Disturbing knocking sound on first startup

[fredmeister]

I would go thru the entire engine while it was out and retime the cams. Since your rebuilder obviously screwed up I feel for you. Hopefully he owns up and makes it right for you.
You might want to look into either advancing or retarding the cams too depending upon how you want to effect the power delivery. I don't know with the 964 cam how much leeway you have here because of issues with intake valve clearance, but something else to look into. My 911SC 3.0 had the 964 cams and it pulled like a mother up to 6800rpm much better than the stock SC cam. At little sacrifice to low end and idle.
Also adjust the valve clearances while it is out of the car as well.
Good luck.

[squidmarks]

I did a leak down test on all cylinders last night. Everything checked out fine (<10% on all). I will be receiving the missing 10 spring seats and extra shims from my machinist today, so I've got a weekend's work lined up. I'll re-check the piston/valve clearance while I'm in there.

Geoff

[juicersr]

Zen and the art of Porsche maintennance....the older i get the more that book rings true.
Damn, i'd be PISSED.

Going out to check my valves right now. Getting ready to install my motor next weekend.

Good luck Geoff and hope nothing serious happened.

[squidmarks]

Wow, that was quite a bit of work. Engine removal, take out the valve springs, shim them and put the spring seats in, put the engine back in. Sounds simple, right? But add in all the little pain-in-the ass steps like what a bugger it is working on the valve springs with the cam cases in the way. I had to invent a few tools to make the job easier. First off, how do you get the stem seals out without making a mess of them? Sure its easy to get a screwdriver on them when the head is out in the open, but not so simple when their buried in a 4' deep hole with the cam case on. I had to make this little tool to get them out:



Its a cheap little wrench that you get with assemble-yourself furniture that has been bent over, opened up and filed so that it slips under the seal without damaging it. It took me about 1/2 hr struggling to get one seal out before I made this tool, then it took 30sec a seal.

Next was getting the valve springs out. Again, with the heads on a bench, just use the standard C-clamp type spring compressor. I have the in-engine spring removal tools, tho. The intake one works great, but the exhaust one depresses the spring just enough to get the keepers out, but not enough to get them back in easily. Again, after farting around with one exhaust spring trying to get the keepers in, I finally crafted a spacer for the spring removal tool that added about 5mm to the spring compression and that made a world of difference. I could the easily pop the keepers back on.



Finally, getting the rocker shafts out is relatively simple, but there is very little room to get an allen wrench onto the nut. It takes what feels like 100, 2deg increments of the wrench to get it out. A normal 5mm allen head socket (3/8) is too long to fit, so I made a short-throw 1/4" drive 5mm allen socket by cutting off a short section of an allen wrench and sticking it into a 5mm socket. Much quicker removal/installation of the rocker shafts.



All done now, leak down looks good, piston/valve clearance is fine, valves re-adjusted and the engine stuck back in. I was going to start it, but I had to get cleaned up for supper. I decided to wait until next weekend to start it and see if I've fixed the problem. I figured if I started it tonight and there was a problem, I won't have time to fix it and it will bug me all week (I need to go to Denver on business this week). So, stay tuned and I'll let you know how it sounds...

Geoff

[notmytarga]

I would enjoy charging MY labor rate back to the machinist. Just how apologetic was he for this screwup? Did the machinist have a trainee working that day? Providing tools is helpful, but simply not enough.

Good work on being suspicious and being a detective and finding the problem.

[911 tweaks]

Geoff... ,my hat is off to you once again!
You always find a way to figure things out efficiently and to the point!!
I think I am way over due for a visit to see all of the progress you have made here!!
Congrats and just think... you are almost there!!
Bob

[Turbo_pro]

Mistakes happen.
This is why you always double check the work.
All machine shops I have ever visited have a sign that say "check cleanliness and assembly before installation".
I am not a Porsche engine builder but whatever engine I have ever built I measure everything. I measure cranks, cylinder bores, main bore and rods. I never trust that a piston has the compression the manufacturer says. It's just common sense. People are human and mistakes happen.
This problem could have been avoided by simply inspecting the work.
I think missing spring seats are easy to notice.

Just my 2 cents.

[sc_rufctr]

All good info but at the end of the day it turned out to be a simple fix.

I am concerned that a professional engine builder could forget to install the seats but compared to some other horror stories I've heard this is relatively minor.

That was one of the many reasons I started to buy my own tools and work shop manuals for my cars.

I started with the basics but was lucky enough to have a friend who owned a Snapon truck. So I started to buy just what I needed for my cars. Now I have enough tools to do everything on my cars except torque the rear hub nuts on a 911. That takes over 300 foot pounds and the the bigger of my two torque only goes to 250 foot pounds.

I have never looked back...

[squidmarks]

Jim, I'm in agreement with you - mistakes can happen. If this was a MotoMeister job, I might be more upset as they have a reputation for poor work, but this was a machinist well respected by the Pelican community and it appears to have been a rare mistake. He was very apologetic. I have not asked for any remuneration, but will expect a freebee on my next job with him. If this were my business, I might be more concerned, but this is a hobby and I learned from the experience and no damage was done.

Geoff

[squidmarks]

Originally Posted by 911 tweaks

Geoff... ,my hat is off to you once again!
You always find a way to figure things out efficiently and to the point!!
I think I am way over due for a visit to see all of the progress you have made here!!
Congrats and just think... you are almost there!!
Bob

Bob, yeah, you're overdue for a visit. Let me know when you have some time to stop by.

Geoff

[squidmarks]

Good news! I started her up tonight and she's as quiet as my wife's sewing machine. Wow, what a difference in engine sound. As I may have said, I didn't really know what a 911 should sound like, so I wasn't really sure if all the clicking and ticking I had heard when I started her up the first time was normal. But now, with the valve springs properly installed the engine makes a nice whine instead of a cacophony of valve noise.

Geoff

[fredmeister]

Now sit down and have a beer and pat yourself on the back. Feels good to accomplish something like that right?

[vreference]

I know how you feel. I bought my car with valve guides worn 6x the limit. It was noisy to say the least. This wear also made it impossible to set valve lash properly. (For future generations, if you set your lash perfectly, rotate the engine and they are all different: You probably have worn guides) Unfortunately I never thought to just grab the valve and wiggle it (I've never come in contact with valve guides that far gone) and I was always wondering if this is just how Porsches sound or was it something I had done wrong.