Big Type 4 VW

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agertz1
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Big Type 4 VW

Post by agertz1 »

Hi, I need skilled advice for, 102-104mm cylinders, aluminum/Nicasil an option. Stroke of 78- 82 mm. I have a welded stroker crank, must check
stroke. E85 fuel, all motor. Liquid cooled heads, with adequate airflow.
Thanks, Art G.
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Re: Big Type 4 VW

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Nobody here builds Type IV's ?
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Re: Big Type 4 VW

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I don't understand what you doing or what the question is.
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Re: Big Type 4 VW

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In other words, specific type IV things to watch out for ? Such as, all aluminum cylinders with steel clamping studs. Because of big difference in
thermal expansion, seems like studs will deform barrels at running temperature ? Clamping is only as strong as threads in the cases. 7075 T6 alum.
is nearly as strong,(tensile), as mild steel. Make studs from this ? Same growth as barrels. OD. bigger than threads with shoulder at bottom ?
Liquid cooled heads with single overhead cams. Cryo all the parts ? Will a 48 mm IDF Webber feed (2) 40" cylinders ?
Thanks, Art.
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Re: Big Type 4 VW

Post by modok »

It's not the first aluminum engine with threaded fasteners, tho I have noticed quite a few porsche enthusiasts who think that way. Not saying you are one. But it is funny.


A stud is a spring. A spring has a rate. Stretching the stud X amount results in X amount of force.

You will need to find a way to make the spring rate of the head studs -low enough- so the clamping force is enough cold, but not too high hot.
Two main ways to do that....for any given fastener,
make it smaller diameter (that will usually need higher tensile material to carry the same load)
or to make it longer (if space permits, a spacer will be needed, the spacer also can contribute to the rate)

Another idea is to use exotic material which expands more with heat, but I don't feel this is a great idea. A stud is only connected to anyting at it's ends.
If the studs are enclosed in a hole in the cylinder this is not a concern, but if the studs are outside the cylinder in the breeze they could be the same temp as the cylinder, or they might not.

Aluminum not function well as a material to make springs from, nor threaded fasteners.
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Re: Big Type 4 VW

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Re: Big Type 4 VW

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JCR wrote: Thu Apr 08, 2021 9:27 pm Go over here. https://shoptalkforums.com/viewforum.php?f=1
yes go to shoptalk if you want no BS but can deal with a few weeks waiting time before all your questions are answered.

Otherwise, visit the Samba but be careful and don't listen to everyone. There a far more people over there and with that comes the morons.
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Re: Big Type 4 VW

Post by agertz1 »

Mr. Modoc,
Thanks for your reply. Aluminum as a spring or threaded fastener, calls into question the use of it in 11,000 hp. +/- Top Fuel engine connecting
rods ? Head/cylinder, steel studs on Type IV engines are necked-down to approx. 5/16" dia., despite being quite long, ( elasticity) ? Air cooled ,
cast iron cylinder shouldn't grow too much. I suspect engineers did this to avoid pulling case threads. They were strong enough for low hp.
applications. Regards
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Re: Big Type 4 VW

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The aluminum rod uses steel bolts.
Top fuel engines?
1 mile or 1 minute service life is good enough for you?
Just use some ready-rod from the local hardware store. :P Just kidding, if that was the idea You would not be asking.
But it sure is a funny question.
A lot of engines use aluminum rods, and sometimes they last a lot longer than they "should", and I agree that warrants more study. For one things the beam of a connecting rod is not under continuous load, momentary load only. Creep has two or three stages and the load is not applied long enough to get into the second stage of creep.
Explain how a 1" bolt in aluminum, is different than a 2" is different than 4" and there isn't any.
A lot of aluminum things have steel bolts and get hot and work fine tho they all would have the difference of expansion problem, right?
So why does your engine have weird springy long studs? because the metal creep in the cylinder heads was a BIG problem.


Creep resistance usually depends on the load VS tensile strength, temperature and time. That's it. But the TIME factor is pretty key.
It is believed that below 50% load, steel has zero creep. In truth this is not true, but the amount of creep is SO LOW, that it is buried by other factors which can cause a dimensional change in the material.
But we still have mechanics backing off the torque wrenches when done, and loosening the rockers for storage so the valve springs don't lose load, and collectors putting the cars on jackstands so the springs don't sag, storing cranks stood up, So they "KNOW", about creep, but in these cases they are "Into the noise" and half the time the results may be opposite what they think. When they put the car back on the ground, it may ride too high :lol: and they may have to go over quite a few bumps before the ride height is normal. When using a torque wrench every day, backing it off all the way results in more wear than leaving it half way up.

Higher temperatures accelerate creep, it could be thought of as time happening more rapidly.
But materials ALSO lose strength as temp goes up, and so the load % of yield strength goes up unless the load is lowered.
So the creep curve VS temp is not linear, for the same load, as temp goes up it increases exponentially.

High strength aluminum IS as strong as mild steel, at room temp....
about 260F things start to change, but just a little. That's lucky, aluminum and water cooling is a nice combination.
Past 350F, the creep resistance of aluminum nosedives, and 2219 alloy is actually one of the stronger alloys.

The aircooled head runs 300- 400F, and the design is a compromise between cooling passages and strength, the head WILL experience a lot of creep and there is no way to prevent this creep, and so the solution is to affix it with springs.
So even if you solve the difference of expansion problem,
the head will still need to have springy studs, because it still will creep.
What that has to do with the cylinders I don't know.
If the cylinders don't run over 260F and the head is water cooled then I don't think there is a problem any different than any other aluminum engine.
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Re: Big Type 4 VW

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agertz1 wrote: Thu Apr 08, 2021 11:34 am In other words, specific type IV things to watch out for ? Such as, all aluminum cylinders with steel clamping studs. Because of big difference in
thermal expansion, seems like studs will deform barrels at running temperature ? Clamping is only as strong as threads in the cases. 7075 T6 alum.
is nearly as strong,(tensile), as mild steel. Make studs from this ? Same growth as barrels. OD. bigger than threads with shoulder at bottom ?
Liquid cooled heads with single overhead cams. Cryo all the parts ? Will a 48 mm IDF Webber feed (2) 40" cylinders ?
Thanks, Art.
What is the anneal temperature of 7075? When it gets there you are done. That is why they used steel studs from day 1
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Re: Big Type 4 VW

Post by modok »

That's how aluminum wire works too, most of the time the KEY is to affix it with enough spring that it stays tight.

You don't see anybody using aluminum screws. Why? Aluminum screws WOULD solve the expansion difference problems....but would introduce even more creep problems.
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Re: Big Type 4 VW

Post by agertz1 »

Thanks for the skilled reply. Likely smarter, not to re-invent the wheel, unless I develop head/barrel sealing problems. Gas filled O-rings a good idea ?
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Re: Big Type 4 VW

Post by Mummert »

I used to build a lot of type 1 volkswagens back in the day. Smaller 8mm stud chromoly material did better with big bore cylinders than oem 10 mm studs. Not because they were stronger but because they left more room in the case for better case savers. Aluminum studs would not be a good idea, the section modulus would require a larger than oem diameter to retain tensile strength.

2024 is the best material for high heat aluminum. Even though it it barely stronger than 6061 at 100F, it is stronger than 7075 above 200F because it has a higher copper content. But I wouldn't do it.

VW type engines usually only require 30ft/lbs of tq on heads studs because sealing area is so minimal. E85 will do more to keep the cylinders round than most of the other things you might try. With gasoline I only used to get about 3 passes on the hill before the cylinders would go out of round and it would start huffing oil. With straight Ethanol I get 6-7 passes before I had to let the iron MAHLE cylinders cool down.

I used to port alot heads for type 4 engines 2700-2800cc range, it take a lot of chamber work to get the compression down and all of them ran the 911 porcshe fan shroud conversion. The only thing that sucked about those things was the 55 amp alternator, but the fan and was amazing. Type 4's have heating issues.
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Re: Big Type 4 VW

Post by agertz1 »

As I understand, Type I and IV both have a 55mm rod journal ? I have Type I Pankl Ti rods, with 9mm bolts. They want a 22mm wrist pin. I want to use
them in this build. This means bushing my pistons to 22mm. Since heads are liquid cooled and using E85, not sure I'll need a 911 style fan ?
Thanks, Art.
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Re: Big Type 4 VW

Post by agertz1 »

Where does one buy 8mm chrome moly studs for type IV's ?
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