Original carbs?

[Ed Young]

I have a 65C with Weber carbs. Was wondering if there would be more value with original carbs and air cleaners when it's time to sell the car. Would appreciate any input.

[David Jones]

Ed, that will depend on the buyer. The original Zeniths cannot breathe well over 4500 rpm so if the engine has been modified to use the better breathing of the Webers it is not going to be a plus to switch back but Zenith carbs are very reliable though Webers are not far behind. Knowing the configuration of the engine will be a plus when you come to sell it. I just finished building a 1720cc engine for my 64C and went with the Zeniths because the reality is that I can exceed the posted speed limit anywhere in the country even if I cannot go over 4500 rpm in 4th gear.

[Mike Wilson]

You could always leave the Webers on the car and include the Zeniths in the sale.

Mike

[Wes Bender]

Hi Ed. David's right as usual. Depends upon the buyer and what he wants to do with the car. Mike's suggestion is good too, if you still have the original Zeniths. If you don't have the Zeniths on hand though, the cost of buying a decent pair might exceed the increase in value.

[Thomas Sottile]

If you have the original and they are in good shape why not use them and mute the problem. It is not just the carbs but also the fuel lines and access to the plugs which make aftermarket parts less desirable . In my opinion

[Ed Young]

Thanks guys for the input I don't have the original carbs, would have to buy them to go with the car. The webers work great anyway. I live at 4,800 ft.elevation and go up from there quite often.

[Mike Wilson]

My adice is to sell it with the Webers. Perspective buyers can drive the car as-is. The next owner can do what they want.

Mike

[Al Zim]

You have two situations with the Weber carburetors. The first is the ventri size which is smaller than the Solex 40 PII but larger than the Zenith. Second is that the right side carburetor will not open as fast as the left side carburetor because the linkage on the base of the carburetor is different left to right.

[C J Murray]

You have two situations with the Weber carburetors. The first is the ventri size which is smaller than the Solex 40 PII but larger than the Zenith. Second is that the right side carburetor will not open as fast as the left side carburetor because the linkage on the base of the carburetor is different left to right.

Clarification... some Weber IDF40s have 28mm venturis, same as Super and C, and some have 32mm venturis same as S90/SC/912. Also, the only Webers that don't open evenly are ones with incorrect levers on the throttle shafts because they were installed by idiots.

[C J Murray]

I should add that Zeniths have 32mm throttles, 24 or 28 venturi, whereas Weber 40IDFs have 40mm throttles.

[Martin Benade]

Is the Venturi size the deciding factor within reason for making a street/friendly torque curve? Or is the bigger throttle diameter a detriment?

[David Jones]

Martin it has always been my understanding that the venturi size governs the torque curve and the throttle diameter while not irrelevant only affects control sensitivity though obviously it will be detrimental if it is very large as the charge will lose all its velocity if the venturi opens up into a large diameter inlet tract. On a race car engine the venturi does not need to be much smaller than the bore size of the carb as you are not looking for tractability but more high end power. On the tiny 28 mm bore of the F Vee I used a piece off brass tube of 27mm ID as my venturi so as to get all the flow I could through the carb. SCCA rules dictated that the carb had to have a venturi installed and that was how I maintained legality. It still idled at 1K rpm but once on the track the rpm was never allowed to drop below 3k or it bogged down on acceleration.

[C J Murray]

There are sweet spots to every dimension from the air intake until the mixture is past the intake valve. The problem is that if you apply all the "correct dimensions" to the design then the hot rod guys can find a better way. The best answer is always found over time by experimentation. Even the car factories can't get to an end result by plugging in numbers to a computer.

So theoretically the ideal relationship of venturi to throttle is 80%. 40mm X 80% = 32mm. 32mm X 80% = 25.6mm which happens to be right between a Normal and a Super. 80% is also what Weber suggests as well as Bell in his 4 stroke tuning book. It all has to do with fluid dynamics I guess. Putting 24mm venturis into 40IDFs probably wouldn't work well. 44 IDF X 80% = 35.2mm, really 36mm, and that is what I run on the 1622cc racer that revs to 8000 and the 2133cc street engine that revs to 6000.

To pick a carburetor size you take the displacement and desired RPM to find the venturi that is recommended and then pick the throttle size that gives you close to the correct relationship in size.

Sometimes all the rules get thrown out because rules don't allow you to use the correct sizes like Vic when he was racing the 1300cc car. Then you make everything as big as possible and don't worry about the ratio of venturi to throttle.

Remember that the throttle is a restriction even when it is wide open so it has to be bigger than the venturi. Oops, then the mixing tubes are a restriction also.

Does your head hurt yet? Mine does.

[George Hussey]

absolutely would be worth more. The more original the more it is worth. However how much would a set of rebuilt zeniths cost and are you willing to do it to make the car more salable? THEN what else is not original about your 356? Numbers matching? Color and interior color same as on the Kardex? Has it had extensive welding? All of these things influence the price and salability. SOME times, people will buy sooner rather than for more money if things appeal to them (such as originality)

However I am saying this from my perspective, the guy who removed perfectly GREAT running 40 webers to install the "correct" solex set on my super 90 roadster. Now the car does not run as well. but then engine compartment sure looks "super" and the concours judges will not nick me!

[Martin Benade]

I would also think plenty of Webers never get their jetting correct. I know I wouldn’t be able to.