Vapor Lock or Heat soak the carb no mo' !

[RobertKB]

My brother owned a '53 Plymouth in 1965 and drove it everywhere, pretty hard most of the time. I drove that car lots. Never a problem with hot starting. I think that now our cars are older, often with dodgy (pun intended) parts, that is some of the problem. I think the biggest issue is the new gas and it has been mentioned many times to lower the float in you carb slightly to help with the problem.

[dlrides]

Hold the pedal to the floor, then crank it.

Problem solved.

Why make a mountain out of a mole hill?

Oh that's right - that's what the "new" generation does - Groovy man.

 

 

Making some signs that say "STUPID KIDS STAY OFF MY LAWN" seems to cure most vintage auto issues.

 

Edited July 7, 2014 by dlrides

[Lumpy]

You know, that flapper thingie in the exhaust manifold (just noticed it in Dodgeb4ya's pic) that directs hot exhaust up under the carb for cold weather...I wonder how many of those are rusted stuck, not working right, and on a hot day making the manifold much hotter than normal? That's the first thing I take out when I get a new old car or engine...I've never had cold running problems by not having it/them in any engine I've ever owned, and I sure don't like the idea of blocking off and restricting the exhaust. I either wire them permanently open, or completely remove them from the manifold, and plug any holes associated with the shaft. 

 

Just a thought.

 

ken.

[Lumpy]

_{I think I hear light bulbs going on.....}

[Tusler 49 New Yorker]

I open the hood and give it a shot of Starting Fluid into the aircleaner. Otherwise I have to hold the gas to the floor and crank for a long time. more than once I was like one crank from being stranded when it finally started.

i did not realize a simple shield would make that much difference. I will make one and give it a try. The L8 in my car gets really hot when I shut it off and boils the gas thru the vent tube into the intake and floods every time.

[Conroe Powdercoating]

^^ post up your results

[greg g]

Lower your float.  Todays gas boils at a lower temp than the real stuff the car was designed for.  Factory settings no longer apply.  Your car is flooding itself, having more expansion room in the float bowl will mitigate that condition.  also make sure you heat riser is in the fully clock wise position if the spring is broken tie it there with some mechanics wire. 

[55 Fargo]

Does anyone have a drawing of a proto type for heat shield. I want to build one and give it a try.

Greg I also have lowered trhe float, this helps, but "heatsoak" and super high underhood temps, may be agrravating the situation. I do know that fuel can not only expand but boil, creating air pockets, perhaps.

I am 12 volts, so it does make a difference. I also changed oil to 15W40 HD diesel oil, that seems to keep my hot engine quiter too...

[_shel_ny]

Does anyone have a drawing of a proto type for heat shield. I want to build one and give it a try.

Sheet of paper, or poster board, you should be able lay out a template for one that fits your particular set up. Then get the metal, and tin snips, and  "git r done"

[Lumpy]

Okay, I've been thinking, which in my case is kind of dangerous, but here goes. I took a trip to the garage, dug out my old single barrel manifold, and gave it and my engine a good study.

 

The idea of a heat shield is a good one, but it's not the whole problem. The intake sitting directly on the exhaust manifold, with passages for the hot exhaust gasses to come right up under the base of the carb is. That is the source of the excessive heat.

 

For that reason, I would take both the intake and exhaust manifolds off the engine. Attack the problem at the source. I know, big hassle...I don't wanna do it! But really why keep putting band-aids on it when you can improve/fix the whole system. And, pulling the intake and exhaust is NOT a big job, problem.

 

The square surface where the intake and exhaust manifolds bolt together with four bolts: Put a thin metal plate, a block off plate between those surfaces. Block that whole thing off. I would make it as oversized as possible, so that on the outside it sticks out at least a quarter inch or so wherever possible...kind of a mini heat shield. Just make sure it is a block of plate, with no holes or passages in it. I know there is room to do that on the side facing forward, reverse, and away from the engine, on my engine. I think that is at least 70% of the problem, especially if there is a heat riser/flapper valve/plate in the exhaust manifold.

 

Heat riser/flapper valve/plate in the exhaust manifold: Trash that POS. You can usually drive out the shaft, then plug those holes with old bolts. They can be stubborn...use a good punch sized right.

 

Get some of that high temp header wrap. You can get it as small as one half inch wide I believe, but the one inch size is easy to work with. Wrap as much of your exhaust manifold as possible with it. Have a helper when you do it...it helps! Wrap what portions of the intake that you can, but I would be most concerned with the exhaust.

 

Then put a heat shield under the carb.

 

Just some thoughts.

 

Now if you really wanted to do it right, some old cars and trucks had water from the block or water pump that went into the chamber. If you blocked that chamber off, as suggested above, you could drill and tap the manifold for two small ports/nipples, and run your heater hose to it, and out of it. That gives the carb heat in the winter, but never lets it get as hot as the exhaust gas system does...in fact it actually cools the intake...but not too much.

 

Having said that, I can't imagine cold running problems, unless you drive the car all year around, and live in a snow-belt. There will still be plenty of heat off the engine and manifolds even with all the mods suggested above, for cooler or cold days. I have taken Lumpy out of the garage in the middle of winter, if the roads were clear, just to give her a run...I've never had my carbs ice up. And of course I never have heat soak problems, because the carbs don't sit directly over the intake/exhaust junction. Even if mine was not blocked off, the heat can't rise directly up unto the carb(s), as they are both offset and isolated from that heat source. You might even want to consider dual carbs. If you keep the carbs small, you'll even get better gas mileage. Bonus!

 

Or not!!! Maybe just too much coffee.

 

ken.

[55 Fargo]

Ken aka Lumpy, all good ideas, and having a blocking plate between the intake and exhaust would no doubt help.

The under hood temp on those 90-100 above days, will be super high, would not the intake and cast iron exhast not heat transfer from 1 to the other inspite of the plate, once the engine is shut off. I can see this working well when an engine is running, but most of us do not have any trouble with the engine running and car driving down the road at 30-60 mph.

Wrapping fuel lines, and exhaust manifolds, with a heat deflector plate for the carb, should add a lot of protection, too, especially once the engine is shut down.

The modern day fuels, are no doubt the main culprit. But really, what were these same veehicle like, back in the 1940s-60s???

[Lumpy]

That is the million dollar question, did they heat soak new? I'm kind of thinking that when the heat riser valve starts rusting up, maybe that's when the problem begins. Fuel must be a big part of it...or is it? They certainly were not running 10% alcohol back then. !! Or maybe it was part of being a car owner way back when. ? I wasn't a kid back then, but it was pretty long ago when I was a kid, and I still remember my dad, and friends, talking about "vapor lock" quite a bit....which I think was used (the term) to describe heat soak also...I kind of think that it was somewhat common.

 

On my old manifold, if you look up into that chamber, that's just what it is, a chamber that surrounds the intake passage, and allows exhaust gas to go all the way up to the base of the carb. I think that a block off plate would eliminate that heat, and then the heat transfer when sitting, engine off, would not be enough, or would be much less...I believe the aluminum between the two cast iron surfaces (would) slow(s) that down (heat transfer) quite a bit too. In stock form, that heat is already there, and only has to go directly to the carb.

 

I'm not sure how much wiggle room there is between those two surfaces, as to how thick of a plate you could get in there...but, the thicker the better. If one could get a thin plate, and a gasket on each side, that would slow the heat transfer down quite a bit.

 

I really think that section of intake/exhaust manifold is the source of the heat soak problem.

 

k.

[desoto1939]

Lumpy: I have a 39 Desoto with the 25 inch block and stock engine setup witht he single barrel carb. Still factory. About 20 years ago my factory heat riser went south. I livee near Valley Forge Pa which just outside of Philadelphia PA. Our winters are cold but not real cold like Chicago or upstae NY.

I was driving the car around Thanskgiving Season and going to our last car gathering. I noticed that when I would come to a stop light the car was acting rough. I stopped and kept the engine running. This was in a parking lot so no one was around me. Opened the hood and noticed that I was getting ici9ng at the base of the carb. So to stop this I pulled out on my throttle cable everytime I had a stop. This kept the car running faster and kep the car running with out the roughness.

Over the winter I had the Heat riser replaced and have not had the icing issue, But this was before we had the new 10% ethinol gas mixture. In the winter time now I still do not have any issues, But during the summer and also on hot days after stopping the car and it has sat for awhile the engine is hard to start.

I feel it is the gas issue with the perculation and not the heat riser issue or not blocking off the unit.

I plan to put a heat shield under the carb to see if this helps. When I get the hard start I then pull out the throttle and this helps get the car started when in hot temps. I also have 00 6 volts cables on the battery.

Rich Hartung

Desoto1939@aol.com

[Conroe Powdercoating]

I can say on a 95 degree day yesterday, I drove 20 miles at 60+ mph, to the bank, turned it off at the teller window, fired right up, went and drove to a customers shop and made a delivery and shut it off and fired right up 3-5 minutes later, went to the taco joint drive through and shut it off and a couple minutes later fired it right up.

BEFORE the shield, that would have NEVER happened, I knew better than it shut it off. With the shield, it worries me no more, she fires right up. the fuel line wrap and exhaust wrap I did helped, but the big resolve or band-aid if you will, was the install of the shield to protect the carb bowl, fact.

[55 Fargo]

Good to hear you all got this problem licked. It isn't 95 here today, but it's about 84 humid, hazy like you wouldn't believe. I would say I would have restart issues today, once the engine was good and heated up.

I am going to try your solution....

[T120]

Heat deflector plates under carburetors were used early on...Phenolic insulator blocks under carburetors were also used...Heat shields were used over the fuel pumps by some manufacturers as well - Chrysler and Studebaker to name two.

Studebaker for one also directed air flow from behind the grille in the direction of the fuel pump on

some models.

Stuck manifold heat valves,(flapper thingy)will cause problems.

Greg's suggestion is a good one and should be incorporated as well -lower the float level.

I've seen combinations of all these used on some vehicles to eliminate fuel percolation.

Edited July 10, 2014 by Ralph D25cpe

[Lumpy]

Well, I was just thinking in terms of the ultimate solution. If heat shields can do it alone, then that's good. I'm thinking that the water cooled/heated intakes was the best idea, but I don't remember what old car or truck I saw that on...maybe IHC?

 

I did have an old International truck, with an inline six, that used to ice up all the time...or it seemed like. From what I know the humidity has to be just right for that to happen...so I guess I was really lucky or something. When I first bought it, middle of summer, it had all this home made sheet metal ducting around the air cleaner, directing warm air from the exhaust manifold to the air cleaner...I looked at that and promptly tore it all off...only to realize the next winter why it was there! That was my first and last experience with carb icing.

 

Another route one could go, if one wanted to eliminate all possible source of carb heat, but be ready for carb icing, and not worried about retaining the stock oil bath air cleaner, would be to use an air cleaner that is set up for carb heat, such as on all the late 1960's and 1970 cars. Something off a slant six would work. One could turn that on with a vacuum switch as desired. The Piper's I used to fly had a carb heat lever, if conditions were right, and you suspected carb icing you'd just pull that on. Cost a couple of HP/RPM, but better than having the engine stall. !! But the same sort of deal, you could give warm air to the carb if desired, and not just cook the carb all the time.

 

Or not!

 

k.