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Did some testing in the driveway again and the pump kept up with pressure for 10 or so minutes while i played.

I was able to get it warmed up totally and get some spark knock going with quick revs and releases after warm up. Retarded the timing and it did it still. I'm wondering if my distributor's centrifugal advance is messing up? I'm wondering if the distributor is just advancing too much and the fuel pump/gauge is doing just fine. I'm starting to look elsewhere for the tell-tale knock.

Pretty simple to make rudimentary analysis of the centrifugal advance system. All you need is a tachometer and a timing light, and estimate timing change based on the degree markings on the front timing chain cover.

You had me thinking, I don't think I've ever heard of spark knock or preignition occurring when just revving a static engine. I believe it requires an engine to be under significant load like accelerating up a grade in a high gear, or at least that's my observation. I suspect your knock is not preignition.

That could also be, although i don't know what would manifest itself this way. If you do some quick revs, it's only on the down side, after you've let off and the distributor jumps advanced in timing with the vacuum that you notice it.

Retarding the timing a lot does help with it. It doesn't do it at all cold, when first starting up. It came on all of the sudden, as it didn't do it about a month ago when i was chasing rough idle, before i swapped distributors/intake/carb.

It does it very little if you disconnect and block off the vacuum advance. It does it mostly at cruise throttle positions, not at no throttle coasting and not at full throttle accelerating UNLESS the timing is on spec and the vacuum advance hooked up. At cruise throttle position, it's very prevailant, and you can make it come and go with throttle postion.

I'm open to other ideas as to what it might be.

I may put the other distributor back in, with this one's vacuum advance canister, tomorrow if i find time.

Also, no markings on the balancer :-/ It was kind of beat, so i found the TDC mark, marked it with a hacksaw, painted it with white paint and then painted over it with clear paint so that i could find it later while doing timing. I do have a dial back timing light, that makes it a lot easier.

Warmed it up today and took the fuel pump off and then restarted it, and still got the knock. It's towards the front of the engine, down in the fuel pump area with a stethoscope, you can pick it up at the base of the 1 & 2 spark plugs and it's stronger a little lower. I'm hesitant to guess a rod bearing issues because it doesn't do it at ALL cold, cruising, wot, what have you...and warm it only does it when cruising rpms down the road, not at idle when the oil pressure is lower and i'd think it could slop around more.

Any more educated guesses? This just showed up a week or so ago, it hadn't manifested itself at all after the motor swap and during any test runs. I'll try and make a video of it later.

Edit: Also put my old distributor back in and set gap, dwell, etc. and used the working vacuum advance diaphragm. This distributor definitely worked in this car with no knocking before. I think i can safely rule out ignition or fuel.

I wonder if this could be a carbon build up issue? Should i try the old water or mist atf through the carb trick and see if it changes or loosens anything up?

I really really hate to tear the bottom end down to find nothing (but i guess better than finding something bad), or yank the head only to find something could have been done simpler.

I did run some MMO and seafoam with the last tank of gas/oil change (15-30). I'm on a fresh oil change now of 30 wt.

Again, oil pressure is about 35 or so idle cold, 10-15 idle warm and 7-12 idle hot. I'd hope the mains are ok, and i'd think a rod issue would be more consistent warmed up. If it's serious, i'd guess maybe piston skirt/pin would be closer?

Once warmed up, is there any change to the sound when you pull once spark off at a time?

Kev, Doesn't seem to be. Again, sitting still you have to rev it and it knocks on it's way on the down side of the rev, so it's just not sitting there knocking.

Under load, you hear it constantly in the cruising throttle pedal range, not so much under heavy throttle or under coasting.

I've pulled every spark wire one by one and reved it and seems to make no difference. It's a very heavy knock, not like a tapping. It seems down low and towards the front of the engine. I can hear it distinctly putting the stethoscope probe on spark plugs one or two but much more down by or on the fuel pump area.

I can't explain how it comes and goes and sounds like spark knock, and can be "played with" or "worked" with the throttle, but it's heavy and scary like a rod knock. I can't imagine what could have happened in my limited road testing lately to cause this all of the sudden.

I will have to make a video tomorrow so you can hear what i mean about it knocking sitting still on the "coming down" side of the rev, just for an instant.

Ok posted some videos. The first is after the car is starting to warm up and you can hear it some when reved and let off.

The second is after letting the car warm up more, you can really hear it when i rev it.

The third is when it's good and hot, and you can hear it like crazy. When i get in and pull the car in you can hear some knocking, that's the exhaust hitting the frame, haven't fixed that yet. There's no engine knock in gear and under load pulling it in and parking it.

Sorry for the finger in the way and mouth breathing.

If i take it for a drive, it won't knock for the first 5% of throttle application, or the last 10-15% near WOT, but it will in between. Timing doesn't seem to affect it at all.

I did a spray seafoam treatment today figuring if it needs a rebuild it can't hurt and if it is loose crap in the combustion chamber maybe it'd help. I've noticed since putting some in the gas and oil before that when i'm working in the driveway and move the car back in, i have a big sooty charcoal area below the exhaust pipe. That's what led me to hope maybe it was a carbon issue and maybe some of it was getting loose and that's what was going on.

Anyway, videos:

Video 1:http://www.youtube.com/watch?v=K6r227cog14

Video 2:http://www.youtube.com/watch?v=JgiXk87xsRI

Video 3:http://www.youtube.com/watch?v=FayGZMPY07c

Have u tried pulling one plug wire at time to see if knock ceases???? Check heat riser for making noise.