Engine wont turn

Unread post by **alan s** » 07 Apr 2004, 05:21

Vanny,
I'd say at first glance it was a sticky valve stem but when you talk about marks on piston faces, that a whole different ball game.
As has been stated here & I have mentioned elsewhere, it is very feasible to fit a used valve providing it is not too worn in the stem or the face.
I understand valve stem seals are a non event on a diesel; they just don't have any so it will necessitate a trip to a machine shop for a few reasons; firstly to measure the valve guide Vs the valve stem to be sure it is within allowable tolerance so as to not end up with an oil burner.
Secondly, whilst it is possible to "hand grind" a valve in, it's a long & tedious process & at the end of the day, unless you have a lot of patience and a soft valve, it will only be half a job. Engine rebuilders should have a gadget that slips into the valve guide and has an abrasive angled cutter that simply cuts the seats back and another with the same angle that faces the valves. They then can either be just reassembled (as the pros do) or if you're keen, they can then be hand lapped in within a few minutes each for a 100% prefect mating surface.
If the head is stripped prior to taking to the machine shop/engine rebuilder, it's a very low cost exercise and one I do just as a metter of course on any engine I strip & rebuild.
Alan S

AndersDK · Unread post by **AndersDK** » 07 Apr 2004, 06:04

Hi Vanny -
I've done the valve grinding on a couple of engines as pr Reblack's description.
Unless you have to mess with a serious cutting of the seat (as pr AlanS), it's a dead easy job by hand, and valves will seat perfect.
With valves out, guides & stems clean & dry, you can instantly compare if the damaged valve guide has different slack than the others.
If you have more slack or (new or s/h) valve binds - then it's AlanS description, to avoid an engine oil burner or sticking valve.
If it feels OK, then it's approx 5-10min's patient handwork grinding in pr valve, and you'll be impressed with the result.
Description of the method used to be found in some of the earlier Haynes. You simply buy a tiny can of grinding paste, either end of can will hold course and fine grinding paste. It's very small amounts you need pr valve, the can will probably outlast the rest of your life with car DIY's.

vanny · Unread post by **vanny** » 07 Apr 2004, 07:03

so thats what the can of grinding paste is for out in the garage! Its been in my dads miscelaneous car bits box for longer than i have been alive! But i doubt he's been using it!
thanks for the pointers guys! Will investigate costs locally tomorrow, see what the pro's say!

jeremy · Unread post by **jeremy** » 07 Apr 2004, 12:43

My guess is that as soon as you start to gring the valves you will find that the sealing surface is pitted and that they are almost impossible to remove as the valves and the seats are made of extremely hard materials. Time for some professional help - many garages who do mechanical work will cut the seats for you with a proper seat cutting tool and (providing it is possible to do so) will reface the valves as well and even grind them for you leaving you to re-assemble and shim up. The consequences of excessive grinding are concave seats on the valves and rings on the seat neither of which do anything for the sealing and longevity.
I gave up trying to grind the things years ago as it was impossible to get good results.
If you do decide to have a go, dont turn the valve through a omplete turn, but just a little way back and forwards, then lift and rotate it a bit and repeat. This is supposed to avoid the rings. From what I remember Holts paste could best be described as coarse and coarser still and of course a really fine paste will give the best seal.
Manufacturers don't grind valves (stopped in early 1950's) but in fact fit valves with a slightly different angle to the seats (1/2 degree) This gives a thin ring contact and works well (you've never had to grind them before have you!)
I wouldn't have thought stem wear was vitally important on a diesel as there is no mixture dependant on manifold pressure.
Piston slap is the knocking of the piston skirt on the cylinder wall and generally is only found on severely worn engines and often is more noticeable when cold, dissapearing as the pistons (aluminium) expand more than the block (iron).
Enjoy Easter!
jeremy

oilyspanner · Unread post by **oilyspanner** » 07 Apr 2004, 16:34

Vanny you found it!
At this point its worth looking for a Payen "Metal" Head Gasket, they are made of a number of layers of thin metal rather than the more usual composite, this may save you from doing it all again when you start to play turbo boosting! next point dont go mad grinding the valve seat, you will only end up needing extra thin shims, a light grind with a new/s.hand valve should be okay. I have a small collection of shims if you need, pistons are likely to be okay (the one damaged by a roadie that i was telling you about on the weekend had six bent valves, a three piece camshaft, smashed cam caps bent studs one damaged guide, it even pushed the rocker cover off! with no piston damage !)
Check BOL for shim calculation (my personal record is having the cam in and out of the head sixteen times)
A Micrometer is essential for thickness of shims, a good engineer will grind old shims to thickness saving lots of time.Any problems let us know, Reassembly is the reversal of dismantling procedure....heh heh
Good luck
Stewart

vanny · Unread post by **vanny** » 08 Apr 2004, 16:03

ARGH
Citroen lied! The valves where only meant to cost £22, but its £43.90 and thats just for one!
This car is starting to look a little doomed

If anyone has a spare valve (or even an entire head) for not a lot of money then i will rip your arm off for it! Why? Why didnt i just stick with the Mi16 that was there? It was in hundreds of parts, but it worked

Unread post by **alan s** » 08 Apr 2004, 16:46

Now you know why I kept telling you how to fit a secondhand valve[;)][;)]
Surely there must be someone with a blown up engine or burnt out car that has one kicking around.[?]
Alan S

noz · Unread post by **noz** » 08 Apr 2004, 17:04

Roy Gardiner who posts on Yahoo XM-L has replaced his head in the last two weeks. I think his new head came complete with valves so he may have the old one spare.
If you're a member on XM-L then just drop him a line otherwise let me know and I'll mail him off list and try to put you in touch.
cheers
noz[8D]