Packard Forum Index » Pre-War (1899-1942)

For many years on my 1940 Super the glass filter always bubbled, but was always able to drive. Until the past few years moved to Vegas. Car started to vapor lock and would bubble worse. I would guess the more modern gas formulas, and the elevated heat caused this. On these cars after a bit of running, everything under the hood gets too hot to touch, even the hood. A couple years ago bit the bullet and purchased a six volt 45.00 electric pump. Connected it to one position of the heater switch, and now when it comes time to start after sitting awhile, or starts to buck on a 110 plus day, turn on the pump for a bit, and all is good.
Also while apart make sure the carburetor drain tube is open, and the check ball in the bottom is free and moving. Closes off so no vacuum gets through.

While my specialty is 32-34 the function of the baffle is similar if not the same. Wide open isn't the final or preferred position. It should actually block the exhaust going into the box below the carb. Not completely, but enough that it's directed down the pipes and through the muffler, the little bit of heat retained on/in the manifolds helps the carb atomize. I'm not seeing it in person, bit that's how the ones work that I've serviced. Let's assume all's well with it open, and maybe this is a new development. What may cause that is a blockage down the way. Maybe a baffle in the muffler came loose and it blocks major flow at speed. Those are my spitballs on the issue. Let is know what you find.

G'day djanspach,
First post, so to PackardInfo. Can't help with your question, however I invite you to include your '37 120C in the Packard Owner's Registry.

Well, regardless of odd, Vegas always wins. Let's put a bet on a muffler obstruction and roll the dice...
and as for the glass bowl filter up by the carburetor, bletchh.

Thanks for everyone's comments and ideas. I think I might have a solution. I was anticipating that the heat riser worked roughly like a choke - closed when it was cold and would open as it got hot.

After studying the pictures and what I could of my manifold I believe it works opposite of a choke. The heat riser flap closes when it gets hot. With my heat riser flap always being open would mean the underside of the intake is always seeing direct exhaust heat.

So to test my theory I built a heat riser block off plate between the exhaust manifold and the intake manifold. Should prevent the exhaust from directly heating the underside of the intake.

This picture from HH56 really helped!

After I get a test I will give an update.

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Good news from my road test. The engine was much more responsive without boiling the fuel in the carb.

It took much longer for the engine to warm up, but once it did it ran fine without issue.

Thanks to flackmaster for the help...