Fuel boiling at shutoff in Stromberg 2brl

[Dave@Moon]

Please see my reply to AOrnest@AOL.com's posting on "65 carter AFB problems" for a more detailed explanation of the problem. A short version is as follows. I was having major fuel leakage out of the carberator in a 1960 LeSabre w/ a Stromberg 2 barrel (WW2 model) at shutoff. Gas would run down the carb throat and seep through the body, dripping at a rapid rate off of the linkage. It was explained to me that the fuel was boiling in the carb due to today's gas having a very low boiling point. The WW2 carb is VERY small for a big block V8, and that made it worse. I fixed the problem with an electric fuel pump and by locating the fuel line away from the engine. I did not see any other cars having this problem, however, at the 1999 BCA National. AM I ALONE???? Is this something really unique to my car or are other people seeing this? I did not change the fuel pump, and did notice gas in the oil (now fixed). However the gas was definately running down the carb throat at a rapid rate after shutoff and I blamed that for the gas in the oil. Could the fuel pump cause this? I must note that as long as the motor was running no gas leaked and none seemed to reach the oil either (long trips did not flood the crankcase).

[Guest]

Your problem is percolation it is common with the new gas. thicker base gaskets can help, lowering the float a bit may help, make sure the float bowl is vented and the gasket has the appropriate hole in it. when fuel boils and has a good vent it it just goes into the air as vapor. if it boils in an unvented bowl it builds pressure and forces fuel into the carb this can create a sphion and draw in more fuel from the supply line. Percolation can dilute crankcase oil but an internal leak of the fuel pump is a more common cause. stuck heat risers can cause to much hot exaust to pass through the intake and realy set off perc. check it out and let me know. JIM

[Dave@Moon]

Thanks Jim, I tried the thicker gasket approach to no avail. I was in the process of building a heat shield out of aluminum sheet stock (there are no available 2 brl. kits) when the electric fuel pump was suggested.<P> As far as bowl ventilation goes, I went through 3 carbs each one rebuilt at least twice, including 2 different professional rebuilds. (Have you ever tried to find a Stromberg WW2/112A {1959} or 113 {1960}? I've been shopping the whole of Hershey and Carlisle for 5 years and I'll bet I've only seen 6, and about 5 kits! Most of those I bought, along w/ 3 or 4 others at smaller meets. There was just an NOS WW2/113 on Ebay last month that went for $350 [bidding started @ $20]).<P> I don't believe there is provision for adequate bowl ventilation in my carb. When this was happening, gas would be seeping slowly out the vent (as liquid), and through every gasket surface on the carb, all at apparantly equal rates. The combined effect was enough to have gas dripping off the throttle linkage @ a rate of about 2-5 drops per second for about 10' until the bowl and fuel line were dry. Even an new, custom made Viton needle and seat on the inlet didn't help.<P> As far as the heat riser is concerned, its free and appears to be operating fine. When I first got the car it had ben running for some time with leaking valve cover and intake gaskets, with leaked oil being sucked in through the gasket forming a solid carbon mass in the exhaust passage there. I sandblasted the passage back open, but it had no effect on the gas leakage situation. Also the fuel would boil only at shutoff, never while the car ran. In 11K miles I've never once had a vapor lock problem or noticed gas fumes while driving. You'd better believe there were fumes at shutoff, however.<P> As you can see I'm at a complete loss here. I've only seen one other 1959/60 Stromberg 2 brl., it at the 1999 Buick National @ Columbus OH, and it didn't seem to have this problem. The combination is extremely rare, the Stromberg by 1960 was relegated only to low compression engines which were only installed on manual tranny cars or on automatic cars where low compression was optioned ($54, more that duals!). Based on the amount of spare parts for this combo I've seen vs. the Rochester 2 brl., I'd say less than 1% of 1960 Buicks came w/ Strombergs. I'm not able to come by advice for this car very easily. <P>p.s. Another weird thing, the car runs great, I got 17 mpg on the trip to Columbus! However, I'm carbon fouling plugs badly. At 800-1000 miles they are so fouled the cars starts to misfire. I can't lean it out any more than is is w/o having it stumble @ idle. I was told it could be valve guides, but there's no blue (or black) smoke in the exhaust, not even a slight hint at startup.<BR>Changing carbs didn't fix this either. Could it be related to the fuel problem?

[Dave@Moon]

This isn't happening to anyone? Just me?

[Dave@Moon]

O.K., I give up. I'm the only one with fuel percolation problems.

[Dave@Moon]

O.K. It's been about 8 months, time enough for a whole new batch of potential problem solvers to find this site. So noone has to go look up the 65 carter posting, I'll summarize the problem here one more time.<P>I have a 1960 LeSabre with the low-compression/regular gas engine option. It has a tiny Stromberg WW2 series carburator sitting on top of a 364 cubic inch big block. About 1997 I began to notice a serious problem, only at shutoff there would be copious quantiies of gasoline leaking out of the carb. It was running down the throat of the carb and oozing out of every available vent or gasket. This would last about about 10 minutes, until the carb and fuel pump were boiled dry. The dripping of gas off of the throttle linkage was truly impressive (and alarming! ).<P>I corrected the problem by using an electric fuel pump and relocating the fuel line away from the motor as much as possible. However, I haven't noticed a lot of cars with this problem even with today's gas. Is there something with the (origional) fuel pump that could've caused this? Did I miss something else? Has anyone else run into this yet?

[Dave@Moon]

Thanks Allan! Do you have a source for those stick-on themometers? I haven't run accross them as yet in my travels (except for fish tanks!).<P>By the way, the angle of the car definately did not matter when this was happening. I tried parking the car on different slopes to no avail when this first started happening. I did this because I noticed that the float spec changed from 1959 to 1960 for the same carb with no other change. <P>I also looked for a phenolic spacer briefly without finding any. the Stromberg WW2 2 barrel was a pretty old design by 1960 and I doubt if I could find an aftermarket spacer for it (the Carter and other 2 barrels were of a different bolt pattern if I remember correctly). I was in the middle of building a heat shield out of aluminum plate stock (a tough job to clear the linkage!) when the electric fuel pump was suggested.

[Guest]

dave, does this change at all based on the slope the car is parked on? i had a bad fuel pump in an old pontiac which used to leak from its weephole when parked on a slope.<P>does not sound like your problem, since you have carb issues, though.<P>one thing you may want to try is to get your hands on some of those stick-on small range chemical thermometers. if you can stick one of those on the carb, and run at highway speed for awhile with one of those stuck to the carb, and see if you can check the temp before and after shutting the engine off.<P>perhaps a jump in temperature happens when the carb is no longer cooled by flowing gas.<P>if that is the case, then a phenolic spacer under the carb might help heat conducted thru the intake body, and aluminum shielding definately will hamper radiant heat.<P>allan

[Guest]

sorry dave, i dont know off hand, but they were in an issue of hotrod or car craft a couple years ago. they came in very small temp ranges, unfortunately (like 12 deg F)<P>but, they respond very quickly to changes in temp.<P>what it sounds like you are seeing is the engine, while running, is pumping enough gas into the bowl to keep the carb body cool enough to prevent the gas from boiling.<P>once the engine is no longer pulling gas out of the bowl, the gas gets hotter, boils, flows out of every opening in the carb (even backwards past the float seat into the fuel line!) and condenses as soon as it hits the air.<P>so, you see gas pouring out of every opening, which looks like the float needle is stuck open and the fuel pump is still going. (of course, that is also an option, but you replaced the needle)<P>you could try running without the air cleaner, which should help the carb body be cooler, at least as a test.<P>basically, that temp spike is likely the problem.<P>do you run a lead additive? try changing brands. i seem to recall hearing a wive's tale once about different lead additives changing the boiling point of gas in different dirrections.<P>if you dont run a lead additive, try one.<P>if you disconnect the fuel line at the electric pump (be careful of residual pressure in the line) and drain the line going to the carb, you can determine if it is instead an over pressure situation, since the flowing will stop once you release the pressure.<P>if the line is empty, and the gas still pours, then it basically has to be vapor lock in the carb.<P>so, then you have to look at spacers, insulators, and shields. you wont find a pre-made spacer for your carb, but look in your phone book for plastic companies that advertise working with nylon blocks, etc.<P>they can cut you a slab of plastic (check the maximum thickness you can have by making loose ball of tin foil, putting on the air cleaner, and close the hood) and you can cut the plastic yourself, or have them use a lower gasket as a template.<P>you neel longer studs/bolts as well. ask them about the thermal resistance of the plastic, you want one that is high.<P>you might want to make that spacer about 1/8 of an inch thinner than you need, so that you can actually make an aluminum sheet to shield the carb fully, all the way to the throttle bores.<P>good luck<P>allan

[Dave@Moon]

Allan, like I said before, using the electric fuel pump fixed the problem completely. I did try all sorts of brands and grades of gas and additives, to no avail. Lead additives don't affect the problem either.<P>If the electric fuel pump wasn't such a bother and so noisy I wouldn't care. I could get a quieter pump, but I think there should be a simpler solution. I can't believe I have the only nailhead with this problem. Somebody has to have solved it before somewhere.

[The Old Guy]

The gasoline we have today is much more volatile than the fuels of old. I use my Buicks only in the summer ,so I completely block all the heat to the carb. You can either plug the holes or get a gasket that stops the passage. Even if you take the car out in cool weather ,it doesn't take long to warm up and this should solve the problem.

[Dave@Moon]

Thanks Old Guy, but I removed the intake and found out that years of leaking valve cover gaskets had plugged the exhaust passage solid with carbon. I blasted it clean with my pressure blaster just to see if the carbon was acting like a heat sink and boiling the fuel, but there was no change. <P>I'm really stumped by this. The only piece of the puzzle I didn't replace before I went to the electric fuel pump was the stock fuel pump on the block. I was working perfectly so I never suspected it at the time. <P>I do have probably the smallest carburator ever installed on a big block motor, so I assumed that the low boiling point fuel was the only reason for this problem. Then I saw a car with my carb at the 1999 Nationals running with seemingly no problems. Could the fuel pump be conducting excess heat to the gas without affecting its performance?

[The Old Guy]

Dave, <BR>When you blasted the crud from the passageway,you allowed exhaust heat up to the carb and that is what causes the problem. I block all heat to the intake and it solves the problem. If I remember correctly , your carb has a passage around the front that allows the exhaust gases to run right under the carb .You might be able to plug hte heat there and not even have to remove the intake.

[Dave@Moon]

Ooops! My mistake, I forgot to mention that the exhaust passage in the intake was cleaned out <B> after </B> the fuel boiling problem became critical. I thought I'd said that, but I'm always my own worst proof reader.<P>Thanks Old Guy! I can try to block the passage to see if it's better. The problem is that the electric fuel pump and relocated fuel line has pretty much fixed the problem (again, with the irritant of having to use an electric fuel pump). If the exhaust passage isn't boiling away the gas now, why would it with the origional fuel pump hooked up? <p>[This message has been edited by Dave@Moon (edited 08-27-2000).]

[Guest]

well dave, if the electric pump has COMPLETELY fixed the problem, then it must have been the routing of the original hard fuel line, or heat soak from the block to the mechanical pump. <P>if you want to go away from the electric, then try insulating the fuel line on the block or put a heavy gasket or two on the fuel pump opening. you could slip some rubber hose over the hardline as a test.<P>allan