"Stock Gene Berg Pulley Size

[dgsaz]

I got my hands on a Gene Berg pulley. The pulley is a stock sized "Achiever".

I confirmed the size on Berg's web site and talked to their office on the subject.
The fellow I spoke to at Berg's office said not to sweat it.........

It measures 6 3/4" and I believe a stock VW pulley is 7". What, if any, impact does the loss of 1/4" have on cooling?

The Berg "power pulley" size is 5 7/8 +/-

What is it I don't know about the missing 1/4"?

Thanks,

dgsaz

[74 Thing]

The one I used to have was 7" in diameter. CB, and JayCee, and Empi (knockoff Berg), had 7" pulleys as well.

Most of the other aftermarket ones are 6 3/4".

[scubaseas]

The 1/4" difference will make your cooling fan spin about 233 rpm slower which is not a big deal. Assuming a 3.750" generator/alternator pulley

The power pulley size if used on a loaded up Bus and driven at high speeds for extended periods will fry the motor pretty quickly. I came by my Bus as it was on it's fourth engine due to a number of "improvements" the PO had made which included a power pulley.
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Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[vwracerdave]

The 1/4" is in the way it is machined. The groove in the pulley could be wider or narrower causing a change in how deep the belt rides in the groove. Berg does not make junk so it's as accurate as it needs to be. You can also change the fan speed by using a wider or narrower belt.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[dgsaz]

[74 Thing]

Your belt makes a big difference as well and how you shim your top pulley.

For instance if you use a wider belt it will ride on the outer area of the lower pulley (turning the fan faster). Likewise the upper pulley if you shim it out and the belt rides lower the fan turns faster.

[scubaseas]

No idea what size the 356 top pulley is. There are lots of pulley calculators on line. If it's a smaller pulley it'll spin the fan faster.

X2 on what vwracerdave posted.

What's the application?

A 233 rpm change at 6500 rpm fan speed/3500 rpm engine speed isn't going to blow up the motor in a bug. With the power pulley the cooling fan slows down about 20% which will effect high speed cooling a lot. As in a seized #3 exhaust valve and hole in #3 piston if going up hills at 75mph with 2000# in a Bus.
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[FreeBug]

[dgsaz]

[scubaseas]

Nice set up. I have the same trans and tires.

Do you have a cylinder head temp gauge on #3? Very enlightening after I installed one. Also might want to check the Air/Fuel ratio with a wide band sensor. Both A/F ratio and cylinder head temp monitoring can make a motor last a lot longer by avoiding overheating.
_________________
Al

08/1970 T2a Westphalia owned since 1980

ASE Master certification. 50 years pushing a wrench
Retired

[Brian]

Use a 38amp generator with the proper pulley and a 900x9.5 belt. That with the berg pulley and you’re good.
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[Splitdog]

The Berg Power Pulley is the exact same diameter as a stock Porsche lower pulley. So you can run a Power pulley, and if you run a Porsche gen pulley up top, you get your exact fan RPM back. I had to do it on my turbo motor. And then run a Porsche belt for a 356. 9.25 X 825mm. PN#999-192-006.50
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