Guys, must carb needles and seats be changed periodically?

Last race weekend (the first of the season) I started to have problems with gas dribbling out of the secondary boosters on my ProForm 750 carb.
I started to run this carb that I bought slightly used a year ago.

I checked the needle and seat for debris and sprayed it with carb cleaner.
I poked a wire down into the hole where the needle and seat was and get some pushback from the float, so I ass/u/me that the float is okay.

The air bleeds appear to be open and unobstructed.
I've turned the needle and seat all the way down and still get fuel running from the boosters at idle.
I have not yet purchased a new needle and seat to try, but may buy one for the primary side as well.
Remarks or advice anyone? I did a search in the archives here.
Thanks!

What's periodically?

Bottomline line is rarely BUT the more serious racer you become, the more serious you get about the maintenance of your car.

25 years ago, I never changed the needle and seat and never had a problem. Now I strip my carbs at the end of every season and replace everything.

That said, I'd bet the root cause of your boosters dribbling is due to the floats and/or fuel pressure being too high and not the N/S.

This message has been edited. Last edited by: 1320racer,

Most needle and seat issues are caused by the o ring and not the needle/seat deal. The o ring can shrink and let fuel by to cause high or flooding float levels. Usually happens when the carb sits for a while. I would think the type of fuel would also impact this too.

To the OP, check the floats, make sure there's no trash stuck in the N&S, check the o-rings, verify the fuel pressure.

----------------------------------------
Ryan,

Ed's post makes perfect sense (to me anyway.)

25 years ago he didn't replace them and never had a problem. (like most of us)

Now, he replaces them yearly as part of his normal maintenance. (because he wants to)

Then he suggests other things to look at as the culprit. (float and fuel pressure)

Seems like a logical and sincere response to me.
--------------------------------------

Tom, haters gonna hate.

Thank you all for the thoughtful responses, guys.

I will remove the fuel bowl to inspect the float for leaks. My liquid-filled fuel pressure gauge mounted on the fuel log reads about 5.5 PSI, from an plain, Edelbrock fuel pump. I don't use a pressure regulator with that pump.

The local parts store had one, new Holley 6-504 .110 needle and seat on hand, so I picked that up along with a Holley 34-7 kit, with a spare adjusting nut, washers, lock screw and an O-ring. I'm kindof a spare parts slut, and my pit buddies occasionally appreciate that. ;^)

By golly, the O-ring on my old needle and seat looks rather flat, compared to the O-ring on the new, spare needle and seat. I can see where that might be a problem........

I'll order in a few new O-rings, too. On Ebay, BPT Performance Carbs is advertising a pack of 100 for $20. Any caveats there, I wonder?

A poster on another board recommends that one put a little brake fluid on the O-ring to prevent tearing the thing when you install it.
True story? He recommended it too for the O-rings on the transfer tube used on some Holley carbs.

Thanks again!
Troy

never use a liquid filled fuel pressure gauge.

quote:

Originally posted by Bad Nusz:

A poster on another board recommends that one put a little brake fluid on the O-ring to prevent tearing the thing when you install it.
True story? He recommended it too for the O-rings on the transfer tube used on some Holley carbs.
Troy

Troy I'm no expert but brake fluid? Why would anyone use a hydraulic fluid over a lubricant? Just about any lubricant would be better in my opinion because that is what it is supposed to do. I'm not saying it won't work because you are only stuffing an o-ring in a hole but how some people come up with stuff like that I don't know.

Curtis

I just use a little squirt of WD-40 when I install them.

If you don't have any lubricant on hand, just spit on it before you stick it in.

quote:

Why would anyone use a hydraulic fluid over a lubricant?

While lubing the o-ring is a minor task I suppose there is a right way for everything. Since they use petroleum jelly for such things when building a transmission, to avoid contamination, it would seem appropriate in this instance. FWIW

quote:

Originally posted by Canted Valve:
Since they use petroleum jelly for such things when building a transmission, to avoid contamination, it would seem appropriate in this instance. FWIW

Sounds reasonable to me.


I also think Tom above must be single.

Curtis

Thanks, Ed and everyone. May I assume the liquid-filled gauges are inaccurate?

Yeah, I thought that using brake fluid didn't sound right. Man, I hate that stuff on my fingers....

Invest in a quality N&S like from BLP. They also sell replacement o-rings for them, they can dry out over time. And I use a NON-synthetic trans gel assembly lube for carbs, like Vasoline, gas will melt and wash it away with no issues.

in 25 years racing and on multiple carbs I never once lubed the o ring on the N/S and never had one leak/fail including the carbs on both my Firebird and dragster that I just rebuilt.

Yeah but I'm pretty sure your hands always have lots of lube on them already.....

^^^Dave Kemblowski 65, formally of The Balance Shop in Reseda Ca

had a reputation for doing shyt work and ripping people off.

^^^^^^^^EDWARD & MONIQUE ******^^^^^^^^
23 BORDEAUX TERR
WEST MILFORD NJ, 07480

Reputation for being an idiot and all around embarrassment to wife and kids.
Most often seen hanging around buy back window on weekends.
Work place phone number available if needed.
Also known to wear size 32 training bra.

Dave Kemblowski 65, formally of The Balance Shop in Reseda Ca

had a reputation for doing shyt work and ripping people off.

home address, phone number and social security number as well family names and addresses available upon request as well his blood type which he'll need donors.

BWAHAHAHAHAHA


Bring it b!tch...and bring it all !! I WILL...

looking forward to it biotch!