The Stovebolt Site Forums The Shop Area Engine Shop The Case of the Weeping Insulator!

Interesting phenomenon, I have a weeping carburetor insulator on my 1950, 216. This is the original insulator, which was actually Bakelite and they probably used asmostus as a filler. The new ones are just a solid plastic, not Bakelite and they don’t look like they have a filler in them. I suspect that after 60 years some of the phenolic resin is breaking down and it has become porous.
I can clean the manifold and insulator with a solvent till both are dry before I take it out for a ride and when I get back this is what I have. The gasket is new, the nuts are tight, and there are no leaks in the carb throttle body itself or any of the plugs.
http://rides.webshots.com/photo/2711907900098611668LgfDym
Denny Graham
Sandwich, IL

How about giving it several coats of epoxy-type paint? There are several varieties of paint similar to DuPont Imron that come as a base paint plus a catalyst, and they cure overnight to a coating that's virtually indestructible. Get a paint supplier to mix a small quantity of a color that matches the shade of the insulator pretty closely so it won't stand out once it's coated.
Jerry

What exactly causes this, if you don't mind my asking? My insulator is weeping too. Although it is not like Denny's. It kind of puddles on the level spots but doesn't run down like that, as far as I have been able to tell, but I will look again, and there is a white film on the insulator, but only while the engine is running.

The original insulators were a phenolic resin impregnated cloth matrix. My guess is that the cloth fibers seem to get saturated over many decades and lose some of the resin. This leaves it slightly porous and the fuel is absorbed and wicks thru to the outside of the Bakelite insulator. The new insulators use powdered filler rather than a fabric matrix so they are not subject to this however they are also not very good in compression and are more prone to cracking.
Denny Graham
Sandwich, IL

Ok.

Our gasoline of today has much different characteristics than the old leaded gas of the 50's. That could have something to do with it.

Denny is the "weeping" liquid gas or something else? My guess is that it is water for humid air and the the air/gas mixture flowing thru the carb is cooling the base of the carb and this is just condensation. I am probably wrong but that is my guess.

I know how it feels to have your cloth matrix weeping...mine does it more often now that I'm 'retired'.

Stuart

I had totally forgotten about it, but it used to be very common for the insulator to collect condensate. I just never gave it a second thought because thats just how it was. There should be a steel sleeve inside the insulator and it gets very cold in full throttle situations.

I’ve never seen one for the Chevy sixes with a metal insert in the bore. No it’s not condensation, it’s fuel.

The Weeper:
http://rides.webshots.com/photo/2711907900098611668LgfDym
NOS Rochester insulator and New Vendor insulator:
http://rides.webshots.com/photo/2524192290098611668BhpEOt
Denny Graham
Sandwich, IL

You can just replace it with wood if you like. I would suggest ash or maple. Oak has open pores and will weep. It won't get hot enough to burn, and the wood will conform and you won't need a gasket.

Otherwise you could buy new phenolic and mill it with a router. Phenolic material has the cloth reinforcement but uses phenolic resin instead of the bakelite resin. Its like fiberglass but a lot more sturdy. Woodworkers use phenolic sheets for tool table tops and router bases, so ask at a well stocked woodworker's supply store for small peices of stock.

Denny I seem to recall putting a few aside in the shed and seeing the metal ring inside at least one insulator. Dont know what that means to you but figured it was worth mentioning.

I think you could be onto something about the insulator wicking gasoline. When I was working on an old q-jet for my wifes truck I kept having the worst time with setting it correctly. Spoke with an old friend of mine and learned the old phenolic floats eventually wick gas and become heavy giving false float issues once assembled. Switched to a brass float, problem went away.

jdl, could that white film be frost? I had issues for the longest time with my Carter YF frosting at the base. Finally was able to troubleshoot it and now only very occasionally and during the inclement weather does it frost very lightly.

Jeff

I think you are right, at least in my case. What has been on mine is water. Nope, not frost, if you run your finger through it, it sticks to your finger, but doesn't melt. I guess a better word is froth.

All of the phenolic insulators I have ever seen have a metal insert in the bore, it protrudes down about 1/4" to 3/8" into the intake manifold. I don't know the purpose but probably has something to do with the weeping thing.

Oh, I've got a NOS insulator, no need to make this one. I’ve got the right part number and all, just thought it would be interesting to some of the guys how the original ones break down over the years. Been looking at shows and it's become quite apparent that it's a common occurrence.
I was looking in the parts book and it does list some insulators with inserts, mostly for the earlier engines. I haven't worked on any pre WWII Chevy’s or big iron so I've never seem one with an insert in it and during the five years I worked as a Chevy parts man back in the 50's and 60's I can't remember ever selling one either. Sold lots of the plain Bakelite insulators though.

And just an up date J', Bakelite resin is, phenolic resin. Bakelite is just a generic term for phenolic products. Bakelite was and still is made as laminate using woven fabrics such as cotton, fiberglass, Kevlar and paper. McMaster Carr sells a line of laminates under their own name, i.e., Garolite but it’s the same thing, just a thermoset phenol formaldehyde resin. The most common usage was in cast Bakelite products like phones, old radio and TV cabinets, and is still used today in many electrical items to numerous to mention. Most of these applications have been replaced with modern injection molded plastics. Some of the most collectable Bakelite products from the past were Catalin radios, costume jewelry, combs and brushes and these were cast from the phenol resin but no fillers were used, which gave them a glass like translucent appearance but also rendered them quite brittle. We still see cast Bakelite in the electrical industry and many of our ignition system parts, caps, rotors, coils and again the carburetor insulators. I’d swear I posted this all before, but the cast products usually used fillers such as asbestos and other loose natural fibers, saw dust, carbon black, walnut shells, clay, etc. bound together with the phonic resin to give them strength.

Denny Graham
Sandwich, IL

As far as I can recall, every GMC I have ever looked at had a metal sleeve in it. I ran across one a week for so ago that the sleeve actually necked down from 1 5/8 to 1". I opened a discussion about it on http://www.oldgmctrucks.com/ and a guy in Washington State has one and wanted another for multiple carb setup. I sent it to him and he claims it is different from the one he has. I am still not certain why some of them are necked down. But I was not aware that Chev did not have a metal sleeve in it.

There are two insulators in gp-3.726 pn-838983 and pn-605392 that do appear to be reducers. They run from 1937 to 1949 engines and have a note that says they are used in place of the standard insulator to slow down engine. I would guess this was a form of governor to keep from over reving the engine? The ID is 1 5/8" reduced to 1 1/16".

A picture of one of thes with a sleave cast into it would sure help to clear the water a bit!

I wouldn't mind reading that discussion at the Old GMC forum, but I went to the link and it just takes me to the main page. I couldn't find which forum it was on and I just don't have the time to join or read through all the threads of another forum.
Denny Graham
Sandwich, IL

Denny,
Is this insulator a necessary item? Neither of my rigs has one of them.
dg

Don't know what ya got DG. If it's a stock inline Chevy, yeah it needs an insulator.
Denny G

Denny, the insulator I had came from a 47-49 model GMC because it still had knee action shocks. A scrap iron hauler was buying gas at one of our stations and I spotted a GMC frame with engine and drive line on the very top of the pile. I recognized it as a GMC because of the Zenith carb. I offered him a little more than scrap. We agreed to unload it on his way back from San Antonio. I was not at our shop when he returned, and the guys at the shop just unloaded it. The carb had disappeared; probably will appear on eBay, but the insulator was still there. The fact that it was necked down caught my curiosity and I checked a couple of my later GMC's. A guy in Washington State wanted it for a multiple carb setup. I didn't photograph it, but he says the one he has is different, which would explain 2 part numbers. I think he is going to post pictures. The discussion never came to a conclusion as to the purpose. I think to save gas is a good theory. We must remember people who drove then were much more conservative then we are. My father, for instance, was born in 1901 and was an adult during the depression. He talked about it being common practice to turn engines off and coast down hills to save gas. Hoof velocity governors were already common to limit rpms. The insulators are necessary because when you turn off an engine too much heat will transfer to the carb and after sitting about 15 minutes, the engine will be difficult to start because the fuel has perculated out of the carb and the engine is flooded. I will take a picture of an insulator with a sleeve that is not necked down.

Photos of GMC spacer http://picasaweb.google.com/crenwelgeoil/CarburetorSpacerGMC#

Are you sure? It's just a black thing that sits under the carb.

A little more than that Jordan, pay attention in your physics classes and you will understand it better. The material is a thermal insulator and as Ken explained, it is a poor conductor of heat and insulates the carb from thermal transfer from the mainifold.
Denny Graham
Sandwich, IL

'Thermal heat transfer'....is there any other kind?

Stuart

Ya know Stu, ya should have been an editor, hows that suit your fancy????
DG

I know that but I was just trying to make sure that DGERTH knew what it looks like and therefore isn't worrying over anything that he shouldn't be. In other words I wanted to make sure that he wasn't just overlooking it and hadn't seen it before.