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?

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

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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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.

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!

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

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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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

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:

http://forums.pelicanparts.com/uploa...1368552902.jpg

Back from the plater:

http://i458.photobucket.com/albums/q...psc3dfb6b2.jpg

http://i458.photobucket.com/albums/q...ps878c897a.jpg

JMD Industries – Zinc Plating | Chromate on Aluminum | Anodizing

They will do only new/clean parts; no restorations but do take on small jobs.

That would probably work but be very delicate without a metal backing. My main concern with that would be backfires from the engine and thermal expansion of the two metal surfaces crushing/crumbling the ceramic between. An OEM gasket with a skin of insulator on each side would provide some insulation but retain integrity characteristics.

The Meredith effect doesn't seem like it is going to benefit Porsche race cars, much less street cars?

Carroll Smith pointed out that aircraft could use deeper oil to air radiators because air velocities were consistently high enough to overcome the decreasing efficiency of fins as air heated up during passage through the radiator. But that race cars ought not to use radiators deeper than something - 3" or so - for that reason.

Seems similar to the venturi effect but considers temperatures. Air coming from the exhaust of a heat exchanger is hotter (no really) and therefore less dense without funneling it down in a shroud. The greatest benefit we found on applications with over 5" of heat exchanger thickness (stacked) was to shroud/funnel air from the widest area in front and allow for provision of a strong exhaust fan pulling from behind. Edit: And on a heat exchanger at the front of the car the discharge/thrust was directly into the engine/firewall behind.

Quick mock up this afternoon to check the clearances... should have done this before I sent it to the plater. Fortunately the cover is able to be removed with the heaterbox/header installed with plenty of clearance. The pipes will be fully wrapped to discourage soaking while stationary

Photo for above post:

http://i458.photobucket.com/albums/q...ps584a8df0.jpg

Have to say one thing...impressive!
Talk about your finned valve covers.
I used to have fins on the old Ford big block...made by Mickey Thompson but they were more for show than heat dissapation.
I wonder if (in class racing) something like this would be a no-no?
Bob

From my past experience with 2 stroke motorcycles, your finning has me wondering. As the fin lengths grew to control cylinder and head temperatures, the engineers found a need to put in numerous supports and vibration dampers between the fins. I would think with the length, width and thickness of your finning, you might want to take this into consideration.
In the picture you can see the cast in supports between fins at the outside, and the 2 rows of vibration dampers to the inside. I always enjoy the look of my GT380 engine with the Ram Air shroud they used over the cylinder heads.
They did find a need to use watercooling on the 750cc version.
Enjoy your project.
http://forums.pelicanparts.com/uploa...1368566914.jpg

Hi Ed,

These did have a harmonic ring on the saw as you might expect. I would guess they would have a ring on top of a running engine as well so they may get small blocks of rubber between to lessen the harmonic ringing effect. Other than potentially annoying to the ear, any harmonics may lead to fatigue and cracking down the road.

Hi Bob,

This is actually my second rodeo with valve cover heat sinks and they do draw the heat. On another toy of mine we added simple sinks and realized 8-12 degrees F decrease in oil temperature under all conditions except stationary along with a noticeable recovery after full throttle pulls. This is on a turbo charged V6 engine (single head - the Cayenne borrowed this design) with small external OEM oil cooler. This example pictured below has a rubber sandwich rather than captured gasket with smaller diameter fasteners. I know the results are real so it's more a matter now of how effective here they will be.

http://i458.photobucket.com/albums/q...9054128197.jpg

I have zero experience with Porsche club racing - perhaps someone with that experience will weigh in if these would be considered outlawed.

Andrew - if you have any interest at all in PCA Club Racing, you ought to read the rule book. Go to PCA.org and drill down the obvious places.

Interestingly, for Stock the rules allow any valve cover. The impetus behind that as of 1992 was that all the early 911s racing had the Turbo exhaust covers, which were not stock on most of those cars. Everyone put those on to try to stop the leaks with their DE cars, which evolved into Club Race cars. And they were not a performance advantage. Yours wouldn't be on a stock motor either.

However, experimenting with Ps and Cs and especially compression is going to get the car pushed into GT, where you don't want to be, as the GT weight rules posit 110 horsepower per liter as part of the weight equation. Lots of us don't quite make that, but anything close to stock on an air cooled motor is going to be seriously underpowered. Which is OK if you don't mind - kind of depends on run groups. If a small race with just one group, you'd find guys to race. With several groups, you might be in the lowest class in the group, and be the lowest powered car in that class. That can affect the fun factor some.

I haven't raced with NASA, but think they use your dyno sheet to class you. Their rules are on line also, so easy to see.

Time attack.

Not looking to do PCA Club racing at this point. Might consider a few light-hearted track days and auto cross events with the Sports Car Club of Vermont but nothing too intense. This car was intended as Thursday-Monday fun during the salt-free seasons. I'd probably start with something less classic for getting into racing... maybe an SC, Miata or my over-improved vw that could stand up to more abuse without the pucker factor.

Ran into a roadblock early on tonight with assembly and this falls in line with what Henry mentioned earlier with this cylinder manufacturer. I'm not here to sugar coat or hide, just sharing my experience so here's what we have:

http://i458.photobucket.com/albums/q...psa30487de.jpg

http://i458.photobucket.com/albums/q...psc6e2636a.jpg

Each cyl is about 2-3mm too wide overall which means they won't install without trimming down the fins. I was primarily concerned about the combustion chamber and height measurements that it didn't cross my mind to check the dimensions of the fins. Not a huge deal, just a little time consuming to buzz them down and repaint.

Home-made tool for installing the clips on the JE forged pistons pictured below. Without this the job would be miserably difficult. Literally a 30 second job to line things up and pop the clip in using this guy. $7 for a 2' section of copper tube from Home Depot which beats the pants off the $200 Porsche tool I've seen around.

http://i458.photobucket.com/albums/q...psc01a875e.jpg

Unbelievable. Porsche has made several changes in spigot diameter and head stud spacing, but I think the cylinder centerline locations have not changed since day one (lots of crank interchangeability). Hard to see how any manufacturer could get this wrong.

Just like Henry said, they pumped stuff out without understanding how it worked. I imagine I'm not the first to encounter this as plenty of cylinder sets have been sold but maybe the first to not sweep it under the rug as google searches are empty on reviews or issues for the QSC 92mm 911
QSC 92mm 911
QSC 92mm 911
(google plugging for the search engine) . I have a date with a belt sander sometime this week.

ARP studs
 

I wonder why ARP requires 38 ft/lbs of torque on the head studs, I was concerned when I did my 3.3, excessive stress on the case stud boss threads. :eek:

It would be cool to get some cylinder head temp sensors, switch back and forth to your 930 valve covers for some data.

I imagine they designed on the aluminum case and applied the same spec to the magnesium without taking the base material into consideration. 38 doesn't seem that terribly high for aluminum when you consider the steel blocks see over 90ft lbs and torque to yield on rather large diameter fasteners. When you look what you're loading against is when you realize it's a horse of a different color. I'd like to discuss the 38ft lbs with one of their engineers to get more insight.

Why: Maybe because no one a ARP has ever built an early 911 engine? who knows?

38 ft/lb is a crazy number for a mag case motor and even too high to promote longevity in any street 911.
The ARP stud and nut combination has been known to come loose under standard use so perhaps the excessive torque was designed to prevent loosening?

Cylinders don't fit? I wonder if they (QSC design team) missed any other critical design features?
Of course I can make an educated guess to that question but it's interesting (kind of sad) to watch Andrew struggle with what I have labeled "an inferior part" ever since he first asked my opinion.

Sometimes if you try to make candy out of shyt, you end up with shyt candy.

I laughed out loud. You did say you were part of the design team over there early on. :p

The machined surfaces were all mic'd out and are fine. The bore was machined out and trued here in the good ol'USA for the JE pistons. I did send a note back to the retailer to alert them of the issue. Struggle? Nah. As much fun as if I didn't have to trim - of course not.

I also said we had nothing to do with the initial design of most of their products.
For the most part, we tested the products and offered design corrections. When they ignored the corrections, I severed the relationship.

In an attempt to preserve our intellectual property, we designed a few parts exclusive to Supertec, where they didn't receive a completed blueprint. Those parts that were my "exclusive" property ended up being sold to the retail market. Interesting to watch them sell a part that was 4 machine processes away from complete.

Sometimes even a knowledgeable, talented builder (giving you credit here) can't correct an inherently bad design.

One last note: all of our custom products are now made right here in the USA. As often as possible by small job shops.