308 GT4 resurrection by Trahanm

3 minute(s) of a 33 minute read

Hello Folks,

I am getting the 308 pretty well sorted out now, and it is driving pretty well. This weekend I installed MSD CD ignition and it runs better, and seems to have stopped fouling the plugs. I also have tried both the red line MTL and the 75/90 NS with 1 quart of MTL. It appears to shift slightly better with the NS. 1st and second are the only difficult gears, with 3,4 and 5 being fine. However, even 2nd is slightly better with the NS GL5 mixture. The info and threads on this site have really helped.

The last main issue I have is popping through the carbs at highway speeds, at light throttle, at 3300 to 3700 rom, exactly the speed you cruise at. This only happens when depressing the throttle lightly.

The engine otherwise drives great, with no hesitation, and pulls strongly in all other rpm ranges. If I depress the throttle heavily at the rpm range (3300-3700) the cars pulls OK with no spitting.

The jets were 200 air, 130 main, and 50 idle. I changed the idle jets to 60, but this seems to have no effect.

Based on what I have read on this site, I am planning to change to a 140 main and perhaps a 220 air correction jet.

The car is a 1979 Euro spec model with the single distributor.

Any comments on how to proceed will be appreciated.

Many thanks in advance.

10-9-2015

Thanks for feedback guys.

I put the hotter NGK 6 iridium plugs in today and removed the idle jets to clean out the passageways with cleaner and compressed air. No change.

I have ordered 140 main jets to see what that will do.

The operation of the idle circuit and its potential to influence this makes total sense. I may even try a 70 idle jet.

Process of elimination. I will keep everyone informed.

I have the fuel pressure to set to 2.5-3.0 psi. It is my experience from the old Lambos I have is that is where the Webers seem to work best. On my Jarama with rebuilt 40 DCOE's the floats would leak when hot at 5.0 psi. 3.0 PSI and the problem gone. A few Weber "experts" I have spoke to also say nothing over 3.0 psi. We will see, if I can get this solved a may try raising it.

However, the car is now driving and running overall very well. Every step it seems I am able to improve it a little with the help on this forum.

10-12-2015

I attached the fuel pressure regulator next to the fuel pump.

Will also check the ignition timing again to be sure.

I should have the jets later this week and will post the results.