I would be curious about the valve shims under those Jerry Woods springs. In any case it looks like the valve fractured at the weak point and the resulting loose pieces knocked out the seat, just a guess. That valve could have been weak from fatigue and the stronger springs did it in.

Mark

DC40's are Dougherty Cams right? Thats what he shows 4.5mm for those cams. You can check with John for your exact setup but he advised us to try 4.75mm and has seen some run up to 5mm overlap.

That engine should scream with that setup. That's the exact same setup we are running in our 2.7 but our cylinders are only 90mm

I just noticed: With those valve springs do they have a custom lower spring cup retainer? I don't see one in the picture of your head or was it not installed?

A broken rocker is a result of the valve colliding with the piston,or valve seat or dropped valve head. One broken doesn,t make them all bad. Is there any sign of valve contact on the other piston? If so then the lack of clearance could have caused a broken valve and the valve head bashing around might have ripped the seat out. I still think the most obvious explanation is a seat fell out first though.

Also the seat could have fallen out on it,s own from previous overheat damage. Were the valves new or reused? New exhausts and seats is always a good idea

I had a motor spec'd almost exactly like yours in my SC (sold quite a few years ago now) and it dynod at 240hp. It ran like a scalded cat too. Looking at your specs I'd say it was identical to my old motor even.

I did run webers not PMO's but Richard Parr at PMO is the guy who recomended and sent me a set of jets. They were bang on...maybe a bit rich on the idle circuit.

That was a great motor.

As far as yours...did the head come off the valve or did the valve drop?

Something happened that's for sure....but you knew that.

Gents,
apologies, the cams aren't dougherty cams. they're from jerry woods smart racing catalogue - [img]http://forums.pelicanparts.com/uploads18
/Screen+shot+2011+04+10+at+12+00+11+PM1302408169.jp g[/img]

the valves weren't changed and neither were the valve seats. i went whole heartedly with the mechanic's reco that they were fine.

i had a look at the heads and can't be sure if the lower retainers were installed. i'll get them opened monday to see if they were.

the other pistons have no sign of damage.

Craig, Mark, John and Jasper, thanks for helping out a complete stranger.

In time, my car will live again.

http://forums.pelicanparts.com/uploa...1302409174.jpg

here's a screen shot

If building my own motor I would probably have re used the valves also. The machine shop I use for head work say they usually need to replace most exhausts on 911,s anyway.The seats rarely fall out but can

Sorry to hear this, man. You may want to go elsewhere for the rebuild. Keep your head up, tho. Soon enough youll be cruisin down the road with that wicked flat 6 whine!

I have read to always use new exhaust valves. When I rebuilt the top end on my 3.2, I bought new exhaust valves and new guides all around. I would think the valve failed and took out the seat.