Thread: Engine Balancing? - Broken Flexplate

G`day ,

seems like Pierre has the right idea , there normally wouldn`t be a bush/bearing in the hub for the auto .

Earlier you say the auto shop replaced the spigot , pressume this means they welded a new end on the TC .

Along Pierres line , if you measure the OD of the spigot and ID of the bush and the figs don`t work that`s all you`ll need .

Maybe not likely if std but is possible for a TC to balloon in days gone by .

It may be an idea to check the crankshaft end float , gently lever the ring gear out and push back , std 4.6 is 0.10mm , 0.20mm range so not much .

genericaly speaking and without delving into things like crank float/position missing adaptor plates/alignment plates (Ive seen that before)

if the Flex plate is pulled towards the TC there are 3 causes.

1. the TC has not been spigoted correctly, either the TC spigot is to large or too long and is not correctly sitting into the spigot bush in the crank shaft or the shoulder on the spigot bush is too far out. tightening up the the bolts pulls the flex plate towards the TC.

2. the wrong flex plat has been used

3. the correct flex plate has been installed incorrectly

if the flex plate has been pushed away from the TC theres a few more causes, in some circumstances 2 or more must occur at the same time for failure to occure.

1. the wrong flex plate has been installed

2. the flex plate has been installed incorrectly

3. the spigot is to short or too small and is not providing the correct stand off

4. the TC is incorrect with one/any/all of the following

• the TC mounting bolt blocks are too wide
• the TC mount spigot is too short
• the tc shaft is too long
• the tc splines are too short
• The TC was not installed correctly
• the TC pump drive flanges are too long
• the pump drive collar is too long

5. The flywheel assembly is installed incorrectly pushing the flex plat too far towards the auto.


In this case I would be getting my hands on a schematic representation of the auto/engine and taking about 300 million measurements then working out where the misalignment has come from.

I feel your pain Recently had THE SAME issues , again with a 1997 Build P38a.

3 flex plates in 100K, engine vibes since car was new, and a chewed out spigot etc etc.

Ended up at 120K with another complete exchange engine. Got the 5 litre treatment , forged pistons, and flanged liners etc etc.

I have had several faulty/ poorly machined/ misaligned crank tunnels etc 4.6 engines in the past. 1 lasted only 6000km out of the crate. On disassembly it had destroyed the thrusts and the crank was using the rear main block turrets as a thrust surface. Absolute disgrace. Total factory machining fail. The other arrived from LR, I removed it from the crate to see swarf spilling from some of the oil ways, and none of the bored surfaces where the poorly installed / scored cam bearings sat had been deburred at all. It went back too.

I would toss the block or at the very least get a full align check of the crank bore and crank balance checked. Personally I would start with another short motor.

JC

I agree that looking at the damage to the plate, i dont believe it is down to the balance of the motor. I'm beginning to wonder whether the TC is somehow out of alignment. I'll take some measurements today, but i'm not sure where i'd find a diagram of what the correct measurements should be.

Here are some pics of the bits all cleaned up.





I have measured the distance of the spigot length which is 18.5mm. The bush you can see inside the aligner is 18.5mm, so this wasnt stopping the TC homing.

Basically, i just want to get this car back together so i can sell it. I lose my garage in a few months so wont have any room for the car

Originally Posted by justinc

I feel your pain Recently had THE SAME issues , again with a 1997 Build P38a.

3 flex plates in 100K, engine vibes since car was new, and a chewed out spigot etc etc.

Ended up at 120K with another complete exchange engine. Got the 5 litre treatment , forged pistons, and flanged liners etc etc.

I have had several faulty/ poorly machined/ misaligned crank tunnels etc 4.6 engines in the past. 1 lasted only 6000km out of the crate. On disassembly it had destroyed the thrusts and the crank was using the rear main block turrets as a thrust surface. Absolute disgrace. Total factory machining fail. The other arrived from LR, I removed it from the crate to see swarf spilling from some of the oil ways, and none of the bored surfaces where the poorly installed / scored cam bearings sat had been deburred at all. It went back too.

I would toss the block or at the very least get a full align check of the crank bore and crank balance checked. Personally I would start with another short motor.

JC

This is the original block. Its been Top Hatted and had the full works. Its supposedly got 9.55:1 Pistons and a High lift cam. At the end of the day, i spent a lot of money on this engine and gearbox, and i just want it working. I've even been tempted to part the car out.

Went and spoke to my local Indy today. He believes that to do that kind of damage the TC spigot is off centre. So on Monday I'll take the TC down to TCE engineering in Ringwood and get their thoughts. He suggested they put a longer nose on the TC as well, which should ensure it is pulled straight.

you dont have to have the original sizings draw up the configuratation and the locations of all the parts and start taking measurements, to .5mm with a ruler is good enough to start with and if that doenst add up then break out the verniers.

Time for an update!

Got word from the Torque Converter boys this afternoon.

It appears that the Spigot on the TC is undersize and was never checked whe not was put in last time However, this is only circumstantial and cant be proven

The Fix:

Split the TC, Fit a larger nose to the TC, and machine out the Spigot Aligner to suit. Check the internals and rebalance. Hopefully, this fixes the problem once and for all. *fingers crossed*