Indycam

"you would need to record 2 channels: the audio and the ignition signal from one of the cylinders."
One channel would be better , imho .
If a sparkplug was used to make the snap noise next to the microphone ,
the snap of the spark would be seen on that one channel and
that would delete the need to match one channel up to the other .

gfunk

That might would be certainly be easier but you have the problem that the signal is already quite noisy so it might be hard to differentiate the two signals. Best would be a two channel digital scope but not everyone has access to one of those.

One other comment on the noise clip:
- There are portions of the clip where you can hear an extra tap in addition to the regular one. I looked at some of these and they are 2 'sparks' away. I'm not describing this very well but if the firing order is 1-6-2-4-3-5 and cylinders 5 & 6 are suspect then I would say the primary noise is coming from cylinder 5 with occasional taps from cylinder 6.

Greg

Indycam

If after the recording started , the spark was removed , then you would know what cylinder was what and the spark would be no longer part of the image .

tall02

Thanks everyone

It's time to take the big dive and pull the engine to explore what the cause of the noise is. I hope it is obvious.

Thanks again.....I will inform everyone on what I find

Best regards

tall02

Dear Inycam

You have a good point but I did run the engine with just the top plugs firing by disconnecting one of the distributors: no change in the rapping.

I ran the engine with just the bottom plugs firing: no change in the rapping.

I even disconnected both plug wires on #4 then #5 then #6 cylinder: no change in the rapping.

This should eliminate any ignition force on the right bank cylinders.

I have pulled the engine and will begin the teardown this week for close inspection

Thanks

darth

Did you investigate if there was any excessive "play" between the rocker arm and the rocker arm shaft? This is the only component which is affectted by oil pressure and has the frequency indicated in your sound clip.

Bill

KirkF

As long as everyone is weighing in with their opinions, here is mine.

One of the valves is bent, and its sticking in the guide. The sound you hear is the valve snapping back to the closed position after the rocker has released the spring compression.

Once the heads are off rotate the cams by hand and look for a valve that stays open and then pops back after a second.

Kirk

stevepaa

Check all the spring heights when you tear down. Then check the ease of sliding the valves in and out of the guides.

tall02

Well I tore down the engine tonight and I could not believe my eyes. #4 piston wrist pin was extended out of the piston bushing close to the cylinder. The one circlip was missing. The piston was held onto the connecting rod by the front piston bushing. The piston wrist pin was knocking on the back piston bushing which is burred up. The wrist pin and connecting rod bushing still fit very good. I believe I will need to replace the piston.

The big question: where is the circlip. I am not sure if we forgot to install it or is it still in the engine. I will use a borescope and a magnet to inspect and fish around. Then I will try and flush out the case with oil. If nothing shows up I will split the case.

I feel very fortunate after running the engine 12 short runs that I did not have a catastrophic outcome.

Thanks everyone for your interest and advise.

Best regards
Keith

KirkF

Was there any damage to the cylinder wall from the pin?

Maybe at this point you should go the extra mile and just split the case? Its not that much more effort, and then you get the added piece of mind knowing that the bottom end bearings have all been replaced?

Kirk

Indycam

Photo ?

tall02

Rapping noise found

Attached are a few photos of #4 piston and loose wrist pin. I am assuming the rapping noise was caused by the piston pivoting on one of the two support bushings in the piston and the pin slapping the opposite bushing hole.

Anyone know where I can purchase a matching 100mm piston? Piston code is:

Tolerance group/ weight class = 1 - - E /15

Regards
Keith

911URGE

Keith - Thanks for sharing the valuable details of your situation. This is great information and the sound clip was very helpful. Keep us all updated on your progress.

altarchsa

Keith,

I've been following your saga. Thanks for continuing to keep us all informed. As an owner of a relatively high mileage car who does his own repairs, I learn a lot from the Forum and it has saved me a lot of time, effort and money. I know how frustrating it is to get a repaired engine back in and find you still have a problem! That decison to tear back into it was tough I know, but it was the only way to know for sure what the problem was.

I was just putting wrist pin clips in my motor yesterday, so it's a good reminder to check, double check and triple check to make sure all the clips are installed and tight in the grooves. Funny, the first clip I tried to put in a few days ago flew out and landed in the corner of the garage. I let it go thinking I would retrieve it later. By the time I got to the last two, I noticed I was one short, thinking I had already collected the flying one. But sure enough, when I looked it was still in the corner. Whew. Another delay waiting for parts averted.

I read somewhere that it was also advisable to spin the clips so that the open ends were toward the crank. I guess they can rotate in the groove and keeping the greater mass toward the piston might keep them in position considering centrifical force on firing.

Sam