willrobinson

Hi all
I may have posted about this fault a while ago in its early stages. Here is the story:
My cam tower gasket had a leak, I removed the cam tower, replace the gasket. Had the engine set to TDC, set the cam to the mark and proceeded to tighten down the cam tower. However in my struggle to set the tower on and keep the lifters in place, I had not noticed I had set the cam to another mark, perhaps I had touched the wheel twice with the pen by mistake. So I tightened until the bolts were stiff to turn and noticed the tower still sitting off the head, that's when I noticed my mistake. I turned the crank back to lower the pistons from the open valves, valves 3 and 6. I tightened it all down, started it up, all good, no leaks, just a lifter tick noise. I took it for a spin hoping they would prime up again, but no luck.

I figured they must have been damaged by the squeeze tightening the valves into the pistons?
So I removed them and fitted second hand lifters. Did a compression check to ensure the valves weren't bent, all even compressions, all ok. Bounced the valves to ensure they weren't tight in the guides/slightly bent, but they all appear ok. Re-assembled everything. Damn thing still ticked took it for a good spin, still ticking
Thinking the second hand lifters were bad I ordered reconditioned ones, primed and fitted them. Still ticking, still soft lifters on valves 3 and 6.
At a loss I tried moving the reconditioned lifters to cyl 1, valves 1 and 2. And put good solid lifters on valves 3 and 6. Still the damn thing ticked!!!
Removed the cam tower again, and found the solid lifters I put on valves 3 and 6 had gone soft and the reconditioned lifters I put on valves 1 and 2 were primed nice and hard, so evidently there is no issue with the lifters themselves.
The cam tower is flat and show no evidence of warp or defects. The lifters appear as firm a fit in positions 3 and 6 as any other. The oil galleries are clear, the gasket used was a Reinz, should be correct thickness etc.
Putting a ruler across the top of all the valve stems the appear to be perfectly even in height, no uneven recession etc. Grabbing the valve assembly by the retainer and shaking it reveals no discernible difference between any of the valves and guides in terms of lateral movement.

I am at a loss to find any defects that are causing the softening of the lifters on these valves 3 and 6.
I have attached some pics to help visualise the situation.
Thanks for any and all help and suggestions.

V2Rocket

i think youre just experiencing the horrible noise that hydraulic lifters make before they are fully pumped up.
a local pelicanite called me in a frenzy a few days ago because his S2 which had been sitting for a few weeks was making an awful racket.
i showed up, he started it and i poked around for anything unusual but after a minute or two it got quiet as oil returned

willrobinson

Between each stage I have taken the car for a drive for an hour, and sometimes several, the tick never goes away, I have revved it hard to keep oil pressure high etc, and I have tried 40 and 50w oil. Never really improved, sometimes it would get quieter, sometimes louder, but always there ticking away

tempest411

Is it possible you're hearing an exhaust leak you'd previously not paid attention to? More than a few people have been fooled by that one. Barring that, you can get one of those mechanics stethoscopes and probe around to very where the sound is coming from. My hunch is with it being so consistent regardless of all the changes you've made, it may not be the valve train at all.

willrobinson

Thanks for the reply.
I hear what your saying, and previously I had tracked a similar but not the same noise down to an exhaust leak.
But in this case with 2 soft lifters I'd say the cause of the noise is definitive. If there weren't 2 soft lifters I'd be pursuing other things a long time ago :/
I just can understand how they won't hold prime in those bores, I may track down an inside micrometer to check for ovality, but there is no visible sign of excessive wear.

Noahs944

I don't know, but what do the experts think about the lobe wear?

Arominus

I wouldn't sweat the lobe wear, that happens, is the lifter cupped? Is the car down on power?

My 944S did this to me after it sat for a few months while i was doing work on it. It took a while for the last tick to go away. Like a week.

Dougs951S

When I got my N/A car running after it had sat for 4 years, it knocked so bad I was sure the motor was toast. I decided to drive it anyway and changed the oil. 500 street miles later its quiet as a mouse.

willrobinson

Thanks guys

The lifters are perfectly flat as far as i can tell with a steel ruler.
I have done 800 miles since the last time I tore it down, the tick remained constant in its pattern, increasing and decreasing as the lifter turned in the bore, it never got any quieter unfortunately.
There is some visable cam wear, its the same on all the lobes though.

Tom M'Guinn

What oil are you using and what is the weather like in your neck of the woods?

When you had the head off, did you clean out the oil check valve?

Did you check your springs to make sure they are all of equal pressure and none are broken?

I would not consider soft lifter buttons definitive, as that seems to be a bit random with these lifters?

willrobinson

Hi Tom
I have not had the head off the engine yet, its the next step it would seem. I have not cleaned the oil check valve, pressure on the gauge seems within reasonable range, anout 2 bar hot idle, and 3.5 or so with revs, that seems to be relief pressure.

The valve springs all seemed ok, no sign of any defects, all equally hard to depress with a hammer handle, though a crude test no doubt.
I have removed both intake and exhaust valve springs and valve stem oil seals on the ticking cylinders, I could find no sign of defects, all valves were free to move in the guides, all with a similar amount of lateral movement. I will check this with I dial gauge next time im home from work to see if this is within specification.

The temperatures are around 35 Celsius 95 Farenheight
I have tried both 15w40 and 20w50, both castrol GTX, no change in the noise between the two, a mild increase in hot idle oil pressure with the 50w.

It is peculiar that whatever lifters I put in these positions go soft, despite being hard before they are fitted.
I am going to use an air blow gun with a rubber tip, regulate the air pressure to 40 psi and press this into the corresponding oil gallery with the lifter in place and turn the cam and check for leakage and compare it to the others. If this reveals nothing, then cylinder head off id say.