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

[Flieger]

Meredith effect - Wikipedia, the free encyclopedia

[Lapkritis]

Originally Posted by 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

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.

[Walt Fricke]

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.

[Lapkritis]

Originally Posted by Walt Fricke

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

[Lapkritis]

Photo for above post:

[HawgRyder]

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

[E Sully]

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.

[Lapkritis]

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.

[Lapkritis]

Originally Posted by HawgRyder

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

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.



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

[Walt Fricke]

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.

[Flieger]

Time attack.

[Lapkritis]

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:





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.

[Walt Fricke]

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.

[Lapkritis]

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.

[Daniel930]

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.

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

[Lapkritis]

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.

[Henry Schmidt]

Originally Posted by Daniel930

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.

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

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?

[Henry Schmidt]

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.

[Lapkritis]

Originally Posted by Henry Schmidt

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.

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.

[Henry Schmidt]

Originally Posted by Lapkritis

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

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.