24 bent valves

[Smallblock454]

Hi Brett,

if a complete IMS kit including bearing was done, there is also a possibility that the timing was mooved, because chain tensioners have to be loosened to do that and there is a possibilty that the chains can skip one or more gear tooth.

Regards from germany
Markus

[flaps10]

The original post says he drove 7000km after the IMS bearing was replaced. Then all peachy until one day it doesn't start.

That doesn't point to someone setting the timing incorrectly that far back.

IMS sprocket shifting on the shaft would still only affect the left cylinder head (the sprocket going to the right head is machined as a single piece with the primary IMS chain sprocket or at least it is with my "bicycle chain" type, so that failure wouldn't affect both heads.

What is more puzzling is that OP stated the mechanic checked the timing and it appears good now.

OP,
Did he test compression, or do you know about the valve contact because he bore scoped it?

[Gelbster]

The valve timing is perfect but you have bent all the valves ?
Can anyone explain that to me?
Like Flaps ,I rebuilt my M96 and am having difficulty understanding this unless....
The torque on the sprocket at start-up caused it to slip on the shaft. Mine is the Hi-vo chain system. That would explain the bent valves.
When you tried to start several more times, the sprocket continued to slip/rotate until it (magically) returned to the original, correct position.
Speculation pointless except for curiosity.
When you rebuild ,pin the shaft+sprocket.I posted a link to John Edwards Costa Mesa R&D doing this job some time ago.
https://www.youtube.com/watch?v=XP6GwqLvD7Q