<VV> engine noise

[James Davis]

Valve to piston contact usually only results in a bent pushrod.  The 
valves are quite tuff and will dig a big hole in the piston before 
they bend.  The heads of GM valves are spun welded to the stems so 
that the stems will bend before the valve heads break.  Having had 
several different steel parts rattling around in a cylinder (usually 
valve seats) with enough force to destroy a cylinder head I have 
never bent or broken a rod.
Jim Davis


>At 08:00 PM 9/11/2006, Lonny Clark wrote:
>Piston had been hit, but it didn't look like it was hit very hard. It looked
>like the soot had been cleaned off of a small crescent where the valve
>contacted it. How hard does it have to hit to bend the rod? If the rod is
>bent, can I expect low compression on that cylinder? If so, how low? Can I
>tell if this is the case without taking the engine completely apart?
>
>On 9/11/06, Mike Kost <vairmike at sbcglobal.net> wrote:
>>
>>Lonny Clark wrote:
>>
>> > Well, I need advice again. After the Portland convention I had a problem
>> > with my newly rebuilt Spyder engine. After throwing the belt, I pulled
>> > into
>> > a parking lot and put the belt back on. When I restarted it, it was
>> > running
>> > really badly and made an awful noise (knock, or clang). I did a
>> > compression
>> > check, one cylinder had zero compression. I posted that information to
>> > the
>> > list, and received the advice that I had lost a valve seat. After much
>> > work
>> > and procrastination, I got the engine out (needed new input shaft seal
>> > anyway) , and pulled the head. Sure enough, ex. seat on #2 was popped
>> > out. I
>> > took the head in, had it welded up, and a new seat and valve
>> > installed. It
>> > cost twice the estimate, but that's a complaint, and not helpful here.
>> >
>> > I reinstalled the head, put the engine back in, sorted out what wires
>> > went
>> > where, and started the car. The good news is it runs great, fires on all
>> > six, revs good. The bad news: There's still a really nasty knock or
>> > clang.
>> > It's rythmic, sounds like one sound per revolution. I can't tell where
>> > it's
>> > coming from, but sounds like it's internal. How do I find this one? Do I
>> > need to rebuild the engine - again? It only has 40 miles on it.
>> >
>> > I'm starting to get upset at the amount of work this car has taken to
>> > get to
>> > this point, and I still can't drive it. (about the same feeling I got
>> > last
>> > year)
>>
>>You may have bent a rod when you lost the valve seat (BTDT). Did you
>>check piston for damage?
>>
>>Mike Kost