Vapor Lock
Thread Starter
HOOK-EM HORNS
Joined: Aug 2006
Posts: 3,517
Likes: 840
From: Port Aransas, Texas Tx
St. Jude Donor '08
Vapor Lock
It got up to around 90 in Austin today and I started having vapor lock problems. I have wraped my fuel line from the Holly to the Holly fuel pump. The 502 is not over heating but putting way to much heat out.
My driveway is 1 mile long and when I pulled in this afternoon I popped the hood as soon as I turned in and it seemed to help as the heat was able to get out easier so I am going to remove the insulation from under the hood to see if that helps. My 69 has no insulation and it never get very cold here in Texas.
Would going to a stainless braided fuel line help as well??
Thanks Paul
My driveway is 1 mile long and when I pulled in this afternoon I popped the hood as soon as I turned in and it seemed to help as the heat was able to get out easier so I am going to remove the insulation from under the hood to see if that helps. My 69 has no insulation and it never get very cold here in Texas.
Would going to a stainless braided fuel line help as well??
Thanks Paul
Racer
Joined: May 2006
Posts: 264
Likes: 0
From: Fort Myers, Fl / St. Paul, Mn
Vapor lock occurs in the vacuum part of the line before the fuel pump. It's fuel vaporizing and the pump can only pump liquid. Either wrap the fuel line back far enough to get away from the engine and header heat or install an electric fuel pump at the tank.
Lars also posted a solution in another thread today.
http://forums.corvetteforum.com/show....php?t=1536830
Lars also posted a solution in another thread today.
http://forums.corvetteforum.com/show....php?t=1536830
Solves it every time...
Thread Starter
HOOK-EM HORNS
Joined: Aug 2006
Posts: 3,517
Likes: 840
From: Port Aransas, Texas Tx
St. Jude Donor '08
Originally Posted by Thinpockets
Vapor lock occurs in the vacuum part of the line before the fuel pump. It's fuel vaporizing and the pump can only pump liquid. Either wrap the fuel line back far enough to get away from the engine and header heat or install an electric fuel pump at the tank.
Lars also posted a solution in another thread today.
http://forums.corvetteforum.com/show....php?t=1536830
Lars also posted a solution in another thread today.
http://forums.corvetteforum.com/show....php?t=1536830
Racer
Joined: May 2006
Posts: 264
Likes: 0
From: Fort Myers, Fl / St. Paul, Mn
If you have a rear mount fuel pump vapor lock is not the problem. Vapor lock happens in the low pressure side of the line when the fuel get hot and above the boiling point at that pressure (or lack of it) and vaporizes.
If fuel gets that hot in a pressure line it could percolate and form as gas vapor. With sufficient pressure and flow it will clear itself.
Do you have a fuel return line? I'm not sure what year your Vette is and I don't know if it came with a return fuel line but it needs one. It keeps the fuel flowing when there is not enough volume to keep it from vaporizing. The return line is the second line on the passenger side. The lines on the driver's side are vapor collection lines only.
Lars' solution sounds right for your setup.
If fuel gets that hot in a pressure line it could percolate and form as gas vapor. With sufficient pressure and flow it will clear itself.
Do you have a fuel return line? I'm not sure what year your Vette is and I don't know if it came with a return fuel line but it needs one. It keeps the fuel flowing when there is not enough volume to keep it from vaporizing. The return line is the second line on the passenger side. The lines on the driver's side are vapor collection lines only.
Lars' solution sounds right for your setup.
Racer
Joined: May 2006
Posts: 264
Likes: 0
From: Fort Myers, Fl / St. Paul, Mn
Lars on a previous thread
By keeping the fuel returning to the tank, the problems associated with vapor lock are greatly reduced. I suggest you keep the return system functional. Just install a "T" in the carb inlet fuel line back by the secondary float bowl, installed a small restrictor, and allow fuel to "bleed" back through the return line. Using such a system has significantly reduced/eliminated issues related to vapor lock on the cars we build out here - especially on hot days.
On Lou's car (vettasy), I drilled a #50 diameter hole after I welded a plug in a reducer fitting on the "T" at the rear metering block. This #50 hole is just the right size to keep constant fuel flowing back to the tank without affecting pressure at the carb.
