Weber tuning frequency question

I have been interested in the Webers because of the authenticity, the look, and the sound. Not having much experience with carbs (I didn't pay much attention in my youth), I thought it would fun to become immersed in them and learn how to make them run well. I have done as much research as I can thus far, but I have a real world question:

I live at 800 feet in the foothills of the Blue Ridge mountains in VA. In 25 minutes I can be at 4000 feet. The weather ranges from 95 F in the summer to highs in the 20's in the winter. My car will see a mixture of street and open track time (no racing). Assuming I have a well built, well set up 302 with webers, how much tweaking would I really have to do to keep them running nicely throughout these conditions? Am I a fool to even consider them (lack of experience considered here...) Other options would be a stacked EFI or the Mass-flo EFI. I am not going to use a standard 4-barrel Holley or similar. I don't mind some tinkering, I just don't want to spend more time under the hood than behind the wheel once the car is done.

Thanks for the input,

-J.
 
EFI also takes a while to get running correctly but once it is dialed in then your altitude and temp roblems are over. I am getting my webers up and running on my 427SO now and then will tackle the GT40 302 after that. I think the 302 will be much easier since their are many more on the road with 302's and starting point jet sizes will be easy to find. The Webers do take some tinkering, however, it is fun once you have the concept down.
 
J Salmon,

You raise an important point about altitude & Webers/Carbs . It is best to set your jetting at the lower altitude you will operate in and live with the slightly over rich situation @ altitude. Im drawing on some of my Jet Boat experience here where several boats that were prepped/tuned in higher areas suffered lean out related problems when the Marathon was started at Sea level. Constant Flow/Mech injection types were also affected and Holley carb types to a lesser degree. This took place with an altitude drop of about 1500/1800 ft max. You have to take into account that the boat spends most of its time at Full Throttle/Full Load so is a lot more sensitive than the car situation.

Jac Mac
 

CliffBeer

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J, one suggestion here which I think will make a very big difference as far as frequency of required tuning: start with new webers. Tired and worn out webers are notoriously hard to tune because of a number of variables. For example, one such variable is worn throttle shafts tht can leak air into the throat and lean out the mixture - there are fixes for this but it's not easy to do. Used webers sometimes have different progression holes drilled into the throat as well - makes coming off idle smoothly difficult. The full set up, including manifold, seems to go for between $3,000 and $4,000, so, not cheap but worth the difference over a used set. Enjoy!
 
J-

For wat it is worth, I have a car using Weber 44 IDFs (not a GT40). The car is based at 400 ft some of the time and 2500 feet some of the time. The temp range is similar to yours. I haven't touched the carbs in 5 years - since they were installed and I dialed them in. The car runs fine. If I were to tweak it, it would be the idle circuit which covers most of my normal driving...idle to 2500 rpms. This can be done most likely with a slight adjustment of the idle mixture screw.

Even if was looking to change idle and main jets periodically, that takes about 10 minutes on my dual carb setup.

If the carbs are installed and dialed in correctly, they shouldn't really require much tinkering in my opinion.

Regards,
Mike
 
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