4100 Fail

Many people are able to run the original 4100 Autolite carb on their ‘Birds, but I’m not destined to be one of them.

Checking the float level on the 4100 as a last resort.
Checking the float level on the 4100 as a last resort.

I swapped out the phenolic spacer, replaced the studs and mounted the 4100 just as it came from the factory. The results were identical to the earlier attempts: the engine would start easily, but would only run at very high revs. It ran slightly better with the idle adjustment screws run all the way out—and not at all with them most of the way in.

All the evidence points to a vacuum leak of some sort, but after all the time and energy expended—flattening and repairing the base, repeated disassembly, etc—I still have no idea where the leak(s) might be.

The oily goo coming up out of the main jets
Oily goo coming out of the main jets

So, I’m done with it.

I’ll donate the carb to my son’s shop class where it can spend the remainder of its years as a learning tool.

Turning my attention back to the Edelbrock, I turned it over trying to remove the check valve only to discover a thick, oily substance oozing from the main jets (and a few other places). Since there’s no way this could be actual oil, I’m assuming it’s some kind of gasoline residue—how or why I don’t know.

Parts of the carb are soaking in cleaner. The seals and gaskets look good, so I’ll try a clean-and-reassemble before I fork out money for a rebuild kit.

More Carburetor Roulette

I’ve been struggling with very hard warm starts the past few months. It first, it was a fairly uncommon event, but lately I’ve been unable to start the car when it’s warm except with great difficulty. Last week, after a short 3-4 mile trip and two hours sitting in the parking lot, I cranked for 2-3 minutes with no result. I finally more-or-less flooded the carb by continuously pumping the pedal to get it running. It fired up eventually, but with enough white smoke out the back to worry the local air resources board.

Well, the car is hardly usable if I have to let it get ice cold between starts. (Cold starts are easy–go figure!) So, I took the car out of commission, pulled the Edelbrock off and—after hunting around in the garage for the miscellaneous small parts I needed—installed the Autolite I worked on a while back.

Mismatched carb stack
Phenolic spacer (yellow part in between) doesn’t quite fill the gap.

Starting it up yesterday, I found the same difficulty I had before. It runs, but only at high throttle. I sprayed a little starter fluid around the joint between the carb and the spacer, and it definitely has a huge vacuum leak there, which seemed a little odd since I just flattened and cleaned up the base.

Looking more closely, I noticed that the phenolic spacer I have under the carb is not a perfect match with the base of the Autolite. I haven’t pulled it off yet, but I’m betting that air is getting past the gasket where the carb overlaps the spacer.

Beaches in the carb
A little hard to see the details, but there are beaches forming in both bowls.

I don’t want to cut down the mounting studs I have (in case I reinstall the Edelbrock) and I couldn’t locate any replacements yesterday, so this project is still in the works. I’m hopeful, though, that I can get the Autolite working this week.

Oh, and the Edelbrock? I pulled the top off it and found bowls full of fine sediment. Chances are the whole carb is clogged up with this stuff! Given that there’s a massive paper filter in the fuel pump (or is there?), I have no idea how this happened. I’ll be installing an inline filter this week too, I guess.