Leaky Fuel Valve Seat

[N2Cobras]

I unexpectedly got two last drives in this week in SW WI, two 50F+ days in December, life is good! When I stopped for the final gas fill before heading home to put it up for the winter, I smelt gas and checked the engine and there was a little gas pooled at the front/mid parts of the intake manifold on both sides. Getting it home and removing the air cleaner, the front fuel valve seat was wet at the top of the carb. Tightened the slotted screw snug to around 5 to 10 degrees rotation and the leakage stopped with the engine was running between 1K and 4k RPM. The engine is a Roush 351W/ 427SR with a Holley 0-80770 4 bbl w/ Electric Choke Vacuum Secondaries, built 6/5/2008. I understand the 0-80770 is a Roush special (of the 4150 vintage?). The engine was built in 2008 and has 15k miles on it.

After searching for this issue, I didn’t find anything on this screw loosening, so my questions are:
1) Does anyone have experience of this screw loosening on their Holley 4 bbl(s) and what did you do?
2) Should I just get new gaskets for the fuel valve screws and replace them proactively or wait to see if it fails/ loosens again?
3) When should the carb be rebuilt? It seems to be running well for the 2k miles I put on it the first year I’ve had the Cobra but I haven’t pulled the plugs yet to see how they are burning, it’s on my to do list at the first of the year. I have no documentation that a carb rebuild has been done on car.

TIA for your input/ advice.
Mike

[patrickt]

Originally Posted by N2Cobras

After searching for this issue, I didn’t find anything on this screw loosening, so my questions are:
1) Does anyone have experience of this screw loosening on their Holley 4 bbl(s) and what did you do?
2) Should I just get new gaskets for the fuel valve screws and replace them proactively or wait to see if it fails/ loosens again?
3) When should the carb be rebuilt? It seems to be running well for the 2k miles I put on it the first year I’ve had the Cobra but I haven’t pulled the plugs yet to see how they are burning, it’s on my to do list at the first of the year. I have no documentation that a carb rebuild has been done on car.

The screw on the needle/seat does not normally back off. And remember that the top of the bowl is not completely under gas either. I would pop the bowl off, change out the needle/seat on that bowl, replace the little o-ring, and if you still experience gas coming out suspect a crack in the fitting. If you set the float so that the gas is right below the sight hole it's likely gas will dribble out the boosters when hot, so you might have to set it a little lower. Those Holley instructions are 60 years old now.

[jhv48]

If the float screw was loose it will leak. If it’s not leaking after you tightened it, you’re done.

[N2Cobras]

Patrick & Jim,

I was trying to see if the fuel screw loosening is a known issue with these Holley carbs, it doesn't sound like it is or whoever has it just tighten it up and call it a day as Jim states.

Since I will probably not get another chance to verify if this is truly corrected with another drive (unless there is some more unseasonably warm days before next April - it snowed last night ), I'm going to go with my initial thoughts of consider it a solved issue, find out what the replacement seals part number is and where to get it in a hurry in case it happens again and always smell the engine after shutting the engine down to catch the leak as soon as possible.

Thanks for your prompt responses, I consider this a closed issue.

Mike

[patrickt]

The fact that your Holley made it 15 years and 15k miles without springing a leak is amazing.

[N2Cobras]

Patrick,

I've only had the Cobra for the last year so what happened the earlier 14 years is unknown as there were no repair shop receipts for any work that may have been carb related. That was part of the reason for my 3) question in the initial post: should I consider a rebuild as preventative maintenance or at least have a rebuild kit in hand for when it will be required?

Mike

[patrickt]

Got it. Don't be afraid of a Holley rebuild. Or popping the bowls off, or the metering blocks, or the idle screws, bowl screws, or accelerator pump, or anything else on a Holley. It's very, very easy and a rebuild kit is like $25 off Jegs. You can do it yourself, I promise you. And you can get your Holley dialed in perfectly as well. Tweaking your Holley to get it "just right" is actually a labor of love. It is not hard and it is not black magic either.

[N2Cobras]

Patrick,

I know I can do the rebuild, I've done it a dozen times in the early '70s, been out of practice since then, as you say, Holley hasn't changed in 60 years.

Tuning is an art/ science as you are well aware, troubleshooting is seldom easy until you figure the solution and add it to your solution library.

Mike

[Gaz64]

I've adjusted float levels hundreds of times on my Holleys, Demons etc, and never had a screw come loose.
A good fitting large flat blade screwdriver hand tight is sufficient.

[patrickt]

On the Holley I'm using now on my FE, it has sprung leaks in a couple of places and the year that the metering block was made was a reportedly "bad year" for that metal that Holley used. I have pics on this forum showing how the ethanol was literally eating the metering block up and causing flaky white stuff which of course clogged up the carb just enough to make the car run like crap literally out of the blue. I read in other forums that I just happened to have the bad luck to have that metering block made during a bad window of time. The replacement metering block that I put in has not had that problem. Another metering block somehow developed a really hard to see hair line crack, again out of the blue, that caused a hard to figure out leak even with the fluorescent dye. Then, one of the little black bowl screw gaskets that I used during a rebuild decided to cause a leak every January or February when the garage got chilly, but never during the summer. After the third straight year of having a January leak when the car was just sitting in the garage I looked at the "new" bowl screw gasket under a magnifying glass and found the flaw. It hasn't leaked since. I still go down to the garage every week in the winter and pop the hood to just see if she's decided to spring a leak out of the blue. The beauty of a Holley equipped FE is that there is always something leaking or on the verge of leaking.

[patrickt]

Here, I found the pic of my metering block. It never hurts to just pop your bowls off from time to time and inspect your Holley.

[sunman]

With time I’ve had the bowl/metering block gaskets swell up blocking the accelerator shot
They swell inward collapsing the hole
Good thing to check