phil996cab99

Is the cylinder scoring related to the IMSB breakdown?

Ahsai

I highly doubt that as I couldn't even feel them with my finger tips. It's not like chunks are falling off the cylinder walls.

phil996cab99

That black gunk on the pistons (?) and that grey gunk on the valves (?) - is that normal?

Ahsai

It's just the lighting. Everything is close to dark grey and black. The engine had 100k on it so carbon deposit is not too surprising.

The marginal AOS didn't help either. I noticed quite a bit of oil in the AOS vent tubes.

Imo000

Yes.

JMLavoie

Ahsai: Do you know enough now about the salvageability of this engine to make a way-ahead decision with this car?

Ahsai

Nope, not yet. Still need to split the case to check the most important parts - crankshaft and the crankshaft carrier.

Ahsai

The rest of the bearing debris at the bottom of the case (those larger pieces didn't make it to the oil sump). They concentrated on the crank pulley side as opposed to the IMSB side.

Also found a broken IMS paddle, which IMHO is a collateral damage. Maybe Jake can chime in. Quite amazing the engine still ran. That broken piece was just held there by the IMS chain tensioner and it's grounded by the IMS timing chain.









The cylinder walls are not bad at all. Just some very fine and light scratches. The piston and rings all look fine except with some matching light and fine scratches on the piston skirts.

Schnell Gelb

Thanks for sharing the gory details. I have just rebuilt mine so it is familiar territory.
With the benefit of hindsight I find it difficult to justify the cost of rebuilding/rectifying a M96 because you don't know the damage until it is totally dismantled.inspected.measured,magnafluxed etc. .Just a few extra broken pieces/collateral damage makes the project financial nonsense compared to buying a 'good,used,running' engine.
That said, it is fascinating if you have the time /$$ for that nerdy luxury :-).
Once I added all the costs,the time,special tools and the uncertainty of how my repairs will hold up,Jake's engines seem an intelligent alternative to 'good,used,with warrenty ' engines. !YEMV

Hardback

Be sure to buy the LN billet crankshaft tensioner paddle if your going to rebuild/resleeve, it's more robust.

Schnell Gelb

You are correct but ...the tensioner paddle was collateral,not primary damage. My obsession was causes of primary damage.
If a chunk of metal starts circulating (primary damage) even a paddle (or any other part) made from depleted Uranium won't save the engine.
If I had bought every engine upgrade component available it would have ballooned the cost even more.And still I wouldn't have the knowledge/experience to be sure all the other details were correct. I obsessed about every detail and spent $ like a drunken sailor - still did not get the assurance of a warranty !
If we were discussing an engine for which every tech detail is available (say LT1 for example) -totally different story. Without that detail I was just a bungling fool. To give just one example - bore taper/ovality of the M96. What are the practical, real-world specs & where/how do you measure correctly ?Heck ,we can't even agree on what the best IMSB is ! But let's not ruin Ahsai's thread with that discussion :-).

alpine003

I'm of this mindset myself. Cost aside, just the savings in time and to be able to drive it sooner than later is also attractive going this route.

Thanks for the update Ahsai. You will be one of the resident experts soon(especially after you take the class).

Ahsai

Totally agree it's costly to rebuild M96s properly. Use this engine as an example, so far these parts are broken and need to be replaced:

- IMS (need to check more closely but it does look like the shaft's IMSB opening got milled as well)
- IMSB
- IMS tensioner paddle
- One scavenge pump (gears totally destroyed)
- Main oil pump (gears have some pitting)

Must replace items:
- Con rod bolts
- Crank carrier bolts + head bolts
- Head gaskets and engine gasket set

While you're there items:
- Piston rings
- Rod bearings and main bearings
- Valve seals
- All timing chains

All of the above is $4k-6k parts. You end up with a refreshed engine.

Re-sleeving will add ~$5k. Reconditioning the heads maybe $1k? but then you end up with a decent rebuilt engine.

Ahsai

Don't know about being an expert but will probably have more opinion to offer

Ahsai

I tend to agree with Schnell on the IMS paddle in this case. However, I think I've also read cases with it being the primary failure. Timing will shift and valves and pistons destroyed when the IMSB remains intact.