Clatter going into forward and reverse intermitten

I recently had a transmission swap done on a pcm 351, I had a bad oil pump on my 1:1 velvet and I swapped to a used in good working order velvet 1:1 that came from my parts motor. I had it done by a shop locally due to my lack of knowledge on transmissions and time. They performed the swap and when I dropped it off I said replace anything that needs it. Specifically the damper. They ended up using one of the two used dampers and I'm trying to figure out if it went south on me already? I've now timed the engine 3 times and got the new motor running very well so I'm fairly sure it's not engine related. What I'm getting is a rattle/chatter noise from the tranny/bell housing. Every post I've read says damper plate. However, it's putting a strain on the engine so much that it kills it most times if I don't goose it a little. I've yet to read of anyone else having it that severe. And finally which stumps me the most is it is doing it intermittently? Any help is appreciated. Btw I'll be doing it myself, I would rather eat the free repair and KNOW it's done correctly

It sounds like your engine is not in as good of tune as you think it is, could be as simple as you have the idle too low, or you adjusted the idle mixture in neutral and not in gear under load. A bad damper would not kill the engine, a really botched rebuild might but more likely is a not quite right engine tune at idle.

To where the prop spins freely? Because it's easy to dial in massive misalignment to within .003".

Agree with joe, engine tune is your culprit if your alignment really is good. Possibly combined with a bad damper.

Could one of you direct me to a thread or tell me how to start back at square one as I'm entering the boat on what to start with first?

Ok, a couple questions...30-35 max at 3000 rpms is at the dock I'm hoping? ;) as far as the idle mixture and idle screw do I leave it where it runs decent in neutral then go into gear THEN adjust idle screw or mixture screws first? That's where I get confused

TRBenj wrote: To where the prop spins freely? .

scootdogydog wrote: did they align the prop shaft?

Joel
Tim's question is a good one. You were asked if they aligned the engine to the shaft and you did check that it's within the .003". However, is the strut aligned with the shaft??? It all starts at the strut!!

Joel,
When you got the .003" difference between the coupling faces, did you do the "quick check" for shaft straightness by rotating the shaft in 90 degree increments?

I am not familiar with the "quick check" I did rotate the shaft in 90 degree increments during the alignment and rechecked my gap. If you have a trick to check it I would love to hear about it

These guys are the wizards, but to my understanding if it were the dampener it would rattle every time, not intermittently, and also mostly just in reverse

Spievy79 wrote: I am not familiar with the "quick check" I did rotate the shaft in 90 degree increments during the alignment and rechecked my gap. If you have a trick to check it I would love to hear about it

If you rotated the prop shaft and checked the difference after each rotation, then you did the quick check. If the shaft is bent, any clearance difference will follow the rotation.

I'm planning to start with the strut to shaft alignment, then motor to coupling alignment and see if it helps. Then move on to the timing and carb adjustments after verifying all 8 cylinders are firing. Sound like a decent plan?

Gotcha. Thank you Tim

I will double check that. I checked and rechecked that ten times when I originally put it in but who knows I've pulled them for fogging and checking plugs since then.

I hate to have to continue this thread but my issues seem to have not gone away. For an hour run I had no issues, it ran perfect. This past week I took her out and it started up fine, idled well in neutral and under load. I ran it for a bit at WOT, then as I returned to idle after a few moments it started coughing and clattering again and died. Started it back up, idled in neutral pretty decent put it in gear and same problem. I limped it back home and decided to order a rebuild kit for the Holley and rebuilt my first carb. I never knew it's condition when I bought the motor so I figured it's a cheap item to rule out. It went pretty smoothly I thought, a lot of YouTube and threads from here and I was confident I did a good job. I reinstalled it started at 1 1/2 out on each mixture screw, hooked up the vacuum gauge again and got to a 14 which from what I've read is possibly a sub par number?? Anyways, it was idling good in gear and I took off it ran good wide open. I started and stopped 8-10 times and it ran perfect then once I hit a channel I idled through and a minute in it started doing it again. I'm at a loss 😤. I have a pertronix ignitor 1 on it with a 40000 volt pertronix coil on. It seemed pretty damn warm but I'm not sure how warm it should be. I'm not sure if it's an ignition problem possibly or if it's just a tired motor in need of a rebuild? Any suggestions I certainly appreciate. The issue never seems consistent so it's hard for me to know what to look at next. I'm happy to put points back in and try them but I don't know much at all about them

from reading it looks like I would just need to pick up a dwell meter then? I already have the points and condenser from when I bought a new cap.. However I don't know that I know where the plate is. May have been misplaced?? Is that an item I might be able to find locally? Or perhaps I have my other prestolite distributor that I pulled which has the screw down cap though. Might that plate work?