Top end tappety type noise

[phazed]

Doing it that way of course it doesn’t matter if there is leakage from the valves as you’re completely replenishing the air supply as you look for the leaks with your soapy water. I can see that this method is a goer!

[blaze_away]

Good debate on the thread thanks everyone.
Valve overlap will clearly be a factor on how much air can be forced out of a leak on the exhaust manifolds but as experience shows it "can" work.
Listening with a tube is good but as we all know on ours you cant get to listen to the undetside of the manifolds. However I will try both methods.
Only issue I have is the noise only appears under load under acceleration at 3100+rpm

[lancelin]

The thing is, are you not blowing dust and muck that's in the exhaust right back into the engine through the some of the valves that are slightly open??!!!!!! Some air and dust will also go out through the air intake butterfly? Are you not undoing all the hard work the air filter was trying to do during normal operation?

[bobfather]

lancelin said:

The thing is, are you not blowing dust and muck that's in the exhaust right back into the engine through the some of the valves that are slightly open??!!!!!! Some air and dust will also go out through the air intake butterfly? Are you not undoing all the hard work the air filter was trying to do during normal operation?

This isn't much air flow and so it won't have the energy to lift any combustion dust from inside the exhaust. Anything that's in the exhaust has already been in the combustion chambers. The new air going in is cleaned by the compressor filter. I think you're stretching the bounds of possibility but if you don't want to do it then don't do it

[phazed]

I agree. What is stuck to the inside of the exhaust system is still there after the car has produced a huge volume of air thrust through the system at full chat.

[BeastMaster]

blaze_away said:

Good debate on the thread thanks everyone.
Valve overlap will clearly be a factor on how much air can be forced out of a leak on the exhaust manifolds but as experience shows it "can" work.
Listening with a tube is good but as we all know on ours you cant get to listen to the undetside of the manifolds. However I will try both methods.
Only issue I have is the noise only appears under load under acceleration at 3100+rpm

Put the car on ramps so you can get under, the exhaust side requires a second pair of hands to direct the pipe you squeeze up between the exhaust and chassis - careful not to get burnt - do this side first while before getting too hot.

During 15 years ownership have had maybe 4 cases of the tick, one has been a displaced rocker pad, all the others have been exhaust manifold leaks - it is hard to believe a manifold leak can make such a mechanical sound, which changes from no sound when hot to a small hammer knocking on a metal pipe when cold.

Have learnt over the years one of the above will happen every 18 months, so during my pre MOT check I remove the rockers and rocker shafts, inspect and replace any rocker pads showing signs of cracks. I also remove the exhaust up to the Y piece and check and tighten all manifold bolts - all do able in a morning. Have found if I do not do this the job becomes a lot harder, because the manifold gaskets will need to be changed, and a pad will drop off causing a lot of concern of where all the metal went.

Pre MOT check last month changed one rocker, and found one exhaust side bolt about 1 and half turns out, it was one of the middle underside, because it was the middle did not produce a tick worthy of note, but if not corrected would have burnt the gasket in time.

The most common are the rear exhaust manifold bolts on both sides top and bottom - have a cut down spanner and can check all these from the top very easy.

[blaze_away]

Just quick update.

Have been unable to find any exhaust leak and using a stethoscope I detected more noise around the rocker area.

So I have stripped the top down and removed the rocker shafts.

On removing them everything looks really good all the push rods are in great nick and the hydraulic tappets all have minimal markings and are consistent with normal wear patterns. Cam visually looks good so next job is to check the cam for correct lift on each lobe.

What I have found is that 3 of the rocker pads are not fully attached to the rockers, one fell out it was that loose the other 2 easily came out just by levering with a finger nail.

Now looking to get hold of some replacements. New thread started for that.

[BeastMaster]

blaze_away said:

Just quick update.

Have been unable to find any exhaust leak and using a stethoscope I detected more noise around the rocker area.

So I have stripped the top down and removed the rocker shafts.

On removing them everything looks really good all the push rods are in great nick and the hydraulic tappets all have minimal markings and are consistent with normal wear patterns. Cam visually looks good so next job is to check the cam for correct lift on each lobe.

What I have found is that 3 of the rocker pads are not fully attached to the rockers, one fell out it was that loose the other 2 easily came out just by levering with a finger nail.

Now looking to get hold of some replacements. New thread started for that.

Thanks for posting your findings, the standard aluminium rockers with the steel pad are not very durable with a high lift cam, as above post check mine every year and change before failure. I have seen steel rockers which means that the pad is not required, but have not used them as I would still be checking for wear every year - my thoughts are that if running a high lift cam better to have cracked pads than valve stem damage due to harder rockers. - Andy

[Sardonicus]

All metal rocker arms are no harder than the pads on those alloy rocker arms to no fear of stem damage

[Classic Chim]

I have steel rockers fitted by Powers. I have the originals about somewhere.

[BeastMaster]

Sardonicus said:

All metal rocker arms are no harder than the pads on those alloy rocker arms to no fear of stem damage

The all steel rocker, and the aluminium with steel pads are only hard on the outside, once the surface hardness has been worn away the softer metal will be exposed allowing the valve stem to drill into the rocker arm. Generally the steel pad version will crack and come off the arm with a instant change in clearance and causing noise.
The steel rocker will not be such a instant change in clearance once the hard surface has been compromised allowing the stem to drill into the steel rocker some way before clearance noise provokes investigation - the rocker will now not be sliding over the surface of the stem top but rocking into a hole.
With high lift cam, double valve springs and shorter guides - all the things required for a tuned engine having a big impact where the valve stem meets the rocker, a weakness which requires careful observation to stop a minor issue becoming a big issue.

All IMHO

[Steve_D]

BeastMaster said:

................ Generally the steel pad version will crack and come off the arm with a instant change in clearance and causing noise................

Depending where the hydraulic lifter is set the lifter may take up any new clearance and will not make any more noise in the same way that a cam lobe can be almost round and still make no noise.

Steve

[blaze_away]

Great stuff folks.

Just fyi I do have a high lift cam (Stealth) double springs too so maybe that's contributed to 3 pads detaching but none broke or fell off just they are loose in the rockers which are indeed alloy.

Whole of the top is lovely and clean, but I'd expect that as it has always had oil/filter changes every 3-4000 miles of course

The noise I was having was only at 3100 rpm and above and only under load.

In my mind I am thinking that a pad(s) are being dislodged at 3100 by centrifugal force to the extent they bounce between the rocket and valve stem emitting the noise. Below that rpm they stay put and don't clatter. That's my theory/hope yet to be proven of course

[Sardonicus]

BeastMaster said:

The all steel rocker, and the aluminium with steel pads are only hard on the outside, once the surface hardness has been worn away the softer metal will be exposed allowing the valve stem to drill into the rocker arm. Generally the steel pad version will crack and come off the arm with a instant change in clearance and causing noise.
The steel rocker will not be such a instant change in clearance once the hard surface has been compromised allowing the stem to drill into the steel rocker some way before clearance noise provokes investigation - the rocker will now not be sliding over the surface of the stem top but rocking into a hole.
With high lift cam, double valve springs and shorter guides - all the things required for a tuned engine having a big impact where the valve stem meets the rocker, a weakness which requires careful observation to stop a minor issue becoming a big issue.

All IMHO

I agree but all things being equal and providing the engine is maintained and of course no pad failure/shearing then the case hardening is very wear resistant I have a full set of rocker arms of a 500 cammed and double spring'd RV8 with 125k + and date stamped same year as the engine with no signs of break through or wear on said pads the alloy arms are not as troublesome as made out IMO unless asked to do competition or solid/mech cam work etc

[blaze_away]

Another update.....

Have now fitted 4 similar replacement alloy rockers thanks to big Al aka classichimi

I also inspected the cam, the lifters, the push rods and all seems well.

Its nearly all back together so wish me luck tomorrow when I will see if the rattle at 3100rpm has now gone.

If it has gone then I will get all the rockers refurbed as preventative maintenance.

[blaze_away]

Well good news I 99% believe the tappety noise has been cured.

Reason its only 99% is I now have another issue which is puzzling.

Car ran perfectlt fine before I did this job replacing 4 rockers.

Now it refuses to idle properly keeps stalling on the driveway cuts out approaching junctions, am a bit stumped to what has happened.

Wont idle steady at all keeps cycling from almost 0rpm to 900rpm back to zero back up to 900rpm does this a few times then stalls.

Tried setting base idle but it wont idle to let me set it. Had screw fully shut then 2.5 turns open and 1/2 increments to 6 turns open no effect on idle.

What next ?

[QBee]

That sounds like stepper motor to me. It is meant to hold the idle steady.
Mine became temperature sensitive, the car stalled when hot.
Replacing the stepper with a known good original one solved it

[Steve_D]

Possibly an air leak. Have you split one of the breather pipes when putting the rocker covers back on?

Steve

[Classic Chim]

^^^^^\agreed. Do an ecu reset just to be sure.
Or a dreaded air leak maybe?

[ianwayne]

I would second the running issues sounds like stepper motor to me. But being unable to set the base idle sounds weird.

Are you completely blocking the bypass hose off that runs to the stepper motor? Because if you are, it sounds like you have a air leak as well. Winding the bleed screw all the way in should cause the engine to almost stall at about 500 rpm. Is the plenum throttle plate closing all the way with no throttle input? Perhaps the throttle cable has some tension in it holding it slightly open.