Spitfire Spitfire carb need help/opinions

[TR_JOE250]

Hello all,
I'm putting together a 73 Spit I purchased recently; rebuilt motor, new clutch, header, free flow exhaust, and have come down to fuel intake. I have the original ZS carb as well as a pair of SU's that came with a complete motor from a MKI all of them will need to be rebuilt if I opt to use them. All of my previous Spits have been stock so I am a bit unsure how to go. Weber? if so, side or down draft? I would like to keep the expense, set up, and maintanence as easy as possible. Any advice or coments would be greatly appreciated. Thanks.
Joe /ubbthreads/images/graemlins/cheers.gif

 

[Andrew Mace]

Frankly, there's nothing wrong with a properly adjusted Stromberg. Dual SUs are ok, but if they're from a Mk1 Spitfire you'll have to source a fairly expensive correct intake manifold. Lots of Spit folks seem to like the Webers; I'm ambivalent about them unless you're prepared to do other things to make using either type of Weber worthwhile (cam, header, etc.).

 

[Eleven]

I am switching my GT6 to SU's. I finally got sick of screwing with the ZS's. The change over has not been easy and I may change my mind but the SU's with the right needles, properly adjusted are almost as good as Webers.

 

[TheAssociate]

I think the Stromberg is a good, reliable design. I've personally never had any problems with them. I have heard however, of people blowing up motors because of improperly tuned carbs. For example, my last Spitfire, a '78, originally had dual SU's that were not properly adjusted by the previous owner. He blew the motor(connecting rod through the block) because the mixture was too rich. The gas began mixing with the oil and ruined the engine over time.
I bought the car, and put my '74 1500 engine with single Stromberg in, and happily drove the car as my daily driver for 65000km.
I think if you have a good budget for tuning and rebuilding SU's go ahead. If you want to keep it simple(and slow mind you) go with the Stromberg.
By the way, I had dual SU carbs, but never put them in because of the hundreds it would take to make perfect.

Adam.

 

[piman]

Hello Joe,

I would go for the S.U.'s purely because of the metal piston versus the diaphragm of the Zeniths.

As for "are almost as good as Webers", well the only place a Weber scores over the S.U. is on maximum power if the engine is highly tuned. For day to day driving, cost and simplicity the S.U. is better. The other comment, "of the hundreds it would take to make perfect." Usually a simple gasket set will be all that is needed. S.U.s's do not wear significantly except at the throttle spindles which affects the idle. I know that people spend a lot to get them in 'show condition' but it is not necessary.

Alec

 

[foxtrapper]

ZS
Good carburetor. Generally screwed up by previous owners. It gets tweaked (screwed up), and gets tweaked even more. The manifold is poor. There are two sized manifolds btw.

SU
Good carburetor set. Work very well. Very effective and common hop-up trick. Your Mk1 HS2's will work, but you will need a different manifold. Fairly common and cheap on e-bay.

Weber downdraft
Good carburetor. Made by the millions. Entertaining problems with bonnet clearance problems with one of the manifolds. Not a hot-rod carburetor, but it's effective.

Weber sidedraft
This is a hot-rod carburetor. Demanding, difficult, tempermental, etc. It's got a well deserved reputation. But when it's right, oh-lala!

 

[cjm]

dellortos are a worthy consideration, su's are workable, although i would insert copper pipes into breather holes, and lead away from exhaust. i used grose jets, not everyones favourite upgrade, still i had no problems with them.bushes on su's need upgrading also.