Never ending problem for the 13th engine rebuild (very long post)......

[Alan L]

Yes, if you are going to proceed from head to head, leaving the previous springs off, your plastic tube over the stem sounds right. You would need to get it right to the base of the guide tho - you don't want it dropping down any distance if you are rotating the engine. (that might prove tricky) Another option might be a clothes peg or bulldog clip. Pay to check each time you are about to rotate that they are all in proper closed position.
Or maybe a light spring that just slips over the stem, then clothes peg at top holding spring?
I'm sure you will come up with something.
regards
Alan

[911pcars]

Originally Posted by Alan L

Good luck. That is good news some good soul is lending you the tools. Don't forget - you need to pressurise the cylinder you are working on. And lock the engine - you don't want it rotating with 100 psi behind the piston. Once your wife gets the new dress I would break the news you also need your compressor in the kitchen/w/shop - for a short while. You need the pressure to hold the valves shut while you push down on the spring. I find a sharp crack with a socket on the keeper before that helps it break free. But it may already break free since engine hasn't been running.
I would try slacking the valves off first - in case the issue becomes clear without having to pull the springs. Then maybe, if the issue isn't obvious then, try adjusting just one set of valves and see what happens.
Regards
Alan

Can also delete the air by rotating crank so test cylinder piston is at TDC. Valves won't open (drop) far (<.500"). Besides, if the valve is bent, you'll need more than 100psi to keep the valve closed.

Restore cylinder before moving onto the next cylinder, then repeat.

Sherwood

[Alan L]

Yes, if you are going to proceed from head to head, leaving the previous springs off, your plastic tube over the stem sounds right. You would need to get it right to the base of the guide tho - you don't want it dropping down any distance if you are rotating the engine. (that might prove tricky) Another option might be a clothes peg or bulldog clip. Pay to check each time you are about to rotate that they are all in proper closed position.
I'm sure you will come up with something.
regards
Alan

[boyt911sc]

Originally Posted by Alan L

Good luck. That is good news some good soul is lending you the tools. Don't forget - you need to pressurise the cylinder you are working on. And lock the engine - you don't want it rotating with 100 psi behind the piston. Once your wife gets the new dress I would break the news you also need your compressor in the kitchen/w/shop - for a short while. You need the pressure to hold the valves shut while you push down on the spring. I find a sharp crack with a socket on the keeper before that helps it break free. But it may already break free since engine hasn't been running.
I would try slacking the valves off first - in case the issue becomes clear without having to pull the springs. Then maybe, if the issue isn't obvious then, try adjusting just one set of valves and see what happens.
Regards
Alan

Alan,

I have a small portable air compressor I could bring inside the house. But that is something she might not like because she watches her favorite TV programs while in the kitchen or cooking. The big air compressor in the garage has enough length of hose to reach, the kitchen area. So I will just crack the door for the air hose to get through while I pressurize a cylinder.

Right now, I've been sitting and waiting for my wife for over an hour with no complain. As soon I get back home tonight, I will start backing the rocker arm adjusters. Stay tune. Thanks.

Tony

[Alan L]

Originally Posted by 911pcars

Can also delete the air by rotating crank so test cylinder piston is at TDC. Valves won't open (drop) far (<.500"). Besides, if the valve is bent, you'll need more than 100psi to keep the valve closed.

Restore cylinder before moving onto the next cylinder, then repeat.

Sherwood

While I agree you can do this there are 2 issues.
1) the force on the spring compression will transfer to the valve on the piston
2_ You have lost about 1/2" of height which will make it harder to remove/install the collets.
Regards
Alan

[911pcars]

Originally Posted by Alan L

Yes, if you are going to proceed from head to head, leaving the previous springs off, your plastic tube over the stem sounds right. You would need to get it right to the base of the guide tho - you don't want it dropping down any distance if you are rotating the engine. (that might prove tricky) Another option might be a clothes peg or bulldog clip. Pay to check each time you are about to rotate that they are all in proper closed position.
I'm sure you will come up with something.
regards
Alan

Might be a good idea to first perform a leakdown test on each cylinder. If there's a bent or stuck-in-the-guide valve (much leakdown), the head(s) will have to come off anyway to repair. If LD passes, you can still confirm each valve-to-guide clearance afterward as a final inspection of valve guide clearance/sealing integrity.

S

[boyt911sc]

Originally Posted by 911pcars

Can also delete the air by rotating crank so test cylinder piston is at TDC. Valves won't open (drop) far (<.500"). Besides, if the valve is bent, you'll need more than 100psi to keep the valve closed.

Restore cylinder before moving onto the next cylinder, then repeat.

Sherwood

Sherwood,

Will do one cylinder investigation at a time. Will install everything back then move to the next cylinder. Will keep you posted. Thanks.

Tony

[911pcars]

Originally Posted by Alan L

While I agree you can do this there are 2 issues.
1) the force on the spring compression will transfer to the valve on the piston
2_ You have lost about 1/2" of height which will make it harder to remove/install the collets.
Regards
Alan

You'll have the same issue if you depend on air pressure to hold the valve closed while compressing the spring.

One trick is to position a suitably-sized socket over the valve retainer (valve stem clears inside the socket), then smack the socket with a heavy mallet. That should break any stiction between the split locks and valve stem groove (cover engine openings and valve spring area with a cloth, just in case the locks want to go airborne). Further manual compression of the spring and the locks should fall out of the groove. It also helps to rotate the engine to counteract gravity.

Sherwood

[Alan L]

Originally Posted by 911pcars

Might be a good idea to first perform a leakdown test on each cylinder. If there's a bent or stuck-in-the-guide valve (much leakdown), the head(s) will have to come off anyway to repair. If LD passes, you can still confirm each valve-to-guide clearance afterward as a final inspection of valve guide clearance/sealing integrity.

S

Good suggestion. If you have the gear, you are half way there anyway.
Alan

[Alan L]

Originally Posted by 911pcars

You'll have the same issue if you depend on air pressure to hold the valve closed while compressing the spring.



Sherwood

No - the valve will stay shut against 100 psi. I have never had them move. That is the sole point of pressurising.
Alan

[boyt911sc]

Prior to the removal of cylinder head#6, suspected of having bent valves, I did a Leakdown test. All cylinders except #6 were tight and good. So I removed cylinder head#6 and brought it to the machine shop. Both valves were placed.

After the installation of cylinder head #6 (newly rebuilt), I pressure tested again cylinder #6 and passed the leakdown test. And this was 3 weeks ago. I will do again another Leakdown test tomorrow morning. It is rather late now to run the air compressor.

Assuming that all six (6) cylinders are good and holding air pressure, would it be best to remove the valve springs when the cylinder is under "Leakdown test" or pressure?

Tony

[Alan L]

I would first slacken the valves and see if you find any conclusions. If you have to proceed further, then you need to remove the valve springs while you have pressure in the cylinder. If you have rotated the motor and there is a vague possibility valve timing/cam issues or something is wrong, you may as well do leak test before pulling the springs. You have everything set up for leak test other than collecting the numbers before you pull the springs, so may as well check. If leak test numbers good - probably no bent valves, in which case, why pull the springs? Unless maybe some coil bind/broken spring etc?
Regards
Alan

[Tippy]

Yeah, pulling valvesprings before trying to loosen all rockers would be a lot of extra work that more than likely not uncover root cause.

I'd loosen rockers first and rotate crank.

I bet your problem will be found.

[boyt911sc]

Originally Posted by Alan L

I would first slacken the valves and see if you find any conclusions. If you have to proceed further, then you need to remove the valve springs while you have pressure in the cylinder. If you have rotated the motor and there is a vague possibility valve timing/cam issues or something is wrong, you may as well do leak test before pulling the springs. You have everything set up for leak test other than collecting the numbers before you pull the springs, so may as well check. If leak test numbers good - probably no bent valves, in which case, why pull the springs? Unless maybe some coil bind/broken spring etc?
Regards
Alan

Alan,

I am confident that all six (6) cylinders will pass the Leakdown test. And I will perform them again prior to valve spring removal. The purpose of removing the springs is to test the valves are straight and has free movement (not sticking to the valve guide).

As suggested earlier, I will back off the rockers and rotate the crankshaft. I anticipate that there will be no slapping noise (?) because the valves have not open up or moved yet. The noise appears/happens after TDC for each cylinder (?). A good test could confirm and verify the root cause of the problem.

Will keep you guys posted. Thanks.

Tony

[Alan L]

If your leakdown numbers are good, then the valves are not sticking - they must be fully closing. A slightly redundant test, based on the above results, would also be to measure the heights by poking a vernier down there. but if one was short of fully closing you should pick it up in the leak test.
Are you getting this noise when you rotate by hand (I think you had the motor running previous to install?).
Alan

[Alan L]

Originally Posted by boyt911sc

Alan,

The noise appears/happens after TDC for each cylinder (?).

Tony

Sounds ominous. I hope you find the noise in the valve train. If it is still there after you slacken all the valves......?
Alan

[boyt911sc]

Originally Posted by Tippy

Yeah, pulling valvesprings before trying to loosen all rockers would be a lot of extra work that more than likely not uncover root cause.

I'd loosen rockers first and rotate crank.

I bet your problem will be found.

Below are the series of tests conducted this week to get to the bottom of my problem:

A). All rockers in place:
Rotating the crank shaft produced clicking or slapping noise as previously observed. Noise occurs after rocker arm passed the high lobe of the cam either in intake or exhaust (?).

B). All rockers fully loosened or back out (max.).
Rotating the crankshaft produced same slapping noises every 120 deg. intervals after each cylinder passed its TDC but slightly later than condition (A).

C). All rockers and pins removed for the next test.
Rotating the camshaft produced no noise. The rotation was smooth as silk.

D). With the help of special tools P7E & P7I, removal of the valve springs with cam head installed was done. I was able to remove and install the valve keepers and valve springs with ease. The valves were tested for movement and they all slide up and down very smoothly with minimal resistance using a magnet. So it is concluded that the valves are not sticking or damaged. They are not a contributing factor to my mysterious problem.

D). After all the valve springs were installed back, rockers for cylinder #1 & #4 were installed too. Valve adjustment @ 0.10 mm gap. Cam timing with 964 cams was measured @ 1.30 mm. Rotating the camshaft produced the same noise observed earlier. Very disappointed and frustrating.

After all the work and time spent looking for an answer to determine the culprit/s, I was back to square one again. I am running out of ideas what to test for. I wanted to call a local PP member hoping to solicit some help or suggestion. And it took me an hour to get hold of him because I misplaced his telephone number and sent him a PM instead. Luckily, he was browsing the Technical Forum and called me.

He informed that he has no experience in engine rebuilding and possibly could not contribute. However, I encouraged him just to think of anything that could possibly be the culprit. Thinking outside the box was what I wanted from him. He said it could be the valve springs (?). The valve springs are not new but tested and calibrated by the machine shop. Maybe this was the culprit (?). Hang the phone and went back to the engine sitting in the kitchen to continue the search........

A few minutes after I spoke to RedDog, I dialed his number and announced to him the GOOD NEWS!!!!!! The culprits were located and identified. And the fix took only a few seconds to execute to correct the problem. Will take some pictures and post them later. I could not have done this without your contributions and encouragement and guidance. Thanks to everyone.

Tony

[Tippy]

When do we get to hear the fix???? You're killing us. HAHA

[boyt911sc]

Originally Posted by Tippy

When do we get to hear the fix???? You're killing us. HAHA

Tippy,

I intentionally delayed the announcement because I am embarrassed and at the same time elated that the culprits were identified. Here are the culprits.....





The two (2) camshaft bolts were the culprits. There were installed but not tight or torqued causing a slippage between timing chain, the sprocket teeth, and camshaft after the rocker arms pass the high lobs of the cams.

I have just applied sufficient torque to keep the bolts tight and everything is back to normal!!!! The crankshaft is rotating smoothly and quiet with no discernible sign of problem. The fix took only several seconds of work but the discovery took me forever! Thanks to all.

Tony

[timchar]

Congratulations Tony.... I love your persistence and never say die attitude...You have helped countless people on Pelican and you are selfless. You are the one that inspired me to do my first engine drop...Here's to many more engine rebuilds. Myself and many others on here KNOW "you know what you're doing"..in the near future, Looking forward to your input regarding my fuel distributor issues...Tim