Have you spoken to the builder yet??? Theres gonna be something laying on top of a piston... I've seen it twice before.. I wouldn't trust reusing a shim gasket...

Hang on just a minute. Your initial post said the motor would turn over fine with the C-body pan/pickup. You suspected the B-body pan/pickup was the culprit and it wasn't. Now that you still have the problem, you're prepared to tear the motor down looking for something in the combustion chamber? The only thing I've ever seen crawl into a combustion chamber without assistance is mice. If it were me, before I started pulling the entire engine apart I'd be pulling the valve covers to make sure I didn't just lose a valve for some reason .

Can you try running each piston up to TDC and then using compressed air blown in from the spark plug hole and try blowing the cylinder clean. Odds are if you haven't dropped a valve as suggested then you have a very small nut or screw in there since you can go nearly 360' around. Heck get #1 up to TDC and I bet you can figure out which cylinder it is by how far you turn it before it locks up and just try blowing out or get a flexible magnet and run it around in there. Just a suggestion if you don't want to pop the heads off again.

Bob

Can't wait to get the final wait to get the final answer to this one Still betting on some simple answer

after you unbolt the torque convertor, but before you do any more... try turning the engine.

I think I would pull out the plugs & put an inspection light in & look around, maybe a nut fell in the intake.
I would also take off the flex plate & crank pulley to be sure a bolt wasn't hitting.

Torque Converter is not bolted to the Motor/Flex Plate at present but turns freely so that eliminates that theory. As for the Motor turning freely before, that is true. However after careful thought over past work I have done on this Motor, i.e. Manifold, HP Exhaust Manifolds, etc, I just might have dropped something inadvertently into it. That is a possibility as I did drop something earlier after the re-build...That was done in 2005...and had to pop a head off to get that pesky washer I dropped into it, After the suggestion of checking to see if a Valve has dropped, might also be the culprit causing the sudden stoppage. Either way I have to tear the top end down to do a thorough inspection and correct what ever is causing this. I re-built the 383 in my 66 Chrysler 300 completely myself and only had a builder complete this motor's re-build for me as I was unable to put the time in due to AF commitments and flying. Just goes to show ya sometimes if you want things done right the first time one might want to consider doing the whole thing yourself. The builder also has a stellar reputation but that doesn't mean that even one with great credentials cannot miss something. As long as the lower end rotating section is functioning as it should, the top end I can handle. Why it might even be time to put some E-heads or 440 source heads on it instead. But I think not....I don't have the spare $$$$'s and I am also re-locating to NW Florida the 1st of the year. So I need to get this issue solved and buttoned up so the car can be transported/shipped to there. Thanks for the inputs and all. Keep them coming and I will continue asking questions as needed.....

Did you ever check to see if a flexplate bolt is too long & hitting the back of the block? Can't remember if you checked that. Had that happen once, just a bit too long & they'll hit.

Butch

Thanks Stubbs300. I know what ya mean. It does get a little redundant at times, but the guys here do have some good areas suggested to check. I think we did that today didn't we??? At least I thought we checked that at least 3 times????

Thanks Butch for the reply. I have checked again to see if in fact I did leave a bolt there but this whole thing started when I tried to rotate the Crank with the Crank Bolt to get the Flex Plate and the Torque Convert aligned so I could bolt them up. It was at that time I discovered this stop while trying to rotate the Motor. The Torque Converter spins freely by itself so that eliminates the flex plate and the bolts. It appears to be coming from the left bank of cylinders. I spent the better part of today actually tearing down the Motor to inspect. I have eliminated the right bank of cylinders as my inspection of the head, valve springs. locks, keepers, push rods and the intake/exhaust valves both top and bottom. All is correct. The pistons are Flat Tops and aligned in the correct orientation...arrow pointing forward. No visible restrictions with the cylinder wells/walls. If it were a ring on that side there was no indication any where of that. I will try and get the left bank/side fully inspected in the next day or two. Hopefully it is something on that side and I can get this thing buttoned back up and ready for my move to Florida in January. If it turns out that indeed it is the lower end, then the whole thing will be buttoned back up and I will get with the builder to correct whatever it is. This is a brand new never run motor that I have had in storage since late 2005. And for those that might ask...there are no "CRITTERS" in the Motor as it was sealed up while in storage and every orifice was sealed with a storage kit I have. Thanks to all keep the ideas coming. As I get deeper and find out more I will post....

You might save yourself a lot of work by getting a borescope and looking in the spark plug holes on that side. You can see what ( if there is one) problem you are having without going thru all this work.

I'm pretty sure the FLEXPLATE is bolted to the crank. If a FLEXPLATE bolt is too long (for whatever reason flywheel bolt mixed up with the rest?) it could hit the back of the block. Easy to check for before tearing it completely apart.

Kevin

I read a lot about the converter bolts but couldn't remember ( as I said ) if the flexplate to crank bolts had been checked. Too easy to look...

Sorry I bothered you...

Butch

Please check the bolts that hold the lower crank pulley on the harmonic blancer and like everyone has been saying, the bolts that hold the flex plate to the crank. Not the ones that bolt it to the converter.

Found the problem. First Thanks to all that suggested areas to check. Those areas all can contribute to similar reasons why I was having trouble. But...none of the suggestions were the cause. It turns out that a Crank counter weight was binding against the bottom skirt of a piston. Specifically the front counter weight was hitting the #2 Piston bottom. And to add further complications, the firm that re-built my Motor is in dire straits and virtually running on empty. The owner even is never around nor his Son who did the work. Locally here there is another shop I have used known as Gray Matter Racing but now running as Simms Automotive. They are a repair shop now but still die hard MOPAR racers and builders. I spoke with them about my situation and they suggested to take a few surface swipes on the counter weight. No this is not a Stroker Motor and the pistons are the standard TRW Flat Tops as this was nothing more than a stock re-build. I asked if doing this would alter the balance aspect of the Motor and they showed me a BB Crank that had had this done and that the change was marginal and that they do this all the time with their re-builds if need be. I mean .010 is really not going to effect an 80 gram weight all that much. Well I took the plunge and surfaced the area that was binding and it solved the problem. The motor now rotates freely with no binding and the Flex Plate is now bolted to the Torque Converter. Risky I know but I have to take the chance on this one as I need to at least get this project put together as much as possible so that I can ship the 2 cars I have to Florida. This project needs to have most all its stuff done so that as a non-op roller it will at least be transportable. The other car is drivable. So to those that offered advise and support thanks. As always, MOPARTS rules....

so what caused it to change? seems awfully weird to me... good luck dan

I would pull the cap off that rod and see if you haven't stacked a bearing. Stock build should not change anything so the clearence should have stayed the same. You shouldn't have to do any grinding to fit.

How about a bent rod that shortened up?