C2: L36 carb gasket leak

[Dan Pepper]

After trying to locate an exhaust leak sound for a few weeks, I think I finally found it: the exhaust cross-over underneith the carb looks like it's blowing-by the carb/intake gasket/metal spacer. I can feel the hot gasses squirting out under the carb, and there are carbon heat marks from the gasses marking each side of the intake.

The carb has been thouroughly rebuilt - so I believe the mating surface isn't warped, and I tightend the nuts tight but not too torqued down to make sure the surface pressure was even.

Question: should I go with a thicker gasket? Maybe layer two together? Also, does the thin metal carb spacer go on top or bottom of the gasket? Think it's on the bottom right now...

Thanks,
Dan

[Joe L.]

Re: C2: L36 carb gasket leak

Dan-----

The stainless steel baffle is supposed to go on top of the carb gasket. Your exhaust leak might originate from the carb pre-heat groove. I'd recommend plugging the holes in the end of the pre-heat groove, thereby eliminating it.

[G B.]

Don't double gasket

When you have the carb off to correct the gasket positions, run a good flat file over the manifold face to see if it is perfectly flat. For more access, you can remove the carb studs by double-nutting them. I would try the file on the carb baseplate bottom too.

If you put an extra thick gasket layer under the carb, you will risk cracking off a corner of the carb baseplate when you tighten it down. This is easier to do than you think.

[Dan Pepper]

Re: C2: L36 carb gasket leak

Thanks for the advice, Gentlemen. I'll make sure the surfaces are flat to start with. If this doesn't work, Joe, how do you plug the holes in the pre-heat groove? What kind of material is used to do this?

[Joe L.]

Re: C2: L36 carb gasket leak

Dan-----

With the manifold mounted on the engine, probably the best way to do it is with drive-in type cup plugs of the appropriate size (these are like small block front oil gallery plugs or "mini"-freeze plugs). Most auto supply stores will have them in the orange Dorman Products boxes.

With the manifold off the engine, I recommend drilling and tapping for 1/4" NPT. Then, install allen head pipe plugs with sealer.

[Joe L.]

Addendum

By the way, the plugs are installed in the holes at either end of the carb pre-heat groove on the front of the intake manifold carburetor flange. These holes go through to the manifold heat crossover passage. POlugging the holes does not interfere with exhaust gas flow through the cross-over passage and, consequently, choke operation is not affected by this mod. Just the carb pre-heat groove is disabled.