Thanks for the drilling and carburetor tips, guys. Follow the inliners link and look at the cut-away photo. As they say, "A picture is worth a thousand words."
I checked the head on the bench and it is drilled at 12 deg. It also has casting numbers like this:
Between #2 and #3 spark plug - on the flat above
B 61 848
850
The head on the in-service 235 has the same external casting numbers.
Under the valve cover on the head on the bench is:
Between cyls 2 and 3 CON 12
Between cyls 4 and 5 H20 2
Neither has a long casting number ending in 848.
On-the-bench head has valve rotators on 6 exhaust valves and hard tips on the two with worn stems.
The Rochester B carb has 5140 stamped on the mounting flange and the bore is 1-3/4 not 1-7/8 on Bouymakers photo. I takes a clamp-type air cleaner. I suspect this is a 235 rebuild carb. It might fall a little short on the top end. I have no experience with Rochester Bs.
I have planned to use the Offy/Zenith setup off the in-service 235. The 235 runs very well (except for the oil consumption) and holds ~ 1- 2in. HG @ WOT at 3,000RPM. That should feed a 261 OK, I think. Odd thing I had pointed out to me a couple of months ago about my Zenith 228s: one of them has "Bendix" cast on the side where the other has "Zenith." I have used identical kits in them and they have the same jets as I recall. Tag numbers are different. They are #3 mounting flanges. As you probably know, GMC used 228s for about 30 years on the inline 6 engines. I took them in part trade for a load of cordwood about 50 years ago.They replaced a Carter YF when I got the Offy manifold.
