Around 10k miles ago I did a leak-down test and discovered one of my cylinders was down around 18% wet. I had the headers off, and using my borescope I was able to determine it was a leaking exhaust valve. I was thinking it was carbon buildup, and kept driving it to see if it would clear itself up. It didn't, and I believe as a result my idle has gotten worse.

I'm thinking it's a bad valve seat, and am planning on pulling the heads off this year to have them refreshed. I know Hoffman will want to replace all of the seats, which is the right thing to do, but I haven't had any success getting a quote from them via their online contact. Has anyone had this work done from them in the past couple years and could give me a ballpark price estimate?

I'm also open to recommendations for other shops. Thanks!

 

Couple years ago forum member Meir had his 3.6 heads done at Hoffman. I saw them when they came back. Thery were done beautifully, some of the best head work I've seen in my half century of doing engines...

Hoffman did all valve seats as they tend to be a problem that can cause catastrophic problems on the 996.2 when they drop out. Which seems to happen on a regular basis...
He also changed out all the valve guides to a hardened sintered bronze iirr, for a better tight fit as they had loosened up.
He also did a stage 3 port job. Looked like he unshrouded the valves nicely. And a sweet multi angle valve job.

In my opinion, don't fug around with a leaky cylinder that might be a lose valve seat ready to drop down completely or a valve head break off, you're playing with fire....

He spent $5000 before shipping iirr...

Ya, good head work is not cheap and labor is intensive. You will get good head work from Hoffman...
A shop that knows/is an expert on the ins and outs of the particular heads they are working on is what makes the difference on engine like the m96.
Good tight sealing heads make for a stable smooth idle and let all the max power the lower can make be available.

Top notch heads are where the real power is made, in my opinion and experience.

Hope this helps.

 

Thanks. Yeah the car is off the road for the year until I get that done, replace my throw-out bearing, and put in new injectors.

 

I jud]srt had a set of 996.2 heads done at Hoffman , full reconditioning with porting. $5000 for all. They are beautiful!

 

For the sake of conversation, don't flog me to death! I have had many cylinder heads rebuilt. Even on a 356 that I had. But never on a modern P car. With that being said, the process is basically the same across the board. Yes, some specs are very specific but a valve seat is a valve seat. A guide is a guide. Whether you get a 3 angle grind or not is still basic machining. I do not know how much seats/valves/guides are for one of these engines, but $2500/head seems excessive to me. I am thinking 2 hours per cylinder, 12 hours at $100/per hour, parts $250 per cylinder. Just looking to understand the costs. Maybe I need to get my head out of 1998!!!

 

I too think $5,000 for a valve job is excessive and I would never do that.

 

I had my heads gone over by Len Hoffman in 2023 when I did a full rebuild to 4.0 due to bore scoring. The cost was a little over $4k. That included pressure testing, ultrasonic cleaning & media blasting, cleaning & grinding the valves on centerless grinder, removing and repairing almost all of the exhaust bolts & threads, new valve seats as these heads have a history of dropping seats, serdi valve , all new guides and seals, new 3.8l valve springs, his "stage 1" porting, diamond milling the decks, re-machining the exhaust flange faces. He even replaces the frost plugs and epoxies them in place.

They looked incredible when I got them back from him and he was incredibly generous with his time talking me through the process and make the best decisions. It's just him and another guy Matt that do all the work there. Had the chance to stop in one evening last fall when I took my 4S down to southern Georgia to visit my mom, was super cool to see the shop and they absolutely know what they are doing. Can't recommend them highly enough. The car RIPS now and their headwork absolutely is big part of that equation.

 

Thanks! Would you happen to know how much it was without porting?

I’m just trying to keep my late-father’s car on the road, not squeeze any extra performance out of it, so if I could save even $1k on the job, while still having it done right, that $1k could towards a lot of other preventative maintenance.

 

I know I’m going to be due for a rebuild at some point in the next few years. This was my cylinder 6 when scoping back in 2024, about 10k miles ago (date code is wrong):



Planning on DIYing the rebuild so I can reuse anything I’ve recently replaced to keep the costs down, and figure head work would be part of the rebuild anyways.

I’m anxious to pull the heads off and check the cylinders directly, and have to admit it keeps me up at night but I have too many car and garage projects before I can get a chance to scope it again.

 

Update that labor rate to $200/hr and you'll be closer to 2026 costs. Not all machine shops are good machine shops.

Chicago/metro Porsche dealer labor is $319-330/hr, Barnaba Autosport, a top quality independent Porsche shop is at $259/hr

I would drive across the country to get competent work done on my Porsche engine for $100/hr

 

Absolutely nothing wrong with that (part of the) cylinder wall visible in the picture. Just drive it and maintain it not rebuild it, after you've had the head refurbished.