Guys - I recently replaced the single barrel carb on my '58 Studebaker with a new (UN2) one from Daytonaparts in Florida. Worked great for several months, and recently became hard to re-start hot. Had the cl***ic symptom of heat soak - chugged to life as tho flooded and had to rev her to life. Ugh! I emailed the company and was told to get a spacer and to move the filter. I'd always had a clear fuel filter just before the mechanical pump, but they suggested moving the filter to after the pump; just before the carb, which I did. I also installed a spacer, with my soft gaskets on top & bottom to make a good seal. When I got home, today I checked for leaks & found none but did hear what sounded like the fuel boiling in the float chamber. Should I add some Marvel Mystery Oil to the gas tank? I have an electric pump I use as a way to prime the system on cold starts, if I haven't run her in a while. Should I try running that a little prior to a hot re-start? I have hesitated doing that for fear I would further flood it. Any ideas would be appreciated! Thank you!
I think what you want is a “phenolic “ spacer between the carburetor and intake. I know you mentioned a spacer but what is it made from?
I used a phenolic that was more close to wood on my girls '60 Lark (I think a hard plastic would be considered a spacer or riser). Only on really hot days does it act up but the engine temp is up there by then. I used a 1/2" thick insulator from here. https://www.dashman.net/category.php?id=13
Have you checked the fuel pressure yet to make sure it hasn't gone bonkers? It doesn't seem uncommon for even new, "imported" fuel pumps to produce excessive pressure. Is the choke working properly? Is it fully open at engine operating temperature? Manual or automatic choke? While you're checking the choke operation, also make sure that the choke unloader adjustment is set properly. This can help you start a flooded engine with less strain on the starter and battery. https://www.hemmings.com/stories/article/the-lost-art-of-choke-adjustment With the engine idling or immediately after it's shut off, open the choke valve and look down the throttle bore. Do you see any liquid fuel dripping from the main nozzles, vent tubes or from anywhere else?
Make sure it actually is a fuel problem [it probably is!] Get the engine bay hot enough for heat soak. Then tip about a teas**** of gas [laquer thinners] down the carb and see if it starts. Then shut it down and play the waiting game again. It also could be the check valves in the fuel pump allowing gas to siphon back It is a problem with modern gasoline that has ethanol and butane in the blend. If you have one of those "flow through" type fuel pumps [Facet / Airtex] it will cure the symptoms of both siphoning back and vapor lock. We did this on our 57 Chevy [It has a Gl*** Filter by the carb] The Facet pump is powered via a relay which has the primary circuit grounding via the oil sender so when the engine is running the fuel pump switches off. On our car it also has an electric choke, so on the "reverse post" off the relay [87a] we connected the choke to this. When the pump switches off, the choke switches on.[and the choke doesn't cycle while the pump is priming] There is no hidden ****ons etc ,the whole system works off the key.
"Worked great for several months" new carb. I had very similar probs. with 2gc rochester, rebuilt by a pro. Finally took it apart and found a bad float-even though the rebuilder said it was new. Flooded like a fiend when motor shut down and heat soaked-ran o.k. when running. New float-end of problems. Just saying---------------------
If the float checks out as mentioned above, try a tank (or partial tank) of pure gas with no ethanol if it's available anywhere in your area. It should have a little higher boiling point, just enough to confirm "heat soak" issues. I used to be involved in turbocharged setups and one of the wrinkles we turbo guys had to do was when we knew we were going to shut down in 5 or fewer miles, we drove low and slow with no load on the things under the hood. This was to help drop the temps at shut down. But ultimately you want to address the "heat" so you can drive how you want to. Eyeball the whole fuel line to see where you can re-route away from heat sources and/or insulate.
I'd try the electric pump to overcome fuel boiling out of the bowl, or correct vapor lock in hot engine compartment.
If by "clear filter" you mean clear plastic filter, please replace it as soon as possible. The gas that is sold these days has chemicals harmful to plastics.
Hard hot start and flooding could be a stuck heat riser on the exhaust manifold. Those things were always problematic. With the engine and manifolds hot, check to see if the thing moves (open & shut). If it's stuck shut it routes the exhaust heat up onto the intake manifold and will heat the carb to more than boiling temperature, causing the gas to boil out the main jet and into the intake manifold/engine on shut off. Often you can free one of these with a mixture of kerosene and graphite. Check the bi-metallic coil spring on it to make sure it hasn't lost its tension. A lot of cussing helps, too Also check the carburetor for a stuck or plugged bowl vent. This vent helps keep the vapor pressure in the fuel bowl down to make hot starts easier. The heat riser is meant to heat the intake system to prevent carb icing in cold humid weather until the engine warms up, then it should open. You can tie the stupid thing open if all else fails.
Are you using alcohol free fuel? It's available here in premium for about a buck a gallon more than the swill they sell as regular now. I use it in anything I have with a carb and the difference is like night and day. The smaller the motor, the more pronounced the improvement. Well worth the extra cost. My understanding is that the vapor pressure of alcohol leads to vapor lock at lower temps than straight gas and yields 10-15 percent less energy. I sometimes wonder if E-10 is always 10% alky. A percent, or two, or three more could help fatten the profits of the poor struggling oil companies. But we know their highly ethical management would never do anything to take advantage of the consumer.
I'm thinking in Iowa the ambient temperature was a good bit cooler a few months ago. The tips offered by others are still worth following thru. Ten minutes after shut down I might open the hood and use a infrared thermometer to shoot the carb bowl temperature. Back in the carburetor days GM has fuel filters with a 3rd fitting for a return line on some cars. Turbocharged Corvairs, big engined cars with AC, etc. I've been thinking one advantage of an electric radiator fan would be allowing running it for 10 minutes after shut down to minimize heat soak. Those AC GF-48 fuel filters as used on 50s and 60s Corvettes always struck me as the ultimate. Rugged gl*** bowl, clear for instant troubleshooting. https://static.summitracing.com/global/images/prod/xlarge/ssh-gf48_sn_xl.jpg 32 US bux in stock at Summit.
As long as we're stuck w/ ethanol fuel, it'll remain a minor problem. Just open throttle a bit on re-start and rrruuUUMMM for a split second. Headers, aluminum goodies....just a minor problem. Longing for ethyl is a bygone thing. Joe
I would think so, and I think far less than ten minutes would help. Once the engine stops producing heat the temperature should drop pretty fast as long as the air keeps moving.
I imagine it wouldn't do a whole lot unless you also had an electric water pump to circulate the water through the motor? Or maybe a secondary electric pump that is in-line somewhere, in addition to the block mounted mechanical pump
As long as the thermostat is open the water will still circulate. Slower ofcourse, but once upon a time motors didn't even have a pump for the cooling system. Besides, it's not just a matter of cooling down the engine, bringing in cool air cools down the carburettor directly.
A number of vehicles back in the day had spacers under the carburetor that were water heated to prevent icing. I wonder if there would be a market for a similar item now, with an external cooling system, with a pump, small radiator, and fan controlled by a thermostatic switch (and relay).
If the carburetor is boiling the fuel, how does a return cure that? Just thinking that the fuel is in the bowl, excess fuel that the bowl doesn’t take gets returned to the tank. I can see it for vapor lock, but what’s in the bowl is in the bowl, what circulates doesn’t go in and out of the bowl. How does an electric fuel pump get fresh fuel into the bowl of the needle is seated? Or are you now priming the bowl with fresh fuel that evaporated? I’ve never had the problem, but curious about what the approach is and why.
If hot fuel entering the carb is a part of the problem, a return type fuel system that supplies cooler fuel from the tank rather than fuel that have been stuck in the lines gathering heat a long time may help a bit. But I'm with you, I wouldn't expect a huge difference. One small step in the right direction?
One of us smart guys ought to figure out a way to relieve the pressure in the fuel line between the needle and pump when the hot engine shuts is off. The pressure is relieved anyway thru the fuel bowl every fuel vaporized and float drops.
A 12V fuel cutoff solenoid in the line between the pump and carburetor would stop any more fuel moving into the bowl to replace what is boiled off, and keep a ready supply as close as the solenoid is placed to the bowl. If the phenolic spacer did not do the trick, there may be no way of keeping (today's) fuel from boiling off after shutdown.
Back years ago Chevy had an issue with hot start from fuel expanding in the line between fuel pump and the carb after shut down overpowering the needle valve. The fix was to drill a small hole between the two chambers of the fuel pump so fuel could go back to the tank. But that does not explain the boiling sound . I would check for a stuck heat riser valve.
Guys - Your advice is great and I appreciate every suggestion! When I click the "image" icon to post a pic, it asks me for a URL as to where the pic is, ***uming it's already online somewhere. My new carb from Daytona Parts has a manual choke (cable) and yes, my little flat head 6 has a heat riser but it's stuck in the open position. These is a place in the next town that sells non-ethanol gas. I'll definitely try that...and look into an electric fan to add cooling! Thanks again & happy motoring all!
Every Casey's and I think every Kwik Star in Iowa has ethanol-free fuel. At least the ones I go to, which I travel for work, so it ends up being several.
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