911 sc knocking, any ideas?

[renopor]

hi all, this is my first post and i wish it where on a better subject (for me anyway!!)ive had a couple of 911 sc's before and have just bought a car 1978 sc, i got her at the right money so spending a few euro on her was to be expected, so heres the story so far, car was standing for over two years and not used at all, i drained all oils and fuel, new plugs, dis cap, rotor,etc etc, and have just adjusted the valves, now to the knocking, it was in it before i adjusted the valve's and i really thought thats what it was, but it is still there, she has good oil pressure and runs great, it is a very thiny sound and really does sound like a valve, it is most noticeable at around 2000rpms and sometimes i could swear it was gone all together, but it is loud from inside the car, doesn't sound to bad at idle and over 3000rpm off and on load, any ideas lads? cheers

[old man neri]

So it's sounds like a tick?

If the car has been stranded for a while one of the things I would do would be to take it for a really nice long drive. That seems to sort out a lot of issues. These cars are like women, you can't just let them sit. You have to take them out often and drive them hard once they reach operating temperature.

Are you sure the valve adjust was done correctly?

-matt

[renopor]

yeah that sounds like a plan, i really hope its nothing major, im kinda hoping its a sticking valve or something, and i done all the valves today and there fine, ive done it a good few times before.

[renopor]

oh and yes is more of a loud tick then a knock, cheers matt.

[sailchef]

How about the cam chain tensioners?

[renopor]

no defo not them, she has uprated 3.2 tensioners, i can hear it at idle but no as loud as when at 2000 rpm, it a defined ticking noise, but seems to be just on one side of engine.

[renopor]

has anuone heared of a sticking valve on an sc before?

[kodioneill]

after sitting that long without running the tensioner(s)can bleed down! use a long skinny screwdriver and use it like a stethoscope. put the tip of the screwdriver close to the origin of the ticking then move it around until you can locate the noise. then you can make a better determination. if you find that it is a tensioner then run the car being easy on the throttle and nurse it along until the tensioner is pumped up. sometimes it can take quite a while. just keep the rpms low.

[Gogar]

Exhaust leak?

[beepbeep]

1. Raise the car with engine running, use long hose and put one end into your ear and poke with other end around header/head join. It will pinpoint eventual leak. Listen around cylinder/head as well, in case you have broken stud.

Have you checked stud tension when you adjusted the valves? Having valve covers off is a good opportunity to check for loose/broken studs.

If exhaust leaks and studs check OK, redo the valve adjustments and check valve stems and rockers for wear.

[renopor]

here with the car now, i adjusted valves yesterday, check head bolts and all are good, there is a stud missing from the heat exchanger but it really does not sound like a leak, going to put her up on the ramp now to see if i can hear better, i have stethoscope and have put it every where but it does not seem to be pinpointing it.

[mjshira]

try some marvel mystery oil. it does a good job of getting to places that might require more lubrication. having experienced a mystery pinging issue myself your issue as you've described it doesn't sound like traditional engine knock/ping. You might (as was said above) just need to drive the car hard and get her good and warm.

if the problem continues then I'd run some race fuel and see if it happens then. keep us posted. good luck

[renopor]

i think it mite the tensioners! will they make noice at idle? it seems to be getting better and sometimes goes completely. does it take long for them to refill?

[mjshira]

put some marvel mystery oil in that engine! you might have no noise after doing so.

[ossiblue]

Originally Posted by renopor

i think it mite the tensioners! will they make noice at idle? it seems to be getting better and sometimes goes completely. does it take long for them to refill?

Unless you have the pressure fed carrera tensioners, yours (hydraulic) don't "refill" and the pressure fed would be retro-fits on your car. Do you know if you have them?

[renopor]

yes it has 3.2 tenioners, and have been told theyt mit have brained while the car was sitting.

[Flieger]

Certainly check the tensioners. Like all mechanical parts, they wear and can fail over time. They can go slowly, where they bleed down while sitting until the engine oil pressure builds. The tensioners will clack-clack chatter at idle and will smooth out when revved a little.