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fixing vapor lock/percolation issues on low compression engines

Started by 47bigcadillac, December 05, 2012, 10:01:40 AM

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47bigcadillac

My 1932 v8 always gave me gasoline issues: percolation (too rich) in winter and a bit of vapor lock (too lean) in summer.

They must have changed the blends in recent time because gasoline seems to be getting lighter by the years.

I did all I could to reduce the heat in the carb and fuel pump using heat insulation everywhere including lines, phenolic carb spacers, re-routing the air supply from a cold place etc..

These measures improved the issue but without totally eliminating it.

The carb is buried inside the exhaust header and everything is engineered to provide heat to the gasoline at the carb level.

So I decided to try modifying the gasoline blend myself, which is at the source of the issue and would be the most logical and also period correct way of dealing with this because the engine is designed for the heavy fuels of the 1930's.

I have been running my car on 20% Kerosene blend for a few months now, and all gasoline boiling issue have been resolved beyond my expectations.

Also, to my surprise, the engine runs smoother and has a noticeable increase of low end torque and power.

On the way to my house there is a steep, long hill. Using the new Kero blend, the car pulls well on 3rd gear all the way to the top, with power to spare. On gas only I always had to switch to second gear mid-hill.

Kerosene has more BTU per unit than gasoline and also burns at a faster rate than the high octane fuels of today, and when mixed to gasoline it seems to burn well in a long stroke, low compression engine.

There is no smoke and no issue with spark plugs or cold starting that I can notice.

Where I live, fortunately ethanol blends are not readily available, but kerosene is sold at any gas station and is tax-free so it comes to about a third less than regulars gas.

Diesel is similar to kerosene but a bit heavier. If high quality, cheap kerosene is hard to find I guess that a 10% mix of diesel would work similarly.
R. Brandys

1932 355B  5 pass Coupe,  Fleetwood          
1935 LaSalle Coupe  5077
1947 Club Coupe      6207

kkarrer

I would think that the Kerosene works somewhat as a upper lubricant for the engine and lowers the boiling point as well as providing some of the other benefits that you've described.  You might also try installing an electric fuel pump on the frame rail and hiding a small toggle switch under your dash to manually operate it.  Sometimes the extra supply under pressure helps to solve vapor lock hard start issues.  That extra pump is also handy as a back up to your manual pump and I use it to help with cold starts when it's been over a week since I've last fired up my '41.  That can save the battery and the starter some extra work.
Ken Karrer 1941 6227D coupe

R Sotardi #11719

20% kerosene? How are your spark plugs? Any tailpipe smoke? How many actual miles have you driven? Please, I'm not being critical. I am hoping for a resolution to a problem that plagues many in the hobby. Is the 32 an updraft carb? In 50s cars the compression is higher and a 20% may be too much. Ron

pauldridge

Hmm..An interesting theoretical solution, but I wonder about the economic practicality.  At 11 bucks a gallon for kerosene (Home Depot), even a 20% mixture adds a couple of bucks per gallon to the cost, and at 10 mpg (at least with my 346) that's not chicken feed.

I remember my Dad regaling me with wartime stories of gas shortages, and how they would rig up two gas tanks on the old Model A.. One with non-rationed kerosene, the other with gasoline.  They would use the gasoline tank for starting, then switch over to pure kerosene once the engine was warmed up, and switch back to gasoline before shutting down.

That would make me wonder about possible starting issues with the lesser volatile kerosene usage.

When I first got my '40 Sixty Special, it was absolute impossible to drive in Texas summer heat.  The fuel would literally vaporize even while driving down the road, thanks to that fuel line passing right over the exhaust manifold.

I finally solved the problem by completely disconnecting the fuel line to/from the engine driven pump (leaving it installed solely for vacuum assist), and running a new fuel line from an electric pump at the tank, up along the back of the firewall and across to the carburetor.  Yes, it does look a little non-stock for those picky guys with white gloves at the judging contests, but the average supermarket parking lot car show spectator would never notice a difference. 

Since this modification, I've not had a single vapor lock issue, and drive the car regularly in 105+ Texas summer afternoons WITH the air conditioning blasting full on./

I like to keep my cars as stock as possible, yet don't mind small modifications that improve the functionality so I can actually enjoy driving them (12V alternator, Air conditioning, etc).  Otherwise, you just wind up with an expensive piece of yard art.
Phil Auldridge
Austin, TX
1940 60S as well as MGA, Stingray, '39 Ford Coupe, BMW 3.0 CS, '59 Jaguar, '51 Hudson Hornet, '64 and '70 Mercedes roadsters, and Nash-Healey LeMans Coupe
[img]http://www.auldridge.org/images/hdricon.jpg[/img]

R Sotardi #11719

#4
Phil, I was just talking to a older friend of mine last night, who told me of a similar story. Diesel & kerosene were not rationed in WW2 so he would mix 50/50 and extend the range... but the 38 Terraplane went down the road like a " wood burner" and the plugs needed cleaning once a month. That adds a price of about $6 per gallon .... eck! Ron

47bigcadillac

#5
Quote from: R Sotardi #11719 on December 05, 2012, 09:08:52 PM
20% kerosene? How are your spark plugs? Any tailpipe smoke? How many actual miles have you driven? Please, I'm not being critical. I am hoping for a resolution to a problem that plagues many in the hobby. Is the 32 an updraft carb? In 50s cars the compression is higher and a 20% may be too much. Ron

I burned about 2 full tanks (110L) on that blend so far and cannot see any tailpipe smoke or spark plug fouling. The smell of the exhaust is a bit different and has a very slight odor of burnt kerosene at times.

I have also started to use that 20% blend on my 1935 LaSalle and again, no issue with smoke, plugs or cold starting now in winter.

No issue with detonation/pinging either, and the timing on my laSalle has been advanced to the max because of cooling issues in traffic this past summer.

That noticeable increase in low-end power and smoother accelerations is really what convinced me that this is the sort of fuel that those long stroke engine require.

The 1932 355b engine is an updraft Carb with a long neck and the intake is mated to the exhaust header. The carb is buried between the headers and lies just and inch or less above the top of the engine; this makes carb heat insulation a real issue.

Most of my problems were due to percolation - fuel boiling in the carb making the mix too rich and the engine quits at idle or low rpm, with a strong smell of gas. Or when heat is soaking after briefly stopping the engine, it won't restart for at least 30 minutes even with cranking it at fully depressed throttle.

Vapor lock only happened once on a very hot day - I was able to pull the choke and get going for a while though.

Gasoline must have been very heavy stuff in the early 30's for the Cadillac engineers to design such a system. Maybe someone who was around in those time can comment...

Because the current blend of gasoline are very volatile, especially in winter, adding 20% of Kero or 10 % diesel is not going to make fuel too heavy overall...it basically transforms the fuel to what it would originally be back then.

Running the car entirely on kerosene is a whole different story though. Also,I would not go higher than 20%.
R. Brandys

1932 355B  5 pass Coupe,  Fleetwood          
1935 LaSalle Coupe  5077
1947 Club Coupe      6207

R Sotardi #11719

Thanks Rob, I'm  trying to find actual results in these theories. I started a thread on the AACA site as well as the Hudson Essex Club(HET). Flathead engines seem to be more susceptible to vapor lock & general drivability issues, than the OHV . Never had an issue with my 50 Cadillac, my Hornet is another issue. I increased fuel pump pressure, insulated lines and placed a mylar pad between the exhaust manifold and top of fuel pump. No issues for two years. Now, I'm studying the volatility issue and it reduction for limited use collector cars by combining additives. I'm hoping  some diesel combo will prove effective, since kerosene is so expensive in small quantities.

Wayne Womble 12210

Quote from: 47bigcadillac on December 06, 2012, 01:10:34 PM


The 1932 355b engine is an updraft Carb with a long neck and the intake is mated to the exhaust header. The carb is buried between the headers and lies just and inch or less above the top of the engine; this makes carb heat insulation a real issue.

Most of my problems were due to percolation - fuel boiling in the carb making the mix too rich and the engine quits at idle or low rpm, with a strong smell of gas. Or when heat is soaking after briefly stopping the engine, it won't restart for at least 30 minutes even with cranking it at fully depressed throttle.

Vapor lock only happened once on a very hot day - I was able to pull the choke and get going for a while though.

Gasoline must have been very heavy stuff in the early 30's for the Cadillac engineers to design such a system. Maybe someone who was around in those time can comment...

than 20%.

This is very much a pain in the A$$ for the 32-33 design.  Not only is the carb bolted to and sitting down under the exhaust manifolds, it also has cast in pathways in the manifold to heat the intake manifold.  As stated, percolation is the problem, not vapor lock.  I have thought about doing this exact thing, but I think I will take it a little further by removing the alcohol, and looking into some different formulations.  Glad to hear it works.