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2 hours ago, Stanglover said:

Sorry John, I disagree. There is a need to remove that fitting to replace the sintered filter inside. However, that is assuming the QF is the same as Holley it that regard.

They don’t have those.

John - 72 Q Code

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18 minutes ago, jpaz said:

They don’t have those.

 Really, I did not know that having not owned a QF carb....... yet! Thanks for the insight John.

Still if ever one does need to change inlet fuel lines, they are still hard to get a wrench on unless of course, there is a "special" type I'm not aware of. (if there is I want one!)

Geoff.

 I learn something new every day!

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Just information for those with fuel lines plumbed for 6AN fittings, AED Performance in Richmond VA. carries a 7/8 x 20 x 6AN bowl inlet fitting that has a 11/16 hex to tighten. Will not fit the 'Ultra" series bowls (they use an 8AN thread). You will need to call them as it does not appear in the catalog that I can see. Chuck

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  • 3 weeks later...
Posted (edited)

So I had more issues yesterday. Car died on the road again after driving around for awhile. And after opening the hood to let it cool down it started. This happened a couple times and I finally made it home.

So once back home I started investigating what was going on. I noticed the fuel moving around some inside the fuel bowls. I have clear glass sights and I can see the floats and fuel level. Then I noticed the gas actually percolating in the bowls. Well, dummy me made a new steel fuel line and it must be to close to the front of the block. That’s gotta be what has been giving me issues. I am going to redo it and see if that fixes it. I tried to run it like the stock one, but it must be getting to hot. 

Edited by jpaz
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John - 72 Q Code

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3 hours ago, Big Red Mach 1 said:

You running a spacer under the carb? If so, how tall? 

No spacer. I’ve never had any problems with vapor lock until this summer. I changed the fuel pump cause it was leaking. I then also made a new steel fuel line. I had fuel injection hose going from the pump the carb, never had a problem. But when I put my new pump on I figured I might as well make a new steel fuel line like it should be. I just got done rerouting it, so hopefully that will do it. If not then I may have to put a spacer on, but not sure about clearance. I have a Blue Thunder intake and it kinda tall. Might have enough for a 1/2 phenolic spacer should need be.

John - 72 Q Code

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When I made up my new pump to carb fuel line, I made sure I had a min. 1" clearance from the block. With stock intake, no ram air, there is room for a 1" fiber or phenolic spacer. I did have percolation issues before the exhaust cross over were blocked, but I don't think the B/ thunder has those, do they?

Pics of my fuel line fix if needed. 

Geoff.

 I learn something new every day!

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Posted (edited)

I have a Blue Thunder. It does have the crossover. I blocked mine with inspiration from Geoff. With ram air, you may or may not get a thin spacer in there unfortunately. At least without modifying the stock plenum. I could not get my Ram Air back in until I went to aftermarket engine mounts and 73 frame mounts which lowered the engine roughly 5/8". Summit sells a 1/4" phenolic spacer. I just bought one.

https://www.summitracing.com/parts/SUM-G1398

Some spacer is better than no spacer.  You may want to pick one up and see if you can fit it. 

Edited by Big Red Mach 1

Chris -  Born in '73 - Drive a '73 / Former U.S. Army 63B10-H8 / 1st Infantry Division - The Big Red One

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Posted (edited)

Vapor lock occurs between the tank and the fuel pump. Any vapor in the line between the pump and carburetor will be quickly purged when the float opens the needle valve. The fuel pump creates a negative pressure in the line between the tank and pump, which reduces the boiling point of the gasoline, and fuel pumps aren't very effective at pumping vapor Between the fuel pump and carburetor it is under positive pressure.

Look for places where the fuel line runs parallel and close to the exhaust, and relocate or insulate it. Setting in traffic allows a lot of heat to accumulate under the hood and under the car, exacerbating the problem.

An electric fuel pump located at, or in, the tank will eliminate vapor lock.

Edited by Don C
Added info
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“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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5 hours ago, Don C said:

Vapor lock occurs between the tank and the fuel pump. Any vapor in the line between the pump and carburetor will be quickly purged when the float opens the needle valve. The fuel pump creates a negative pressure in the line between the tank and pump, which reduces the boiling point of the gasoline, and fuel pumps aren't very effective at pumping vapor Between the fuel pump and carburetor it is under positive pressure.

Look for places where the fuel line runs parallel and close to the exhaust, and relocate or insulate it. Setting in traffic allows a lot of heat to accumulate under the hood and under the car, exacerbating the problem.

An electric fuel pump located at, or in, the tank will eliminate vapor lock.

I have the fuel lines running in the factory positions. The only thing I changed was the fuel pump and line from the pump to the carb, nothing else. I have not had any problems like this till now. I may think about the electric fuel pump, sounds like a good idea.

John - 72 Q Code

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6 hours ago, Big Red Mach 1 said:

I have a Blue Thunder. It does have the crossover. I blocked mine with inspiration from Geoff. With ram air, you may or may not get a thin spacer in there unfortunately. At least without modifying the stock plenum. I could not get my Ram Air back in until I went to aftermarket engine mounts and 73 frame mounts which lowered the engine roughly 5/8". Summit sells a 1/4" phenolic spacer. I just bought one.

https://www.summitracing.com/parts/SUM-G1398

Some spacer is better than no spacer.  You may want to pick one up and see if you can fit it. 

I don’t have ram air and I am going to see if I do have enough room for a spacer. I thought I had one around here somewhere but can’t find it. I’ll just go to my local parts house and get one. It sure can’t hurt. I’m actually surprised I have never had a problem with this before. Combination of it being 90 degrees and switching to a 192 thermostat must also be a factor. 

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John - 72 Q Code

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7 hours ago, Stanglover said:

When I made up my new pump to carb fuel line, I made sure I had a min. 1" clearance from the block. With stock intake, no ram air, there is room for a 1" fiber or phenolic spacer. I did have percolation issues before the exhaust cross over were blocked, but I don't think the B/ thunder has those, do they?

Pics of my fuel line fix if needed. 

Mine doesn’t have the crossover. I am pretty sure that most of my issues are because I had the new steel line too close to the engine. I have moved it away now, so hopefully it will be ok. I had a small fuel leak after I started it up this morning, so I sell gotta fix that. Got the part to do it but I won’t get to drive it till tomorrow. 
I was looking for the pics of your fuel line but I couldn’t find them. I actually tried to go by what you did, but I did put it way to close to the front of the block.

John - 72 Q Code

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11 hours ago, jpaz said:

Mine doesn’t have the crossover. I am pretty sure that most of my issues are because I had the new steel line too close to the engine. I have moved it away now, so hopefully it will be ok. I had a small fuel leak after I started it up this morning, so I sell gotta fix that. Got the part to do it but I won’t get to drive it till tomorrow. 
I was looking for the pics of your fuel line but I couldn’t find them. I actually tried to go by what you did, but I did put it way to close to the front of the block.

Sounds like you may have it fixed by now, but here are my pics just in case they still may help, It's frustrating as hell I know, been there-done that! I too am experiencing a minor fuel problem. It suddenly started to loose rpm's and stall until it is fully warmed up. It has done this for the last few time I've driven it, just haven't had time to find out why, wifey got me doing yard work! 

fuel line 2.JPG

fule line 4.JPG

fuel line 3.JPG

IMG_0987.JPG

Geoff.

 I learn something new every day!

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1 minute ago, Stanglover said:

Sounds like you may have it fixed by now, but here are my pics just in case they still may help, It's frustrating as hell I know, been there-done that! I too am experiencing a minor fuel problem. It suddenly started to loose rpm's and stall until it is fully warmed up. It has done this for the last few time I've driven it, just haven't had time to find out why, wifey got me doing yard work! 

fuel line 2.JPG

fule line 4.JPG

fuel line 3.JPG

IMG_0987.JPG

Thanks so much Geoff! I do have these pics somewhere. But anyway I did run my line very similar to what you did. I do have a/c, so it was pretty difficult to get the bends right. Now after I moved the line out and away from the front of the block, I hopefully won’t have any more problems. I will try to take a few pics, but with the a/c compressor there it’s hard to see. Anyway thanks again!

John - 72 Q Code

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2 hours ago, jpaz said:

Thanks so much Geoff! I do have these pics somewhere. But anyway I did run my line very similar to what you did. I do have a/c, so it was pretty difficult to get the bends right. Now after I moved the line out and away from the front of the block, I hopefully won’t have any more problems. I will try to take a few pics, but with the a/c compressor there it’s hard to see. Anyway thanks again!

 John, I know what you mean. It was hard enough with just the PS pump in the way. It still took me 3 tries to get what I wanted and there was till room for improvement. I too was wondering about adding insulation on the lower portion where the line goes under the pump, but had no problem, so not needed.

Geoff.

 I learn something new every day!

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