Put a cam in my brothers car. Well we went to tune it after tune it ran great for about a minute then it started misfiring. Back 2 cylinders dead on each side. Well tuners thought it was an electrical problem of some sort but we couldn't figure anything out. Well today my brother pulled the valve cover of the driver side and found broken valve seat pieces. What are the odds of some of these pieces making it into the block? Also can this cause 4 dead cylinders?

 

Doubt you are seeing valve seat pieces in the rocker area. I think you are referring to some other part.
Is it the valve guide??
Did you check for piston to valve clearance when you put the cam in?
Did you check retainer to guide clearance?
Did you put the correct springs on?
If it's the guides that are broken, it's likely the retainers hit the top of them, and broke some pieces off.

As for the pieces.. could be in the lifter valley, the pan.. Time to pull it down, and find the trash.

 

Tell him to investigate further... It's not valve seats he's finding under the valve cover and if it is... Some one left some valve seats under the valve covers at some point.

 

Do you mean spring seat?

 

Yes I meant valve spring seat. Forgot to put that in. What would cause a valve spring seat to break? It came in a complete kit with seats so I figured there would be no problem.

 

Been there done that. Except my car didn't miss a beat, and I drove it that way for a while. I only found out when I had a piece of the seat stuck to the oil drain plug magnet.(oh ****!) I was able to find all the pieces, drain plug and some stuck under the spring. In my case it was reassembled wrong after cam and spring swap ,the little steal spring cup was put on before the seat. Not by me... Was pissed, but no damage done so I was lucky.