F355 valve hit piston

How many miles ago? Were all valves replaced with new at the time?

 

Does a crack exhaust manifold result in a lean-running cylinder? If so, it does not explain the excess carbon build up on the back of the valve.

 

A cracked header or leak in the exhaust usually results in excess O2 in the exhaust. If it's before the O2 sensor this will push the engine towards a rich condition as the ECU will add fuel to try to eliminate the excess O2.

 

An O2 sensor induced rich condition would affect all four cyiinders of the same bank, not just one cylinder.

 

Exactly, so it won't result in a lean running cylinder.

 

Assuming this could have been detected from fuel trim data? Would that bank be reading positive or negative?
And how excessive?

 

Unless you hate money, you keep the valves that are in spec, which should be most or all of them....valve stems don't wear like, say, rod bearings.

 

We can kinda gauge based on the final price of the invoice. This is one of those things people do what their wallet is comfortable with.

 

$6K in 2003 prices for a machine shop to do a valve job? 40 hours of labor? That owner got ripped.

 

I believe OE steel guides were used. If I recall correctly, those are roughly $100 each. That’s $4k in guides alone. Manganese bronze guides are $15-20 each.

 

Previous owner of my Rosso Corsa did OE steel guides. I will opt for manganese bronze guides for my Nero 355. Will I replace all valves? I’m still 50/50 on that.

 

Given that budget, I’d do manganese guides ($15/each) + 40 brand new valves. Seems like a safer bet to me than 40 steel guides + 10 new valves. That’s just me.

 

… wait.. what?

heads were removed twice? Second time just for valves?

 

Judging by the rail design, it does appear you have the more updated OE manifolds. Early 355’s have a curved rail design.

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That's was what I had done to my car back in 2013. 40 manganese bronze guides. 40 new valves and 14 rebuild tappets. It wasn't expected but an engine out was part of the purchase agreement and once out it was found that guides were needed. The selling dealer said the shop doing the major for him wanted an additional $6k. I said that was a deal breaker. So we split the cost. $3k to me. Parts alone were over $5k, plus a grand for the machine shop, not to mention the labor to R&R the top end. 15k miles later and all is good.

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$6k was a great price if the machine shop was actually good. Need to drive over 6k rpm to find out .


Around 2015, I was quoted roughly $4400 by a machine shop and that included everything but valves. If I wanted to replace all valves, they would be roughly $100/each. $8400 by comparison. CHE Precision manganese bronze guides. The machine shop was one close enough to me and personally recommended by CHE Precision.

At the time, replacing all valves sounded pricey, so I was considering replacing only what needed replacing and keep whatever was still in spec. The machine shop had no issue recommending this route either if I wanted to save $$. They’d still warranty their work for 2 years.

However, Dave L recommended all valves replaced. I was 50/50 before, but it just jumped to 90/10 after this thread .

 

I will take that back. 40 hours for a mechanic to remove engine replace head reinstall engine is what it takes. But, it does not take 40 hours for a machine shop to do a job on a couple heads.

 

Sounds like car never diagnosed. Fixed symptoms and result nit cause. Mixture control is the likely problem and root cause. 100hp/L in late 1980's design cutting edge for it's day with barely capable engine control foiled by Italian electronics.

 

If the intake valves are in nice shape I don't see any reason to replace them.

I would replace all exhaust valves however. JMO