puzzeled by a Vapor Lock Issue

mbalbritton

mbalbritton

#@$%!
Joined
Mar 22, 2005
Location
Lakeland, FL
Last Weekend I Swapped out my carb and Intake. went from a Holley 4 brrl Intake and Carb to the stock Cast Iron Intake and Carter 2 brrl. This is on a late 70's 318LA.

after swapping out, I'm now having what I've narrow do to, with 99% certainty, Vapor Lock. What I don't get is why it started now? Best I can come up with is that maybe I'm running leaner now with higher exhaust temps???? (Hard line runs close to headers)

Why I think it's Vapor lock? After sitting at a light or sitting still, It will go for a few seconds and then die. Check fuel lines between Pump and Carb and they are dry. The fuel hard line comes up the frame rail about an inch-inch and half away from the headers. Touch the hard line and it's pretty damn hot.

Last night it happened again, so I poured some water over the line where it was hot. it cooled the line off, I walked around and it fired up. As long as I keep my RPMS up while sitting still it won't do die on me. which leads me to the theory that I'm keeping the fuel flowing fast enough that it won't vaporize in the line.

but why now? Only thing I've done is swap the carb and intake. makes no sense.

anyone?
 
Old Mopars with the cast iron intakes have always been notorious for vapor locking. As a kid I remember wooden clothes pins clamped onto the metal fuel lines. It seemed like it was almost standard equipment on Dodges. They acted as heat sinks and pulled the heat out of the line. As far as the change from the aluminum intake... It transfers heat roughly twice as good as cast iron and it may even have a heat riser block off. Not sure if those are all of the contributing factors, but dont feel like the Lone Ranger, it has plagued Mopars since the late 60's.
 
This morning I cut up a couple of Sprite Cans (hey! It's what I had!), and Wrapped them around the fuel line. Came in with out a hitch.

But this is a band-aid for whatever the cause is. I had this intake on previously and never had this issue. Guess I could reroute the hard line too.

thanks for the info on the inherent issue with mopars on this.
 
Grab youself a piece of that orange heat proof covering the race cars use and sleeve your line with it. Thats what it was designed for. You can grab it cheap on ebay under used race parts or nascar parts. After thinking about what the real issue is from then untill now...Maybe:poop: gas formulation? I dunno'.
 
Ya, This is a Dodge Aspen Front end and Motor in a '67 D100. So the routing isn't exactly Factory, but it does run right along side the header Which of course aren't factory either. I'll just reroute it.
 
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