MTFCA Forum

How far should the bumper stick down past the brass plug?

I considered it a bumper not a stop, so when I did mine, maybe 1/8" below the metal. I do not recall having to trim mine and that is about were it ended up when installed. Seemed to work fine. Just make sure it is seated before trimming. I think it is there to prevent metal to metal contact when the throttle is pulled open for that raw burst of speed! (And yes I am a fan of the L4 Kingston's)

You shouldn't have to trim it at all, just shove it all the way into the metal screw head and whatever is left sticking out (usually 1/16 to 1/8) is enough. It isn't rocket science, it is just to keep the metal flap from getting stuck to the top of the throat whilst the throttle is not wide open. The ones you usually pull out of the carb usually only have about a 32nd left out for the bumper and still worked quite well, but they are also usually compressed and or rotted away too.

I've run a Kingston L-4 for the last 40 years in my car and never had any problems with one, once the mixture needle is set, you never have to fiddle with it again, especially on starting. The only other carburetor I'm thinking of trying is the Simmons Super Power carburetor...it's basically a Holley Straight Thru, but with a low speed idle flap like in the Kingstons, but it is on the choke side of the carb and not the throttle side, but from what I understand it works the same in evening out the idling temperament of a Straight Thru....we'll see.

Thanks, I made the little plug out of maple, I didn’t have one to go by, I left about 3/16 sticking out. Thanks for the help, Bob

That might work (?), I think the originals were cork.