carb gasket sealant?

[Marty Levenson]

Dear Don,

I'm about to reassmble my carb and am wondering what type of sealant you prefer to use with the main gasket?

thanks yet again,
Marty (Vancouver)

[Don Moyer]

Marty,

We use no sealer on the main bowl gasket, or on the flange gasket.

Don

[Marty Levenson]

carb lower/upper fit?

Dear Don,

Thanks - I always worried about sealant getting into the delicate carb...I like the idea of not using any.
However, my upper and lowers carb faces (4 screw aluminum carb) show a good gap (almost 1/16") at the bow end...above the choke. I have sanded them a little on sandpaper on glass, so they are flat, but the lower seems slightly slanted. I'm wondering if I should:

1 - keep sanding, trying to correct that slant. Or find a different way to seal that end better. Holding it to a bright light, with the gasket in place, I do see light at the bow end.
2 - Would it be crazy to drill and tap a fifth screw there? I notice in your book that later carbs have that fifth screw. When I press hard there, the light disappears.
3 - Or...use sealant just at the bow end?

Any ideas greatly appreciated,
Marty (Vancouver)

[Don Moyer]

Marty,

If you can close off the light by pressing the two housings together in the front of your carburetor, my guess is that you don't have far to go, so my first choice would be to continue the sanding process until you get rid of the separation. If perfection continues to elude you, a small dab of Permatex wouldn't be a bad fallback technique.

The importance of achieving a good seal in this area relates to maintaining a good distribution of inlet pressure within the float chamber and the idle system of the carburetor. You will notice passageways in both the upper and lower housings which connect with a small opening in the upper part of the intake throat of the carburetor, just above the area of the choke valve. These passageways then connect to the space on top of the fuel level within the float chamber, as well as to the small chamber in the upper housing which provides air to the idle system. This inlet pressure varies with engine RPM, and by modifying the pressure within the float chamber, it ends up fine tuning the fuel mixture that eventually gets drawn up through the main discharge nozzle (above approximately 1200 RPM) and through the idle system at lower RPM.

In summary, inlet pressure tends to be somewhat lower than atmospheric pressure, which means that inlet pressure above the fuel level in the float chamber has a slight attenuating effect on the amount of fuel the venturi would otherwise be able to draw up through the main discharge nozzle at any particular RPM. Absent this attenuating effect, slightly more fuel mixture will be drawn up through the discharge nozzle, which tends toward a slightly richer mixture. While we have never been able to accurately define the
effect(s) of various sizes of leaks within the inlet pressure chamber by actual "apples to apples" testing, my own instinct is that larger leaks probably account for the tendency of many of the early to mid-seventies carburetors to run a bit on the rich side (creating the typical black sooty look on plugs).

Best regards,

Don Moyer

[Walter Pearson]

Carb housing separation and clamping

I see there is a bracket on the carb photo shown in the parts section that appears to function as a clamp to draw the housings together. Is that bracket something I can order? If not, could I get drawings to make one? Years ago, I abraded the housings but did not achieve good fit, so applied a piece of butyl tape over the seam after assembly. It probably did seal any leakage, if any, but the whole area does get gummy over time and I'd like to improve things.

Walter Pearson
'76 Late Model

[ndutton]

Walter,
I've looked at the picture in the catalog and can't figure out what bracket you're talking about.

Sounds like you're a candidate for a new carb sooner or later. Why not sooner and be done with it?

[Dave Neptune]

This works for me.

Once the carb is assembled and "clean" I take a rag and clean off the gap area with acetone. Then I use "RTV Hi-temp" and put a bead around the outside over the gap. It seals well and I have had no trouble with the RTV breaking down. I have had to cut it away after three seasons and it's integrity was still sound.

Dave Neptune

[dvd]

Walter

I recently replaced my old carb with a new Moyer carb. It was quick and easy to install and now its perfect. Cost: $240.00 but well worth it. I also added a polishing filter between the fuel pump and new carb. Cost for the filter kit with all hoses and everything you could need: additional $26.00. Once again well worth it.

DVD

[Walter Pearson]

Thanks for replies. I'll probably clean it off and use Permatex or RTV next time. The photo showing the bracket is here, along with Moyer's explanation:

http://www.moyermarine.com//forums/showthread.php?t=2759