DCOE 45 on race car...pushing fuel out air horn.

[MNDATSUN]

I'm running triple weber 45 152's on my vintage race car, and the center carb has begun dumping raw fuel out the air horn at all RPM's on one throat only.

I've re-checked and cleaned: float level, needle and seat, idle jet, acc pump jet...so far nothing has helped. Other 2 carbs are happy.

 

So, I'm about ready to remove the carb for a teardown and thorough cleaning, if anyone has a suggestion on what the culprit might be I'd appreciate it.

 

These were purchased new from redline a year or so ago...have been generally reliable once I had the proper jet combo. I am running higher than "normal"

fuel pressure (4.5 lbs), but it hasn't been an issue, and is something this engine likes at WOT.

 

–Thanks

[cygnusx1]

Sticky intake valve.  Vacuum leak.  Just a couple of random thoughts,

[yetterben]

What are you pulling for vacuum on that carb. Is it just one barrel or both on that carb? I echo a valve issue if its just one barrel. Chances of a carb being fubar after 1.5 is slim unless you dont run filters.

Edited April 4, 2010 by yetterben

[MNDATSUN]

Great input guys. Typically I would suspect a valve, but this head just came back from a fresh rebuild by Paul Rushman, so I doubt that's it. I'm with you that it's more likely a vacuum leak, perhaps the soft mount is buggered somehow on that throat.

Thanks again.

[Drax240z]

Sounds like a float valve not closing to me. I'd double and triple check that first for all the trouble it is. Brass float or plastic float? Is the float itself filling up with fuel? (ie: hole in the float)

[BRAAP]

MNDATSUN,

Received your E-mail and replied. Let me know if you you got it.

 

As mentioned, verify the float is "floating", not sinking, and able to close the needle and seat sealing it 100% from fuel flow into the float bowl when full, also verify float level bowl fuel level is correct. The 4.5 PSI fuel pressure should not be an issue.

 

Hope we are able to get you back on the race track soon.

Edited April 5, 2010 by BRAAP
Added fuel pressure comment.

[Daeron]

Sorry for the troll post, but that is a *sweet* looking race car!!!!!!! Stem to Stern, Tires to paint, she is NICE.

[tube80z]

I'm running triple weber 45 152's on my vintage race car, and the center carb has begun dumping raw fuel out the air horn at all RPM's on one throat only.

I've re-checked and cleaned: float level, needle and seat, idle jet, acc pump jet...so far nothing has helped. Other 2 carbs are happy.

 

So, I'm about ready to remove the carb for a teardown and thorough cleaning, if anyone has a suggestion on what the culprit might be I'd appreciate it.

 

It's odd to hear fuel running out the throat. In my experience a high fuel level will cause problems with both barrels not just one. And generally you'll have fuel coming our the air vent hole too. If you run the car when it's stationary can you see this? Things I'd check are the acceleration pump circuit (make sure one isn't leaking after they squirt) and make sure the choke circuit is turned off (I seriously doubt this has anything to do with the problem). Check your gaskets as sometimes they do fail and cause leaks.

 

Also make sure the venturi is properly seated. A loose grub screw will allow the barrel to rotate but you'll generally have an issue with the car missing if that happens. You didn't mention anything in our post about that. Everything works fine except for the leak?

 

It also sounds like you have other things to look for too.

 

Cary