Inconsistent street performance
 

I need some advice. I have a 71 911 t which I drove about 5 miles to the pub on city streets this evening after letting it warm it up in the driveway about 5 minutes and it ran perfect - smooth and silky.

Upon leaving about an hour later on the same route back it ran like crap, including a very loud backfire while deaccelerating down a hill from 45 mph in 3rd gear!, not even after down shifting.

It does this a lot, it's like I have two cars in one.

Any ideas! Thanks

Gas percolating in the float bowls when sitting after getting up to temp. Percolates out and straight down the throttle bodies.

There are phenolic spacers you can put under the carbs that act as insulators.

Thanks for the tip. I will try it.

You might have to live with it since the gasolines today are not suitable for carburetted engines as the oil companies have been raising the Reid Vapor Pressures (RVP) for emissions on fuel injected engines and are no longer concerned about carburetted engines.

Might be a loosing battle.

Joe