I do have a nephew, (Biginchmopar) that's gonna come over and help me pull my tranny this weekend. It's ready to come out, just a couple bottom bolts and one tranny mount bolt. Now I don't have to worry about wearing a 727 case. I pray the problem will be exposed when we get the trans out. Will let ya'll know.

Well?????

Well, have narrowed it down. My nephew came over Friday afternoon, we pulled the tranny. Still locked up. Pulled the damper, timing cover water pump. Everything was clean and good. Still locked up. Had this old man up till 10:00 with parts and tools scattered all over the shop. Bob suggested I pull the valve train. T&D set up, which made it easier. Saturday, took right side first. Still locked up!!!!! Took off left side, Walla, freed motor up. Pulled all the lifters, #7 one lifter had a small ding in it. Everything else looked perfect. Still haven't found the culprit that was rattling. Will pull the left side head off Monday. Today being Sunday will attend Sunday school and Church services. And pray that God will direct and guide me to his Glory.
Many thanks to my nephew Bob. I enjoyed having him here we did some serious bench racing too.

Sunday morning brain fart. It wasn't a lifter dinged, it was the last lobe on the cam.

Time to look at the bottom end for a loose rod or broken bolt

That doesn’t usually turn out very well.

No Bueno.

Suspension is killing me. Studied for Sunday school this morning. But couldn't keep my focus. Have both heads off, pistons, cylinders and heads just like everything else I've looked at perfect. Just appears that cyl's 5 & 6 are a little rich. Layed under the car and checked every rod bolt, check every cyl. crank and rods. Like I just put it together, except the oil still dripping in my face. No reason to pull engine. BUT one last thing and can't think of anything else to check. Haven't yet pulled the flex plate. It has to be something between the flex plate and block. Not going to do it tonight, that red locktite is hard to break loose. If not the problem, is anyone interested in a 73' 350 SL mercedes?

Unbolted the flex plate. Nothing there and not any positive proof that anything had been there. Checked every rod bolt, didn't go to full torque. Enough to know that was not the problem. Turned the motor over by hand, with a light and checked every cylinder. Very carefully looked at everything. Not a sign of any dings or scratches. Rechecked rocker arms, valves, springs and everything I could think of. Whatever it was at one point fell out or vaporized. So,,,,,, my son and haven't asked my nephew yet, we are putting the motor back together this weekend and put the car back together. With a prayer !

Did you leave the fuel pump rod in the engine?

To recap....first it was totally locked up in both directions, then you unbolted the flexplate, and now you can turn it over by hand?

If I read this correctly (maybe I didn't), it kind of seems like a clue there

Did you check the valve lash before you removed the rocker arms? If one of the rocker arms got sloppy enough you might have jammed a pushrod against the adjuster. Once you took off the rocker arm assembly you freed up the engine. I've locked up engines before during assembly by having the pushrod slip over and jam against the rocker body.

It's a KB solid low deck block, 9.700 deck. Running on methanol and mechanical pump. Before it locked up I turned the motor over several times checking valve train. Checked various valve lashs. All were very good. I can't replicate the rattling sound it made at the track. But it was like it was maybe flexplate, valley pan or something similar that would make that sound. As closely as I've checked everything I feel okay about reassembling everything.

"Well, have narrowed it down. My nephew came over Friday afternoon, we pulled the tranny. Still locked up. Pulled the damper, timing cover water pump. Everything was clean and good. Still locked up. Had this old man up till 10:00 with parts and tools scattered all over the shop. Bob suggested I pull the valve train. T&D set up, which made it easier. Saturday, took right side first. Still locked up!!!!! Took off left side, Walla, freed motor up. Pulled all the lifters, #7 one lifter had a small ding in it. Everything else looked perfect. Still haven't found the culprit that was rattling."
Is what he posted prior

Thanks. It's too much lol.

The lifter with a ding in it probably points to the next place to look.

Am sure I found the rattle problem. I'm very anal about gettin as much thread engagement as I can on everything. Flex plate is .125 (1/8") , depth of thread on toruqe convertor is .500, totaling .625, (5/8".) Measureing bolts from bottom of bolt to under head of bolt .625. No compression of flex plate when fully torqed. I did notice when motor was locked up and was trying to move it back and forth with pry bar on ring gear. The flex plate moved on the bolt I could see. So I believe it developed some harmonics when it was coming down in rpm. That would explain the rattleing sound. Now the motor lock up situation? Still not sure about that. But am going to reassemble. Nephew suggested as I'm mounting rockers as I put on each cyl's set adjust then check to make sure motor will turn over. I think good idea. I'll just slowly assemble everything and carefully check each piece as I go. Thanks for all the replys.

i can appreciate full thread engagement, but bottoming the bolt is worse than having a few threads short. if you have a thread or two more engagement than the bolt diameter, that is all it needs.

Here is a rule of thumb that you cant go wrong with
1 X thread diameter in steel
1.5 X thread diameter in cast, bronze etc.
2 X thread diameter in aluminum
Any more than that is of little gain (fastener will usually break first) any less and dramatically reduces strength and threads will pull.

correct. i was just using the example for steel because it was a flexplate/converter application.
as for aluminum, if possible, i like helicoils [or variations thereof] or studs, still using the 2 times thread diameter.

The bolts bottoming out was a mistake on my part. I'm quite aware of the results of bottoming a bolt out. The old rule of thumb of thread engagement being equal to dia. of bolt. Equals bare minimum. You should not establish a standard for thread engagement. Just far too many variables. Such as in steel, alloys, heat treat etc. In aluminum and bronze, you deal with cast and billet and different alloys. How many engine builders have you seen strip threads out of a head. When using stock bolts to hold rocker shafts down? Just one example. Maximum thread engagement is very critical in engine buildiing. And I screwed up by going too extreme.