Judson Advice?

[fanbelt]

Im thinking about building a judson powerd 36. Now with being said is there anything I could or should do while putting said motor together that would complement the judson? After speaking with George Folchi I understand a hotter cam is not a good idea but what about head porting or longer stroke crank and are any of these even available?

Also Im concerned about my or any old 36 case being usable. How can I tell? What are bearing retainers? Who can I trust for machine work? Who can rebuild my heads? And so on and so on..... Frankly its giving me a headache. If anyone can help with one or all of these question i would appreciate it.

[Braukuche]

[gimmesomeshelter]

Hello-

Last year I sent some time researching superchargers. With a 36HP engine, there are two major issues you have to contend with. The first is that the 36HP engine isn't the best foundation to work with. They'll run forever if you leave them stock, but they have a reputation for having very weak cranks. To remedy this situation you'll either have to baby the engine, have a custom crank made ($2K+), or buy the Pre-A Porsche crank from NLA Parts for $1K.

The second issue is how to deal with all the extra heat. You'll probably want to run cooler plugs, install a 40hp fan, use stainless steel valves, install slightly stronger springs to compensate for the higher compression, and lower the base line compression. If you have the money, you could install aluminum cyldiners from LN Engineering, but that will cost you 3.2K for the cylinders, pistons, and studs.

In the end I decided to go the Okrasa route. Admittedely, it's going to be as expensive, if not more, than a Judson, but at least I know it will fit under my decklid.

To answer your questions:

All things being equal, a longer crank will increase your compression, and that's not what you need. If you went that route, you would either install a Porsche 356 crank, or one of the 69mm Okrasa cranks.

Regarding you case, you'll need to have it inspected by a credible machine shop for cracks, wear, etc..

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[oval-55]

[fanbelt]

Gimmesome this is the first time hearing about 36 cranks being weak. Granted i havent had much xp with them but but the judson only puts out 4 to 5 lbs of boost. Is that really going to be an issue ? Seems people have been useing them with stock cranks for 50 someodd years and still are. Not that a stronger/counterbalanced crank isnt a good idea . It just seems like over thinking it.

[gimmesomeshelter]

Oval-55

Before you purchase a cam from Mr. Okrasa, I suggest you contact Dema Elgin to see what he can do. First, my understanding is that cam for a supercharger is quite a bit different than a cam for a standard performance engine. Second, my machinist frequently has Elgin create custom grinds to fit a particular customer's engine/trans/driving style.

Thanks,

Paul
_________________
"I would rather have questions that can't be answered than answers that can't be questioned."

Richard Feynman

[John Moxon]

You know, fitting a Supercharger to a 30hp VW engine is the most straightforward Vintage Speed enhancement you can make. It requires neither special skills to fit nor special knowledge to get running correctly, you just follow the instructions supplied. You see the supercharger isn’t an engineering solution to getting more from your engine, it’s a bolt on accessory designed to overcome the shortcomings of the normally aspirated.

If you bought any supercharger kit “back in the day” they were simply a bolt on and go solution. Be it Judson, MAG, Pepco, or Shorrock, designed to be used without the need to open the case.

Unless you have specialised knowledge of supercharging and its pricipals don't think about modifying you engine to suit.

That's not to say you can't take advice but the average aircooled VW workshop will have very limited practical experience...if they tell you it will break your crankshaft, then walk away.

Crankshafts
Crankshaft failure is a product of overrevving...cranks in stock engines fail but in all the time I've run my Judson website (8 years+) I've never had anyone tell me their crank had failed.

So does running a supercharger protect you from crankshaft failure? It would be a brave man who claimed that but supercharging produces its increase in power in a different way from multiple carb applications. Supercharging produces extra power (torque) at the same revs over the stock configuration; i.e. it doesn't need to spin the engine faster to produce the gains. Infact Judson tell you to make all your gearchanges in all the same places as before.
Judson's "A Few Facts on Supercharging

Camshafts