4.2 Series 2 Engine Rattle

[SimonBrown]

Hi All, I have been trying to trace an engine rattle on my E for ages. Top end of engine, only when cold, light pitched rattle from the head area at engine speed, not cam speed, only on the cusp of changing from load to over run.. I have replaced cams and bearings, valve springs, cam followers (short and long), adjusted top chain, checked valve clearances all to no avail.
It doesn’t do it immediately after a cold start, but it is loud after about 10 secs running. Once, thoroughly hot the noise disappears. Sounds like a loose bag of bolts under the cam covers. Struggling to identify which side.
No witness marks on follower guides to indicate guides moving.
It sounds particularly bad on upward gear changes as engine momentarily comes off load, and is getting worse.
Any help would be much appreciated
Thanks
Simon

[mgcjag]

Hi Simon....sorry to hear you still have this....after so much work I thought you had it sorted......have you checked out timming(distributor) and carb tunning...im just thinking out loud as i know youv looked at a lot of other things.....Steve....ps I'm thinking you may have to take this into a specialist for a chat and a hands on opinion...

[SimonBrown]

Hi Steve, Thanks for coming back and good to hear from you. I have checked timing and carb set up and all fine. I was starting to think “little end” as the noise is throttle sensitive. But the noise appears to be in the upper part of the head.
I have tried disconnecting plug leads by turn and the noise does not change, which kind of discounts that. Do you know of a cylinder head specialist, hopefully local to me in Solihull?
Simon

[mgcjag]

Hi Simon...do you know Neville Swales (building the legend) he has a workshop not far from you....has some very good people working there...Bedworth i think...Steve

[SimonBrown]

I don’t, but I’ll give them a call. Only 30 mins from here. Thanks for info

[Simonpfhc]

Simon,

Are you running any very thin shims in your valve buckets? If there are any around the 75’’’ mark, they could be just below the valve retaining cap and create a slight rattle.

[SimonBrown]

Hi Simon
The shims are all between 86 and 95 from memory. I did notice it is very dry of lube around the shim area and assume as the “bucket” is inverted it is quite difficult for oil to get there?
Thank you
Simon

[Simonpfhc]

Ok, so the shims shouldn’t be the issue then. Both cam towers get flooded with oil so oil will always get down into the buckets. Actually, have you removed both cam covers and checked oil is flowing out of the feeding pipes?

The other source of potential clattering is worn can hear verniers. You can check them by holding the cams with Mole Grips and seeing if there is any play by looking at the inner verniers plates.

[SimonBrown]

Hi Simon, Thanks for coming back. I am happy there is sufficient oil flowing.
Worn cam verniers are something I haven’t checked, appreciate that.
So, if I hold the cam with mole grips,in which direction should I pull/turn the sprockets in order to check for wear?
Excuse my ignorance as I am not sure how these work
Simon

[mgcjag]

Hi Simon....three were different serated plates used in the sprockets at various times...have a look at this thread...you dont want the plate with the curved cutouts that have wider and less teeth....they have been known to move in the sprocket....Steve https://www.georgiajag.com/Documents/Camshafts.html

[Simonpfhc]

Simon, you need to rotate the cams very slightly cw and ccw whilst keeping an eye on the serrated vernier gear. You might even hear a slight click which is a sign of wear.

Also, Steve is quite right, check the design of the vernier as per the link he sent.

[SimonBrown]

I think I have at last found the cause of my engine rattle!!!
At least one of the exhaust side cam lobes is running perilously close to its follower guide, .001 inch.
For the first time I have found a witness marks on the guide from contact, under a magnifying glass.

Would anyone know:
How close should these run and is there a measurement from the top of the guide to the cover face so I can establish they are fully home?
As I have tried to gently drift the guide down, and it hasn’t moved a hold down kit is unlikely to press it in further?

Really appreciate all your help with this, without the info and ideas from the people on this forum I would not have found it

Many thanks
Simon

[mgcjag]

Hi Simon.....you may have to check with a machine shop or a call to Rob Beere..or measure all your guides it get an average........but I did find this
"You might measure the distance from the cam cover face to the tops of the
tappet guides with a depth micrometer and keep a record for the future.
I measured them on a 140 head G4686-8 and they ranged from .622" to .634".....Steve