New guy here with a 54 Chevy. 235 with a 3speed manual. 95% sure heat riser is in the open position. Stock carb and still a 6 volt car. Engine turns over great and will start every time.... if the engine is at ambient temperature. Once the car runs, it will turn over, but will not start. I can take a cold rag and place on the intake under the carb for 5 minutes and it will crank right up. Will an aftermarket insulated carb spacer be my fix?
Possibly, being the inline the fuel line shouldn’t be that close to the manifold to cause vapor lock, but with this crap they call gas these days it is possible. Put the insulator on it and see how it reacts, you might have to put some line cover on from mr gasket which should insulate some.
First off.. tip a bit of fuel down the carb to see if it is actually fuel related! Then to see if it is actually vapour lock, run a garden hose over the fuel pump while idling, before you shut the engine down. Vapour lock is caused by vapour pressure being greater than fuel pressure. The ethanol content boils at 170 deg, and most engines have a 180 deg thermostat , so modern gas is the main culprit Sometimes a simple "Check Valve" in between the pump and carb will lessen this. But usually an electric pump before the mechanical pump is the best remedy. DELCO EP11 is a 6 volt inline pump The next best is a return line from next to the carb and back to the tank [using a restrictor to maintain fuel pressure]
I forgot to add, leave the heated manifold alone. These old Blueflames stumble at part throttle without it [ they become a pig to drive around town ]
Thank you for the solid advice. Fuel lines are cool to the touch, as is the fuel pump. Once the engine is warm, there is much heat on the carburetor. I really thought the heat riser butterfly was shut, but after reading numerous posts on here, it is stuck open. I can cool the intake and the plantum with a cold, wet cloth and it cranks right up. I’ve had the carb boil over once after I parked it and left it running after a long drive. It has no insulated spacer. It is Bone stock. I’m just wondering if an insulated carburetor spacer would help enough. I can’t drive it anywhere without leaving it running, or I’m stranded until it cools. This car is to cool not to drive! Wish I could show you a picture! Sent from my iPhone using The H.A.M.B. mobile app
These things need heat in the manifold to keep the fuel vaporised [vaporised ,not atomised] or you'll have low air speed issues with the end cylinders being lean and the centre 2 cylinders being rich. You could try a phenolic spacer under the carb [carb heat is a parasite, manifold heat is needed] But the real problem is modern fuel. Modern EFI's need 40 psi at the injectors and some run returns and some are dead-head. When you park the fuel vaporises because their is no fuel pressure to prevent this, so vapour pressure is greater than fuel pressure. Most mechanical pumps have 2 check valves [1 each side of the diaphragm] so you can easily run a "lift pump" near the tank ,which will push fuel through the existing mechanical pump . I would rather wait 5-10 seconds for an electric pump to prime, than wait 5 minutes for it to cool down. Cool Car by the way. If you got rid of the Rochester B and swapped the carb for a Holley "1920" or Carter YF off a Ford 6 it will make the car a real pleasure to drive. Also buy yourself a "digital advance" timing light, and set it up at 32 deg at 3000rpm to the ball marker on the flywheel. "Digital advance" timing lights don't require timing tape just a TDC mark which makes it easy on these ol' monsters
Thank you sir for this advice. This is the reason I joined this group. This completely makes sense to me now. I will start with the spacer then add an electric fuel pump if needed. Can I bother you for 2 more questions? 1. Is there a fuel additive you would use? 2. I’ve also been told if I’m not going to convert the car to 12v, to buy an 8 volt battery as this improves cranking, etc. what is your thought? Thanks in advance for your time! Sent from my iPhone using The H.A.M.B. mobile app
Old timers used to add a pint of Kerosene or Diesel to a tank of gas to combat vapor lock. You might try Marvel's as it has some other utility as well. Can't hurt.
Hi. Something else to check is if you have a flex line anywhere between the gas tank & fuel pump you may have a rotten hose collapsing from suction.. Gives you the similar effect as vapor lock. Sucks hose closed and engine runs out of gas & engine dies and releases suction on the line and it opens back up. I have had that happen on more than one old car or truck in the past. Good luck, Jimmie
It sounds like you have fuel percolation problem, and an insulator under the carb should help. Does the engine crank slower when it's hot? You may need to repair/replace the starter, check for good grounds and make sure the battery cables are the proper gauge for a 6 volt system. Do you have an automatic choke? Make sure it's working and properly adjusted. Check the carburetor choke-unloader adjustment as well. This will help cure a rich, no-start, hard start condition. Hold the throttle wide open without pumping the pedal and crank the engine for a few seconds at a time to help clear excess fuel puddled on the floor of the intake manifold. This will help prolong the life of your battery and starter. It should work so that at wide open throttle the choke valve is also held at least partly open. Though it seems similar, a vapor lock condition only occurs on the vacuum side of the fuel pump. Air in the fuel inlet pipe prevents the pump from delivering liquid fuel to the carburetor, resulting in a lean condition. What you're describing sounds like fuel being heated in the float bowl which percolates and gets pushed into the intake causing a rich condition. Both conditions are heat related and seem to be more common with modern fuel blends.
I have a '61 235 in my '37 Chevy coupe, which is also 6V. I had the exact same problem and thought it was fuel related. I went through everything several times and finally, out of desperation, tried a NOS coil I had stashed away, but still the same problem. Went through everything again and I finally got a brand new 6v coil from NAPA - the problem disappered, never happened again and that's been over 10-years ago and many thousands of miles.
Why has no one recommended the wooden clothes pin trick?. Seriously though I had the same kind of issue with our 47 Hudson. Although I never did remedy it completely I did make it better by a carb spacer and I also would add a quart of diesel to every full tank and it did help. I also carried a small can of gas and a pump sprayer with me for those times it would vapor lock and die on me sitting in traffic. I had it down to a pitstop like process. I would hop out pop the hood, cool down the fuel pump, intake and carburetor, splash a little gas down the carb and be on my way. Sent from my iPhone using The H.A.M.B. mobile app
Many thank gentlemen! I will be slowly be working thru the issue part by part. I’m going to start with an insulated carb spacer. I also found a small gas station close that sells ethanol free gas! I’m going to replace the coil and probably add an 8 volt battery. If it still acts up, in-line electric fuel pump will be next. I’m grateful for your advice. Sent from my iPhone using The H.A.M.B. mobile app
Look into the cost of an 8 volt battery , they are not cheap! Your regulator needs to be tweaked so it will charge the 8 volt battery correctly. I did this on my 53 Chrysler and it worked well. Good luck,follow the advise given and you should be golden Keep us posted on what works
1: The best fuel additive is to use the lowest octane fuel the engine can live with. Lower octane fuels have less short-chain-hydrocarbons and oxygenates You cannot battle the ethanol content vaporising at atmospheric pressure .Your engine is distilling off the ethanol so no matter what additive you use, the heat of the engine will boil off [or distil ] the ethanol. Increasing pressure also increases the boiling point [similar to a radiator cap] which is why you don't have vapour problems with the engine running. 2: The problem might be cost. Especially 8v batteries . If You're smart , you can hook up 2 x 6 volt batteries in series [with a solenoid in between] to start on 12 volt with the solenoid activated by the starter button. Then parallel wire the batteries with 2 relays wired "reverse post" to switch off when the starter button is activated This way you have 12 volts for starting and 6 volts charging. I did this on my old Lotus Cortina that had a piss weak Lucas starter motor and 12:1 compression [24v starting and 12v charging] But in your case the cost 2 x 6 volt batteries would probably be more than a 12 volt conversion.
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