Holley 750 puking fuel

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Kern Dog

Build your car to handle.
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Yeah I know… you read the headline and think Hey….just adjust the float level!
I have. It isn’t so simple.
I’m tinkering with this car…

F4201ED9-A3BE-4EEE-97DA-7302D98D5761.jpeg


It is a fairly mild 360 with a MP 280-474 cam, Weiand intake, cast iron manifolds and a Holley 600.
The 600 is fine. I have a Holley 750 I got from a friend that I wanted to test so I’m using the Dart as the mule.
82BC6EAF-9ECD-4B83-AA57-DC82ADE0ECA4.jpeg


First off, the car started and ran great with the 750….then it started to stumble and die. I thought I was out of gas. No, there was fuel dripping through the top of the secondary boosters. Yeah, the float level was too high. I replaced the needle and seat and started over. I had the float set to the middle of travel. Yeah, I’m aware that there are specific measures to follow for float height but I did it the bonehead way.
Still, the flooding persisted.
I have a gauge in the fuel line but it shakes like a triggered epileptic dude.

61313FB2-4609-4A7C-9A19-E3A9ECB17423.jpeg

It sweeps around between 5 and 11 PSI. I had no overflowing/flooding issues with the 600.
I pulled the fuel bowl to get a look.

03B59FB3-89C7-4E48-A255-FB89ED15AE02.jpeg


4E8E8B66-F0A7-4355-88AC-283D586D2375.jpeg


It is clean inside. No obvious problems. I tried another bowl with a new needle and seat in it.
Same problem. The float seems fine.
I have the float set all the way down…

0C874D3E-91BC-4459-A054-243DFC2350C8.jpeg


When the needle and seat housing is flush with the bowl, you can’t get the float any lower. Now it runs great for longer before it eventually does the same thing and overflows. While running, I’ve pulled the sight screw out of the side to drain off excess gas and it just pours and pours out. The overflowing stops up top and the engine stays running but why is it still flowing when the float is at the lowest point? The needle isn’t stuck, it moves freely.

4BEE08F6-4A6C-4843-8EF8-C8A896ABF082.jpeg


Is there supposed to be an O-ring in this recess?

80E90B09-AFDA-4CE3-879F-71C3DBA34DFB.jpeg


Until it floods over, it idles great and has excellent throttle response.
 
I looked through the stash.
Years ago, I bought out the car stuff owned by an old timer. In with it all, he had some Holley parts. Here are some needle valves I just saw.

3126C7B4-D708-4D24-86D8-84ED9153D5BF.jpeg


Those have seals/o-rings.

F1B33413-AECE-4BD9-B5C7-B75B04A08D77.jpeg


New ones still in in the plastic don’t.

FE6709BB-9250-42CE-8B9A-B1CD38165028.jpeg


I found these.

05EE1456-5ACE-4331-AE7D-C0172533C9E0.jpeg


Remember 35 mm film?

EA80BD79-9E34-4584-B995-915292FFB9BE.jpeg


Can it be this simple?

79E3CCE5-9C30-4822-A335-76655EDAB1C1.jpeg
 
I just found the first one that I took out.

29977388-A0D7-48A5-87BD-79F33BD53DF0.jpeg


I see my mistake. This seal is flush with the body of the cylinder. It probably wasn’t sealing. Then I put in one with NO seal/o-ring, making it worse.
I’m going in for the night. I’ll get back to this tomorrow.
Thanks!
 
You are missing O ring from what I can see.
I like to put some lubricant on it before I install it, silicone spray/ Vaseline to help it install easily.
 
Yeah I know… you read the headline and think Hey….just adjust the float level!
I have. It isn’t so simple.
I’m tinkering with this car…

View attachment 1716305809

It is a fairly mild 360 with a MP 280-474 cam, Weiand intake, cast iron manifolds and a Holley 600.
The 600 is fine. I have a Holley 750 I got from a friend that I wanted to test so I’m using the Dart as the mule.
View attachment 1716305825

First off, the car started and ran great with the 750….then it started to stumble and die. I thought I was out of gas. No, there was fuel dripping through the top of the secondary boosters. Yeah, the float level was too high. I replaced the needle and seat and started over. I had the float set to the middle of travel. Yeah, I’m aware that there are specific measures to follow for float height but I did it the bonehead way.
Still, the flooding persisted.
I have a gauge in the fuel line but it shakes like a triggered epileptic dude.

View attachment 1716305826
It sweeps around between 5 and 11 PSI. I had no overflowing/flooding issues with the 600.
I pulled the fuel bowl to get a look.

View attachment 1716305820

View attachment 1716305822

It is clean inside. No obvious problems. I tried another bowl with a new needle and seat in it.
Same problem. The float seems fine.
I have the float set all the way down…

View attachment 1716305824

When the needle and seat housing is flush with the bowl, you can’t get the float any lower. Now it runs great for longer before it eventually does the same thing and overflows. While running, I’ve pulled the sight screw out of the side to drain off excess gas and it just pours and pours out. The overflowing stops up top and the engine stays running but why is it still flowing when the float is at the lowest point? The needle isn’t stuck, it moves freely.

View attachment 1716305835

Is there supposed to be an O-ring in this recess?

View attachment 1716305836

Until it floods over, it idles great and has excellent throttle response.
Yes. It's missing an o-ring there.
 
Uhhh….

48EBC91C-8C86-4811-B289-EDBDF9A18B26.jpeg


It took about a minute to pull the seat out and it HAS the o-ring.
Don’t you hate when you think you found the problem but you didn’t?
 
Another kit had a needle and seat with the seal in it.

37A38828-CD0C-4BBA-8733-2A8C84604446.jpeg


This one has a wider foot to it.

04E561FE-7833-47F5-B83B-2D16EC8978F9.jpeg

Here goes….
 
If you're seeing 11 PSI, that's likely the culprit. These fuel pumps sit up and the diaphragms get hard, giving the pump spring more resistance and raising the fuel pressure.
 
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