K Series Rattle

[p.mole1]

Hi Jonathan I'm not that clever but Revilla has posted on it page 2 it looks like it may be a blown spark plug ?

[Jonathan Kay]

Doh, I'd missed it!

Sorry

Jonathan

[garybee]

You can do a very rough check of the big ends by dropping a bar down the plug hole and measuring the backlash.  If a big end is wrecked there will be a delay between reversing the direction of the crank and the piston crown moving.  Obviously this is better with a DTI but you can easily feel it by hand with a screwdriver when they're really bad.  It doesn't sound heavy enough or rhythmic enough (to me) to be that though.

I'd also lean towards something light bouncing around in the cam box.  

[garybee]

USB endoscope cameras are very cheap now and surprisingly good.  I have one I paid less than a tenner for.  Very handy for a quick check of the piston crowns through the plug holes.

[Ivaan]

I replaced all the valve caps and collets on my K series on the advise of Dave Andrews. Some are cast rather than forged and the valves can pull through. Changed all without removing the head using string down the plug hole trick.

 

[revilla]

Hi Ivaan, do you have details of the valve spring compressor that you used? I've often read of the string trick but never seen a compressor that would fit a K Series head from above only, if you know what I mean. As one who has done it, it be very grateful if you could share any info! Thanks.

[garybee]

I made my own to do the same.  Stout section of flat bar drilled to match the bolt pattern on the head, welded a bolt on the top to make a hinge, lever arm attached to the bolt with a foot on it to push on the valve cap.  Worked nicely.  

Edit: I'll knock up a drawing at some point.

[revilla]

Thank you.

[ECR]

On my Vauxhall you can check for a broken valve spring by pushing down on the cam buckets with a wooden dowell. Work your way along the head pushing each one and you will recognise any that are broken as they compress more easily. This assumes that you can see the top of the cam buckets on a K.....

[Ivaan]

As Gary, I had to make up a tool. Mine was just a piece of pipe, with cut outs in the side, to get the collets out. I think I used a ratchet strap wrapped right around the block to compress the springs. Not as neat a solution as Gary's but it worked.

[RogerB]

Thanks again for the helpful suggestions.

I was coming down on the likelyhood of a broken valve spring, however I couldn't feel a difference when pushing down on the valve buckets.

Also tried barring over with a screw driver on the piston crown which also seemed OK.

I have a couple of Caterham friends coming around for a listen tomorrow. 

However I feel it's looking like a strip down.

[RogerB]

I have had my Caterham pals round and its been good to get some more ears on the noise. Its all pointing towards a broken valve spring on one of the No 4 exhaust valves. I'm going to attempt removing the springs without lifting the head as discussed here. 
Issues I see here are :

How to get the string between the piston crown and valve head. I guess once the string is fed through the plug hole the engine is barred over until it pushes against the valve head.

Retaining the valve timing by marking the belt against the pulley teeth and getting the timing marks on the bottom pulley and two cam pulleys in the correct positions.

Gary I don't suppose you could post a photo of your spring compressor jig. 

[Mechanical Moz]

The lever type valve spring compressor tools can be bought pretty cheaply on ebay. I briefly considered this method when I had a failed stem seal but in the end removed the head to replace all 16.

[garybee]

Roger - Apologies I missed your post before.  I'm not sure I still have it after a garage move but will go and have a look this evening.  If not I'll do a sketch and post that up instead.  

[revilla]

I'm not trying to sound negative but ...

On a few of the K Series heads I've stripped down, the valve caps have been very tight indeed on the collets. I've always used a large "wrap around" type valve spring compressor, sort of like a big G-clamp, but sometimes even with that wound up as tight as possible the cap wouldn't "pop" off the collets without a few good clouts on the end of the compressor with a hammer (at which points collets fly across the garage never to be seen again!).

Given that a K Series has a pent roof combustion chamber with the valves at significant angles, if the collets come loose easily then there won't be any great load on the valve (the compressor will press down on the cap, the string in the chamber will only be there to cushion the valve and stop in dropping in). But if they are stuck and it takes any force to release them, all of that load will be borne by one edge of the valve due to the angle (any of the load taken by the spring won't be contributing to releasing the collets).

If it decides to cooperate I can see how it would work, but if it decides to be difficult I can see a risk of a bent valve?

However you choose to do it, you're going to have to remove the cam ladder, clean off the old anaerobic sealant and the reseal it. Personally I think I'd rather take the head off, strip it clean it, fix the problem, put it all back again clean. And probably take to opportunity to check for any other problems and change the stem seals while it's apart to save you having to do it again later.

[oilyhands]

What he said.. in my experience (850+ heads), the collets are pretty much welded to the caps and require a sharp tap with a loosening tool (made for the job) to release them, my tool holds any collets captive if they pop out.  A bent valve is unlikely if you give the cap a sharp tap, but it is always a risk. I would lift the head..

Oily

[MADMALC]

Hi Roger it's Malcolm here, take 'oilyhands' advice, he knows. His advice is free but it is worth a lot.

[David Brown]

Roger, I’ve a valve spring compressor which you are welcome to borrow if you decide to take the head off. Can’t remember if you said you had verniers or not but also have clock gauges c/w brackets if you need to retime them. 

[RogerB]

Thanks guys, looks like head off then !

And loan of valve spring compressor would be great, thanks David.

[Wrightpayne]

Roger,

any update on your findings?

Ian

[rj]

It's not as simple as a valve cap that has given up? Have had that and it sounded dreadful. It was not very easy to find and I ended up stripping the bottom end before realising what had gone wrong. The collets had simply been forced through the collet.

I have a tool that makes it possible to change springs with the head on. Like sugested, you attach a bracket at each end of the head, a bar through and then you have someting like a deep socket with cuts and a lever something to push with. I apply a soft pressure and knock with a hammer.

Air pressure through the spark plug hole and cranck locked with the given cylinder at TDC. Sounds more complicated than it is.

 

[RogerB]

Hi Guys,

The investigation has come to halt due to other priorities as the car is off the road for the winter. 

So using air pressure in the cylinder do I need to make up a connection to screw into the plug hole ?

I will update once I make some progress.

[rj]

Yes, you need to screw something in the plug hole. Remember to lock the engine at the ring gear and to "park" the cylinder you're working on at TDC.

[RogerB]

I have eventually got round to start removing the cylinder head to investigate the rattle. Following the instructions when I have the crankshaft pulley mark lined up with the safe mark on the timing cover the cam pulleys are one tooth out from the alignment marks. If I get the alignment marks together the locking tool won't insert between the cam pulleys and the safe mark on the pulley is about 10mm out from the crankshaft pulley mark.

Expert advise much appreciated.

[revilla]

It sounds like your cam timing is all wrong!

If one cam pulley is one tooth out, then by trying to align the two timing marks you end up with them aligned but half a tooth away from the centre position, so the locking tool won't go in. Try lining up one timing mark on one pulley with one tooth either side of the timing mark on the other pulley (probably in the direction which brings the crank pulley back towards its mark). You do have to get them very accurately aligned to get the locking tool in.

The main idea of getting everything in "safe" position before stripping down is that if the cams suddenly whip round under the pressure of the valve springs (they probably will at some point) the valves can't hit the pistons. With the crank pulley anywhere near its timing mark, the pistons are all approximately half way down their bores and well away from the cams so don't worry about risking damage if it doesn't all align before you strip it.

Once you've got the cam belt off, before slackening the head bolts or removing the head, turn the crank back to the correct alignment. You probably won't be able to turn the crank once you take the head off, it will seize as the block distorts as you remove the load (it will free up again when you torque the head back down again later). Just turn it the short way, i.e. by a tooth or two, not all the way around, as you don't want the pistons going far from the centres of their strokes with valves down. That will leave the bottom end correctly aligned for reassembly and quite safe to bolt the head back on, whatever position the cams are in. Once the head is back on you can align the cam pulleys, lock them and fit the belt.