Valvetrain noise at idle
12-19-2011, 06:52 AM
#61
At this point I'm thinking that previous damages were caused by the faulty new OPRV, which still didn't work as it should after I modified it.
Though I now have a good used OPRV in there I'm still using camshaft and lifters that may have been damaged as they were used with the previous OPRV.
I found a third, used cam housing, complete with corresponding lifters, it's in the mail.
Gustaf, do you have anything in mind that suggests this could be caused by the head?
Though I now have a good used OPRV in there I'm still using camshaft and lifters that may have been damaged as they were used with the previous OPRV.
I found a third, used cam housing, complete with corresponding lifters, it's in the mail.
Gustaf, do you have anything in mind that suggests this could be caused by the head?
12-20-2011, 10:19 AM
#62
Nordschleife Master
I really hope you solve it soon, not being able to make progress with problems can really drain all your energy!
12-20-2011, 10:32 AM
#63
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Were any of these parts bead blasted before install? I know you cleaned the oil passages, but IMO the best way to clean a head that has been bead blasted is to throw it in the scrap heap and get one that has not been bead blasted. Those little buggers hide everywhere and come back to haunt you later.
Cheers,
-Joel.
Cheers,
-Joel.
12-20-2011, 10:59 AM
#64
Gustaf, yes it's frustrating, though I'm hopeful it wll be the very last issue I will have had on the way to building a healthy engine, after a leaky headgasket and leaky turbine seals.
Joel, no parts were bead blasted or underwent any particular industrial cleaning process before being assembled.
One thing has just come back to my mind : as I was running the faulty new OPRV, whenever I would turn off the engine I would notice a "smell of heat" coming from the area of the cam housing.
Since I have been running the good used OPRV, this smell seems to have disappeared, or at least much reduced.
Joel, no parts were bead blasted or underwent any particular industrial cleaning process before being assembled.
One thing has just come back to my mind : as I was running the faulty new OPRV, whenever I would turn off the engine I would notice a "smell of heat" coming from the area of the cam housing.
Since I have been running the good used OPRV, this smell seems to have disappeared, or at least much reduced.
12-20-2011, 11:58 AM
#65
Rennlist Member
At this point I'm thinking that previous damages were caused by the faulty new OPRV, which still didn't work as it should after I modified it.
Though I now have a good used OPRV in there I'm still using camshaft and lifters that may have been damaged as they were used with the previous OPRV.
I found a third, used cam housing, complete with corresponding lifters, it's in the mail.
Gustaf, do you have anything in mind that suggests this could be caused by the head?
Though I now have a good used OPRV in there I'm still using camshaft and lifters that may have been damaged as they were used with the previous OPRV.
I found a third, used cam housing, complete with corresponding lifters, it's in the mail.
Gustaf, do you have anything in mind that suggests this could be caused by the head?
12-20-2011, 07:32 PM
#66
Addict
Rennlist Member
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Another couple of “stabs in the dark”:
When is it most noisy (at idle), when hot or cold?
If it is noisiest when cold, then the oil may be too viscous to flow enough through the small feed holes in the lifters.
What type of valve springs do you use?
If too hard, they may eject more oil form the lifters that can be supplied with the current pressure and oil viscosity.
Instead of the bolt above the OPRV you can have a hollow fitting made for measuring the pressure in the cam housing oil channel.
When is it most noisy (at idle), when hot or cold?
If it is noisiest when cold, then the oil may be too viscous to flow enough through the small feed holes in the lifters.
What type of valve springs do you use?
If too hard, they may eject more oil form the lifters that can be supplied with the current pressure and oil viscosity.
Instead of the bolt above the OPRV you can have a hollow fitting made for measuring the pressure in the cam housing oil channel.
12-20-2011, 08:18 PM
#67
Rennlist Member
Another couple of “stabs in the dark”:
When is it most noisy (at idle), when hot or cold?
If it is noisiest when cold, then the oil may be too viscous to flow enough through the small feed holes in the lifters.
What type of valve springs do you use?
If too hard, they may eject more oil form the lifters that can be supplied with the current pressure and oil viscosity.
Instead of the bolt above the OPRV you can have a hollow fitting made for measuring the pressure in the cam housing oil channel.
When is it most noisy (at idle), when hot or cold?
If it is noisiest when cold, then the oil may be too viscous to flow enough through the small feed holes in the lifters.
What type of valve springs do you use?
If too hard, they may eject more oil form the lifters that can be supplied with the current pressure and oil viscosity.
Instead of the bolt above the OPRV you can have a hollow fitting made for measuring the pressure in the cam housing oil channel.
12-21-2011, 05:10 AM
#68
Laust,
It is as noisy when warm as it is when cold.
Valve springs were new turbo springs at the time they were installed 16k miles ago, preloaded as mentioned in the FSM. I will check preload next time I have the cam housing off.
The last time I had the cam housing off (before shooting the second video) I tried to push the valves open with each lifter in my hand, and some felt more difficult to open than others. I was able to open valves #1 and #2 but not others. Not sure if this is because other valve springs are more preloaded or because I ran out of muscles after the two first ones.
Since lifter #4 was consistently damaged in the past, valve spring preload sounds like a good thing to look out for - I will check this next time I had the cam housing off.
By the way, has anyone on here successfully removed valve springs off a 944/951 head without taking the head off the block? I have seen methods for doing it on other engines but I'm not sure what kind of valve spring compressor could be used safely on a 944/951 head?
It is as noisy when warm as it is when cold.
Valve springs were new turbo springs at the time they were installed 16k miles ago, preloaded as mentioned in the FSM. I will check preload next time I have the cam housing off.
The last time I had the cam housing off (before shooting the second video) I tried to push the valves open with each lifter in my hand, and some felt more difficult to open than others. I was able to open valves #1 and #2 but not others. Not sure if this is because other valve springs are more preloaded or because I ran out of muscles after the two first ones.
Since lifter #4 was consistently damaged in the past, valve spring preload sounds like a good thing to look out for - I will check this next time I had the cam housing off.
By the way, has anyone on here successfully removed valve springs off a 944/951 head without taking the head off the block? I have seen methods for doing it on other engines but I'm not sure what kind of valve spring compressor could be used safely on a 944/951 head?
Last edited by Thom; 12-21-2011 at 01:41 PM.
12-21-2011, 09:25 AM
#69
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Thom, I remember a post from a while back that you were asking about how to set up the head. It appears that you had a machine shop do the seat and valve cuts but you did the stem height and springs
How did you determine the stem height and if the shop did that each valve was set for each hole it was in at that time. That also goes for each spring with said valve. Spring tension must be checked at the recomemded height and then shimmed to get that setup . every time the seat and and valve is cut the stem is higher in the head then top of stem has to be cut and valve spring shimmed to maintain the correct seat pressures. All of which the machine shop should have done .
Clifton
How did you determine the stem height and if the shop did that each valve was set for each hole it was in at that time. That also goes for each spring with said valve. Spring tension must be checked at the recomemded height and then shimmed to get that setup . every time the seat and and valve is cut the stem is higher in the head then top of stem has to be cut and valve spring shimmed to maintain the correct seat pressures. All of which the machine shop should have done .
Clifton
12-21-2011, 09:34 AM
#70
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Thom, addiing to thiis if a valve stem height is to high you would be at the outer limits of the lifter and that would wipe out lifters and cams quickly. This should have caused the engine to miss if it was off enough to keep the valve open . If stem height is to low then it would be very noisy because the lifter would not be in its operating range of hydraulics. That could also wipe out the lobe as the lobe comes down it would slap the lifter instead of following it all the way around beating the lifter face .
Do a compression test to see if the one that is wiping lobes off is low compression or higher than the others. If the cam is wiped during the comp test it will be high.
Just some food for thought hope this helps
Clifton
Do a compression test to see if the one that is wiping lobes off is low compression or higher than the others. If the cam is wiped during the comp test it will be high.
Just some food for thought hope this helps
Clifton
12-21-2011, 10:06 AM
#71
Clifton, thanks for your input.
Yes, the shop did the seats taking account of valve stem height. In fact I remember them saying they do not touch valve seats unless they are provided with all the valves that go with them.
Valve stem height now is at 13.5mm to the mating surface of the block to the cam housing, which is fine according to the FSM, so I suppose this might not be the root of the issue...?
Earlier in this thread I was asking if Ti valve retainers required any special adjustment, as I installed them as if they were standard retainers.
Also, the last time I did a compression test the figures were excellent.
Yes, the shop did the seats taking account of valve stem height. In fact I remember them saying they do not touch valve seats unless they are provided with all the valves that go with them.
Valve stem height now is at 13.5mm to the mating surface of the block to the cam housing, which is fine according to the FSM, so I suppose this might not be the root of the issue...?
Earlier in this thread I was asking if Ti valve retainers required any special adjustment, as I installed them as if they were standard retainers.
Also, the last time I did a compression test the figures were excellent.
Last edited by Thom; 12-21-2011 at 01:41 PM.
12-21-2011, 12:04 PM
#72
Rennlist Member
Laust,
It is as noisy when warm as it is when cold.
Valve springs were new turbo springs at the time they were installed 16k miles ago, preloaded as mentioned in the FSM. I will check preload next time I have the cam housing off.
The last time I had the cam housing off (before shooting the second video) I tried to push the valves open with each lifter in my hand, and some felt more difficult to open than others. I was able to open valves #1 and #2 but not others. Not sure if this is because other valve springs are more preloaded or because I ran of muscles after the two first ones.
Since lifter #4 was consistently damaged in the past, valve spring preload sounds like a good thing to look out for - I will check this next time I had the cam housing off.
By the way, has anyone on here successfully removed valve springs off a 944/951 head without taking the head off the block? I have seen methods for doing it on other engines but I'm not sure what kind of valve spring compressor could be used safely on a 944/951 head?
It is as noisy when warm as it is when cold.
Valve springs were new turbo springs at the time they were installed 16k miles ago, preloaded as mentioned in the FSM. I will check preload next time I have the cam housing off.
The last time I had the cam housing off (before shooting the second video) I tried to push the valves open with each lifter in my hand, and some felt more difficult to open than others. I was able to open valves #1 and #2 but not others. Not sure if this is because other valve springs are more preloaded or because I ran of muscles after the two first ones.
Since lifter #4 was consistently damaged in the past, valve spring preload sounds like a good thing to look out for - I will check this next time I had the cam housing off.
By the way, has anyone on here successfully removed valve springs off a 944/951 head without taking the head off the block? I have seen methods for doing it on other engines but I'm not sure what kind of valve spring compressor could be used safely on a 944/951 head?
12-21-2011, 05:28 PM
#73
Burning Brakes
I did it on my car using a combination of a tool bought on the web and a bar we made up and bolted to the housing. We also used compressed air to hold the valve in place once it is unsupported, due to this you have to do it one cylinder at a time. Even so we managed to drop one valve into the cylinder when the compressor cut out, took a while with a very small magnet and supporting the valve from below but we got it back through the hole in the end!! There is a fitting you can use to screw into the spark plug hole that goes onto an airline. I do not believe there is any special requirement for Ti retainers.
Last edited by nick_968; 12-22-2011 at 04:50 PM.
12-22-2011, 01:45 PM
#74
You can use a screw type compressor. I like the one from napa with the removable screw **** best. If you drop a long extension down each cylinder hole you will find the top of the piston. Then use small zip ties to hold the inner and outer springs together. New valve stem seals will help the valve stand tall. I did this to install new turbo springs on my na. Btw the valve will only drop around a quarter inch with the piston at top for that cylinder. Good luck
01-08-2012, 03:40 PM
#75
Quick update.
As I started the engine today to go for the usual weekend drive, I noticed there was no clatter whatsoever - the engine would idle just quiet.
As oil warmed up, the noise came back progressively, again only when the engine idles.
What does this suggest, if anything?
As I started the engine today to go for the usual weekend drive, I noticed there was no clatter whatsoever - the engine would idle just quiet.
As oil warmed up, the noise came back progressively, again only when the engine idles.
What does this suggest, if anything?