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

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

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

Additional equipment added.......
 

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

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

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

OK will do as suggested......
 

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

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

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

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

Leakdown test........
 

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

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

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.

Sticking valves.....
 

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

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

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

Weekend update........
 

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

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

I am embarrassed to announce it......
 

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.....

http://forums.pelicanparts.com/uploa...1456001427.jpg

http://forums.pelicanparts.com/uploa...1456001457.jpg

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

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

H Tony,

Congratulations and well done!

Whilst you will be probably be frustrated at the amount of time it has taken to rectify, think of all the good you have done by documenting everything here for the rest of us backyard Porsche mechanics.

Thanks for your contribution to this wonderful knowledge base.


Cheers,

Harry.

Oh, I thought you redid the timing which requires torquing of the cam bolts?

Great you figured it out!

Tony, I'm confused about what was "slipping"? The pin locks the sprocket to the cam. The bolt and washer simply keep everything in place.

The cam gear can be walked back and forth with the pin in the hole. The pin doesn't solidly lock the cam in place all by itself. Redo the cam timing procedure now.

Camshaft sprocket and camshaft flange.......
 

MReid,

The pin does not lock the sprocket to the camshaft per se. The adjusting pin sets or aligns the sprocket to the camshaft flange. The camshaft flange and woodruff align with the camshaft. Without the sprocket mounting bolt and washer installed tightly (sufficient torque) there is a small play or movement between the sprocket, flange, and camshaft. It was this very small sudden movement or travel of camshaft from/to the rockers that was something peculiar with my camshafts caught my attention.

Without any rockers installed, you could turn the crankshaft without experiencing or hearing the weird noise (whatever name to call it). But once you install a rocker/s, the noise starts to appear after going over the high lob/s.

After I applied some torque to the camshaft sprocket mounting bolt with washer the mysterious sound disappeared. And you don't observe any slipping or jerking of the camshaft during crankshaft rotation. If you have some doubt, loosen your camshaft bolts and do the test.

Tony

Tony, I'm glad you got it. That's the .15 movement between front and back of the locator hole.
Everybody learned something and your extended descriptions are thought out.
Bruce

Cam timing........
 

John,

I will torque the cam bolts to spec and repeat or redo my cam timing several times like I always did in the past. Like you said, the pin alone does not lock the cam in place. Thanks for sharing the information because some people might be thinking I was imagining this mysterious and sudden rotational movement of the camshaft.

Tony

Words from my mentor......
 

Bruce,

I would not be in this position rebuilding engines without your unselfish assistance and help. Someday, I will come and visit you. I still owe you some $$$$ for the parts you gave me. Thanks.

Tony

This is great news.

Good news - disaster averted.
90 ft/lb?
Alan

Thanks, Tony, that makes sense. Great lesson! I never would have thought that little bit would make that much of a difference.

Congrats. I was entertained. :)

Good job finding the cause and solution. Time to bolt it all up and get it installed. :)

The chain under cam tension would have been riding the slightly mis aligned tensioner/cam teeth, then dropping into place under load. Had the same thing a couple of days ago as I was timing the cams. Noticed the chain slightly riding the teeth. But the cam sprocket at that point was slightly out of line as it hadn't been torqued up.
Alan

Update for another setback.......
 

Thanks Al lkosmal for the oil pressure check. I should have posted it here than having it in the other thread. Anyway, for those of you who have followed this never ending saga, there is another added chapter.

While I was able to get the engine to run after replacing the defective fuel distributor (FD), there is another problem I am having now. The oil pressure seems to be a problem. The engine test stand I am using was basically built for CIS troubleshooting. It does not have an oil pressure gauge connected and it was only a few days I ago that a tachometer was hooked up.

The engine starts and run every time you turn the ignition switch. Everything seems good when the engine is cold. But once the engine gets warmed up and sits for about 30 mins., an engine restart would reveal another problem. A very loud and tapping/knocking noise is coming from the engine during the initial warm re-start. Less noise after another re-start and a third re-start seems to get lesser annoying noise. The abnormal noise is very reproducible when the engine is hot and warm but nothing when the engine is stone cold.

Without a suitable pressure gauge connected I have no idea what oil pressure I was having. So the next action is to install an oil pressure gauge and monitor the oil pressure during start (cold and warm) and during idle. Any suggestion or recommendation are highly appreciated. Thanks to everyone.

Tony

Valve to piston clearances.......
 

It was suggested to measure to the valve to piston clearance @ overlap (360° from TDC).

Here are the information I gathered this week after measuring the number of turns of the valve adjusters before coming in contact with the top of the piston/s:

@ Overlap:
Cylinder #1 intake valve--------------3.25 mm (3 turns + 1/4).
Cylinder #1 exhaust valve------------3.75 mm (3.5 turns + 1/4).

Cylinder #2 intake valve--------------3.25 mm (3.5 turns + 1/4).
Cylinder #2 exhaust valve------------3.25 mm (3 turns + 1/4).

Cylinder #3 intake valve--------------3.25 mm (3 turns + 1/4).
Cylinder #3 exhaust valve------------3.65 mm (3.5 turns + 1/8).

Cylinder #4 intake valve--------------3.50 mm (3.5 turns).
Cylinder #4 exhaust valve------------3.50 mm (3.5 turns).

Cylinder #5 intake valve--------------3.25 mm (3 turns + 1/4).
Cylinder #5 exhaust valve------------3.75 mm (3.5 turns + 1/4).

Cylinder #6 intake valve--------------3.75 mm (3.5 turns + 1/4).
Cylinder #6 exhaust valve------------3.75 mm (3.5 turns + 1/4).

Another set of measurements done @ TDC and numbers were very similar to the above data.

I was expecting to see some obvious problem from the data but can not imagine what is causing the tapping noise coming from the engine. Could anyone tell anything from the numbers I collected? By the numbers above, there is ample clearances between valves and pistons. So what could be the culprit causing the knocking or tapping noise coming from the engine?

BTW, a mechanical pressure gauge was installed to determine oil pressure during cranking and run. Picture to be posted later. Thanks.

Tony

Did I mention my loose cam drive gear? Gear was clicking back and forth against the woodruff key on the crank. Very noticeable when hot. But quiet when cold. Unfortunately it required welding and a replacement gear. Noise went away after repair.

Picture of mechanical oil pressure gauge installed.......
 

In order to monitor the oil pressure during cranking and actual operation, a mechanical oil pressure gauge was temporarily installed.

http://forums.pelicanparts.com/uploa...1468193252.jpg

During a brief run, oil pressure gauge showed about 30 psi. (2+ bar). I have been calling and contacting people from this forum seeking advices, ideas, suggestions, recommendations, etc. to get to the bottom the problem. The response and support I get from some members of this forum is overwhelming.

Tearing the engine apart now without knowing or understanding the root cause of this problem will probably bring me back to the same situation. I welcome any idea you could bring to the table or PM me. Thanks.

Tony

Will consider this one......
 

VFR,

When I get to the point of tearing the engine apart, I will place this suggestion on top my list to check. Were you referring to the gear sprocket/s? I could inspect them right away. The noise seems to be coming from the chain box but I could be wrong. I was thinking it was a failed tensioner but they have not collapsed.

Would installing a mechanical tensioner for test run a good idea? I was discouraged not to try one. Any opinion? Thanks.

Tony

Oil pressure hot or cold? Was 30psi measured whilst your problem tapping was occurring?