Carburetor Alternatives, Holly ??

[Mukilteo911]

Before you read this please set into your mind not to beat me up over the question.

I have looked low and high and found very few alternatives,( none that are inexpensive ) to the Weber Carb for early 911 engines.
As one to play the devils advocate, why doen't someone make a manifold to use the hot rod manifolds for the V8 on a flat 6 ?

It seems logical that if these cheeper carbs can create so much power on V8 hot rods that they should be able to do the same for us.

I do not know much about carbs, but I do not see why it can't be done with good results, other than getting beat up by your local porsche buddies.

[masraum]

Potentially I could see a setup with three holley two barrels on a 911 on a custom manifold.

I remember a while back a guy selling a manifold for, I think, a single four barrel carb for 911 engines. It's an interesting idea. I guess the biggest question would be can the other carbs handle the cornering without causing problems. I would guess yes, but don't know enough to say for sure. Interesting idea. It would be kinda neat if done right.

[911tmaster]

i think it would work. my buddy has a 4 barrel hooly on his sandrail. its 4 cyl. vw engine bored out to hell but it always runs great and he catches alot of air and it never stalls out or anything. if i could get a manafold i would put a holley on my car

[emcon5]

This came up once before:

Planning bolting Holley on 2.4T

I think 6 side draft Mikuni's salvaged from motorcycle engines would be much cooler.

Tom

[dean]

One problem would be carb icing. Another would be hospital bills because you friends would be beating on you. ;-)

[911pcars]

You cannot substitute a Holly for cubic inches.

A single carburetor, even one with 4 throats, is not an effective method of delivering equal amounts of air/fuel to six or eight cylinders. A better method is to have one throat per cylinder (Weber IDA-3CI). An even better solution is to have one throat per cylinder with variable air/fuel mixture control (EFI). An even better solution is to have one throat per cylinder with variable A/F mixture control with variable intake tract length (VarioRam). It's called progress. A Holly would, IMHO, be step backwards.

Sherwood Lee
http://members.rennlist.org/911pcars

[Mukilteo911]

I agree that the individual gas air mixture achieved with seperate injectors throats carbs would likly be best. But mine is more a question of possibility and a way to achive that possibility. There are several manufacturers of very hi performance carbs that would seem to be suitable for our flat six engines, other than the webbers or injectors. It would be cool to find a way to take advantage of those other carbs for us hot rod builders so we can take a majority of a $2000. carb budget and put it somewhere else in the car. Not to mention that it is getting hard to find good webbers.

[HawgRyder]

There is another possibility....SU's.....
They have no accelerator pumps...you can change the slide needle (mixture profile) easily...they should give excellent gas milage.
Bob

[A Quiet Boom]

A Holley as good as it is would be a step backwards, simply because IR (individual runner) intake systems are proven to make more useable power and torque. The idea of 3 two barrels is a good one though because it allows longer intake runners for better low end torque but 3 Holley two barrel carbs and a custom intake set up for IR would probably cost as much as webers anyway. There is a cheaper alternative if your willing to put aside conventional wisdom as well as do a little work and that's Zenith carbs. You can get 36mm venturis for them, you can drill the idles and mains larger and they have two things that webers don't, torque boosters and individual accelerator pumps. I use 36mm venturi 40TIN Zeniths on my 3.0 and LOVE them. Sharp throttle response, excellent drivability, great power and they hold their tune fantastically. I'd only be happier with IR aftermarket EFI.

[HawgRyder]

OK...because of several enquiries about SU carbs.
SU carbs are from older british cars mostly.
They are a variable venturi non-choke style carb.
Enrichment is by moving the main jet lower in the fuel passage...thereby making the fuel much richer.
The vertical moving slide is the top of the venturi chamber...and as it moves upward it pulls the profile pin out of the centre of the main jet (up=richer)...and the venturi rise is governed by the vacuum and pressure of the intake manifold.
A side benefit is altitude correction...it happens automatically...as the air pressure goes down....so does the intake pressure.
They can be a real bear to tune...also need to be looked at regularly....but they can flow air when that slide is open and the throttle plate is at full....they are straight through.
Bob

[911pcars]

The problem with carbs and long intake paths is that the intake system is trying to move an air/fuel mixture some distance; from the throttle valve to the intake valve. The longer the path, the more the tendency for the air/fuel to separate. This drawback is probably minimal for full throttle operation where air velocity is relatively high. However, at low and medium engine speeds there would be a throttle response issue and a need to run rich to compensate.

With fuel injected close to the intake valve, the intake system merely has to move air, a lot easier task.

Sherwood Lee
http://members.rennlist.org/911pcars