Converter knocking? Flexplate/starter connection

[Battlewagon]

Alright....if I'm not on the right path please set me straight because I'm learning as I go and I havn't gone very far yet!  428 with a c6 transmission and a knock has been noticeable after warmed up.  A friend with a good ear and loads of experience under the hood figures the knock is possibly coming from the torque converter. He said the late 60's Ford converters had issues.   I've researched most of tonight and began to wonder if the flexplate could be the source or linked somehow.   I've had consistent issues with the starter not engaging, with an audible spin/whirling noise finalizing the attempt to start. Not a grinding. The whizzing almost always happens from cold starts.  A few tries and she fires up.  After the motor's been running I think I have heat soak issues so that's a whole other problem a hi-torque starter may solve.  Could the flexplate be out of balance which results in the knocking and also potentially a reason why the starter will not engage all the time?  The knocking is when its warm, where I've also noticed my oil pressure is running quite low at idle, 5lbs or below.  Up to 40lbs when driving.  Blow-by / blow-back.... I have an issue there so I'm due to do a rebuild I'm betting.  So what should I do/check first?  I was told to disconnect the converter and start the engine up and see if she still knocks.  If so then I focus on the engine but if the knock is gone then we know its plate/converter related.   

[jayb]

Welcome to the forum, Scott.  Its been a while since I've looked at a stock converter, but if I recall correctly the C-6 converters have studs coming out of them, which engage holes in the flywheel.  Nuts on the studs secure the converter to the flywheel.  This means that you can't unbolt the converter from the flywheel and run the engine separately; the studs will still be in the flywheel holes.  Somebody here please correct me if I'm wrong about this.

On the starter, if it is just whizzing, the gear isn't engaging the flywheel.  You can probably repair that starter with a new gear (we used to call them a starter Bendix), but if you have a hot start problem also the high torque starter would be a good solution to both problems.

The knocking issue may be a rod knock rather than a converter problem anyway, especially since it is happening after the engine has warmed up.  Since you need to freshen up the engine anyway, I'd just pull it and look for the problem on the teardown.  Good luck on the project!

[Lowrider]

Two things come to mind regarding the convertor knock if that's what it is. One, the 4 nuts that secure the convertor to the flexplate sometimes get loose and that could cause it to knock. And two, sometime the flexplate will crack where it bolts to the crankshaft.

[Heo]

If im not wrong you can move the converter to the rear
enough for the bolts to clear the flywheel.
On most autos you can do that

[My427stang]

Stock flywheels crack all the time, unfortunately, factory Ford converters with studs usually do not go back far enough to rotate the engine separately

[Leny Mason]

My thought's are cam plug backwards and the cam is thumping, drain plug in converter not lined up with the hole in flywheel and bending it, causing it to take out the trust bearing. Leny Mason

[machoneman]

Cracked OEM flexplate is my guess 

[fekbmax]

II had a similar issue years ago. Dull knock . It was the flex plate. Once I removed the trans and converter I could actually push on the flex plate and hear it pop. Never found a crack or anything but changed it and never had the dull knock again.

[Art67]

Had the same issue a few months ago, 390 C6, started vibrating a little, replaced a stiff u- joint.  On the test drive it  quickly started vibrating more, then got noisy with the knocking while driving toward home.  I tried to nurse it home but it left me stranded a couple miles from the house. 

[Rory428]

About 35 years ago, in my 390 powered 64 Falcon, I noticed a knocking noise coming from the engine. To me, it sounded like a rod bearing knocking,so I dropped the oil pan, and checked all the rod bearings, they all looked fine. So I pulled the engine to check more closely. When I went to rotate the crank with the flexplate, I noticed I could rock the flexplate back and forth a bit, without the crank moving. I was using a factory 390 flexplate with the reinforcement ring. When I removed the 6 flexplate bolt, and removed the reinforcement ring, there was a 360 degree crack, all around, and just inside  the rings OD. A new flexplate, and she was good to go for another couple of years.

[blykins]

Hey Rory, you need to fix your signature line.   Running 9's is impressive, but not at 12.54 mph.

[57 lima bean]

Hey Rory, you need to fix your signature line.   Running 9's is impressive, but not at 12.54 mph.

 
 

          Maybe it's a .129 60'

[cammerfe]

I once found, in a 20K mile C6, a piece of casting swarf that must have come loose after all those miles of driving. It was inside the bellhousing, and only made noise (loudly) on occasion.

KS

[Rory428]

Hey Rory, you need to fix your signature line.   Running 9's is impressive, but not at 12.54 mph.

OOOOOPS, funny nobody (including myself) never noticed the error on the Fairmonts MPH, now corrected. Thanks Brent.