valve guide replacement

[Arts911]

Hello
I took a set of cylinder head to a local machine shop to have the valve guides replaced, valves resurfaced with new seals
When I picked them up I looked threw the exhaust and intake ports to see in the guides were replaced and notice in the exhaust port that the stem on the lower part of the exhaust guide was cracked and will this effect the cylinder head in time ?
All of them came back with a crack at the lower tip and One came with a piece missing.
The person at the machine shop told me that this happens with a new guide is press in..
I would like to know in these heads are toast and I should be looking for another set ?



Thanks for any advice Arthur

[roblav]

If the guides are cracked and NOT the port area of the heads, then the heads are probably still good. IMHO, the guides should not be cracked there. You ought to send them to someone with experience with these heads. The problem is that cracks tend to propagate. The exhaust valve guides are pretty critical on these engines due to the heat. A picture would help.

[Steve@Rennsport]

The machine shop failed to do the job properly and cracked the guide bosses for you.

These heads need to be welded up, re-shaped and new guides reinstalled, correctly.

[Arts911]

Thanks for your resonse

The guides arent cracket. Its the port area to the cylinder head. Ther is a 1/4 inch crack in aluminum and I was thinking too that they need to be welded up.

I cant post pictures, cause my friend wants to take them to another shop to get a second opinion

Thanks Again

[afterburn 549]

Your run of the mill machine shop can ruin porsche heads.
There are like 10 more steps to a decent valve job compared to a generic Ford GM Nepindenso
valve job.
Trust the borg of thought here

[Steve@Rennsport]

Originally Posted by Arts911

Thanks for your resonse

The guides arent cracket. Its the port area to the cylinder head. Ther is a 1/4 inch crack in aluminum and I was thinking too that they need to be welded up.

I cant post pictures, cause my friend wants to take them to another shop to get a second opinion

Thanks Again

Love to see some pictures,.....

Welding 911 heads isn't for someone who has never done them successfully before. If that is needed to fix them, I'd recommend either procuring another set or finding someone with a proven track record with these things.

With a 1/4" crack, I would be looking for replacements (and I do repair these).