8N won't start - ran perfectly an hour before...

I thought I had everything covered on my 1952 8N springtime tune-up - Starter overhauled, new head gasket, new wiring harness, new plugs, points & condenser. Carb cleaned and rebuilt with basic gasket set. Fresh gas. Started her up, and she ran GREAT with plenty of power - I was able to run the brush hog for about 3 hours, absolutely no problems. "Oh, you elite tractor mechanic, you" I was thinking to myself.

Then I went in for dinner.

I come out to start it up - the starter cranks but the engine won't start. It will a-l-m-o-s-t start - enough to release the Bendix on the starter, but it won't start or idle. I got spark. I opened the drain on the carb and yup, there is gas flow. If I spray a little starting fluid into the carb it'll catch and run for a second.

Any idea's as to what's going on? I don't "see" any cranks in the manifold, and the tractor was running perfectly when I shut it down. I let it cool down for a few hours, but it still refuses to start.

IN FACT, the plugs are 100% dry and clean. It looks like the carb isn't doing its thing.

But I just had the carb apart earlier in the day, put the new gasket set in, and ran it for 3-4 hours no problem.

Is there something specific in the carb I need to be looking for? They are pretty simple. I found 3 brass jets inside, took them out, cleaned them, and made sure to put them back in the proper place. Other than the float and gaskets, I don't see a whole lot that can go wrong in the carb, but maybe I missed something???

Roger in Iowa

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Yeah, I tried replacing all the wires on the coil, cleaned contacts, etc. This is a side-mount distro. The wire from the ign. switch to the coil is part of the new harness, but just for sniks I jumpered around that. I took the coil off and cleaned the body to make sure it has a good ground. I checked continuity of all wiring, and resistance is very low where it should be. Nothing helped.

When the coil is warmer is seems to get flakey-er, I guess. It definitely when I tap the coil itself the engine will stumble.

An then, while I'm fixing that, I look real close and I see a fine crack in the manifold, near the intake on #3 /#4. Dang!

So I guess I've got intake troubles after all. Maybe I'm chasing down more than one problem?

Is there any fix for the manifold that works, or is it just time to replace it?