Tweet
Whenever my 66 390HP sits over a day or two (I generally drive it at least once a week) the holley carb "loses its prime" and you have to crank the starter until the bowls refill to start it. There are no external leaks, and I can find no evidence of an internal leak. I have not seen any liquid fuel dripping inside the carb (unless you pump the accel pump), and the engine starts Immediantly and idles perfectly on a hot restart. Even cold, if the bowls are full, just set the choke, give it a couple of slight pats to prime, and it takes off and settles to a fast idle. But let it sit, and you have to refill the bowls. I'm beginning to wonder if the gas could be "siphoning" out of the float bowls back through the fuel pump after shutdown. Do fuel pumps have an internal "check valve" to prevent this? Has anyone ever heard of this? The pump is not orignal, IIRC, it was from a high horse 396.
-
-
Re: 1966 L36 carb or fuel pump
Kevin,
I'd have to guess from your description that you are having the same problem that a lot of other people are having lately. Your problem is common and most likely caused by the "new fuel" that's being used today. For reasons that I don't understand, the evaporation rate has gone up dramatically in just the last few years and especially in the last few months. Boil off can and does occur, especially on hot engine shut down, within a day or two. I'm far from being a chemist and have no idea what is actually causing this but maybe someone that does know can explain it to all of us. Duke comes to mind.
Another problem that I've noticed is the fact that older cars with carburetors do not like their original float settings with the "new fuel". Holley's, for example, run best when the level is set about 1/8" below the sight hole instead of at the same level. Hot perc seems to occur frequently and occasional unexplained flooding is also common problem. The lowered float setting seems to mostly eliminate this problem.
Michael -
Re: 1966 L36 carb or fuel pump
Kevin,
I have a 63 vette with a Carter AFB and a 67 vette with 3810 and both cars act the same as yours when they sit a few days. I spoke with Chuck Smith who rebuilds carburetors and he said the problem is today's gasoline. He also said to set float levels lower because of the reasons Mike said in the previous post. I think today's fuel systems are closed so the evaporation does not occur and our old carburetors are vented to atmosphere so the problem exists. One other problem I have with the Holley is that when the gasoline evaporates, the gaskets dry and start to leak internally starting as a rich idle condition and getting worse from there.Comment
-
Understand, guys...
the fuel bowls on carbs are open to the atmosphere via the 'vent' stacks and they will naturally drain via evaporation. When cars are driven daily, this isn't a problem, but for our 'weekend warrior' use profile we are pushing things, notwithstanding today's alcohol blended fuels.
Two tips:
(1) Get a tiny squeeze bottle with a 'flip' top nozzle of approximately 2 oz capacity. Fill it with gasoline. Before you start the car after it's been sitting for a while, remove the air cleaner and squirt gas down the vent stack until the FRONT fuel bowl is full. Then, go start the car effortlessly.
(2) If you don't have squeeze bottle handy, then learn a new technique for starting the car to lessen starter motor strain. Climb in and set the choke (push peddle to the floor fully) and 'pump' the accelerator with three partial strokes (3/4 peddle travel). Crank the starter and STOP if she doesn't fire within 5-10 seconds. Wait a second or two and re-pump the pedal and crank 'er again. Within 2-4 short engine cranking episodes, you'll have enough fuel in the bowl for 'er to fire and run like she should!
If you LAY on the starter and continuously crank while fluttering the pedal, you'll really eat into your battery, wear the starter, and risk flooding the carb when the fuel bowls finally fill. So, try repeated short bursts on the starter instead!Comment
-
Cool Fuel
Good suggestions Jack. There are a few alternatives though, if you don't want to fiddle with gasoline. Atter a drive, (hot engine) allow the engine to cool a bit, then remove the air cleaner lid and place a pair of rubber plugs over the verticle vent tubes (Holley carb only) which will seal the fuel from the atmosphere. If the Holley primary side is equipped with a mechanically operated bowl vent, block it closed.
Another tip would be, don't shut the engine off at operating temp before weeks of storage. Allow the engine to come down to ambient, then run it again for just about 15 seconds, enough to refill the bowl with cool gasoline. 60% or more of the initial evaporation happens in the first hour or two after a hot shut down. You may have noticed that sometimes your car fires up easily after a week of storage and other times there's no start because the bowl is dry. That is most likely a result of the two different conditions in which it was shut down.
Ultimately, I prefer the cool shutdown AND the sealed bowl vents. I really don't like the thought of gasoline evaporating away in my carburetor or FI bowl because there always seems to be some residue left at the bottom of the bowl. After several of these cycles, that residue will be a layer of rubberized gasoline.
BTW, don't forget to remove the plugs before starting the car in a week or so. If your memory is anything like mine, a note taped to the steering wheel would be mandatory.
MichaelComment
-
Re: Cool Fuel
I go through this drill after the long Michigan winter "hibernation", and if any of my cars have sat for more than a week or so; a plastic infant feeding syringe makes it quick and easy. About three ounces does the trick, and they fire immediately.
Comment
-
Re: Cool Fuel
John, I always like your cures. The coffee can plastic lid for door handle removal has been a favorite. Thanks.Comment
-
Re: Cool Fuel
Now you have my curiosity peaked. Would you please share the coffee can plastic lid tip again? Sounds like it could be useful.
Thanks.Comment
-
Re: Cool Fuel
Cut a U-shaped protective shield from a plastic coffee can lid to use when using the window crank removal tool, to protect the door trim panel from damage; stick the plastic shield between the crank and the door trim panel, then insert the tool between the shield and the window crank to pop the "Omega clip" off. The shield has a slippery surface so you can work the tool, but it's tough enough that the tool won't go through it and damage the trim panel.Comment
-
Cool Tip.....Thanks!! *NM*
Comment
Comment