Recently installed an old rebuilt (rebuilt years ago & sat on a shelf) WCFB from a '51 Buick on my flathead. Figured I'd tempt fate and fire it up w/o opening the carb (and I didn't have any gaskets) - runs OK. Idles well, pulls strong on acceleration, but surges at part-throttle cruise. The slower I am, the worse it is. First thought was lean, but the plugs don't look lean - they look darn near perfect. I haven't fiddled with it much other than idle mixture screws to make it idle nicely (sitting right at the "standard" 1-1/2 turns out). If it matters, it's on an 8BA w/GMC Bubba converted SBC vacuum advance window distributor. Originally, I thought perhaps the throttle lever arm I fabricated was too short and I was inducing the surge. I lengthened it a little bit and it seemed to help a tiny bit (but could be my imagination too!). Got a gasket kit for it and figured I'd do some Christopher Columbus work (don't know where I'm going, don't know what I'm looking for, don't know what I'll do when I find it), but figured I'd see if anyone had any ideas first.... TIA
There is some crap in there partially plugging the flow of fuel through the jets. Open up the top of the carb and see if you can remove enough/blow it out. You should be able to reuse the same gaskets; just don't rip them when you take it apart. If you want to go all the way just buy a can of carb dip from NAPA. Take it all apart, all the parts into the dip for an hour or two. Just don't put any of the gaskets into the dip. When you remove the parts, spray with water, then a shot of carb cleaner and an air hose to dry it off. Reassemble and you will be good to go. You can rebuild your carb this way without buying a rebuild kit and in fact without even resetting the float height. It is OK now so it will still be OK when you put it back together. Your only problem is some crap in there someplace from the years of storage.
Just a very generic test...run it at full surge mode, pull out choke slowly...add a pull wire if automatic or disconnected. If it is lean, at some point in this it will get better. If not, it will get worse. I would expect a straight 8 application to be on the rich side due to lengthy manifolding.
Sounds like a vac leak. This carb had a screwy auto start thing beside the throttle. See if the plunger is free to move. Better yet, block and plug all that stuff off. Also check to see if the base of the carb and manifold is all sealed by the gasket.
Assuming you meant 1952 Buick, and not 1951; the engine would have been a 320 CID. What is the displacement of your engine? Migrating an O.E. carb from one engine/transmission/body to another different combination works best if the receiver engine is plus/minus 3 percent of the donor engine in CID; and has a WOT of roughly the same RPM. Thus the 1952 Buick WCFB could probably be used successfully on a similiar RPM engine from 310~330 CID. Placed on a much smaller engine will mean less air velocity than design with a correspondingly lean mixture; especially at part throttle. Jon.
51, 52, whatever it takes! Mostly stock 239 (slightly higher comp, will get a cam very soon, headers & duals.... Surely they can be tuned like any other carb... This is counter-intuitive to me. In my experience, too large a carb results in "soggy" performance (rather than "crisp"), bogging, and rich mixtures due to poor atomization. Can you explain further?
A carburetor is designed to flow a certain amount of air AT a certain velocity. It is the velocity of the air passing perpendicular to the pickup points that creates a negative pressure within the fuel passages and allows fuel from the metering wells to be pushed into the venturi area. Too large a carburetor will have less air velocity for the same air volume. The lower air velocity will cause less negative pressure in the fuel passages, thus less fuel will be pushed into the venturi area - lean mixture. Since air velocity allows aids in atomization, one will also see poor atomization when one increases jet size to compensate for the lean condition. FOR STREET USE, the most important aspect of tuning is starting with the proper sized carburetor for the application. And yes, the WCFB is one of the more tunable early four-barrels. While these are still too large, better street results might be obtaining using a WCFB from a 1955 Chevrolet (265 CID) or a 1955 Plymouth (270 CID). Even the Holley 4000 from the 292 CID Ford should work better on the 239 than the WCFB from the Buick. Jon.
Thanks for all that info - still counter-intuitive from a practical perspective (ie - my experience with combos that are over-carbed), but I understand your logic. Still, it seems to perform very well on acceleration (very crisp & good throttle response), the plug color is very good, and high-speed, part-throttle cruise seems to be OK, it's the slow-speed, part-throttle cruise where there's some surging... I still haven't opened it up...
The choke pull gives a crude instant way of richening the mix at suspect speed and condition to see if the thing is indeed lean.
Gonna try that, Bruce. Got a mech choke hooked up already. Hmm...forget where I set timing before - prolly highest vacuum - ran fine with single 2bbl - no surging - the surging came with the carb swap, so while it could be timing, it's more likely the carb - I'll double check it. I also need to figure out where the vacuum advance is too - it's an adjustable one... One other variable I failed to mention in my original post is I initially got it running before I left NM & was living at 7000' & working at 5000'. It was slightly rich then, but I left it alone because I knew I'd be moving to sea level. The mixture "feels" good - very strong. Will try to fiddle with it some tomorrow - been tinkering with the old Harley flathead the last few days, actually.
OK - lots of flathead carb work today. Went through the Linkert on the old Harley 45 flathead WLC. Then cranked up the 8BA in the '36 - played with it. If I very slowly opened the throttle, at about 1/4 throttle, it wanted to die. It would help some if I pulled the choke, so off it came. Opened it up to find there was some sediment in there, but perhaps more importantly, it looked like the air bleeds (I assume that's what they were) might have been dirty. Cleaned it really well, cleaned all the passages, took note of all jet and rod sizes (in case it didn't work), popped it all back together, and it runs great. My fault for sticking it on and running it since it'd been sitting so long. It was an old rebuild that sat on the shelf for years. Looked great on the outside, but inside was not as nice as the outside (wasn't horrible inside, but enough to bung it up). Thanks for all the tips!
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