Loose valve guide :-(

[ardee_selby]

pete...I have access to some bloody big ovens.....think your head would fit one half of one shelf.....thsy do tend to run at 230C......if its any use.....I might get an odd look trying to 'smuggle' it in... but I can ask... cheers g

(http://books.google.co.uk/books?id=b66Q ... &q&f=false)

Note the above link includes 180c and "not exceeding 200 degrees Celsius" when fitting valve seats, with a lower temp (150c) for installing guides & follower sleeves.

Cheers - Richard

[elansprint71]

Yes, I had checked Wilkins, he recommends baking in an oven at 150 degrees and basting every half an hour. He also says that to drop the valve seats in heat to 220 degrees, so I'll watch the temperature.

Thanks for the comments Rohan (and others). I've been otherwise distracted this last couple of days but have established that none of the valves are bent or worn, the only guide which is worn is the one in question; no sign of the circlip and also the one next door is missing too. I've tried to pull out the spring platforms- none of them will come out, it really looks like the circlips are fitted on top of the platforms (apart from the two missing ones and the platforms on those two have come out with the springs).
It really does look like a case of bad assembly. Will try to photograph tomorrow.

[rgh0]

The spring platforms can sometimes be hard to remove as they can jam on the outer edge in the head or inner hole on the circlip depending on the assembly tolerances . I would be very surprised if the spring seats are fitted 'under" the circlip as the hole is larger than the fitted circlip - or at least it should be.

cheers
Rohan

[alexblack13]

Looks like you might be right Pete. Mind you I would suggest very unusual to get a bad bodge up from the people you mentioned. More like the thing you get from hopeful amateurs. I doubt the guides were fitted with the spring seats in place as the hole is bigger. The ring circlips fit into a small recess too and almost disappear. If the head has been assembled as you describe, you are one lucky guy to have found it in time and it need attention fast. It's not difficult. Heat the head and drift them out. NEW ring circlips onto NEW guides. All ready? Heat the head. Then they tap in easily..

Valve seats ok? Yes = re-cut them gently when you have the new guides in. You should need to gently ream out the valve guides to 'fit' your valves. Then don't mix them up. BTW.. What thickness of shims are in the head (on average?)

Good indicator of seat life...Thin shims, less than say .065'' = seats are a bit deep/ worn. Check also that the valves have not been topped (top of stem ground to get valve clearance) I would not be surprised given the other aspects of the build quality. Or lack of it!

You will fix it mate..

Good luck.

Alex...

[elansprint71]

Not the easiest place to photograph! First shot shows the circlip above the level of the spring platform in an adjoining cylinder, I have six like this. From what I can see there is only one circlip in the "fully home" position, i.e. in the recess in the casting (this is the one I referred to as possibly missing above). And of course one which actually was missing!



This one shows the situation where the valve guide was loose.



Apologies about the poor quality of the images.

Thanks again for your support, I'll wear it often.

[ardee_selby]

Pete,
Anything more to report?

Not sure how accurate the illustration is, but wrt Rohan's checklist...7 out of 8 wrongly assembled? or wrong interference fit?, which isn't that great if at the bottom of Miles Wilkins quoted spec (i.e. 0.0005")

Q. Is the same interference spec applicable to both iron & bronze guides?

But a bit surprised something didn't occur long before the 20K miles, though...

Cheers - Richard

[curly type 26]

Hi Pete, I used to repair electrical appliances in a past life & some ovens can be way out on temp, borrow or hire digital thermomoter to confirm stat settings b4 cooking head I have one somewhere if stuck. Good luck Curly

[bigvalvehead]

Hi All
on engines I've built in the past I've used guides with a retaining collar machined on the guide. I think Cosworth used such a guide. No circlip to fall off or snap that way.

[john.p.clegg]

If it helps,150 is Gas Mark 2 and 220 is Gas Mark 7.

John

[ardee_selby]

Hi All on engines I've built in the past I've used guides with a retaining collar machined on the guide. I think Cosworth used such a guide. No circlip to fall off or snap that way.

Like the attached from the US, in manganese bronze? (not Colsibro)

Cheers - Richard

[elansprint71]

Anyone know a UK supplier of these? Looks a far better solution than putting little bits of bent wire in there.

[types26/36]

I got a set of the shouldered type from Rapier Services a couple of years ago, I also got a couple of sets from the US (not D.Bean) about a year ago and they were much cheaper.

[elansprint71]

Thanks Brian, I e-mailed Bean earlier today and also JAE parts in California too.

[types26/36]

Pete, this is where I got mine from in the States although he has not got any listed at the moment.
http://myworld.ebay.co.uk/aptfast321&ss ... X:SELLERID

[elansprint71]

Two replies from JAE! They have them in stock with standard o/d, +0.002 and +0.005. $8 each plus about $25 for shipping.

Pat Thomas has four exhaust guides (only) but they require some machining to the taper.