valves cliketing noise

[Zef]

Well...valves were adjusting 500 miles ago...no noise since...but yesterday when coming home from work and while stuck in traffic jam...heard that !"/$%?& cliketing sound from right hand side of engine...when arrived at home and in the garage, I can heard clearly that cliketing sound on the right hand side...question : Is it possible that a valve went out of adjustment...and it was OK for 500 miles...but now decides to go loose...I will put the feeler gauge on that side this weekend...but still not understand why after 500 miles...!

[T77911S]

check the rocker shaft, make sure it is not lose. if all checks good, you may have a bad valve guide.
i just did my valves. adjust for a very snug feeler gauge. i had been setting them on the lose side until i compared the backside meathod to the front side. i found that if i adjusted for the backside meathod, could not get the .004 gauge back in. but if a adjusted for a very snug .004 on the valve side, the .003 was also very snug on the cam side. i may start another thread on this later.

.

How many miles are on that Carrera. Could be the infamous valve guides. Warm weather and traffic makes the engine a little more noisier

WTF Stupid buttons!

[Zef]

The clock show 90 000 miles...and no smoke at the exhaust...

[88911coupe]

So this is saying the backside method adjust valves slightly on the tight side? This would be a little better for performance but also risk the valves getting hotter than normal since they spend less time in contact with the valve seating surface...correct?

[Zef]

IMHO...The valve adjustment is not in for the valve cooling...The only moment the valve is cooled is when the valve is contacting the seat...the adjustment is between the valve tip and the rocker assy...so I think that .003 or .004 don't change the valve contact seating time.

[T77911S]

when i read about the backside method i thought this was a sure fire way to get an exact adjustment. after all, with a go at .0025 and a no go with .003, how much closer could you get? when i did the backside on the exhaust, i found i could not get the .004 to go in. it started to bother me that they might be too tight. so i readjusted for a very tight .004. when i checked the backside, the .003 was also very tight, about the same as the .004. i usually adjust the .004 for just a slight resistance, but now i think a may have been setting them too lose.
so in the end, i think using the backside method may leave the valves a little too tight, which may be fine on the intake, but not the exhaust.

it is a very small amount, but too lose and you have the "clicking" and too tight you burn a valve. so to narrow it down to a clicking valve or a clicking valve guide i would set the valves to a very snug .004.
a worn shaft or rocker bushing may also be the noise you here. may someone else out there knows if that would click, but most likely guides.

[glenncof]

I just did my '85 at 176K miles (after 45K on last adjust). Backside 0.003" NO GO and tight 0.0025" GO. Adjustments rate is 1mm/turn so 0.1mm gap is 1/10 turn, not much and locking nut must be torqued.

I had to wiggle the 0.0025" quite a bit to get it in* since I triple checked the first bank and found I was running them too loose initially (by measurement). They also bobbled in/out of tight/loose somewhat.

Initally some valves tight/some loose but not by much. No valve noise before or after.

* Correct feel seems to be like pulling/pushing across a magnet. 0.0025" hard to get in since not very stiff.

[T77911S]

glenncof, just curious, did you check to see if you could get the .004 in after doing the backside.

[glenncof]

I had the front-side feeler tool. I used it when evaluating front/back side methods. I had a hard time getting it in and getting the feel (this was my first valve adjust on this engine.)

No, I did not check using front side method. That was my plan originally; Adjust backside, verify frontside.

I checked the math on backside though and geometry is geometry. Since the backside gap is smaller it would be slightly more susceptible (~33%) to measurement error theoretically.

Due to the bobble I mentioned I could have continued all day loosening and tighting. I looked at the cams and they looked great, no scuffs or pitting.

Overall I don't think the gap is actually that sensitive but it's easy to loosen too much.

[T77911S]

i just was not that comfortable doing the exhaust the backside way, so i redid them with the .004. i plan to start it tonight and see how it runs/sounds.

[2.7RACER]

The "backside method" utilizes simple math.
The rocker arm ratio at the base circle of a standard Porsche cam is 1.4 to 1.
Divide .004 by 1.4 and you get what? Hint .002857".
It happens to fall between 0.0025" and 0.0030".

No big deal.

If the 0.0025" feeler slips in and the 0.003" does not, then the gap at the rocker and valve will be somewhere between 0.0035" and 0.0042".

So if the 0.0025" Go Gauge is snug, but slips in, the gap at the rocker will be 0.0035". Well within specs and safe. Quiet too.

If the 0.003" NO GO gauge slips into the rocker/cam gap, the gap at the rocker/valve will be more than 0.0042". This would be too loose.

At the base circle, the ratio is approximately 1.4 to 1.

Cams with a smaller base circle than stock will contact the rocker closer to the tip of the rocker. This has the net effect of reducing the rocker ratio at the base circle to less than 1.4 to 1. Go small enough the ratio could even be 1 to 1.

The rocker is by design, variable ratio. That is at the tip of the cam lobe the rocker is contacting the cam lobe much closer to it's pivot point. Typically this ratio is approximately 1.5 to 1. This number will vary with the total lift of the lobe. More lift the higher the ratio.

To prove this, simply look at the tip of a rocker where it contacts the cam lobe. You will find a polished area of contact close to 1/2" long.
At the base circle the rocker is contacting the cam closer to the tip of the rocker. When the rocker is on the tip of the cam lobe, as I stated earlier, the contact point has moved closer to the pivot point, thus raising the ratio.

[glenncof]

2.7Tracer,

Just to make this complete...do you know the tolerance on the 0.004" (0.1mm) spec ?

[Zef]

Simple question...what you mean by backside and frontside method...???

[glenncof]

http://www.pelicanparts.com/techarticles/911_backside_valveadjust/911_backside_valveadjust.htm
http://www.pelicanparts.com/techarticles/911_valve_adjust/911_valve_adjust.htm

See these articles.

[T77911S]

i thought the backside sounded like a great idea. but after trying it, i dont want to leave my exhaust valves that tight, especially if the frontside would be LESS than .004, as was stated, ".0035 to .0042. when i set the no-go of .003, i couldnt get the .004 in. maybe .0035 is ok, but porsche did not make that the spec.
if porsche says to set them to .004, i dont think anything less than .004 is acceptable. this is just my opion, all i am doing is making others aware so they can try both methods and decide for themselves. i had to askmyself, is it worth a burned valve?

[2.7RACER]

This method has never advocated setting the valves to a snug .0035".
Although this is perfectly safe.
To get .0035" at the rocker valve gap, you must adjust the Go .0025" snug at the rocker cam gap.
It does provide a method which allows you to check the gap with ordinary feeler guages. It tells you instantly if the valves are too loose or too tight.
It is apparent to me this method is not appropriate for those that choose to mis-interpret the information provided.
Please continue to adjust as you please, but don't knock a method that has been proven to work by people all over the world.

[2.7RACER]

For folks that want to know what Porsche spec's are for valve adjustment I give you the decal supplied with '87 911's.


This may be difficult to read. It says Valve lash .004" plus or minus .002"