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Vapor lock signs?

H

Henry K

Donation Time
I have a '67 Alpine with a Weber 32/36 and a pertronics ignition. If I drive until it gets hot and stop for 10-20 minutes, shortly after start up and within a 1/4 mile or so it seems to want to die, as if it's not getting fuel. But if I just keep going it will come out of it and drive along fine. I have a mechanical fuel pump which I rebuilt myself..... so that can't be the problem (LOL). I have run the fuel line from the fuel pump across the front of the engine and wrapped another hose over it for insulation. Could I be experiencing vapor lock? If not, what is it? I do have a plastic fuel filter between the fuel pump and the carb, but it it not against the engine and doesn't seem to be hot. Any ideas on this quirk? What are the signs of vapor lock? Thanks.

Henry
 
Ken Ellis

Ken Ellis

Donation Time
Is there a spacer between the carb and manifold?
Does the intake manifold touch the exhaust manifold (anywhere but right at the head)?
 
Robbo

Robbo

Donation Time
How long have you had the weber set up? Has this problem just started? If just installed, is it jetted properly? I experienced these issues too when i first installed my weber set up on my sv. A few things you may want to consider. First make sure no vac leaks. The spacer will certainly help that with a good gasket there too. It also helps to get those elusive nuts tightes down under the choke Also check around the manifold Like mentioned earlier, my new manifold was also touching my exhaust manifold and i had to machine it a bit to have better spacing You my want to consider an electric fuel pump. I installed a carter pump and it seemed to supply fuel a little better for my weber. Check the pcv valve and make sure its clean and operating properly. You may notice it effects your idle if its stuck or cruddy. Makemsure the fuel line is clear. I had residual flakes in my old plastic line and ended up just replacing the whole line with a new stell one and two filters (before and after pump). Then i ran it behind the oil filler to avoid the hot areas en route to the carb. Hope this helps. After these areas were addressed onmine i was quite happy with the weber set up and pertronix system too. Good luck!
 
H

Henry K

Donation Time
Thanks for the replies. I do not have a spacer under the Weber. I bought one (3/8 in) but didn't have the longer studs required for it and couldn't locate any on-line so I never put it on. I'll try looking again for the longer studs and put in the spacer. I had checked for vacuum leaks and didn't detect any.

In regard to jetting, I have done it numerous times trying to get it right. Right now on start-up it smells a bit of unburned gas and emits carbon, but that all goes away after driving for a while. I burns cleanly after I've run it for a while. I thought my idle jets may be too big, but it doesn't seem to run as well when I installed smaller ones.

I don't have a PCV on it right now. Could that be a contributor to my problems? I'll replace the fuel filter, but since the issue only occurs after it is hot and then sits for a while, I was thinking vapor lock.

Thanks again for all of your help. I've almost got it to be a reliable driver, but it does worry me sometimes. (I joined AAA just in case!) And I also haven't gotten all of the oil leaks solved yet.

Henry
 
M

moonracer

Donation Time
Over the last few years I have fought this problem with my car also. At first it would vapor lock and I found out the breather was plugged in the fuel cap. I drilled it out and the car ran better but the problem was still there. this fall at the Sunbeam Invasion I was looking around at the other cars and noticed that my crank case breather system was all hooked up wrong. I have since routed everything correctly and purchased the correct hoses and the car has run better than it ever has. I noticed you said you weren't using the pvc system, mabey hook it up and see if it helps.
 
H

Henry K

Donation Time
Thank you, Moonracer. I will check my gas cap. It could well be plugged up. Not sure where to drill it, but I'll check into that. I routed the hoses to bypass the PC stuff since I didn't have a pc valve and I was changing out the intake manifold any way. Could that really be the problem? I just vented the thing without re-circulating any of the gases. The problem doesn't show up until the car is hot, then sits for a short time. What do you think?

Thanks again for your suggestions.

Henry
 
M

moonracer

Donation Time
Henry,

All I did was leave the cap loose to see if it helped. After it was better I drilled the little hole out in the bottom of the cap. When mine wouldn't star/start hard I would go back and open the cap and you could hear air sucking into the tank.
 
PETER CLAYTON

PETER CLAYTON

Donation Time
vapour problems

Would advise fitting the spacer block under carb, heat transmission can cause the symptoms you have,under hood temps get very high & fuel lock due to conducted heat is extremely likely.
 
H

Henry K

Donation Time
Thank you, Peter. I will definitely do that. Any idea where I can get longer studs to accommodate the spacer? I got the manifold from Pearce manifolds but they don't seem to have any. Thanks.

Henry
 
Alpine 1789

Alpine 1789

SAOCA President
Diamond Level Sponsor
I just bought the proper length studs at my local Ace hardware store. Lowes and HD carry them too. Are you sure you are looking for the right studs?

BTW: for what its worth, I ran my 32/36 for several years without a spacer and never had any problems like you have described. Adding a spacer is a simple thing to do and might fix it, but I will be surprised.
 
B

Bill Blue

Platinum Level Sponsor
Keep in mind that that heat soak problems can be caused by weak coil/condenser/module. As you drive they cool down to the point they can perform adequately. Before pulling all your hair out trying to solve a vapor lock issue, try swapping out the coil. If that does not solve the problem, try going back to points and condenser.

Bad ignition components can do a wonderful job of imitating fuel starvation.

Bill
 
Alpine 1789

Alpine 1789

SAOCA President
Diamond Level Sponsor
Henry K said:
Thank you, Jim. Did the spacer do anything to improve performance?

Henry
Click to expand...

Not that I ever noticed. I had it on when I first installed the Weber, then forgot to re-install it when I replaced the manifold, and ultimately put it back on when I installed a Bill Atalla header. I never really noticed the difference, but figure it is better to have it one than not.
 
puff4

puff4

Platinum Level Sponsor
Bill Blue said:
Keep in mind that that heat soak problems can be caused by weak coil/condenser/module. As you drive they cool down to the point they can perform adequately. Before pulling all your hair out trying to solve a vapor lock issue, try swapping out the coil. If that does not solve the problem, try going back to points and condenser.

Bad ignition components can do a wonderful job of imitating fuel starvation.

Bill
Click to expand...

Yep... as the old mechanic's adage goes... most carburation problems are electrical. ;)
 
H

Henry K

Donation Time
Bill, I want to explore the ignition as a possible source of my problem. This is the 3rd coil I have put on the car. When I had the points ignition, the coil got so hot you couldn't touch it for long. That coil died. I put on a .8 ohm ballast resistor and still fried another coil. I switched to pertronics (with a different distributor) and left the external resistor on it (despite my internally resisted coil saying I didn't need one). The coil doesn't over heat now. But I'm experiencing the issue I had previously described: i.e. what feels like fuel starvation after the car is run for a while then sits for a short time. Do you think I have mis-wired the ignition or could this be unrelated? Why do you think my coils were heating up so much?

Thanks for your thoughts on this.

Henry
 
Ron67Alpine

Ron67Alpine

Silver Level Sponsor
Henry, did you try what moonracer suggested? I swear that: "what feels like fuel starvation after the car is run for a while then sits for a short time" sounds like vacuum lock. Our cars are vented fuel systems. Meaning that they should be open to the atmosphere. The fuel cap should have a small hole in it, that opens the tank to atmospheric pressure. If that hole is blocked then it becomes a closed system. As the fuel lowers, a vacuum is created in the tank, which stops the fuel from flowing. Letting it set for a little allows the outside pressure to seep in and equalize the pressure, then it runs...until the next time. As moon racer suggested, run it w/the cap off, maybe something loosly on the throat, to minimize any backsplash. If it continues to die, then look to something deeper. Sometimes it's the little things that kill us.
Good luck
Ron
 
H

Henry K

Donation Time
Hi Ron. What I did after Moonracer's suggestion was to open the cap and run a small brad into the opening in the lower side iof the cap to see if it was obstructed. As I pushed in the nail, it seemed as if it were clear and I pressed against something inside (it felt like a spring mechanism) which gave way. I didn't drill anything as it appeared to be clear and functioning. (Not sure if it is since I don't know what it is supposed to do.)

Henry
 
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