Searching for a phenolic carb spacer

[29 Tudor]

With the percolation problems I (and others) seem to have with the gasohol we have now, I have been searching for a phenolic spacer to see if that will help by isolating the carb from the intake manifold. So far, no luck finding one. Has anyone got an idea where to find such an item?

If no one has a source, I might try to talk a machinist friend into tooling up and make me one (or more?)

Any thoughts?

Thanks,

Steve

[Richard Wilson]

A man in my club made a spacer out of wood. The main problem is that you will have to re-engineer the choke/gav rod connection as the rod will no longer line up with the carb. The man said that the spacer did help with the gasohol boiling / vapor block problem on hot days on his coupe.

[BRENT in 10-uh-C]

This topic has been discussed here before and while some say that it did help, I am of the opinion it really did not cure the problem by installing an insulator. The reason I feel this way is because ethenol enriched fuel tends to evaporate quicker which generally has a cooling effect. The problem is it has a lower boiling point. Just as Richard mentions, there will be alignment issues but the thing I think that is the greatest issue is the stock carburetor is a heat sink from ambient air. After our last discussion on this, I got to thinking later that one thing that might help would find a damaged intake that has the heat-plate damaged and then remove it totally where the exhaust manifold cannot transfer heat as easily into the intake.

Just curious Steve, which fan are you using, are you using engine pans, and which carburetor are you using?

.

[steve s]

Since you're into fabricating stuff, here's another idea for how to go. My buddy made this heat shield out of sheet metal. After he figured out his problem was engine timing, he gave it to me. As you can see, I also had insulated my fuel line with slit rubber fuel line wrapped with real duct tape. It all helped, but, for me, the ultimate fix was to get one of the more-modern Zenith carbs, made for many applications but most frequently bad-mouthed on this forum as the "forklift carburetor."



FWIW, here's a picture showing that the vaporization problem is not just a carb problem. That shiny bubble in the top of the sediment bowl is a bubble of gasoline vapor that I watched form and periodically burp on down the line and then reform, over and over, as the engine idled on a warm day. I tried many many things to fix it, including worrying that that oil filter was blocking cooling air from the fan, so I got an adpater that moved it out of the way.

I agree with those who point the finger at ethanol. But, it's not as simple as ethanol itself being low boiling. The problem is that neither gasoline nor ethanol are happy being together, so the vapor pressure of the mixture is raised as both try to get out (what, in the trade, is called a positive deviation from Raoult's Law). Modern cars cope with it by using fuel injectors and fuel pumps submerged in the gasoline tank that can keep things moving along.

This is a contentious subject that always reminds me a bit of PMS; those who have not personally had to deal with it are convinced that those who have are somehow making it all up. The problem is that two Model A's owned by the same guy running the same gas on the same day can have one vapor locking like mad and the other running like a top.



Steve

[29 Tudor]

Richard: I had not thought about the GAV/Choke alignment issue. Thanks for pointing that out. I think I need to rethink the spacer idea.

Brent: I am presently using a 4 blade fan but I have an aluminum 2 blade to put on it as soon as I replace the leaking water pump. Yes, the car has the engine pans and I was running a Zenith 1. Now it has a professionally rebuilt Zenith 2 on it.

Steve: Thanks for posting the picture of the shield behind the carb. That was another thought I had. I did insulate the fuel line with thermal shielding and wrapped that with aluminum duct tape... the shiny real aluminum stuff. I also added some Marvel Mystery Oil and after that, it seemed to be much better but it wasn't as warm outside as it had been.

I'm sure this will be an ongoing saga but that's part of the fun of these old cars. Right now, the car is "resting" in Central Florida and I'm headed to Texas so it will be a while before I get back to it. I really appreciate all the helpful ideas and suggestions.

Steve

[29 Tudor]

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Kind of an update on the spacer idea. After I posted this, a gentleman contacted me (can't remember who now....) and offered a phenolic spacer. He had a spare so I got it from him. It's a 1/4 inch spacer and I recently installed it, along with a gasket top and bottom and the GAV still fits and works fine. The temperatures now are in the 40-65 range and there doesn't seem to be a problem but this summer will tell. I am also running Shell premium which is supposed to have less alcohol since we can't buy fuel without alcohol here in south Texas. I am also using MMO at the rate of 4 oz per 10 gallons or so.

I'll try to remember to update this when the weather warms up.

Steve

[Bob-A]

I read somewhere that stainless steel hex bolts can be used to mount carbs and that stainless steel does not conduct heat as much as regular steel. Also a guy is selling the 1/4" thick phenolic insulator spacers for Model-A's on eBay right now: item number = 261234192174.

Bob-A

[Tacoma Bob]

I have made several phenolic spacers and given them to friends. All report a big difference in using them. Northenr tool sell phenolic material. I use a carb gasket for a pattern and cut the spacer out on the band saw. Drill the holes and done. Takes about 20 minutes start to finish.

[Paul from Maine]

I've seen frost on my TT's Holley NH on muggy summer days, so I am wondering how hot does a cast iron Zenith really get? The fuel available in the late '20's was half kerosene, so it stands to reason that the engineers wanted the carburetor to be as warm as possible to aid in the vaporization of the crappy fuel then available. I run a Tilly and have never had vapor lock issues, but I have no idea how warm a Zenith might get being purposely placed in such close proximity to the exhaust manifold. Maybe adding some kerosene to an A's fuel would solve everyone's vapor lock issues! After all, that's what type of fuel (a mixture of kerosene and gas) a Model A was designed to burn! My '27 T came with a Holley Vaporizer carburetor from the factory which was similar in design to the carburetor on the Fordson Tractor which was started on gas, but run on kerosene! Ironic that Kerosene is now more expensive! Though I hate the crappy ethanol contaminated gas we have now, at least we have plenty of it and it is far superior to what was available in the late twenties. If you read the automotive literature of the time, writers were lamenting the scarcity of quality gasoline that had been available in sufficient quantities to meet demand just a few years previous. Some late twenties publications predicted horrendous fuel shortages in the near future. The Model T may have put America on wheels in the twenties, but production of quality fuels in that era couldn't keep up with the demand created by the explosion of the number of drivers. Hence the crappy gas that required exhaust manifold heat to vaporize the low quality fuel. Today's fuel might just vaporize too well at too low a temperature to work well in the Model A's fuel system that was designed for fuels with much higher temperatures of vaporization! Really, someone should mix some kerosene in their fuel if they are suffering from vapor lock! I am going to try it just for fun this summer!

[29 Tudor]

I have tried mixing diesel in the gasoline (10%) and it didn't seem to help when I was having the problems. I found that if I stopped the car (in the summer heat of Florida) and opened the hood, I could HEAR the gasoline boiling in the carb. If I restarted then, the engine ran TERRIBLY for quite a while. I also found it would act like it was running out of gas when pulling a mild hill.

Since installing the spacer, I have not had any hot weather to try it out in but it was fine in the 70 degree temps we had today. I am now using Shell premium which I have been told is the lowest in alcohol we can get around here as well as MMO. We'll see what happens this summer but I can tell the Zenith is considerably cooler with the spacer. I have the hood off right now for some other work which I'm sure helps as well.

[AL in NY]

I did some IR temperature readings on my Model A engine last week checking for any hot spots. The ambient temperature that day was 55 degrees and after the engine had idled for 30 minutes, I took some surface temperature readings on the head, block and intake manifold. First I checked the oil pan temperature which was 178 degrees. With my 180 degree thermostat, all the reading on the block and head were + or - 10 degrees of 185. The coolest spot on the entire engine was just above the carburetor on the intake manifold, that temperature was 105 degrees (80 degrees cooler then anywhere else on the engine. Unfortunately I didn't take a reading on the carburetor.

[Arlen]

Grainger sells the stuff by the sheet. About a square foot in size in probably 6-8 different thickness. I buy the sheets and cut it up into body pad shapes. I like the stuff a lot better for body shims then the rubber ones.