Piston + Valve: How Much Damage Is Too Much?

[bmwman91]

OK, so I had an intake valve spring poop out. The head is off and at the engine builder getting overhauled. My question to r3v is about the severity of the damage to the piston.



So, what are my chances that I can just put the head back on after it is repaired and drive it? If a wrist pin or rod was bent, I assume that I could check it relatively easily with a depth gauge by comparing piston #3's height below the deck to piston #2's. Thoughts?

The smaller burr is not really a concern to me since it doesn't take a lot of force to do that, and I can remove the burr myself to prevent a hot-spot. It's the larger indentation that worries me since it probably takes considerably more punch to do that.

Thanks.

[cabriodster87]

I have seen far worse than this put back in service, it is not that bad at all. imo

edit: make sure the top ring is not pinched near that spot

[bmwman91]

Thanks. How can I check the top ring without disassembling the bottom end & having to re-hone the cylinder?

[bmwman91]

Oh, and here's the valve that did this...the valve looks like it "lost" the fight lol.

[!kid]

I've never seen a valve with that pattern before. what engine is this?

[AndrewBird]

Thanks. How can I check the top ring without disassembling the bottom end & having to re-hone the cylinder?

As long as you don't replace the rings, there is no need to re-hone. You would however need to replace the rod bolts as they are torque to yield and stretch.

As far as the damage, I would say that is very minor. I'm not even sure if it is possible for a valve to bend a rod. The valve would break off before any damage was done to the rod.

[digger]

I've never seen a valve with that pattern before. what engine is this?

looks like a MM valve

[MR 325]

I'd just clean up any sharp edges where it contacted the piston and keep running it!

[96Formula6spd]

I've debured worse with no issues. Clean up any sharp edges and slap the head back on.

[bmwman91]

I've never seen a valve with that pattern before. what engine is this?

looks like a MM valve

Yup. They are covering everything at no cost to me.

As long as you don't replace the rings, there is no need to re-hone. You would however need to replace the rod bolts as they are torque to yield and stretch.

As far as the damage, I would say that is very minor. I'm not even sure if it is possible for a valve to bend a rod. The valve would break off before any damage was done to the rod.

Hmm, interesting. I assume that I would need to make sure that the rings did not rotate their position in the piston at all to maintain the wear patterns? I am going to try to avoid doing this lol.

And yeah, thinking about it, the valve stem would obviously fail before the rod since the rod is like 20x beefier.

I'd just clean up any sharp edges where it contacted the piston and keep running it!

Thanks. Hearing it from a veteran definitely gives me some peace of mind!

[MF DOOM]

Seems like youve been having nothing but problems with the mm engine. What have they said about it?

[jeffnhiscars]

Those pistons look no worse than my barn find (with the broken TB) as long as its just a ding and no crack.

Im surprised an MM engine did this. An idea why ?

[bmwman91]

Seems like youve been having nothing but problems with the mm engine. What have they said about it?

Those pistons look no worse than my barn find (with the broken TB) as long as its just a ding and no crack.

Im surprised an MM engine did this. An idea why ?

Broken valve spring. They are dropping Ferrea as a spring supplier because it sounds like I am not the only one that has had a spring go south in the last year. They are going back to their tried and true dual-spring setup that they have used on race engines for decades without problems. The Ferrea springs were fine up until about a year ago when something changed and they started having these quality issues.

I actually had a valve spring die about 70 miles in with this engine. MM took care of everything...shipped the entire engine from CA to MO and back at no cost to me. Since they had used Ferrea springs for 4 years without issues, we all figured that it was a 1-in-a-million fluke. Then about 1100 miles later another one broke, and MM decided that it was not just a coincidence. So, they are tossing their stock of Ferrea springs and using the tried and true dual spring setup from now on. I actually got them to pay all of the shipping for my original M42 engine core since I put this damaged cylinder head on the same pallet, and they are now in the process of tossing all of the Ferrea springs and replacing all of the springs, hats & retainers with their dual spring setup.

Just to illustrate the point that MM is working hard to get me a solid engine:
Jim at MM did not like how the intake cam was wearing either, so he is also having that re-done by the cam company. It turns out that an EPA regulation that removed zinc phosphate from engine oil in 2008 has caused all sorts of hell with high lift performance street cams, and he is going to have ~0.020" of lift knocked off of the nose due to the newer EPA mandated oil not protecting the nose when it runs up the edge of the lifter. Doing this will knock 4-5HP off of the engine, but it's not really a big deal since the changes in EPA regulations basically mean that no commercially available oil would work well otherwise and that's beyond anyone's control. I guess that they could try to retrofit larger diameter lifters, but I don't want to be the guinea pig for that lol.

Anyway, MM seems to be as reputable as their reputation makes them out to be. They are bending over backwards to make this situation right, at considerable expense to themselves. Custom work like this is, as far as I can tell, sort of a perpetual work in progress. While certain methodologies and practices are always to be observed, external factors like supplier consistency and EPA guidelines are always changing. A high strung engine is just going to be more sensitive to all of it by its very nature. MM is going to great lengths to understand every aspect of what has gone wrong or could go wrong and is taking preventive action for me. I am generally happy that they seem to have the same level of paranoia and anal-retentiveness about things as I do.

[Exodus_2pt0]

As Mr325 said get rid of the sharp edges. Especially if you are running boost on this engine, anything that sticks out is a potential hot spot.

[bmwman91]

Affirmative. I will probably tackle that with a chisel and de-burring tool. High speed rotary abrasives seem like a bad idea in this environment lol.

I am also planning to remove all of the carbon crud with a plastic putty knife and the shop vac.