[JBanna]

Thanks for all the responses!

My carb number is 17058253, which I believe was the one I had on the 403 according to Cliff, but my memory isn't good enough to remember for sure (I also apparently had a 17057262 from a '75 Pontiac 350 in June of 2009, but I can't remember what happened to that carb); anyway, Cliff rebuilt both in the time period of 2005-2009). Since Cliff isn't personally rebuilding carbs anymore, I asked him to send me a rebuild kit for the 17058253, using my engine specs. Because I was going through my engine to diagnose and fix the blown head gasket, I decided to go through the carb too, which was probably overkill since it looked fine upon disassembly; in any event, the motor is malfunctioning in that I can't get a smooth idle and acceleration, no matter the mixture or APT screw settings, and I have to advance the static timing to about 30 degrees to even get it to stay idling or running, especially under load and decelerating (my manifold vacuum is less than 10 inches at idle and only about 20 inches at 2000 RPM). I still have to do a compression test, but the leak down test showed problems with #5 and #6 cylinders, and my machine shop says that's probably because the hydraulic lifters in those cylinders were just hanging up a bit and will rectify itself, something common in a rebuild start-up?

So, the bottom line is I originally thought I screwed up something during the carb rebuild, but I was very careful and specifically followed the guidance from Cliff, his book, and other online videos, so I'm thinking it may be something else...oh, I also checked for vacuum leaks using both carb cleaner and propane, which was negative. The PCV valve is also new and functioning properly.

A few other things - my initial setting of the rockers was too tight, and of course I had no compression in any cylinders; however, I went back through them and noticed the leak down issue with #5 and #6, but the motor started and initially idled ok (but not great), so I went with the advice from the machine shop who went through my heads and buttoned it up, only to have the problems described above. I had also pulled the motor and removed the oil pan and timing cover to inspect the cylinders, pistons, timing chain/gears, etc. - it looked pretty pristine and there was no metal to be found anywhere. Finally, I'm pretty sure a slipped harmonic balancer led to the head gasket failure as I was chasing the timing for a few months before the failure - the new balancer is marked very well and cannot realistically be the timing issue now.

I think that covered all questions and comments above, but in case I want to send the carb out to Cliff's successor, can someone give me the contact info please? That may be my course of action if I can rule out a mechanical issue; I don't dislike Rochester Quadrajets, but in this day and age of declining expertise in older vehicles, I'm reaching out for that expertise...

Thanks again to all responses!