Carb boilover solved

Well not really but now I have a valid explanation why I have to live with it.

I got an answer from a well versed and highly experienced mechanic via Auto Restorer's magazine.

The answer in short is to "live with it". Not quite the answer I was looking for but the explanation seems valid.

In summary the fuels today are quite different than 1982 fuel the car was designed to run efficiently on. California fuels especially since they can contain up to 10% ethanol depending on the season. He went on to explain that the boiling temperature of gasoline is much lower with ethanol content and in addition (I can't remember the term used) the effect of altitude on the fuel makes it vaporize at much lower temps. Thus will all else being correct, mixture, timing, temperature the carb will continue to boil over after shutting off a hot engine.

So, last week when I went to the Ford show in the L.A. area I noticed no fumes and no boilover at essentially sea level. The ambient temp that day was 75*. Nothing everything was hunky dorey.

When I got home to 2,200 ft altitude and 80* ambient temp there was boilover. No, I'm not moving to LA. Yesterday the temps here got up to 93* and there was no noticable boilover but we have already switched to the summer blend of fuel. I don't know what the heck the fuel has in it now but it seems to be somewhat less of a problem but still occurs.

This theory of altitude and fuel content seems to be true and I've met several people that have battled the same problem only to give up as it seems to be non-correctable. I do worry about the amount of fuel but it seems to be little but just enough to cause hard hot starting and a puff of black smoke out of the tail pipe. There's been no dilution of the oil.

Just another reason why California should allow conversion to fuel injection.

 

I think one of these has the Altitude adjustment diagram:
http://1bad6t.com/Maverick/diagrams/emission.html

The neat thing about those pages is they have the middle digits to the part numbers. RockAuto's part system shows the interchangeable part numbers.

And his other page on adjustments:
http://1bad6t.com/Maverick/repair/fuel_system.html

and this:
http://1bad6t.com/Maverick/repair/emission_controls.html

Here's the main page:
http://1bad6t.com/Maverick/maverick.html

Mine doesn't boil over, but it did run-on once until Andy tweaked it.

 

Real good info. I do wonder how much gasoline is in a gallon. No wonder our old cars aren't so efficient.

 

I think ours is at 15% ethanol.

Step back a bit. Atmospheric pressure is at 15 PSI at sea-level. Does it get higher above that?

Vacuum for our engines is ideal above 18 PSI. Mine runs at 21 to 23.

If one of the PVS or valves or hoses is leaking, then that would affect the boil-over. None of the valves are adjustable, but some components can be, Carb, Distributor advance.

My 6 doesn't have that big cannister at the bottom of the exhaust manifold, like I saw on the 1981 Capri six, and I wonder if that adds to the chance for boil-over, as well. I've just got the old-style stock 1978 200 CID manifold.

Does any of those help out with the issue?

 

I think the issue is not solvable with current fuels.

 

There is only one gas available up here that does not contain ethanol, that being Shell V-Power 91 octane. That's all my new engine has ever seen and I don't plan on switching.
Although I run standard 87 ethanol-cut gas in the Chevy!

 

Steve - Have you tried 91 or 93 octane, or any gas additives. Wonder if that Stabil product 'Start!' would help?

 

I have not but it's a good thought. I may try but I'm cheap.

 

No, it goes the other way. That's why the boiling point of water (or anything) decreases with altitude and thus why they make pressure cookers.

At sea level, atmospheric pressure is 14.7 psi. It drops to about 12.2 psi at 5000 feet, which is about the elevation of Denver, Colorado. Water's boiling point drops by about 10 degrees F to about 202 F at that altitude. So if you're boiling those potatoes, they'll take longer to cook.

 

That explains why Ford added vacuum amplifiers. I wonder why they took them out after 1977. Good info.

 

Here's a good explanation about the vacuum amplifier. It looks like they brought it back with the OBD systems:
http://www.aa1car.com/library/egr.htm

There's a section about EGR Troubleshooting halfway down, discussing the amplifier.

 

You most likely have a Motorcraft 2150. I installed a 2100 on my Eagle and when the temps risen recently, I also had some boilover problems. After doing some research, I found a thick gasket, Felpro 60716. It solved my problems by insulating the carb from the manifold. If your carb is sitting on a thin gasket this may help. You may have to change your carb studs.

 

He and I are running the Holley 1946 single barrel, but that sounds like a cheap fix.

 

I do have a Motorcraft but it's the Holley 1946 version. I have a gasket that's close to 1/2" thick. I've tried a heat shield, lowering the float, advancing the timing and the only time it has not slobbered fuel out of the bowl was when I was in LA last week at sea level. The only thing I haven't done is to actually measure the manifold temperature but I can hold my hand on it for about 10 seconds with no burn so that tells me the intake is less than 140-150 degrees.

 

Just ran a quick search on BING.COM and got very few hits, but I did get this:
http://www.ytmag.com/farmall/messages/437897.html

This one discusses it under the flooding section:
http://info.rockauto.com/Tomco/Trouble.html

This is the closest especially with Ethanol mixes:
http://www.hagerty.com/NewsManager/templates/template_ethanol.aspx?articleid=1169&zoneid=72

Now this is an interesting article from Australia about the VaraJet Rochester carb. Use the browser's Edit... Find for boil...
http://holdenpaedia.oldholden.com/index.php/Varajet_Carburettor