Stinky AFB Follow Up

[Ken B.]

Re: Stinky AFB Follow Up

Not real sure if this is really gonna help but...A friend of mine had a similar problem...He talked to a few people in the racing business and was told to paint the underside of the intake with white heat paint.It seems to keep disipate the heat a little better.Just thought i would throw that out there..

[Stuart F.]

Re: Stinky AFB Follow Up

Thanks Clem and Howard.

I ordered the spacer this morning and I have a bunch of gaskets and SS baffles to choose from. I will study them carefully to be certain I get a good seal w/o any vacuum leaks. As I recall, the L-75 uses a SS baffle between the carb and spacer, then a base gasket under the spacer to the cast iron manifold. The gasket and spacer both have the passage for exhaust preheat - none of which are of concern to me other than I want to block off that passage effectively top and bottom. Matching up an L-76 base gasket to an L-75, it looks like it will seal it ok.

Howard; I spent last March out in Phoenix with my Brother who had just turned 80. My 73 year old brother, my wife and I accompanied him in his new 4-door pickup on a tour all around Arizona. We had a blast, specially at the canyon which is color perfect in the early spring. My older brother (80) did all the driving too. he wouldn't share his new truck. I think it's something in the water or from the heat, Ha!

Stu Fox

[Stuart F.]

Re: Stinky AFB Follow Up

Ken;

Thanks for that suggestion. If I can't get good enough results with the spacer, I expect to have to pull the manifold (first time ever), block or restrict the heat riser passages and clean/paint (as you noted) the bottom of the manifold. Good idea. I need to repair a crack in the manifold anyway at the oil fill tube boss. Last time I installed a new tube (1976), I got carried away and drove it too far. You can't see it, it don't leak, but I know it is there. Too bad I can't get an Edelbrock Air Gap manifold to fit under my hood.

Stu Fox

[Stuart F.]

Re: Stinky AFB Follow Up

Just another NOTE in follow up;

When I filled the tank the other day it was down to about 1/8 tank full. On removing my original gas cap (w/ simple vent hole), I got a whoosh of air (in or out, I'm not sure). As soon as I got home, I removed the original cap and changed to a new replacement cap which has a PRV and Vacuum valve (2-way valve).

Then yesterday, I drilled the vent hole out on the original cap to 1/8" and put it back on. This morning, the garage smelled to high heaven of gas. The smell was specially strong at the back of the car. So, well, I changed caps again. WOW! you wouldn't think that little hole enlargement would make that much difference.

Just a CAUTION for anyone else contemplating such an improvement to their original cap - don't! You'll earn the "Bubba" label.

Stu Fox

[Joe M.]

Re: Stinky AFB Follow Up

The WCFB on my 1960 is doing the same thing and I am in the process of having a phenolic spacer built (actually 2 for $125). The first thing you need to do is find out how much clearance you have between the air filter cover and the hood. Place several pieces of putty on top of the air filter cover and close the hood. The hood will flatten the putty to the correct clearance thickness. Most of the phenolic spacer distributors recommend using a carb gasket on the bottom and top of the spacer; so factor that thickness into your equation for the maximum thicknes your spacer needs to be.

John at Jomar Performance (248-322-3080) builds phenolic spacers. I have not used him yet; so can't vouch for his product and don't know the price.

[Clem Z.]

Re: Stinky AFB Follow Up

Just another NOTE in follow up;

When I filled the tank the other day it was down to about 1/8 tank full. On removing my original gas cap (w/ simple vent hole), I got a whoosh of air (in or out, I'm not sure). As soon as I got home, I removed the original cap and changed to a new replacement cap which has a PRV and Vacuum valve (2-way valve).

Then yesterday, I drilled the vent hole out on the original cap to 1/8" and put it back on. This morning, the garage smelled to high heaven of gas. The smell was specially strong at the back of the car. So, well, I changed caps again. WOW! you wouldn't think that little hole enlargement would make that much difference.

Just a CAUTION for anyone else contemplating such an improvement to their original cap - don't! You'll earn the "Bubba" label.

Stu Fox

remember the gasoline that comes out of the underground tank is at 55 degrees and i think you are in Fla so the outside temp could be 20/30 degrees higher and this will expand the gas and maybe causing some to escape somewhere. never fill a tank to the brim.

[Stuart F.]

Re: Stinky AFB Follow Up

Thanks Clem for the reminder. I usually just fill to just under the filler neck. Then, by the time I get the car home, it is down from the neck by an inch or more (I go about 10 miles to an ExxonMobil station. The only one closer is a BP, and that's what I put in last and had so much trouble with - not that I am blaming their gas, rather the ExxonMobil station has a lot more turn over sales and I trust their premium to be fresher.

The test I ran this morning was with my "B" carb with the Tomco valves (the one w/o accelerator pump action). I reset the floats back up to 1/4" (7/32" std.). I also found a pump intake check ball valve that was not seating and replaced it, so I now have good pump action - no stumble/hesitation. When I put the carb back on, I used my old laminated insulator (3 aluminum plates w/2 gaskets) plus a gasket on top and another below. I wanted to jack up the carb an amount which is close to what I will have with the phenolic insulator I have on order. I had to rework my filter to carb hose and reposition it to clear the air cleaner better. Then I checked for hood clearance as well.

After a full warm up, and idle adjustments, I shut down and let it hot soak. I checked temperatures during the cool down with my I.R. gun and recorded a 25 degree difference between the manifold and the carb body. That's a 15 to 17 degree improvement and NO percolation. The jury is still out on this, but I think I made some progress.

Thanks for all your advice and encouragement, and thanks to all the others who contributed to this thread. Looking good.

Stu Fox

[Stuart F.]

Re: Stinky AFB Follow Up

I suppose you might all be getting tired of this story, so I'll make it brief;

Today I removed my AFB "B" carburetor and installed an L-75 insulator spacer. At first I tried to install it with one base gasket underneath the insulator and one SS plate on top (just like an L-75). I had checked out the fit on my other carb upside down to make sure everything would seal w/o any vacuum leaks. I still wasn't sure. When I fired it up I got such a load popping noise from my exhaust that I assumed I had a leak, so I shut it down and replaced the SS plate w/ another gasket on top of the spacer.

Then I noticed - I had not removed my car cover on the first test and the tail pipes were trying to blow the exhaust through it!!! That's what made the popping sound. I got fooled!!

So, to make a long story short, it works like a champ. I really think I have the percolation on the run. My temp differential between manifold and carb is now 35 to 40 degrees (as opposed to 5 to 7 degrees w/o). I have raised the carb 9/16" w/o any hood interference. Just to make sure, on my test ride, I sought out bumps (not hard to do) and railroad tracks.


Incidently, the 340 hp base gaskets from LIC work better for this then the Paragon pieces as they are wider at the back area of the AFB where the vacuum passages are for the PCV valve tap. I am running 13 to 15 " hg. at idle, and the idle screws have to be out about 2-1/2 turns (instead of 1-1/2) @ 800 rpm to get this. The electric choke gives me much more operating range here in our Florida ambient conditions, i.e. will close completely for a cold start (75 degrees ambient) and open up completely within a few short minutes of operation - much better starting and smoother warm up cycle.
I'm Lovin It!

Don't forget to set your clocks back tonight.

Stu Fox

[Stuart F.]

Re: Stinky AFB Follow Up

Just a correction on my last post;

The source of the best/correct 63 340 hp L-76 carburetor base gaskets is "Dr. Rebuild", not LIC. I get the two confused.

Stu Fox