Side drafts or 4 barrel??

[dan67]

Ok, I decided for a 4bbl carb.
My question is, what is better for a turbo setup.
4bbl. with mech. secondary
4bbl. with vac. sec.
What about DEMON carbs.
Thank you for your help.
Very cool site!

[Brent]

I origionally posted the question with a DEMON carb in mind. Demons are nice because they share the same jets, power valves, and just about all of their components with holleys, so any carb or performance shop should be able to tune it without having to buy special parts. I perfer demons just because they look cool, but from what my v8 friends tell me theres plenty of little details that make them vastly superior to holleys. I believe the main bonus to the demon carb is the float bowl design, but i can't remember what it is that makes them so much better. I hope i'm somewhat helpful.

[JohnConnolly]

I don't know much about the demon's, other than they are pretty, and EXPENSIVE.

I like the vac secondary. Once it's tuned, you can drive it like a stock car, never bog it. Like I said, get an 1850 (model carb), the spring kit, the jet kit, and the quick change kit for the secondary spring. I also get a quick change kit for the jets, another $30 or so.

You'll have $250 in the carb, then all you have to do is mod it for the external powervalve reference, and you are done. I ran 69 pri and 82 sec on mine.

[Lo Cash John]

I agree totaly. Holley 4 barrel carbs can't be beaten when it comes to "Bang for the buck". I also think vacuum secondaries are the way to go on such small motors (Any VW motor is small compared to a BB Chevy!). Properly set up, a Holley will give the same driveability as a side-draft Weber/Dell/Mikuni, but can deliver considerably MORE air/fuel as needed. Buy a book on Performance tuning Holley carbs, read it, think about it and UNDERSTAND IT.

[This message has been edited by Lo Cash John (edited 09-26-2001).]

[dan67]

Thanks for your help.
John, I got lost on the external powervalve mod. Could you explain how thats done,please
thank you.

[Lo Cash John]

As for how it works, I can't explain it any more simply. Just read the above text and THINK about what is happening, how a turbo works, and what POSITIVE manifold pressure means as far as manifold vacuum is concerned. As far as changing the power valve's reference point, it depends on the carb you have. With the 4011 (spread bore) we are using, Tracy just welded shut the port that leads from the powervalve chamber down to the plenum under the carb. The cover for the powervalve (powervalve on this carb is located under the float bowl with it's own little cover)was then drilled and tapped for 1/8th NPT fitting. This fitting was then plumbed over to the "T" manifold anywhere after the turbo. At idle a vacuum exists in the ENTIRE MANIFOLD,THERFORE THE POWERVALVE IS CLOSED. As the engine revs up with a load on it, the turbo starts to PUSH air into the "T" manifold (THUS DECRESSING VACUUM AND APPROACHES BOOST) while it DRAWS HARDER on the carb manifold (STILL A RELATIVE VACUUM). When the vacuum in the "T" manifold equals the rating of the powervalve you are using (measured in inches Mercury) , the valve opens and the extra fuel flows at a rate determined by the powervalve jet(I forget the technical name, but it is not readily changed so don't bother trying). It is quit simple really, just take time to understand it.

[This message has been edited by Lo Cash John (edited 09-27-2001).]