Any change with engine temperature?

Could be a bearing in the cam tower, wrist pin slop, ovalled rocker bore. The ovalled rocker bore would be more difficult to check. It might set correctly but have extra slop in the range of motion.

You can eliminate the broken valve spring relatively easily. Get the #5 cyl to TDC and then you manually depress the valve via the rocker arm. You will need to fabricate or improvise a bit of a lever to do this. I have done my entire engine this way (on a 930 - which is harder than an SC). You will be surprised how easily they will go once you have it right. Then compare against another easy to get to valve. You will feel the difference if one spring is broken.
Alan

The general clatter in the engine compartment seems a little worse with a cold engine, but I haven't checked with the stethoscope so its hard to say for sure if my infamous clack is any different then. Most of my listening has been on a fully warm motor.

Cam tower bearings: when the shop had the cams out for the top-end rebuild, would they have inspected these bearings and been able to detect problems at that time?

Ditto wrist pin slop and rocker bores, since these would have been inspected on the rebuild, though of course new problems can develop.

Arghhh I was hoping I didn't have to tear this sucker down until next winter... :mad:

Use a stethoscope or just a long metal pin to determine the origin of the sound. If the sound is clearly in one cylinder my guess is that that cylinder has seized and is now tilting causing the typical clatter sound. I have been there, and even with a small USB camera through the spark-plug hole it is hard to determine. If it is in one cylinder there is little you can do without taking of the heads and looking in the cylinder to check. You can even take the heads and cam-tower assemble off as a whole with the engine still in the car. It does not take that much time. You just need to get on with it, spring is coming!

Let me make sure I'm understanding this correctly. You're saying one cylinder could have seized... tilting the barrel and causing the piston to make this clatter on its travel. Is this correct?

How likely is a seized cylinder on a rebuild done just 4K miles ago? I've owned it for the last 2K miles and its always had the clack under my tenure, so if this had happened it would have been not long after being rebuilt. Sure its possible, but what would cause that to happen? I bought the car from a fellow P-Club member and he was really forthcoming about all aspects of the car, seriously doubt he ran it out of oil or something like that. If it already started clacking right after the rebuild I doubt he knew.

The term "seized" means not moving, stuck. Perhaps what's needed is a different description that causes excessive piston slap to occur after relatively low miles.

At any rate, I think you've eliminated most of the easy-to-access sources of the noise. If you decide to disassemble yourself, examine each of the pieces as they're removed. You'll eventually locate the source of the noise. Hope it's not too deeply embedded,

Sherwood

Just tuned in...symptoms are very similar to my 912 engine after a recent rebuild. It had a clack clack clack pinpointed to one cylinder via my $15 stethoscope. It sounded like a very bad lifter hammering and was heavier than excessive valve clearance might sound. In the end I found that one piston was touching a head due to excessive head machining (long story). The piston sat 1 mm down in the cylinder at TDC but the dome interfered with the combustion chamber. It wasn't enough to stop it turning over and the contact was very light. I pulled the engine twice before I found the problem. I don't think there is an easy way to check this without dissassembly. Hopefully your issue is easier to resolve.

I have had it just after 50 km on a brand new rebuild engine. In my case it was probably a bore-wash caused by a defective carburetor that broke the oil film.
I don't say this is the issue in your case. But sound is similar and I you have checked all the easy options. Hopefully it is not the case and it is something easy like a valve spring. But if you don't see anything out of the ordinary under the valve-covers you have not a lot of options left except taking the heads of and checking the cylinders. If that is not the case it might be a rod issue

On the other hand changing a cylinder and piston is easy if you compare it to a rod issue. Main issue is to find out why it went wrong.http://forums.pelicanparts.com/uploa...1424250961.jpg

Slightly OT- Heinz, is that really from fuel wash? *Someone I know* once put a rod bearing in wrong so that it covered the rod oiling hole that squirted oil up to the piston in a water cooled engine. It didn't take much more than idling for a few minutes before the engine started "squeaking." The piston looked exactly like yours. The sound still haunts my dreams!

The set went to Mahle in Germany to see if it had any flaws in it. I spoke to the engineer who did the assessment and he explained me that the damage was evidence of a broken oil film. Whether that was caused by a bore-wash or something else he didn't know. What I found out is that one of the valves in the carburators was stuck. Probably just by sitting on the shelf during the rebuild. When I checked the carburator level, petrol just came flushing out. I replaced the valve and it was OK. But enough OT on my engine.

Hey guys-- I don't consider your posts OT at all, I'm learning a lot from the additional information, so thanks! SmileWavy

Did you ever find out what the root cause of the sound was?

Yes, more or less. I had the car into two P-mechanics I trust for a listen, and they both diagnosed it as noise from the valves closing. Once again, pretty frustrating that the previous owner didn't get the motor redone correctly, the heads haven't been touched.

On the bright side, both techs said to get out and drive it so long as the noise doesn't change any. Now its three years and 5K miles since I bought the car, and its been on numerous long trips and P-club drives at high revs. Runs like a clock and doesn't leak a drop, I'm driving the car and not worrying about it. I am also saving up the cash to do a complete no-compromises rebuild, when the time comes.

Atta Boy Evan. Drive it when the weather permits. I just finished my 3.0 full top to bottom rebuild as a first time engine rebuild experience and it started up fine and revs with no weird sounds along the way to 7K.

Now I am going to drive the wheels off this 914-6 conversion.

cheers

A little further update to my old thread: I've now had the car four years, and my mechanic's advice to keep driving it seems to be working just fine. I'll rebuild when time and funds allow.

However: I had the engine out this winter for a gearbox rebuild. While it was out I did a valve adjustment, and really took my time. Went over every valve 4-5 times over a few evenings to be sure everything was good, using 3 methods: traditional with angled feeler gauge, Kirk tool, and backside method. Everything got adjusted to spec: traditional method (which I prefer) gave a good resistance on the feeler.

Unfortunately I have a new clack on the 1-2-3 side, which is intermittent. Shows up for a minute or two, then disappears, then comes back. The sound follows RPM directly (gets faster with revs), seems to be slightly better when warm but still shows up. Oil pressure is good. I'm going to pull the covers on that side and check adjustment again, but thought I'd share a video in case anyone has comments-- this was my first complete valve adjustment:


<iframe width="560" height="315" src="https://www.youtube.com/embed/4HFTUHl6lVM" frameborder="0" allow="autoplay; encrypted-media" allowfullscreen></iframe>

Sounds like a loose rocker to me

Checked all of them for side to side and general movement when the covers were off. The only mechanical change is the valve adjustment. Not disagreeing with you, just seems unlikely?

<humbly reports back to forum> I isolated the noise to the upper drivers side and pulled the cover off to check valve adjustment. Short version: I think we're looking at a busted valve spring.

Long version: When I got to number 2 and I went to tighten the screw to start at zero lash, it just kept turning, easily. So I pushed on the rocker with a screwdriver and it was easy to push in. Not as easy with a thumb on it, but I can move it. Per usual procedure I rotated to numbers 1 and 3 to compare the force required and these were much stiffer. So it looks like one of the the intake valve springs is broken... I tried to see in there with my boroscope, but no go.

Also, when rotating the engine by hand, as the #2 intake valve opened (reaching TDC for 3 or 1, I can't remember) there was a loud "tick" from number 2. Did this a couple times in a row. Thats my (new) clack noise.

When I adjusted the valves on the stand a month ago, all of them went fine-- each would defintely bottom out at zero lash and go no further. So this a new problem. Given the motor has 165K miles on it and plenty of other noises, I'm debating if it is time to just bite the bullet and rebuild. As always, input welcome.

You can replace the spring without removing the engine. Pelican sells a spring compressor that attaches to the cam towers.

Thanks! I've seen some threads on this so I'm thinking I'll give it a try as a stop-gap fix. Would be nice to be able to use the car this season and then consider a rebuild for next winter's project.

Besides getting the tool and springs, are there any other parts that will need replacement, like the retainer/keepers or anything else? Sorry for the noob question , but ordering parts where I live takes time so I can't afford to be missing anything.