holly sh^t Dave... that is a knock!! Can you rev the engine slightly to get a sense of how the knock goes with changing engine rpm and up load that too?? Sorry to be a pain in asking.
I want to say it sounds like low oil pressure, but if that, what knocks?
I will stick with con rod at crank or wrist pin at piston...
After hearing that, I would not drive it... I believe you said the tub is totalled.
Best of luck in figuring it out whats making that noise!!

Bob

Dave, that almost sounds like something dropped into the intake and the piston strikes it each time it comes to TDC. Broken valve spring keeping a valve open? probably not since you said the adjustment went fine.

Loose wrist pin? Broken head stud laying in the bottom of the case?

I guess its out of the car now so let us know what you find when you tear it down.

Almost Sounds like piston slap, I had that real bad in my 912 engine once. Does it get better as the engine warms up?

Bob - the engine's already out and torn down, buddy :) - I don't waste time.

We have a winner to be announced shortly - I got the top end torn off and the problem was immediately apparent.

Incidentally, I have now named this engine and his name is Philip.

Pics coming in a few mins!!!!!

To recap, this was a headscratcher. Oil pressure was fine, zero broken head studs, good compression and ~6% variance, no top end oiling issues, no valve lash issues, no strange oil leaks, nothing unwelcome in the sump. My final bets were broken valve spring or a wrist pin issue. I was wrong - Jamie was right. Feast your eyes:

http://forums.pelicanparts.com/uploa...1203221655.jpg

http://forums.pelicanparts.com/uploa...1203221733.jpg

http://forums.pelicanparts.com/uploa...1203221770.jpg

http://forums.pelicanparts.com/uploa...1203221811.jpg

http://forums.pelicanparts.com/uploa...1203221856.jpg

Insult to injury: Alusil cylinders I think - no magnetic response and dulllllll flat grey. Are those Alusil? Fully threaded Dilivar head studs (24) - are those 993? If so I will leave 'em...Any body got a spare head?

funny, That looks like a drywall screw. i don't recognize it from any CIS related part.


I have a spare early SC head but not a small port.

hey Dave... was it a dry wall screw that found its way in there? It looks like such a screw head in the pic.
Make sure when you source the head, piston & cyl that you get ones from the same size group as the others on the engine i.e. height, weight, ect.
Mystery solved, yeeeeeeeee hahhhhhhhhh!!
Get it fixed and sell her as the other vitals were good from the diagnosis right?
Bob

Yeah, I have no idea what the screw is. I don't recognize it from anything on the car. Really annoying. Yep, I know about height & balancing etc etc. Although, I will probably just part the engine out as it is (it is from a parts car, after all).

Really was hoping for a bad spring or something less destructive. This engine was otherwise tight as a drum - even the bad cylinder was putting out 145 lbs (lowest of the six measurements, go figure), despite a nasty groove in the cylinder. It does not deserve to succumb to such a fate!

And in true Pelican fashion: anybody needs engine parts - call me :)

dave. I left you a vm earlier today. If you get a chance, buz me back at 508 747 2314
Take care and I am glad for you that the mystery solved!
Bob

DTW

Er, your tensioners look fine (modest gap under the collars).

Last laps at enduro at Texas World Speedway. Listening to wife go by driving our car. Oh oh - it doesn't sound right. But the likely cause was easy to find after the race was over when I pulled the filters off the carbs. The machine screws I'd used to hold the air horns on had vibrated loose on one side. Some were lying there. Others were MIA, and you know where they were.

I was able to reuse the heads and one of the pistons after cleaning things up a bit. One piston had the top ring land compressed a bit, so it was added to the junk collection. But these were smaller screws than what your engine injested, but 10.3/1 Mahles in a 2.7.

Is the culprit stuck face up in the head? If so, shouldn't the noise have gone away? Mabye clearance in that area is smaller than I think, though.

I take it this mystery screw scratched your Alusils (yes, if a magnet has no attraction they are Alusils)? Otherwise looks like you could put it back together and it might run just fine. It is the sealing surfaces that count most, and the valve/seat may have escaped. It couldn't get at the head/cylinder joint. Clean up the high points so they don't cause preignition.

However, get another head and a new P&C set, and you've got a rebuilt motor. Or almost.

Throwing a rod through the case creates parts motors. This one sounds like it is pretty intact.

That screw could have gotten in through a spark plug hole while changing plugs or checking compression/leakdown. But why would one be hanging around ready to fall in?

Does the air box show any signs of repairs? Someone had the intakes off to replace gaskets? Obviously the engine was apart, other than perhaps splitting the case, to replace the studs. But wherever that screw was hiding out, you'd think it would have gotten sucked in past the intake valve not too long after the engine was first started.

Wierd, wierd, wierd.

Walt

Dave,

Glad you found the issue. Will call you on parts. Need to get some work done on current projects but It is a good time to start collecting parts.

Is that head really scrap?
I wouldn't trust the piston but couldn't you just sand away the rough parts in the head and call it good, if it isn't to deep?