My 483 ci. wedge. Has 6 mild passes, not one full throttle pass on motor. Backed car out to line up and load on trailer, pulled up to ramp. Just as I started to shut it off it developed a rattle in the motor. Not a rod or lifter noise, was like something loose. Got it home and jacked up the front end. Pulled valve covers off and oil pan. Everything looks perfect, not a scratch or ding visible. Rocker arms, push rods, valves, and springs all woking and intact. Took all the plugs out and hit the starter, spun over clean and quiet. So decided to let car down and put up on blocks. Just as it was almost all the way down I heard a clink, best discrip. I can think of. Was going to turn it over by the crank and check each cyl. rockers. Put a long ratchet on it and bingo. It would not move, what ever clinked wedged somewhere and can't turn the motor either direction. Pulled the drive shaft and the trans. turns using the output shaft. And looking at the flex plate and convertor, what I can see. Nothing.
Any help on this would be deeply appreciated. Short of pulling the motor and trans I'm stumped !!!!! Help!!!!!

Try priming the engine. Could be a broken oil pickup tube.

I have no idea what the sounds would indicate , but I am fairly certain it is coming out.
Is it locked up in both directions ?
That just doesn't sound good.

Flexplate is one possibility. Check for cracks and see if it will rotate backwards 360* while checking too.

Nothing fell in from the starter area? Did you unbolt the flex plate from
the trans

Balancer locked up from rubbing on the T/C cover. Converter bolts locked against the back of the block. How was the oil pressure before problem. If it welded a bearing to the crank she can lock up tighter than a tick with no appearance of problem. Broken Cranks can to. Sorry to be the harbinger of doom, hope it is something easier.
Todd

Can't unbolt flexplate. Won't rotate. I don't use a oil pick up tube. Have a single pick up on side of oil pan. What ever it is, it's from the trans pump forward. Timing chain and gears appear to be clean and clear also.

Thank you for the reply. Oil pressure was good, about 50lbs at about 2000 rpm. The entire valve train was functioning before the little tink. And the bottom end looks perfect. Starter is intact. I thiink my first major move will be to pull the trans. I'm about 90% sure its not in the engine. But that other 10% scares me.

Flex plate bolt is my guess.
Maybe try unbolting trans some and see if it turns over .

Pull the starter and see if you can move it with a long screw driver on the
ring gear.. if not your gonna have to pull the trans(slide it off the conv
while the conv is still bolted to the engine..or pull the engine and trans
together so you can get it apart

I had to cut off a backed off convertor bolt laying on my back at Norwalk 25 years ago. I had to use a hacksaw blade holding it in my hand because it was jammed up top. Never even missed a time trial but what a pain in the butt.

Just a long shot, pull the distributor and look in there.

I'm going with converter bolt (had one stop the motor from cranking, ruined the bolt boss) or broken converter drive plate. Hopefully it's simple and cheap!

Am thinking we're on the right track. Started to remove the trans this afternoon, but at 75 yrs old pooped out. What a pain, flex plate shield, trans blanket tabs. And cutting off a bolt with a hack saw blade in hand. Not at my age. I'll break out the air tools tomorrow. Thank you everyone for your input. Will keep you informed on what I find. May have to wait till weekend if I can talk my son into helping. Thanks

I'm right behind you nearing 70.
I found that doing a little, walking away a few times during the day, you get more accomplished.
I'm sure you'll find the problem and good luck.

Mine did the same thing last fall. Thought it was a torque converter bolt. Turned out to be the jankety 440Source balancer came apart and was bouncing off the timing cover.

The motors talking to you, it saying
AKA aside those noise are a good warning, please let us know what you find

It does sound like a converter bolt issue. I always coat mine in red Loctite and try to let em cure overnight before firing the motor. That and I only use the ARP converter bolts after having issues w/ the piece of crap MP bolts that would stay tight no matter what I did.

I am betting the converter bolt is sandwiched inside the top freeze out plug on the engine.

You know you have a nephew that can come give you a hand.

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.

I always hated Mopar convertors because of how they bolt up. I love the thru bolt setups that they used on the GM convertors

I'm with you on that pittsburgh. Always minimum thread engagement. At least the aftermarket uses larger bolts. Hate to admit I like anything GM, but I agree.