Vapor Lock? - or a carb problem

[wdsj]

59 Silver Hawk 256 4brl Carter, run after rebuild

Engine cranks up idles good, revs good. When engine in hot (water flowing) the thing runs great. Turn if off, try to recrank and it wont crank. Engine turns over and over and over, tries to hit every now and then, but will not crank. Let it sit for a couple hours and it cranks right up[?]

I have a clear gas filter at the carb, and it is full of gas. I have heard of vapor lock all my life but never exerienced it. The gas line is full at the filter which is about 4 inches from the carb inlet. I always thought vapor lock was due to gas vaporizing in a too hot fuel line. The hood is still off the car and there is no excessive heat around any of the gas lines as far as I can tell.

Checked gas flow out of accel pump and flow is good. Checked spark at plugs and there is spark. Only other problem I know of right now is the generator is not functioning, but the battery is well charged.

Bottom line, it cranks cold, runs cold, runs hot but will not crank hot.

thanks for any ideas.
dell

Dell
59 Silver Hawk
64 GT Hawk

[BobGlasscock]

I admit I get stuck in ruts, but it is always the rut that worked for me, so I hope it will work for others. My flathead had all the vapor lock symptoms, and I did all the cures except for the electric fuel pump, which was next. Went for a drive with my brother (who is a highly trained auto technician) and drove till it 'vapor locked'. He took the carb apart and adjusted the float to book instructions and all has been fine since. The float would supply enough gas for idling and working on it, but after heating up by driving a distance, it would cough, sputter and die. And not re-start for 30 minutes or more.

The driving range prior to the fix was anything between 2 and 25 miles. But always after engine temp reached normal.

'50 Champion, 1 family owner

[Studeman]

I'm going to assume you have a Carter WCFB 4bbl.
The "trouble" is the modern gas. It is very volatile and vaporizes easily. It also is much less dense than the gas of the period that the carb was designed for. This causes the floats to run on the high-side. IE- it takes more gas in the bowl for the float to shut the gas off. This results in percolating of the gas into the intake after shut-off... effectively flooding the engine, and making it very hard to start.

Take the carb top-cover off and reset the floats 1/32" LOWER than the specs call for. Then install a Mr. Gasket #98 heat dissipation shield kit under the carburetor. This is a stack of alternating aluminum and composite gaskets. This will raise the carb about 1/2" and limit any heat-transfer from the intake manifold. Don't worry that the venturi holes don't quite match up with the WCFB (they are for an AFB)... It won't be a problem. You should even notice an increase in performance and better torque.

I would also switch to a Pertronix electronic ignition... and add a booster electric fuel pump back at the tank (it doesn't need to run all the time, just b4 starting). You'll be much happier with starts and performance

Ray


Specializing in Studebaker Restoration

[wdsj]

Ray, your assumption is correct, Carter WCFB (the same one with jets installed wrong, thank you very much)[^]

Float adjustment makes sense, I think there is gas percolating after shutoff.

Off comes the Carter, again [8D]

Dell
59 Silver Hawk
64 GT Hawk

[buddymander]

Nine out of ten "carburetor problems" end up being electrical..Check the spark color before and after it "vapor locks". I suspect a bad condenser or worn distributor shaft. Coils fail when hot also.

[jeryst]

I'm a little confused as to your terminology. When you say that your engine does not "crank", that typically means that it does not turn over. So do you mean that when its hot, it wont turn over, or that it turns over, but wont start?

If it wont turn over when hot, then you may need a new starter. If it turns over when hot, but wont start, then you may have vapor lock, there may be a problem with your choke, or it may just be flooded.

[wdsj]

I should have said, will not start. The engine cranks. I believe the engine is flooding like Studeman noted above. Been busy this week but plan to check the floats today.

Dell
59 Silver Hawk
64 GT Hawk

[Rerun]

I have experienced similar problems on a Stude V8. It turned out to be a failing coil that was OK cold, but would develop high resistance when hot.

Jim Bradley
Lewistown PA
'78 Avanti II

[wdsj]

OK, I lowered the floats from 9/64" to 3/16". Now the engine floods when it cranks, never starts. When I stop cranking, gas continues to flow from the jets (not just purcolate)[B)]. Seems like the needles are not seeting at all. I am going to pull the carb and check again. I made the problem worse somehow.[V]

Dell
59 Silver Hawk
64 GT Hawk

[buddymander]

You dismantled a carb to change the float level just over 1/16" but less than 1/8". If your carb had a float level problem causing a no start condition, you can be sure that it would amount to much more than 3/64". You may have made the problem worse, or you may have created a whole new problem. I've rebuilt and modified more carbs than I can remember, and I STILL attack each problem as if it were electrical. Carbs are simple enough to be inefficient, but complicated enough to be practically impossible to dial in for a specific motor, once it's lost its calibration. Check the dwell when it's cold versus when it's hot to determine if there's a distributor wear problem; at several different rpm's with the vacuum disconnected, because vacuum advance moves the breaker plate off center changing the point setting. Switch with a known good coil. Replace the points and condenser. THEN tear into the carb. I hope you're just removing the carb top and not the whole thing, creating the opportunity for vacuum leaks. Fuel percolation can usually be traced to a heat riser valve that is stuck shut.

[wdsj]

I agree an electrical is a more likey culprit for problems that appear to be carb related. However I am not don't understand how an electrical problem can cause gas to trickle into the engine after the engine stops? I am certainly open to suggestions.

As stated in the first post. The engine started great, ran great. But when I turn if off, gas trickles into the engine, then it would not restart until it sits for about an hour. It seemed logical that the gas trickle after stopping the engine was a carb issue.

When I get it running again, I will check the dwell and coil as suggested. I rebuilt the distributor with new points (same condenser) and installed a new coil. Of course that does not mean they are good.

One more thing, the car does not have a heat riser valve. It was that way when I got it.

thanks
dell




Dell
59 Silver Hawk
64 GT Hawk

[buddymander]

The gas trickle is one of four things. Percolation from a hot intake manifold, high float level, bad needle/seat, high fuel pressure. Drip some water on the intake by the side of the carb on the crossover passage (on a hot engine) and see if it boils. Drop that float 1/4" for a real test. If that doesn't do it, then replace the needle and seat. You could then install a fuel pressure gauge if all else fails, but it's probably a bad needle or seat. Spring for a new condenser. If it cant absorb spark, then the points will burn that much faster. There could be a multitude of problems here, so a systematic approach will decrease frustration.

[wdsj]

Lowered flots to 1/4". Cranks, start and runs. Switch engine off, no gas trickling into engine. Turn it off, crank it up. Seems to have fixed the flood problem. No gas percolation.
Also, the dwell is 28 cold and 28 hot.
Looks good for now, just hope the floats are not too low. I'll know that when I get it back on the road.

thanks

Dell
59 Silver Hawk
64 GT Hawk

[buddymander]

Who knows, the float may have been correct and you might have had a speck of dirt in the needle valve. Adjust your idle mixture screws in until it drops stutters or stumbles, then back out a half turn. Retard the distributor within the highest idle spectrum. If it cranks hard, then retard it further. Then you can hand choke it while it's warmed up and see if the idle increases. Or you can just squirt some WD40 down the carb and see if the idle picks up. If it does; then either the float is too low or you have a vacuum leak, or the jets are too lean.