Loose valve guide :-(

Post by: **elansprint71** » Wed Mar 09, 2011 9:22 pm

Readers with a long memory, various CLOGs and other kindred spirits might recall that my Sprint developed some rather strange smoking habits last year: for a lot of the time there would be no smoke, then it would be like a destroyer at the Battle of Jutland. It could happen during acceleration, when cruising or when I stopped at a road junction, but really whenever it saw fit.
Assembled experts at Le Mans last year were baffled by this, it gave no definite clues to the usual suspects, i.e. either rings or valve stems.
On my return I took the head off and was then overtaken by "other events". This evening I finally got around to removing the exhaust cam and valves and imagine my surprise when #3 valve came out complete with the guide!

The guides seem to have been fitted by QED about 20k miles ago.
I'm thinking that this guide might have taken to wandering up and down the stem, sometimes sticking in the right place, sometimes dropping down and allowing bad stuff to happen. What do you think folks?

And how to fix?

Post by: **types26/36** » Wed Mar 09, 2011 9:44 pm

elansprint71 wrote: What do And how to fix?

Pete, Lotus used to supply guides with oversize out side diameter although probably only in cast iron, it shouldn't be a problem for a good machine shop to make up a bronze guide and bore the head to suit.
Just another thought, the machine shop could probably find one from another car/truck with similar dimensions and modify to suit....as I recall there used to be some from Bedford's trucks or such that were similar.

Post by: **alexblack13** » Wed Mar 09, 2011 10:01 pm

Blimey Pete! Not seen that for some time!

You found the issue though!

Any head damage? As you will know,the guides are a tight interference fit and it looks like that guide is now quite slack in its hole. If there is no damage in the head itself, have a new over-sized one made (or buy if available) What did QED say? or have you not spoken to them yet?

I remember removing the guides on one of the +2's and having the head in the oven, then onto the kitchen table. Special little drift that fits down the guide stem hole and a sharp tap with a tapometer and they just knock out. Not difficult.. Check the head aperture carefully before fitting the new one. Where is the little retaining ring? Gone? If so where? Looking at the picture Pete the retainer ring groove looks misshapen / badly worn. Looks like the guide could have been 'driven' down by the valve ass'y. Got big 'lifty' cams in the motor?

I'm sure some of the head experts will see you right.. Rohan will be right with you no doubt...

Hope it fixes ok for you & I am sure it will, but it might be time for a head overhaul I think. You certainly need to check the rest out.

Alex...

Post by: **mr.vman** » Thu Mar 10, 2011 1:02 am

Pete, If the valve contacted the piston, it could bend the valve stem. The bent valve stem "locks on" the guide forcing the guide out. Over-rev? improperly adjusted valve timing? There have been various "tech" bulletins on engines that sit for some time could have deposits form from our modern fuel on the stem and guide, acting as an adhesive. When the engine is turned over the guide can be forced out when the valve opens. Good luck on this one, hope this helps. Steve V. +2 going together in Arizona, I hope in time for LOG this year!

Post by: **ardee_selby** » Thu Mar 10, 2011 10:21 am

Pete,
H*lls bells...
As said above, looks like the circlip groove has had a hammering. Does the valve to guide clearance seem OK, through it's travel? Was everything else intact? Any tell-tale marks?

No doubt you've seen the QED site by now. Up to +0.030" oversize guides are listed. Hopefully the head can accept reaming out OK

Miles Wilkins says interference fit should be 0.0005" to 0.0015".

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

Bon Chance - Richard

Post by: **GrUmPyBoDgEr** » Thu Mar 10, 2011 11:44 am

Sounds like you've had a very lucky escape when looking on the bright side of a nasty.
Seems from the previous posts that oversize guides are readily available.
If I were in your position I'd get the lot done for peace of mind.
Just think of the expense you could be saving :shock:

John

Post by: **twincamman** » Thu Mar 10, 2011 12:15 pm

Pete--- buy a lottery ticket --RIGHT NOW --you are very lucky ---ed

Post by: **trw99** » Thu Mar 10, 2011 3:24 pm

Pete

Seems to me you need to change your kitchen roll. Just thought I would make a contribution here to be helpful.

Tim

Post by: **elansprint71** » Thu Mar 10, 2011 3:35 pm

My wife wants to know why I woke up in the night screaming ZEEEETEKKKKKK!

Thanks for the comments and suggestions chaps, I'll be along later with sensible responses and thoughts (that will be a first).

Ed, I hope you are correct- the Euro-Millions lottery is 68 Million this week! Does anyone know a good helicopter-owner's forum? :idea:

Post by: **GrUmPyBoDgEr** » Thu Mar 10, 2011 4:16 pm

elansprint71 wrote:My wife wants to know why I woke up in the night screaming ZEEEETEKKKKKK!

Thanks for the comments and suggestions chaps, I'll be along later with sensible responses and thoughts (that will be a first).

Ed, I hope you are correct- the Euro-Millions lottery is 68 Million this week! Does anyone know a good helicopter-owner's forum?

Ugh! visions of very messy sheets :shock:

68 Mio. is totally perverse!
7 winners with ~ 10 Mio. each would also be very, very happy & have difficulty spending/investing such an amount.
Needs regulating, I think. :roll:

John

Post by: **types26/36** » Thu Mar 10, 2011 4:52 pm

elansprint71 wrote: Does anyone know a good helicopter-owner's forum? :

Here you go :lol:

http://www.heliguy.com/Forum/

Post by: **alexblack13** » Thu Mar 10, 2011 4:54 pm

Agreed John, Now throw one decimal five over here...

Not a lot to ask! is it??

PS.... you would not see me for dust..

I would go fixed wing Pete... I've still got the ticket to fly that. No medical! But hey! you can't win them all... :lol:

Quick comment.. Sitting here watching the TV.. Maserati factory following the building of the new drop top. Aw man!! That is one stunner of a car.Hand made and NO robots... 2-3 years from now and it will be affordable... Can't wait! Now that would be a nice retirement prezzie...

More likely to be the camper van though..

Just blown away watching this.....

Sorry!

AB...

Post by: **alexblack13** » Thu Mar 10, 2011 5:07 pm

Did they ever run a helicopter?

Chapman had a few fixed wing aircraft and I have a picture of myself and one of them at the factory. It was, I am sure a Navajo (spelling!!) twin. Piston engine plane in JPS colours.. I drooled over it for quite a while. Then went back and drooled some more!

Got me thinking now and I'm off to look for it.. 70's pic' mind but I am sure I can find it.

Al' .....

Post by: **bcmc33** » Thu Mar 10, 2011 5:22 pm

Pete,

I've just made a print of your valve to show the guy that built the head for QED in their previous life. I'm at his place tomorrow to pick-up the new tall block he's machined for me.

How long have you been running the head?

Post by: **CBUEB1771** » Thu Mar 10, 2011 6:08 pm

bcmc33 wrote:I'm at his place tomorrow to pick-up the new tall block he's machined for me.

Sorry to hijack this thread any further. Brian, is this the new casting you ordered in January? If so what bore did you go to?

Loose valve guide :-(

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