bluestreak63

Since I've got the 63 back up and running, I've been doing shake down runs around the neighborhood. After putting it in the garage, I went to remove the neg battery cable and smelled more fuel than normal. I took the air filter off and noticed fuel dripping at about a second per drip. It was coming from the primary Venturi assembly choke side. But it didn't seem to be coming from the nozzle in the assembly, it was wet with fuel above the assembly if that makes sense, so it seemed to be dripping from there (pic below). It was also coming out of the air horn /body on that side and dripping onto intake.

The carb was rebuilt back in 2013 by me and hasn't really been run until recently. I used an echlin kit from Napa. We it was first started up a few weeks ago and has been run probably half a dozen times, I never noticed this leak before. I'm always checking things out before running, during running, and after running.

Could the rebuild have failed in that timeframe? Could that be a reason fuel would make its way into the crankcase?

I ran it up to about 180* and parked it off for about 30/40 minutes and then started it back up and pulled into the garage, so I can't imagine it was percolation.

Thoughts?

plaidside

When fuel drips from the boost venturi it normally is caused by:
High float level
Float rubbing on fuel bowl
Dirt under the needle and seat
Worn needle and seat
Fuel pressure too high
It could be fuel percolation but i would check the above items first.
Joe

MOXIE62

Carb to hot or fuel pressure.

Frankie the Fink

A "run around the neighborhood" shouldn't be enough to cause percolation....I'd check fuel pressure first; pressure will spike briefly sometimes when you cut the motor off.

A regular vacuum gauge is also a fuel pressure tester, simple to do. Anything over 5-1/2 or so is pushing it.

tbarb

If it's ethonal fuel my guess is that the float level along with some fuel percolation is pushing out of either the second idle air bleed or the main circuit air bleed. I think it's a good idea to set the float level down 1/16 from the factory setting just for this reason. The fuel is simply dripping and running out the side of the throttle shaft.

Believe it or not that's not uncommon, but I agree that you should check the fuel pump pressure.

bluestreak63

Thanks guys... I removed he carb and broke it down...went a lot quicker this time...

Gonna try another echlin kit and will check the fuel pressure before putting it back into service.

I think i remember seeing how to test it in the shop manual. Any tips or tricks outside of what the manual instructs? I take it it's a two person job, one to crank and the other to take the reading and making sure the fuel goes into a jar.

One thing I noticed is that the gasket between the intake and carb base stuck so bad to the base of the carb, I had to use a razor blade to scrap it off. When I originally rebuilt it back in 2013, the gasket that was on there was a gasket material with metal core. Below is the gasket that was on there so I used the same one that was in the kit when I rebuilt it.



But after doing some research it seems I should be using this gasket for the 327/340?

Frankie the Fink

Checking fuel pressure is easier with two people or one with a remote starter, I usually position the mason jar and gauge so I can see them from the driver's seat and crank from there... Be a bit careful, have a fire extinguisher handy and have that ignition coil disconnected and NO sparks...

bluestreak63

Bought a new napa echlin kit and rebuilt it. And this time used the carb/intake manifold gasket that I posted second above. Started her up, took a little bit, 3-4 cranks to fill the bowls, then goosed the accelerator and she fired up. I'd let her run for a couple min, shut down, check for leaks, start back up, let her run for 5-10 min, shut down, check for leaks. Finally letting her come up to normal op temp and no post leak like there was before. I did have to adjust the floats when I rebuilt this time. They were fine before. How do they get out of adjustment?

I did not check fuel pressure. I would assume if it was a pressure issue, it would be leaking again, correct?

One thing I noticed when I finally shut her down, with the air filter off, in the primary Venturi bowls area, there was a light fog, almost vapor like. Not sure how to describe it, but I blew it out with a breath and then it would slowly come back. Eventually it subsided. Is that normal and I just never noticed it before?

DansYellow66

I believe ethanol starts to vaporize as low as 140 degrees. I suspect the fog is just fuel vapor from the intake rising back through the carb.

If you replaced the float needle and seat, slight dimensional differences in those components will affect the float height.

SWCDuke

Ethanol boils at about 170F

bluestreak63

So the vapor would be normal then on a hot engine? Didn't hear any bubbling or percolation. Or see any other evidence of leaking.

PAmotorman

a lot of carb kits the gasket that goes between the needle seat and the carb body has too big a inside diameter and do not seal well unless you are very careful on assy. the original gaskets actually screw onto the needle seat threads not just slip over. I pressure test this seal with a leak detector before putting the top on the carb. on original carbs I saved the OEM gaskets and used them over again

bluestreak63

Yeah, the needle seat gasket on the napa echlin kits do have to be "screwed" on the needle seat. They won't just slide on, unless you forced them which would probably distort/damage them.

bluestreak63

Question.

Say you turn off the engine and it sits for a week or two. Should the fuel bowls still be full of fuel?

I have reason to believe fuel is getting into the crankcase, by my nose smelling oil from the dipstick and the fact that the oil level has ever so slightly increased since the last time I started it a couple weeks ago.

I was going to pull the carb again, but decided to fully engage the accelerator lever, which in turns pushes down the accelerator pump for that pump shot of fuel through the pump discharge nozzle. However, nothing, nada came out, after several full tugs on the accelerator lever.

If there is supposed to be fuel in the bowls, shouldn't a full tug on the accelerator level yield squirts of fuel from the nozzle discharge?

Frankie the Fink

Yes, you should see a healthy jet from both primary squirters

bluestreak63

So even after it's been sitting for a one, two, three, even longer, the bowls should still be full and full tugs on the accelerator level should result in healthy squirts from the pump discharge nozzle.

So if nothing came out, that would mean the fuel bowls emptied while it was sitting, which probably explains why I smell fuel in the oil, but how did it get out of the fuel bowls if it was sitting? The primary and secondary jets? Do jets go bad and leak?

Frankie the Fink

Both of my cars could sit for weeks and start right up, but I have heard that fuel evaporation is an issue, mostly in Holleys. At any rate, your bowls should fill up after 5 seconds or so of cranking provided your fuel pump is working. Then, blipping the throttle should absolutely give you strong squirts of fuel...

A smell of fuel in the oil is another indicator of a bad fuel pump. I would pressure/volume check it before going any farther, and, do a physical inspection. Enough fuel in your oil can wash down your cylinder walls of lubrication and make a simple problem MUCH worse.

J.Moore

Interesting topic that has been discussed. AFB's hard to start after sitting. Frankie is correct again on his tips.

Mine was too but found my choke not closing all the way. It would close to about 1/16 of an inch and be hard to start even just sitting 1 week or less. Reset choke for a full close but not "tight" and that helped alot.

My AFB will start right up with 1 press of the pedal to set the choke if car has sat for less than a week. If 2 weeks or more it takes cranking the engine a few seconds longer to get fuel to the bowls, then it starts.

I thought the same thing, fuel leaking into the intake and emptying the bowls but after talking with several AFB "experts" they all said the same thing and that it is usually todays ethanol based fuel that is evaporating unlike leaded fuel from the 60's and 70's.

And, I hope they are right about the fact that it is nearly impossible for fuel to leak from the bowls into the intake on the AFB design unless there are hairline cracks in the bottom of carb base.

Also, from your first post you showed the pic of fuel drips from the venturi after shutdown, mine did too so I pulled the top off and lowered the floats 1/32 and reset the drop and seems to have corrected that.

MOXIE62

I tried this and it worked. After engine is warm up, loosen the carbmounting nuts and the nut holding the filter down if you car has this. Cut a piece of poster board that will fit between the mounting carb studs. With the nuts loose slide the poster board in under the carb and let it sit for awhile. Remove board and see it shows fuel leakage. Poster board is thin enough to slid under but rigid enough to not bend.

bluestreak63

I rebuilt the carb twice and didn't notice any cracks even after dipping in carb cleaner.

So if not for any hairline cracks, chances that fuel is leaking from the carb fuels bowls, into the manifold, though any open valves, and down over the pistons past the piston rings, while the engine is dormant, is slim to none.

Yeah, as previously said, looks like pressure test is gonna be the next step. Anyone have recommendations on fuel pressure testers? Most of the Ones on Amazon go up to 100/140 on the gauge and from what I've read I'm looking for 5/5.5, which is like a sliver on these gauges. Any manufacturers that you have and they work? Some reviews I read said they read once and now the needle on the gauge is stuck.

If the fuel pump pressure tests out acceptable, the fuel pump could still be a problem and leak fuel into the oil return hole, right? Because if I'm not mistaken, it's the spring in the fuel pump that controls the pressure, so the pressure could be fine, but the diaphragm could be bad...even only after 3/4 years.