Recreated the vapor lock issue!
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Recreated the vapor lock issue!
Well I was able to duplicate the problem. Took the Vette out Saturday and it ran awesome for 30minutes. Then I noticed it start stumbling under heavy throttle. Finally I could here the carb just sucking air when I tried to give it throttle. Started chugging and finally died. Front and rear bowls were empty. Let it sit for about 30-45 minutes and it fired right up and ran good again. Mechanical pump maintains a consistant 7psi before the trouble starts.
Looking more and more like it is a vapor lock issue. Running by the speed shop after work for some fittings to build a return line.
Wade
Looking more and more like it is a vapor lock issue. Running by the speed shop after work for some fittings to build a return line.
Wade
Instructor
Joined: Jul 2003
Posts: 210
Likes: 0
From: eaton rapids mi
identical symptoms i had last summer. Had to replace fuel pump with one that had return line. The fuel pump GM recommended with the new crate engine had no return line. Have had no issues since replacing.
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Be sure to let us know when this works out for you Wade. Learning how to fix these things is part of the fun, if you want to call it that.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
I have said many times how to solve the problem....stick a electric pump in back near the tank, and forget that return line crap, as totally not necessary....use a CARTER electric pump...
and if necessary, use a inline pressure regulator.....most likely for a Qjet.....
it works....
and if necessary, use a inline pressure regulator.....most likely for a Qjet.....
it works....
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
I have said many times how to solve the problem....stick a electric pump in back near the tank, and forget that return line crap, as totally not necessary....use a CARTER electric pump...
and if necessary, use a inline pressure regulator.....most likely for a Qjet.....
it works....
and if necessary, use a inline pressure regulator.....most likely for a Qjet.....
it works....
Gene,
Why would a electric FP solve my issue. I would think that the engine can only use so much fuel at a given time so you would still have fuel sitting in the line heating up even with an electric FP. Not disagreeing just asking.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
that and on that heat riser crap, take that out/off the car, you maybe leave the passage under the carb open, but you don't need a valve to force hot gas under the carb, all that does is boil the fuel outta the thing.....
Years ago, almost all engines I had I filled the exhaust crossover/heatriser passage with plaster of paris, it's heat proof, let harden overnight, install in the morning....cured that crap of boiling/overheated carbs in a second......trick is, I didn't live in Minnesota for winters....so for Maryland that idea worked great....but gotta make sure that heat riser is OPEN or better yet removed....
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
I had this problem also.... drove me CRAZY
My fix was to dump the holly with its front/rear bowls and replace it with an Edelbrock with side bowls. fixed it permanatly 2 years now...
But just ordered a BG mighty demon last night and I am worried about the problem comming back.
My fix was to dump the holly with its front/rear bowls and replace it with an Edelbrock with side bowls. fixed it permanatly 2 years now...
But just ordered a BG mighty demon last night and I am worried about the problem comming back.
Instructor
Joined: Jun 2005
Posts: 140
Likes: 0
From: Bovingdon Hertfordshire
Same problem a few years ago having upped the jet size after chatting to Lars - he suggested a small electric boost pump by the tank to help the poor old mechanical one out - worked a treat, no probs. since.
Jeremy.
Jeremy.
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Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Thanks Gene! My intake does not have the heat riser ports so I am good to go there. Electric FP does make sense. I hate to dump my mechanical Holley but if it fixes the issue then it will have to go. I did get the fittings already to hook up the return line. If this does not help then the electric pump is next.
Well I have been planing on switching to a dual Edelbrock AVS setup but was wanting to get some other things done first. Hmmm may come sooner than later.....
Lar's is the one that actually told me I need the return line with the Demon. He was saying that it is a common issue he had run into before with Holleys and Demon's. He told me to setup the return as close o the carb as possible preferably coming off of the fuel log. I have a T fitting that I am sealing the back outlet with JB weld and then drilling a 1\8" hole in it to act as an orfice. Run the return line off of that.
Thanks for all the comments guys.
I had this problem also.... drove me CRAZY
My fix was to dump the holly with its front/rear bowls and replace it with an Edelbrock with side bowls. fixed it permanatly 2 years now...
But just ordered a BG mighty demon last night and I am worried about the problem comming back.
My fix was to dump the holly with its front/rear bowls and replace it with an Edelbrock with side bowls. fixed it permanatly 2 years now...
But just ordered a BG mighty demon last night and I am worried about the problem comming back.
Thanks for all the comments guys.
Melting Slicks
Joined: May 2007
Posts: 2,415
Likes: 154
Well I was able to duplicate the problem. Took the Vette out Saturday and it ran awesome for 30minutes. Then I noticed it start stumbling under heavy throttle. Finally I could here the carb just sucking air when I tried to give it throttle. Started chugging and finally died. Front and rear bowls were empty. Let it sit for about 30-45 minutes and it fired right up and ran good again. Mechanical pump maintains a consistant 7psi before the trouble starts.
Looking more and more like it is a vapor lock issue. Running by the speed shop after work for some fittings to build a return line.
Wade
Looking more and more like it is a vapor lock issue. Running by the speed shop after work for some fittings to build a return line.
Wade
Race Director
Joined: May 2003
Posts: 10,956
Likes: 409
From: California
Heel & Toe
Joined: Nov 2008
Posts: 19
Likes: 0
I have a holley blue electric mounted in the rear and originally had a dead head regulator near the carb and it would vapor lock all the time.
Since then I have wrapped my headers and replaced the dead-head reg with a bypass return style reg and ran a 3/8" return back to the tank and have not vapor locked since.
Since then I have wrapped my headers and replaced the dead-head reg with a bypass return style reg and ran a 3/8" return back to the tank and have not vapor locked since.
Thread Starter
Safety Car
Joined: Oct 2000
Posts: 4,282
Likes: 172
From: Lake Wylie, South Carolina
Well I have the log built for the carb with the return line coming off the back T . I still need to JB weld the barb and drill a 1\8" orfice. I also connected a 5\8 rubber fuel line to the return port on top of the tank but still need to tuck it into the frame rail. I also did not get enough fuel line. I thought 10 ft would do it!!! So I have to get a brass connector and join the line together.
Heading to the beach tomorrow for a week so no more progress for a few days.
So I have to get a brass connector and join the line together.Heading to the beach tomorrow for a week so no more progress for a few days.
