Packard Forum Index » Post-War (1946-54)

Ever since the engine on my 50 Deluxe 8 was recently rebuilt, it seems to be running hotter than I remember it running before. I realize there are contributing factors, namely the recent rebuild - everything fits tighter, the fact that it was bored out to .030 over - it now has a larger compression chamber, and that the supplemental gauges I added may not be accurate - but I digress.

The real question is about the effect of the engine heat on the carburetor and the glass fuel filter bowl. I have observed bubbling in the glass bowl. Dare I say it looks like the gas is boiling. Is that common? Or is it really some other phenomenon taking place that is making the gas bubble? If that is possible that the gas is actually boiling, has Packard ever had some kind of heat shield under the carburetor and fuel filter bowl? I suppose that would only make a difference if the heat was primarily coming from the exhaust manifold, rather than the entire engine compartment being just as hot as the area immediately around the carburetor.

Anyone have any thoughts on this?

On my '40 356, there's a heat shield over the fuel pump and insulation on the portion of the fuel line from the pump to the fuel filter.

I also have an auxiliary 6v electric fuel pump close to the fuel tank which seems to help if I get vapor lock, which has not happened for a long time.

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There was a somewhat small shield on some models with the 356 engine which mostly just fit the area of the carb . There was nothing other than the fuel pump shield listed for most other size engines. If you wanted to try one you could probably make something similar adapting it to the bolt spacing of your carb. It might help a little but since the filters were optional and just outside the shield area I don't think it will provide much protection for the fuel sitting in the filter bowl. A more likely reason for the bubbling could be that todays gasoline is more volatile than the gas of the era so it will "boil" easily. It does seem a more frequent issue and I remember one photo of an engine where someone had built a shield that covered almost the entire manifold.

Here is a link to an earlier thread with photos and dimensions of the 356 carb shield.packardinfo.com/xoops/html/modules/newbb ... .php?post_id=139744#forumpost139744

Good Morning...I have a 23rd series Deluxe 8 which is a 1949
Model. We run 87 grade gas which is enough for our engines and burns cooler than the higher grades, I have been told. If I am wrong, someone kindly correct me. We also purchased a carburetor shield for between the carburetor and the engine as well as a non-metal block that sits between the manifold and carburetor to help stop the heat transfer and also a fuel pump shield...these parts came from Max Merritt and I believe that they make them in their shop...they helped. Also we run Marvel Mystery Oil in our 87 gasoline...at 1.5 times the ratio on the bottle. It seems to keep the gas from bubbling (boiling) unless things really get out of hand. Miss Princess likes it. Just as a side note, we run the same Marvel Mystery Oil Mixture in our 1931 Model A...that engine is also happier with the Marvel Mystery Oil in the summer...and it gets plenty hot in the Arizona Desert in the summer...I will drive the cars in the morning in the summer...at sun up...and about 95 degrees...any more heat than that and I want my Air Conditioned Jeep! These are just our experiences...hope they help a bit...one other little thing, we keep a big magnet in the glass fuel bowl...it traps any tank rust and I can easily see what has been collected and clean out the bowl and wipe of the magnet...Enjoy your Packard, she may be a chubby chick, but she is a great car...Ernie in Arizona

I don't think it uncommon with today's ethanol gas that people have been observing bubbling in the fuel bowls. Gasoline composition changed quite a bit since '49. I've compared specifications in the past, maybe on here(?). Plenty of info on effects of ethanol on boiling curve. But has to be fairly hot to do that.
First I'd check/tighten the fittings to make sure no air bleed, and try non-ethanol gas, if available in your area.
Never hurts to isolate carb(s) from a manifold such as this which has both intake/exhaust temperatures. I just went through this precautionary exercise on my modified Cad which has a central runner for exhaust based on erroneous understanding of the day.
My '49 the fuel bowl is immediately forward of the carb. And there's wide open spaces, so I didn't observe any issue with it idling for long periods, but others complain. It idles at ~400 rpm.
It's imperative to make sure all the inner panels are installed to direct the air flow through the radiator so the fan does it's job. Autos are air side controlling.
You don't mention if you did anything to the radiator, perhaps it's in need of attention. A infrared camera scan will tell.
Ernie is correct, no need for high test in a low compression motor. I'd argue the mystery oil add but I like to argue. Why would anyone use anything that's a "mystery" ie, not knowing what it is, is a mystery to me... I'm not as trusting.

Thanks, gentlemen.