International Vintage Volkswagen Forums

Hi,

Iam building a 30 horse engine with a Judson supercharger for my microbus! But I am not sure whether to stay with the original crank or buy one of the Mr. Okrasa 69.5 mm stroker ones. I think the advantages of the stroker are:

o Stronger, less change of breakage (This is my main reson, I want to build a reliable engine)

o More power (although not the main reson)


Disadvantage:

o Longer stroke means higher piston speed -> more heat



I am planning to run a 25 horse fanhousing (it is an old bus) in that way making the 30 horse looks like a 25 horse.

What would you suggest for a reliable engine, buy the stroker or keep the original crank?

Thanks very much for the advice.


Jeroen

In my experience the fragility of the stock 30hp crankshaft is overstated...unless of course you drive it hard and regularly overrev it.

Supercharging doesn't require you to rev the engine faster to take advantage of the increase in output. The extra power comes from more efficient filling of the cylinders which gives you the most useful of attribute of supercharging, extra mid-range torque.

Using the 69.5 cranks will increase the capacity to 1300 cc(?) which when using the Judson designed to fill 1200cc will mean you'll not get optimum boost pressure.

Money would be better spent on a 30pict carb and a suitable non-vacuum distributor. There's a member on my forum who has driven his Judson Supercharged Beetle for 50 years in the heat of California...no broken crankshafts and no overheating.

If you want to know how to do it PM Gert Gehlhaar on The Judson Register Forum.

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Hi John,
thanks for the advise. I can follow you! Thing is, I heared a lot of stories about broken crankshafts and one of my friends broke one in his freslhy build 25 horse! I am planning to balance the rods and pistons to keep the forces on the crank to a minimum.

thanks,
jeroen

Balance the engine, yes, always a good thing, but as I say Gert bought his first car a '55 Oval in 1957. It had the Judson already fitted...he still drives the same car with the same Judson and the only thing he's broken in more than 50 years is one camshaft.

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