Vapor Lock ......Help

The vaporlock problem is a modern problem we didn't have "back in the day".

This situation is brought about by modern fuels more than anything else. Most of us have eliminated vaporlock by either using the above suggestion, and/or installing an electric fuel pump back by the tank. I personally have completely done away with my mechanical fuel pump and the Jet runs on a Carter electric rotory pump exclusively.



Jerry

53jetman

I had this problem on my '51 C8 a few years ago (Technically I guess it's not vapor lock, which term I understand to mean the fuel turning to vapor on the suction side of the fuel pump, not the pressure side). Whatever you call it, in my case I noted the engine compartment was awfully warm, and figured the best way to deal with that was reduce the temp of that big ol' engine block. I put a modern style radiator core in it, with a 160 thermostat, and the problem disappeared forever.

Vapor lock??? This is such a good subject!! I feel there are several reasons for this concern,many of which are described and talked about already.I also have messed with the growing concerns of engine vapor lock,especially on Twin-H equipped vehicles.You discover the vapor lock concerns after the engine is completely assembled and running,driving.As I said,the descriptions listed in this thread are all solutions to this concern,BUT,look at the manifold before installing it onto the engine.This is ESPECIALLY true with the Twin-H.If you separate the manifolds-exh.int,while off the engine,you will see 3 & 3,plugs in the bottom of the intake manifold for each carb.These must be removed,and all the heavy carbon cleaned out.If you look at the design,it is a trap for carbon.These cavitys go back under the carb areas,as they were designed to do for constant heat at the base of the carbs.,fill almost completely with carbon,and while driving down the interstate at cruise speed,the carbon begins to glow.Picture you charcoal grill with glowing ambers?.This is what I have found takes place in the inside of the intake manifold exhaust passage.Once this carbon is glowing,it will not cool off until the engine has set and completely cooled off.Picture taking your carbs and putting them over a fire and think there would be any fuel left in them??Also in just an overnite cool off period,the engine heat has boiled all the fuel out of the carbs and then creates a long crank time to fire the next day??.When removing these plugs,be extra careful.Don't drive them in,drill a hole in the plugs and use a dent puller to take them out.Once you have them removed,you will see the carbon build up.Not all manifolds will be real bad,but most are.I think the build-up depends on the miles,and the condition of whatever the manifold was on.I have removed these plugs and it is solid carbon and it takes awhile to remove it all.I also suggest if you manifold is full of carbon,remove what you can with a pick and screw driver,then take it somewhere to have it boiled or tanked until it is clean.Also where RE-installing these plugs,make sure you have the correct size,and don't hit them too hard to make them swell.The carbon has eat up some of the seat these go in,and pounding on them to hard will break the seat off into the manifold,and will require some welding to repair.Remember,just sticking the air hose in the passage in the center of the manifold will not clean the carbon from beneath the carb "Pods".it might seem clear,but they usually are NOT.I hope this other bit of info helps these problems of fuel vapor locking.

Don't forget...altitude can be the culprit in vapor lock. The less ambient air pressure, the faster fuel will vaporize. Couple that with engine heat increase on steep grades...not good. Usually happens while your car is parked in the restaurant at the top of the hill. :cool:

My 36 Terraplane was vaporlocking, and I found the fuel-pump screen plugged, thus drawing a high vacuum on the gas which turned it to vapor, which or course, the pump is not designed to handle. No problems since cleaning the screen.

Hey All,

This interaction is why I like Hudsons and Hudson people. What a great exchange of info.

This ametuar, self taught, shade tree mechanic solved vapor lock on a V8 Stude with the Mopar fuel filter and a line back to tank. allows foamed fuel a path of escape. As mentioned, modern gas has a much lower boiling point, so any measure one can take to resolve is good. I've also used an electric fan instead of water pump fan to move hot air from domed engine compartment at speeds below 30mph

I prevented vapor-lock on a 262 by using headers before installing in a Commodore. Separating heat of exhaust from intake works very well. This is certainly not a contradictory solution, but another alternative. Wish someone would come up with a set of headers for 254 I'm rebuilding.

Thanks for letting me share,

Kim

nick s wrote:

I too have had pseudo-vaporlock issues. Had a line sucking air and also had an inline filter element actually collapse. be sure to check out your entire fuel system, including the pick-up tube, for leaks and obstructions.

One section of Murphy's Law states - "In an over-all evaluation, all errors will be cumulative" - In other words the more stuff you add on to improve reliability, the less reliable the system will become. Ditch the inline filters. One of our club members here had incessant troubles with the vacuum tank on his '26 Essex. cursed it all the time, and eventually threw it away and installed an electric pump, and still had problems, due to his in-line filter allowing air to be sucked in. Paradox is that his vacuum tank already had built-in filters. Another guy figured it was a waste of time draining out the bottom of the vacuum tank regularly, so just installed an in-line filter between the tank and the carb. Result, eventually the gunk built up in the bottom of the tank, and blocked the tap off! "If it ain't broke - don't fix it."