I just returned from a 4,000 mile road trip between Tucson AZ and Seattle WA round trip. The truck is my '51 3800 equipped as in my signature and loaded with a C11 Avion camper. Gross wt. is ~8800 lbs.
The 2 carbs are what I believe to be Zenith 228s with adjustable main jets but one had Bendix cast on the float bowl. I bought the pair of them decades ago for $25. They are for the 216 size manifold so I had to slot the base to fit the 235 bolt spread. Anyhow I had LOTS of time to watch the vacuum gauge and tach. It has the 848 head w/bronze guides. The engine pulls quite well above 2500 RPM and keeps pulling until it runs out of carburetion somewhere north of 3400 where I never turn it when I'm far away from home.
Just to get a fix on CFM requirements: At full throttle, where it spends a great deal of time, it will pull less than 1 inch of vacuum at 2900 RPM which is 62MPH. So It appears to me that those two little bitty Zeniths will feed my 235 all the air it needs at any useful RPM. And it behaves well even under 1,000 RPM. But it you try to lug it pulling off a stop like you would a big diesel it will bog. Keep it about 800RPM and its fine.
The cam is a Crower RV grind that Bruce Crower suggested about 15 years ago. I think it's a little hot for heavy truck use. High lift @0.440 but still pretty long duration at 220 deg at 0.050 lift. Split duration but I advanced it 4 degrees. I'd like to have it pull best at about 2600 rather than 3000. If I run it continuously above 2800 the oil starts to heat up.
