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32 Pontiac Carb & MPG ???


Tom Beggan
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Hi,

I've got a 32 Coupe with a 6-cylinder and I'm curious about a few things:

1. Should my Carburetor be leaking? It drips constantly while the engine is running and for about an hour or so afterwards. I doubt this is normal, but you never know.

2. Any tips on where to find a good rebuild kit for the carburetor?

3. What should my MPG be? I'm getting between 8-10 and that seems low to me. I had a 34 Pontiac Touring Sedan with an 8-cylinder and it did about 14-15.

thanks!

Tom

New Hampshire

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No it shouldn't be leaking.

It is a fairly simple carb to correct leaks and to set the float level on.

Carbking might know where you might find a kit. I was never able to find one for my car so I cut my own gaskets and modified a rochester needle and seat to fit.

My Pontiac gives me about 17 mpg around town and about 21 mpg on the highway at a steady 55 mph (provided there is no headwind.

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Reid, that's good news on both counts. I bet a lot of my MPG trouble is a direct result of that fuel leak.

Also, you say your car will do 55mph? I've been keeping mine to a max of 45mph but I'd absolutely LOVE to get another 10mph out of it!!! I just tend to be extra careful with babbitts and extra long rods. I've never been sure they'd handle the extra RPMs.

I tried 50mph a while back and speeds up that high would make the engine spray oil all over itself and send smelly burnt oil fumes into the cabin. It turns out that I had two leaks that only caused trouble at the higher speeds.

1. The oil dip stick had no seal on it, so oil was splashing up through the dip tube. Now fixed.

2. One of the spark plugs had no crush washer fitted to it and oil was leaking out of the plug hole. Now also fixed.

Now that these are both fixed, maybe I should try 50mph or 55mph again.

Have you modified anything to get up that high? Do you think my 45mph limit is a bit overly cautious?

thanks as always,

Tom in New Hampshire

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My rear end is 41:9 (4.55/1) I run 550x19 tires .

At 65 mph (actual clocked speed) my engine is turning over at 3418 rpm (checked by tachometer).

I have run at this speed for times up to half an hour. I have no problem at all driving at 55 mph on the highway all day. At this speed I use about one quart of oil between changes (3000 miles).

If you go back to the 1700 feet per second piston travel, which is supposed to be the optimum I shoud be cruising at 43 mph.

When I first started driving my car I drove it between 45 and 50 the same as my Grandfather had. One day when reading the advertising about the car it said max hp was at 3200 rpm and that the carb economizer operated up until 55 mph. The next time out I tried 55 and 60 and 65. On occasion I have been up to 70 mph when passing someone.

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Hi Tom,

How is it going? I am the Tech Advisor for 32's and we corresponded a while back. I thought I would chime in on your questions.

Regarding your carb. Are you running the original Marvel in your car? I am not sure your leaking is due to a float problem. If it were the float it would only seem to be a problem when the car is running. It would not leak when the car is off. It sounds like the drain plug on the bottom of the bowl may be leaking or you have a crack in the carb body. The original ones are pot metal and a bit fragile.

The other comment is on speed. While Reid's car has the same final drive as your coupe you are probably running 18" instead of 19" wheels. That would mean that for the same speed as his car our engine has to run about 3.5% faster. For our cars the 1700 fps is about 49 mph. I tend to not drive mine much faster than that unless I really have to. I have had it up to 65 before. The other factor is brakes... stopping can be an issue, as you probably know. But Reid is the expert on those old 6's.. he has a ton of miles on his car.

My car gets about 15 mpg and it has pushed close to 20 on longer tours.

Can you upload some pictures of your car the the Facebook site? I would love to see it.

Rob

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Tom and Reid - repair kits are readily available; just call.

No carburetor (including the infamous marvelous Marvel) should leak while the engine is running.

However, it is not unusual for a gravity fed updraft carburetor to "seep" fuel when the engine is turned off. This can happen because of a number of reasons; and is why there is a fuel shutoff on these vehicles. I learned this lesson as a lad of about 15 when I failed to turn off the fuel shutoff device on our John Deere "A" after having been admonished to do so!

Never made that mistake again! ☺

Jon.

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Great to know that rebuild kits are avaliable! I need to get one for my Marvel. I am currently running a Zenith that came out of an industrial engine.

I agree with the comments on gravity fed carbs but that is not the case with the '32 Pontiac. the fuel level is below the carb and needs to be pumped. My car does not leak fuel. If the car sits for a month or two the bowl will be empty but that appears to be due to evaporation. I have never seen any fuel leakage with mine (unless there was a problem).

My gravity feed experience came with a Caterpillar 22 at my grandfather's ranch....yep they can leak.

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Thanks again for the input guys. I have just checked and I am NOT running the original Marvel Updraft. I've actually got a Carter BB-1 Updraft in there instead. I've done a bit of research and evidently this Carter Model was OEM equipment in Chrysler, Dodge, Plymouth cars, and Chevy Trucks. It was also a very common model to use as a replacement for failed OEM carbs. I suspect that's how this one made its way into my car.

When I called a carburetor specialty shop to ask about getting a rebuild kit, I told them the model number but that wasn't enough. They said they needed a tag number too because they make 18 different kits for the Carter BB-1 (depending on slight variations) and that I'd better find that number before I place my order. I did spot a shiny brass tag with some letters stamped on it, but it's obscured by a few components and the darn thing is so reflective that I can't read the letters. I'm thinking I'll go take a few pictures of it and adjust them in the computer like a crime lab tech. :rolleyes:

And thanks for the warning on the 18" vs 19" wheels. I am running 18" wheels, and the fastest I've had the car is 55mph. Somehow it just feels happier if I keep it to 45 or less. Maybe it's the sound it makes or the chassis harmonics, I'm not sure, it's just a feeling I get that says "that's enough" at 45mph.

Edited by Tom Beggan (see edit history)
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No carburetor (including the infamous marvelous Marvel) should leak while the engine is running.

Hi Jon, just curious....... I've seen/heard a few indicators that "maybe" the Marvel carbs don't have a very good reputation. Is that the case? Or am I imagining things? The other reason I'd be curious is just in case I ever decide to pull off the Carter in favor of an original spec Marvel. If they're junk, I'd squash that thought before I ever got close to doing it.

thanks, Tom

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New update........ I just went to get a closer look at the carb and when I pulled back on the throttle linkage (to get a better look at the brass tag), gasoline poured right out of the carb and it continued dripping for about 15 seconds. I'd say I got enough to fill about 1/3 of a shot glass, maybe more. There's definitely something wrong here.

Jon, what's the number to your carb shop?

thanks, Tom

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