two things

first, has anyone had any success with a holley carb regulator? I installed one this weekend, as I find realized why I was back firing so much during deceleration. I can adjust the PSI from 0 to 15.. so if I a drag racing or hwy cruising, I can adjust for MPG. I should being running at 2.5 to 3 and it was running at 9 PSI. I was loading up and flooding. Hopefully this will be a long-term solution.

Now for a question I should know, but I am feeling lazy now that I am done fitzing all week. What is the sidewall number on a tire dimension? 205x15x65 what is a low-profile and what is the tallest sidewall that can be run on 15" Fuchs?

Yes, I run a Holley fuel presure regulator on my T4. My electric pump put out something like 9 psi. I don't know how the poor Webers ever ran with that setting, but they kinda did. Then I added the regulator with a gauge and set it up at 3 psi. Performance is much improved on both throttle response and at constant throttle. This should be a requirement for all Webers. Can't speak to other carbs.

The sidewall "height" is a % of the tire "width". The sidewall height on a 185 x 60 x 15 tire is 60% of 185 mm or 111 mm or 4.37 inches. This gives the overall tire diameter of 15 + 4.37 + 4.37 = 23.74 inches.

Tire sizes are typically limited by rim width. You can't always get the exact width you want without going to a wider rim. The Tire Rack webssite is real good about matching up sizes and rim widths. There is no formula for this.

I also have a holley regulator, been on the car for 11,000 miles. Many electric fuel pumps put out quite a bit more pressure than can be utilized with webers, zeniths or PMO carbs. Don't adjust for MPG. Set it and leave it.

angela

Looks pricey. How much does one of those puppies run?

I got it from Ken at Aircooled automotive... for the gauge and regulator it was ~$60 and another $10 in reducers, clams and gas line.

That's not Holley ! ! That's a cheesy copy from Ebay. Holley doesn't come in that nasty "chromed" finish. Check the "Holley" logo cast into the side boss, betcha you can barely read it. Looks like it MIGHT say Holley, but not really sure?

Be careful, they're junk!

It CLEARLY says Holley on it, on the box it came in and it has a Holley part number. I did not buy it from ebay, I got it from a local VW guy. He says that he installs one on every engine that he builds with great success. If it limits backfiring and loading... it is not junk to me.

Try this....
http://www.lesschwab.com/tiretech.asp

Maybe this will help, here's a really good tire calculator: http://www.1010tires.com/TireSizeCalculator.asp

And as for your fuel pressure issue, i just installed this fuel pump in my speedy:
http://www.cip1.ca/ProductDetails.asp?ProductCode=ACC-C10-5630

all i can say is WOW, that fuel pump solved all my vapor lock issues, and what i really like is that it's a one shot deal, fuel pump and regulator in one unit, it's slick, i mounted mine under the tank. Night and day difference compared to my stock pump and chrome dial type regulator!

martin