[71GreenJunk]

Thanks. Tried to swap it over today. Used a pair of pliers to twist it out of the bad carb and just lightly tapped it into the decent carb. Seems to fit well, fairly tight in the "new" carb. Hopefully that will stay nice and tight and sealed. Think I'll use the ported vacuum to break-in the cam on my new engine and then I'll work on switching to manifold vacuum for the advance. I had got to reading about advance and remembered the '80s LM1s IIRC, that had a thermal switch that switched the advance to manifold vacuum when they started to get hot to cool the engine down and I do remember a big difference in how the old engine ran when I got it and when I pulled it, when I bought the truck the timing was retarded about 20 degrees and it didn't have a temp gauge then but I know it was running hotter and running much rougher than it did when I timed it to stock spec. I've had the same crate engine I'm buying and it ran 17" Hg vacuum at idle so I'm going to get an advance canister that is fully advanced at 15" or a bit less so the advance won't fluctuate. It'll be an interesting experiment if nothing else and if it doesn't work I can just switch it back. IIRC, the LM1 is pretty much the same build as the 350s that came in these trucks.

I'll have to look into national carburetor. This is about the 5th core I've bought to find a decent one. I'll have more in this than one would cost from them once I put new throttle shaft bushings in it and a good rebuild kit figuring in the cost of the parts carbs.
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