A Sideways Look At Head Sealing

[BOBTAIL]

Ask yourself, why do ,say 96's seal better than 104's.

Its all about surface area, even stock cylinders leak.
So think about how to create more surface area on a 104
Think of an air filter, you know "pleated"?
Try machining a ridge on the top or say a series of grooves down the top sides of the barrel.


Keep thinking outside the box

[kdanie]

Oliver uses a small sharp ridge machined in the top surface to seal 103s. He says it works well. I think there were pictures posted here somewhere.
ken

[Wally]

Originally posted by BOBTAIL
Ask yourself, why do ,say 96's seal better than 104's.

- More heat, same or less wall thickness?-

Its all about surface area, even stock cylinders leak.
So think about how to create more surface area on a 104
Think of an air filter, you know "pleated"?
Try machining a ridge on the top or say a series of grooves down the top sides of the barrel.


Keep thinking outside the box

- Definately!, Porsche also used an extra seal in a groove on the sealing surface area cylinder/head of the 100mm (Nikasil) 964 cylinders...-

Bobtail,
The more servere problem with the larger steel bores is IMO that due to the extra heat, which they cannot dissipate quickly enough, the barrels go too much out of round and become oval shaped so to say. I suppose this could/will give cylinder wall blow-by which might be as bad for power as head leaking. Curious what a set of Nickies of the same diameter would do for power on your car.
I do agree that the added ridge you have made on top of the steel 103's in your turbo bug (as you described many times) must work excellent! Compliments!

Walter

[kdanie]

Oh yeah, I forgot about the heat problem. I've got a cure for that too. There is a high tech coating that would help them get the heat out. If you use a dryfilm lubricant on the piston skirts and ceramic coat the piston tops/combustion chambers you just eliminated much of the heat anyway. The tech is out there, A/C VWs just need to take advantage of it.
So for the cost of the P/Cs, cryo treatment and coating they should be pretty good and last as long as other iron p/cs

I have done all this to my 94mm p/cs. I hope to have the engine running soon.
ken

[Ephry73]

So if dissipating heat is the problem, how about increasing the ammount of air going through the cylinders?

Kinda like a 911 setup



E

[BOBTAIL]

Ephry,
Your not tryin' to start a flameout again are you?

Just ask yourself, If someone can add boost pressure and the extra heat that goes with it, thru turbocharging, using 103/4 and/or 5's then why can't I use them normally aspirated?

Wally yes you are correct the barrels do go square (Russ had that happen on the first incarnation of his latest setup)
He ran the piston barrel clearance a bit too tight and the mixture was a bit lean.
He has had the pistons and intakes ceramic coated to insulate the parts from excessive heat.
Funny you mention nickies cos an option we're still considering is the stock 100mm 993 pistons with dome top and whopping compression,so we can use the 100mm nikasil barrels from Porsche.

[Ephry73]

No, I was just curious


I will definitely look into Cryo'in' the 103's just to see if the metal retains the shape better... we'll see.



E

[Wally]

Originally posted by BOBTAIL

Funny you mention nickies cos an option we're still considering is the stock 100mm 993 pistons with dome top and whopping compression,so we can use the 100mm nikasil barrels from Porsche.

Bobtail,
Double funny since I already have a set of those and they will go on an engine (for the square :-)). Luckily I have a friend doing the same and he is a porsche tuning machinist. I will not eleborate on that subject any more since the thread I started last time about that subject, it was not very succesfull/pleasant...(they had to close it....)

One more idea I thought of today for sealing 103's: using chr/moly head studs. They are not only stronger but also stretch less when warming up. Therefore as the steel cylinder expands probably more than the chr/moly stud, the force pressing the head sealing surface and the cylinder surface together will increase with more heat. As long as your studs don't break, that might be a good thing for sealing purposes...or am I wrong here?

I hope its outside of the box enough for you...

Greetings,
Walter

[Ephry73]

What if by not stretching enough they just pull out of the case? I think there should be some amount of play amongths all of the components....

103's cryo'ed(pistons and cylinders)
71mmc/w crank(cryo'ed)
Rods cryo'ed (rod bolts from ARP cryo'ed as well)
86a Web Cam/lifters(cryo'ed)
Cylinder studs std, but cryo'ed
All bearings and valves cryo'ed as well.


It seems to work for the people that have tried this process, and since the 2,366cc engine is of a bad rep with head leaks and the like, why not the added insurance?

My problem is still figuring out the carbs for this engine.


E

[BOBTAIL]

Wally are you going to force feed that aswell? hmmm

Russ is using Raceware barrel studs and is very happy with them, it adds up what you are saying,about the cyl growing mure than the studs.And he is only using 4 per barrel now i.e no 5th or 6th studs required.

Ephry, that sounds like the right thing to do as for carbs , er, aren't they a bit "old hat?"
By choice i would always use FI unless my requirement was the sound of duals

BTW I am using my friends 2.4 with twin 40 IDF's and it sounds and goes just great runs late 14's but after my vanagon D it feels like a rocketship................

[Wally]

No, just N/A; the square is my daily driver now. To boot, it will run on LPG and since LPG (very common in the UK as well, I thought) has a higher octane rating than the best gasoline available (LPG has above 100 octane IIRC) I will set up that engine with a compression ratio between 1:10 and 1:11. That way I do not have to shave down the porsche pistons all the way, which is a good thing too.

Ephry, as for the ARP studs: The thread in the aluminium case is about an inch long and fine threaded M12. I don't think it will rip out that easily.
I also believe that cryoing will give the metal more durability and more wear resistance, but it doesn't change the heat conductivity properties of it. It still gives off its heat at the same (poor) rate.
Nevertheless every improvement does help I guess.
For carbs, the obvious choise to me for a 2366cc would be a set of 44IDF's with 36 venturis.

Greetings,
Walter

[Ephry73]

Thanks for the input Wally. I grew up between NYC and the Latin Caribbean. There you find a lot of LPG conversions, on almost every vehicle. My fahter actually has a 100lb tank in the rear luggage area of his '93 Land Rover. How do you like the conversion on the aircooled vehicle? I ask, because I haven't actually spoken to anyone that had it on an aircooled car.



E

[Wally]

Cool! I have my 1600 square with original twin 32 Solexes now running on LPG. The original gasoline system is working fine as well. The extra 60 liter tank has been mounted on top of the original tank. Since regular gasoline is 3 times as expensive and I am using it as my daily driver now, it does make sense to me. It has been given new, 'unleaded' heads when the conversion was done in 1998 (by the former owner). It runs fine. I believe LPG has a little bit less caloric value (less 'energy' in itself) but if I boost the compression ratio a little, that would equalize that. I don't notice any power loss even now when I change to gasoline while driving (there is a button to switch over). Also in general the milage is a bit less (less mpg).
The still liquid gas from the tank is routed through the exhaust (there is a tube welded in) to warm up the gas and then the gas evaporates controlled in a 'evaporater' and is routed to the top of the carbs. In water cooled cars, the liquid gas is routed through the (hot) cooling water in order to warm up. Thats the only difference.
Nowadays there are more modern ways for LPG induction, like direct and computer controlled injection. Maybe for the type 4, I will go a similar route, since I will need the injection system anyways to keep it all under the deck lid and have some good flow as well.

I'am sure your 2366 cc will run very strongly when assembled rightly and the ingredients you mentioned seem all fine to me.
Keep us posted on the results!
Walter