the heads with more convective surface on the lower valve covers, though at least the inserted gasket design, in addition perhaps to less leakage, would yield a larger conduction path to the covers. But there are two discontinuities - head to cam carrier, and carrier to cover. Willl be interesting to see how this works out.

[Flieger]

Jet cooling uses a concentric duct around the exhaust pipe if I understand correctly. The high speed, high energy exhaust gasses flow through the middle, and the exhaust pipe ends before the outer duct. The exhaust gasses pull gas through the outer duct. I believe that you would need the outer duct venturi shaped, wih the exhaust pipe ending in the throat.

[Flieger]

Originally Posted by Walt Fricke

Cooling the heads seems like it is the key. The current water cooled 911 motors pull 11:1 CR with a single plug. Somewhere (Anderson?) I've seen it asserted that when Porsche tried 4 valve heads on air cooled 911 motors they had heat problems. Which they solved for the 962s and such with water cooled heads.

Hard to say how much more heat can be carried away from the heads with more convective surface on the lower valve covers, though at least the inserted gasket design, in addition perhaps to less leakage, would yield a larger conduction path to the covers. But there are two discontinuities - head to cam carrier, and carrier to cover. Willl be interesting to see how this works out.

That was because there wasn't enough room for airflow, but a water jacket could get in there just fine because less mass flow rate was needed due to the higher specific heat of water, not to mention water's greater density allowing for less volumetric flow rate for the same m dot.

[Lapkritis]

Originally Posted by Walt Fricke

Hard to say how much more heat can be carried away from the heads with more convective surface on the lower valve covers, though at least the inserted gasket design, in addition perhaps to less leakage, would yield a larger conduction path to the covers. But there are two discontinuities - head to cam carrier, and carrier to cover. Willl be interesting to see how this works out.

Early on I was considering adding the sinks to the turbo lowers that came on the engine... once I found the Hargett parts there was no doubt about which direction this was headed. The primary conductive path for the lower covers will be shared between the 11 mounting studs on each and any contact made at the gasket surface. The head to cam tower will receive thermal conductive gasket the same as the cylinder to head.

[Walt Fricke]

Thermal paste will keep the oil where it belongs as well as 574 and the like? Not that I have a clue about the actual conductivity of 574 or other sealants, nor the sealing properties of Arctic Silver or something else.

[Walt Fricke]

Flieger - right about how the jet cooling system works.

Apparently it made for an unacceptably loud exhaust sound. Fletcher also used this on aircraft engines, so it seems it works. It would be cool (bad pun) if it could be used to replace the air cooled motor's fan, or to slow it way way down. Race motors don't have to worry all that much about idle temperatures. Or to allow use of electric fans on cars which can use batteries as ballast to meet class weight minima.

But Andrew didn't bite, so his rifle picture hints at something else.

[Lapkritis]

Originally Posted by Henry Schmidt

This conclusion is completely backward and we proved it.

The cylinders are designed to pull heat from the heads not the inverse. ...edit... We installed a Bug Pack head temp sensor (sensor under the spark plug) and discovered high head temps.
I took the engine apart, installed E cylinders and no other modifications then drove it again. Low and behold, no more detonation.

The temperature flow direction will depend on which part is hotter while running. I don't have the data from this one yet but if the cylinder is hotter than the head then the flow will be to the head under basic equilibrium rules. Given the relatively low thermal conductivity of the cast iron cylinder, this lack of equilibrium will be more pronounced if the cylinder is hotter than the head... I could see this as being plausible.

Did you happen to gather cylinder head temperatures for the aluminum cylinder under the same conditions headed to Vegas? Without cylinder temp data to go with it it's difficult to say which part was overheating and throwing things out of whack. It's possible to speculate that the cylinder was overheating and conducting that heat into the cooler head without data.

[Lapkritis]

Originally Posted by Walt Fricke

Thermal paste will keep the oil where it belongs as well as 574 and the like? Not that I have a clue about the actual conductivity of 574 or other sealants, nor the sealing properties of Arctic Silver or something else.

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[Lapkritis]

Originally Posted by Walt Fricke

Flieger - right about how the jet cooling system works.

Apparently it made for an unacceptably loud exhaust sound. Fletcher also used this on aircraft engines, so it seems it works. It would be cool (bad pun) if it could be used to replace the air cooled motor's fan, or to slow it way way down. Race motors don't have to worry all that much about idle temperatures. Or to allow use of electric fans on cars which can use batteries as ballast to meet class weight minima.

But Andrew didn't bite, so his rifle picture hints at something else.

Hard anodize Military Spec MIL-A-8625(latest version), Type III, Class 2 black. A venturi system to create a low pressure area over both lower covers would be another project.

A simple shroud on each and a thermostatically controlled electronic fan to force convection or enhance the venturi would be easier to fabricate... of course this all depends on getting the heat to that sink.

[Daniel930]

Andrew,

What was your reasons to run the iron cylinders vs the Alum/nick's, since you have put some work into removing as much heat as you can with the lower valve covers mod's. Your coating job on the exhaust ports of your heat exchangers look's good!

[Jeff Alton]

Andrew,

My suspicion is that if you took Henry for a beer you guys would get along great and have fantastic conversation.... I have had a few differences online with Henry over the years but we have spoken on the phone when I have orderd some stuff from him and even exchanged
seasons greatings online and on the phone. I hope we meet someday. I think he is a good human.

Is he stubborn? Sure. Is he experienced and knowledgable? Yes.

That said, continue with your path, nothing but good to our community can come from it. Looking forward to the results.

Cheers

[Lapkritis]

Originally Posted by Daniel930

Andrew,

What was your reasons to run the iron cylinders vs the Alum/nick's, since you have put some work into removing as much heat as you can with the lower valve covers mod's. Your coating job on the exhaust ports of your heat exchangers look's good!

Thermal expansion of the aluminum cylinder tugging on the magnesium case. The iron cylinders don't expand as much and almost match the stud expansion rate (ARP or another steel) that would pull on the case.

The heat exchanger/header port coating will be like the rest of the thermal barrier ceramic - will have to see how it stands the test of time. HotRod magazine tested the performance in horsepower output only of ceramic coatings ( A Look at High-Tech Engine Coatings and What They are Worth - Hot Rod Magazine ) showing a slight improvement and that was part of the encouragement to give this a shot.

The header is another heat soak that can push heat back into the head especially after shutdown and during hard operation due to exposure to exhaust gases. Gasket choice will be an insulator type dressing between heat exchanger and head applied to both sides of the OEM gasket. This should at least reduce the transfer of heat from the exhaust back into the cylinder heads.

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[HawgRyder]

Andrew...going in the direction of back heat...how about something in the ceramics department for a gasket in the head to header area?
It could be cast I think...with grooves on both sides to allow for a Viton type Oring for sealing...and would not transfer heat the same as a metal or even organic gasket would.
Bob

[304065]

Originally Posted by Walt Fricke

Flieger - right about how the jet cooling system works.

Apparently it made for an unacceptably loud exhaust sound. Fletcher also used this on aircraft engines, so it seems it works. It would be cool (bad pun) if it could be used to replace the air cooled motor's fan, or to slow it way way down. Race motors don't have to worry all that much about idle temperatures. Or to allow use of electric fans on cars which can use batteries as ballast to meet class weight minima.

Old (1957) Cessna 310B had "augmenter tubes" which were used instead of cowl flaps-- air flowing in the front of the nacelle was pulled out of the nacelle by augmenter tubes mounted around short exhaust stacks. The outflow of hot exhaust gas pulled the air out of the nacelle. These were regarded as "noisy" (no kidding) and so Cessna dropped them later in the production run. These also increased the thrust.

Also used on the Flying Potato:

[Lapkritis]

Back from the plater:





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