johngandersonjr

Wondering if some can tell me if these plugs can be repaired or if I need to get new fuel bowls? they are leaking on all 4 plugs. 2 on top and 2 on the side.

GearheadJoe

I am aware of three possible options for solving this problem:

1) Take the bowls off and re-swage the perimeter around the plug. Some people report success with this method.

2) Cover the entire plug surface and the perimeter joint with epoxy. Some carb rebuilders do this routinely. It works but it definitely has a non-stock appearance.

3) Buy some brand new reproduction float bowls. These are available for the 3310 carb.

I went with option 3 and have had no leaks, but each option is a possible solution.

johngandersonjr

Do you know where I can get the float bowls?? is the 3310 the same as the 3810? I saw some on ebay for $150, but wondering if I can get them cheaper elsewhere?

LouieM

Over the years with various 67s I've never been able to make those plugs not leak. My fix is to replace the 67 float bowls with units from a 66 Vette, Holley 3367, which then have externally adjustable needles/seats and thus allow you to tune your float level without taking the float bowls off.

johngandersonjr

I was thinking of that, but found the right carb at carlisle this year and wanted to be correct.

GearheadJoe

I'm pretty sure that Holley is reproducing those float bowls, so maybe you could check with them.

Here's what I know. Several years ago I found a rebuilt, correct 3310 (?) carb for my '67 300 HP on ebay. The rebuilder had put epoxy on the plugs to seal them. I emailed him to see if he had any alternate bowls that did not have the epoxy. He responded that Holley had just started reproducing the bowls and he could substitute those for a small up-charge. I've been running that carb for several years with no leaks.

I'm not sure how a 3810 compares to a 3310, but from your photos the bowls look identical to what I think is a 3310 on my '67 SB. Maybe I'm remembering the number incorrectly.

Another reason why I think Holley has the bowls available is that they sell a complete 3310(?) carb for vintage cars. I've seen photos of that carb and the bowls look identical to the bowls on my carb.

SI67

Joe,

As you conjecture, you are remembering the number incorrectly. The 3310 is a manual choke 750 CFM carb. The correct carb for a non-A.I.R. '67 small-block Corvette is the 3810.

GearheadJoe

My apologies. This is what happens when I respond when I'm away from home and have to speak from memory.

For the OP, the bottom line is that he can get brand new reproduction float bowls from Holley (or even a complete 3810 carb). The reproduction bowls on my carb appear to be identical to the originals, and so far, the new ones don't leak.

And, if the OP does not mind experimenting a bit, the two "repair" methods I mentioned have worked for at least some people.

johngandersonjr

I actually just ordered new bowls from Chicago Corvette. I contacted Holley and they said they are not reproducing those bowls anymore.

He gave me the part numbers, which are:

34R 5978A - Primary
34R 5972A - Secondary

I was able to find the secondary for sale but not the primary from anyone other than Chicago Corvette, so I just got both from them.

Jackfit

I agree

jack

PAmotorman

there are "O" ring seals under those plugs and putting the bowls in carb cleaner eats up the "O" rings. I have sealed them using clear 'fuel proof' model airplane "dope" after a good cleaning of the area.

lars

As stated above, the plugs have O-Ring seals on them, so the seal is at the O-Ring and not at the swaged area - the swage only prevents the plugs from popping out. If the plugs are leaking, it's because the O-Rings have shriveled up, and fixing a leak by smearing epoxy on the outside of the plugs is a bad way to go - it will leak again, and when it does, it will spray gasoline under pressure all over the top of your hot engine...

Also noted above is that Holley is no longer making these early float bowls. Chicago Vette has a few NOS ones remaining, but they're not going to last long.

The bowls can be reliably repaired, although it won't be NCRS appearing. I repair them regularly as follows:

Using a high speed sanding disc, I carefully sand off the swaged retaining lip around the plugs. Once the lip is removed, I drill a hole in the plug so I can hook it, and I pull the plugs out.

The bowl hole for the plug is just slightly larger than the tap drill size for a 1/4" pipe plug. Without drilling the plug holes, I run 1/4" pipe tap into the holes and do a "shallow" tap job.

I then use 1/4" socket head ("allen head") pipe plugs. These plugs are typically long enough that if you were to installed them flush with the carb bowl surface, the end of the plug would interfere with fuel flow inside the bowl passage. So I sand off the end of the plugs with my high speed sander to shorten the plugs, being careful to leave the plugs just long enough to leave about .060 - .080 wall thickness at the bottom of the hex recess. I test fit the plugs to assure that they will tighten up nicely in the tapped holes with the top of the plugs just below the bowl casting surface. Re-tap the holes as needed to achieve this.

I then coat the threads of the plugs with JBWeld and screw the plugs into the threaded bowl holes. The plugs are screwed in deep enough to get them slightly below the casting surface, but not deep enough to impede fuel flow inside.

Once done, the entire plug is given a coating of JBWeld, which flows out smoothly and evenly in the slight recess from the plugs being installed just below the casting surface. This produces a smooth, perfectly round, grey circle which almost looks like the stock plugs. Since the pipe threads produce a positive seal with the JBWeld coating on the threads, this repair is permanent and reliable.

Lars

johngandersonjr

I replaced the fuel bowls with 2 new ones from Chicago Corvette. after a couple of rides, I now have fuel coming out of the rear vent. I am assuming that the float is bad or the needle/seat are dirty.

does anyone have a recommendation on how to set the fuel bowls? should they be facing slightly downward or parallel to the top of the bowl?

Thanks!

Desert Nomad

Thanks Lars, I know I'm going to looking at doing this soon. Sounds like an excellent fix. I'll put this in my file along with the "Clutch fix info" that you told us about a while back. That McLeod clutch worked out great for me.

tbarb

Usually the secondary float level is set lower than the primary because of acceleration and decelleration effecting the spill distance. They should appear slightly down, it's been reported in the past where these side hung floats can bind slightly at times.

You need to be sure the float is not heavy and does not bind then set the level.

FWIW, sometimes the gasket sandwich for the secondary metering plate can leak and the result is fuel entry from the transfer slots and it runs out the throttle shaft onto the manifold.

lars

Glad to hear the info is coming in handy for some of you! Good job on the work!

Lars