918-S

Stopped by the local machine shop to check on my heads. They started the repairs. Check out the deep port repair. Very tricky and very well done.

So far I'm very happy.

Here's the source of the damage the exhaust valve was punch through the intake seat (very hard!) and buldged the intake port.



Split and buldged deep inside the port



Port repaired



there was a valve seam sized hole that fractured the seat and was punched into the head 3/4" deep buldging the port The repair looks in finish as stock.



Still some finish work left but I'm on a down hill roll now.

SeanR

It looks pretty rough in that seat, but what do I know. I just enjoy watching you put that beast back together.

Keep us posted. Besides, if you ever get it in the DFW area, I want a ride.

Bill Ball

It took me a while to figure this picture out!

918-S

Ya, There's some work left there but it's coming along nicely.

BTW: I've driven this car to Cali and back with a stop at the Big Texan!

sublimate

I still haven't figured it out.

Lizard928

the intake valve is sitting on the exhaust valve,

perrys4

Wouldn't it just be easier to get a new head? I'm a newbie to this stuff so be gentle....

918-S

The exhaust valve stem broke. It's about 1" long. The piston punched it into the head next to the Intake valve. It's fugglee

Mrmerlin

I wouldnt even mess with the damaged head its better to get a used head and do a good valve job, no telling what other damage has been done that you cant see, IE to adjacent water jackets, and ports

918-S

I purchased a set of euro "S" heads but they were shave past the minimum spec.

My heads were at the limit. I will probably need to do some other work to protect the valves to piston clearance.

SharkSkin

Wow, that's a real interesting position that exhaust valve got itself into. I understand why it's worth the work to keep the heads -- looks like they did a nice job on the work that's been done so far.

Daniel Dudley

What happened to the rod ? Block I am assuming is fine, but that is a big assumtion.

918-S

The block cracked, piston broke, not sure about the rod yet but I won't be using it.

I left the short block together until I get the heads back. I am going to set up the cams as a mockup with lifters only for only one cylinder and rotate the assembly with silly putty in the cylinder to check valve clearance.

There were several thoughts expressed in another thread I started about how much heads could be cut before there are valve clearance issues. My heads were at spec after the last rebuild. The factory manual states you need to run the thick 1.4mm gasket after machining. I didn't. I think my heads in combination with an advanced right cam was my undoing. That's what I get for rushing through things. Summer is over here and I will be done working for the year soon. I hope to shed some real light on the subject.

There are alot of other guys with a ton of engine experience (non 928) that would like this info when building their next 928. I like building my own stuff. I just need to do the research on this one.

mark kibort

Dont worry about the clearance. it will clear. the only thing that happens, especially with the later year euros, is that the clearance will be smalller. maybe you could skip 3 teeth on the timing belt, but now only 2 (or something like this) remember, a euro cam will drop the valves about .3" until they hit the piston cut outs. (thats at TDC) however the valve chase the pistons down so they really cant touch. rotating he cams with out a belt, is really the purpose of the valve reliefs, as well as a little margin for error when things do break. max lift wont happen until near 90degrees past TDC, thats why the S4s need to be turned to 45 degrees [btdc, because thats a point where none of the pistons are at TDC, so you can rotate the valves at max lift, and the dont tough..

why we clay the pistons up with the 5 liter 2 valve conversions, is to make sure the cuts are correct, as often, the cuts by the machine shop are just off and a dremel needs to widen the cuts by 1mm diameter.

are you sure you dont want a brand new 4.7 euro short block, ready to go?

mk


QUOTE=918-S;4670952]The block cracked, piston broke, not sure about the rod yet but I won't be using it.

I left the short block together until I get the heads back. I am going to set up the cams as a mockup with lifters only for only one cylinder and rotate the assembly with silly putty in the cylinder to check valve clearance.

There were several thoughts expressed in another thread I started about how much heads could be cut before there are valve clearance issues. My heads were at spec after the last rebuild. The factory manual states you need to run the thick 1.4mm gasket after machining. I didn't. I think my heads in combination with an advanced right cam was my undoing. That's what I get for rushing through things. Summer is over here and I will be done working for the year soon. I hope to shed some real light on the subject.

There are alot of other guys with a ton of engine experience (non 928) that would like this info when building their next 928. I like building my own stuff. I just need to do the research on this one.[/QUOTE]

JEC_31

Wow. That"s a new one to me.

Hats off to the shop that made THAT tricky repair.


Good luck with the re-assembly and thanks for keeping us posted on this most interesting project!