Disturbing knocking sound on first startup

[jluetjen]

I've got a c-clamp style valve spring compressor if you're interested. I just PM'd you. Let me know.

[squidmarks]

Originally Posted by jluetjen

I've got a c-clamp style valve spring compressor if you're interested. I just PM'd you. Let me know.

John, thanks for the offer, but I've got one of those as well. I contacted the machinist who did my heads last night and he's going to send me the tools that allow engine-in-car valve spring removal.

Geoff

[304065]

Do a leakdown test on #5 to see if the valve is bent. That would influence the decision to tear it down or not.

[squidmarks]

Originally Posted by john_cramer

Do a leakdown test on #5 to see if the valve is bent. That would influence the decision to tear it down or not.

Good idea.

Geoff

[sc_rufctr]

How did this workout? Did you confirm the valve spring seat was missing?

[squidmarks]

Originally Posted by sc_rufctr

How did this workout? Did you confirm the valve spring seat was missing?

The tools to do the in-car removal the valve springs should arrive in the next few days. I'll let you know when I get the springs out.

Geoff

[lucittm]

Geoff,
If you can depress a stock valve spring on an assembled Porsche engine with your hand (no mechanical advantage levers, etc.) ...

Remind me to never shake hands with you!

The book says that it takes 95 lbs to move the valve off the seat (seat pressure) !

You are The Man.

Mark

[fredmeister]

Originally Posted by squidmarks

Ok, I think I've found the problem.

Just so you all don't think I'm crazy, here's a video showing how easy it is to push the #5 exhaust valve open. The #5 intake is the same.

I also looked down the valve springs on all the exhaust valves and noticed that I can see the valve spring seats at the bottom of the other valves, but can't see one on the #5 exhaust valve. The valve seats are the cad-plated yellow color which makes them easy to spot against the aluminum. On the #5 valve, tho, I can just see the aluminum seat the valve spring assy sits in.

A valve without a seat would explain why its so easy to depress and would likely float to kiss the piston (hopefully a very tender, gentle kiss).

Does anyone in MA have the intake and exhaust valve spring compressor tools I could borrow?

Thanks.

Geoff

I see a problem with your video that shows pushing the valves with your thumb. Remember that a spring force increases as it is compressed. The #5 valve is easy to press because you are pressing it at its lowest load when the valve is seated. This is simply the preload setting which should be found in the factory spec book for the car. The other valve (#4 I think) that you could not move was way compressed so the force would have been much greater from the spring. Not to say you still don't have problems, but find out what the spring seat force from the manual should be and that will give you an idea how much force you should push with your thumb to move that #5 valve .
Now the only guy that can move springs with his finger is Chuck Norris according to the lists I have seen on him......joking.
Good luck.

[fredmeister]

As a further check, rotate the engine to get the #4 valve seated or TDC on number 4 and then press it. If the force to move it 1mm is the same then #5 is no different than than the others and it may be something else.
Just a thought.
Also ask the rebuilder what the spring seat pressures and spring heights he set everything to were. This confirms he actually checked and installed them properly. Someone before mentioned 95lbs. don't know if this is right though.

[squidmarks]

Originally Posted by fredmeister

I see a problem with your video that shows pushing the valves with your thumb. Remember that a spring force increases as it is compressed. The #5 valve is easy to press because you are pressing it at its lowest load when the valve is seated. This is simply the preload setting which should be found in the factory spec book for the car. The other valve (#4 I think) that you could not move was way compressed so the force would have been much greater from the spring. Not to say you still don't have problems, but find out what the spring seat force from the manual should be and that will give you an idea how much force you should push with your thumb to move that #5 valve .
Now the only guy that can move springs with his finger is Chuck Norris according to the lists I have seen on him......joking.
Good luck.

Yes, in the video I did try to move #4 and #6 as you indicate, and that's not really valid as the valve springs may already be partially loaded by the cam. But, I did check each valve spring's pressure with each piston at its TDC. I can depress all the valves with very similar force except for those on #5 which are much easier.

Geoff

[squidmarks]

Ok, so I rec'd the tools and additional valve spring seats/shims from my machinist to allow me to do in-car removal of the springs. I just removed the #5 exhaust valve spring and, as I suspected, there was no spring seat. So, what do I do now?! How do you properly shim a valve spring? I have a handful of shims, but how many do I put on? Do you typically use some sort of load cell to measure spring rate, adjusting with shims as necessary? Or, do you measure the spring height and adjust with shims to some tolerance?

Thanks.

Geoff

[TdiRacing]

This is why one should always double check the work of others. That should have been easy to spot before assembly. Good lesson to learn. Sorry it had to be you. Mistakes happen, hope you get it sorted w/o damage to you engine.

[Eagledriver]

The number I have for seat pressure is 75 lbs for a stock SC. There are numbers for the spring height but since you have 5 others to look at you could just measure one of them and match it.

my book has the following numbers for installed height of valve springs for 78-80 SC:

intake and exhaust 1.35-1.37 inches (34.2-34.8 mm)


-Andy

[911pcars]

Carefully install a spring seat, spring retainer and locks, but w/o the spring. Using a vernier caliper, measure the distance between the seat and the bottom of the retainer. That distance is the installed height. Adjust the spring seat thickness to meet specs.

S

[squidmarks]

I am using a 964 grind cam on my SC. Since this has a higher valve lift, should the installed spring height be modified? If so, does anyone have these values?

Thanks.

Geoff

[911pcars]

Valve lift determines how far the retainer moves toward the head. Thus, when setting up valve spring height, there must be adequate clearance so the valve spring doesn't stack (close up completely) nor allow the valve lock to contact the top of the valve guide.

To measure if there's adequate clearance, assemble a valve seat, valve spring and retainer assy. in a a bench vise and compress to the specified installed height. Mount a dial indicator to measure further jaw travel, then compress the assy. the amount of valve lift and see where everything ends up.

Are the valve spring coils almost touching. There's a min. suggested clearance.

This compressed distance between valve seat and bottom of the retainer should be more than the distance the valve guide projects from the head.

You might have to look up the exact numbers somewhere or maybe Steve or Henry or ?? can suggest those values.

Something like that.

Sherwood

[squidmarks]

Originally Posted by 911pcars

Valve lift determines how far the retainer moves toward the head. Thus, when setting up valve spring height, there must be adequate clearance so the valve spring doesn't stack (close up completely) nor allow the valve lock to contact the top of the valve guide.

To measure if there's adequate clearance, assemble a valve seat, valve spring and retainer assy. in a a bench vise and compress to the specified installed height. Mount a dial indicator to measure further jaw travel, then compress the assy. the amount of valve lift and see where everything ends up.

Are the valve spring coils almost touching. There's a min. suggested clearance.

This compressed distance between valve seat and bottom of the retainer should be more than the distance the valve guide projects from the head.

You might have to look up the exact numbers somewhere or maybe Steve or Henry or ?? can suggest those values.

Something like that.

Sherwood

Sherwood: Ok, I got the proper installed spring height and procedure to measure this. Once I get the springs in and properly shimmed on #5, I will be able to compare how easy it is to lift those valves versus the others and determine if I need to pull all the valves out to check.

Geoff

[fredmeister]

Since you found this error with one valve why not remove the engine and recheck all of them to be sure they are correct? Get the specs on spring seat pressure and installed height and get them all to spec.
You will likely feel better doing it this way as you put another 150k miles on the engine before the next rebuild.
Peace of mind is worth alot.

[squidmarks]

I pulled the engine out of the car and installed the intake valve shimmed to the proper height and, lo and behold, I cannot depress the valve with all my might. So, I removed the intake valve from #4 and found that it, too, did not have a valve spring seat. What I thought was the cad-yellow colored spring seats were actually shims. So, none of my valves have spring seats, it was just that #5 had no shims. Looks like I have my work cut out for me.

Geoff

[JohnJL]

...and a refund on the way I hope!