weber 38 fitted to a chevy 250

Hi all

I have fitted the above to my Chevy L6.

Motor idles a lot better than the old monojet so that was good.

I used a matching intake for the weber so did away with my original intake. I got the weber jet sizes for my motor from a carb shop that has done this conversion on the specific motor before, so hopefully they gave me the correct sizes.)

The problem that I am having is that after about 10kms of driving on the freeway, she stumbles and looses power, I have to takie my foot off the gas and then gently apply pressure to the gas, but sometimes it takes time for it to accelerate nicely again.

It is also running a rich as the new plugs are now black and the tail pipe is also black.

I have also advanced the timing to 10 degrees BTDC as the weber prefers more timing according to the internet.

Btw I am using 195 airs, 140 mains and 55 idle jets.

What could the possible problem be? Any advice appreciated.

Thanks
Kavesh

sounds like jetted too rich, but first, are you running a pressure regulator? 3.5 psi for the 32/36 but not sure on the 38. due you have a heated intake? stock intake gets heat from the exhaust manifold. no heat in cold weather can also do this.