This question may have been asked before but here goes.
How feasable is it to change valve guides.
It is a 4 cylinder sidevalve engine and as they are worn I would like to get them changed.
As I have no experience of doing this can it be done at home or is it best left to the professionals.
If it can be done how would you remove and replace them i.e best or suggested method
Thanks
Richard
I've only changed OHV guides but that's dead easy. Measure how far they stick out of the block either into the port or the crankcase. Drift the old ones out into the port so they don't jam on the carbon on the OD. Drift the new ones in as far as you measured in step 1 above. Make sure you use a good drift so you don't mushroom the end of the new guide and close up the bore. For OHV engines, I use an old valve with a sleeve on the stem. That fits snugly into the guide and the sleeve should be small enough to pass through the casting. An old guide can be filed down slightly for that but then slip a nut onto the valve first so the old guide doesn't split as it pushes up against the valve head. If you've got a lathe, turn up a suitable drift first. When You've done all this either recut the valve seats or be prepared for a lot of grinding in as the seats may have worn to suit the old guides.
John
Often a real PITA.
The valve guides are in the block so it needs to come out.
If the valve guides are a separate item they can be pressed out and replaced _if_ you can get spares. Often they are just drillings in the block casting so these would need drilling and sleeving. In both cases a serious hydraulic press is required.
I would question the need for a press. I've not changed that many and all have been in OHV engines but a 2lb hammer's always moved them. The important thing is to drive them into the port so the clean oily part of the old guide is being driven through the casting. Go the other way and the crud will make life much more difficult. Side valave may be different but I can't see why.
John
John,
Whilst there is nothing wrong with your method I also would advocate the use of a press as it applies even pressure on the guide which is less likely to do damage to the guide. I would even suggest putting the guides in the fridge to shrink them before fitting, apply shock loads not only causes mushrooming but also may crack them.
I'd favour the 'by hand with a hammer' method myself as it is easier to feel if the guide jams on the carbon. A hydraulic press offers little feel & if the guide is not well supported it might be possible to split the block. Just a thought ...........
regards,
Kim Siddorn
"John" wrote (snip)
I guess limited access may preclude driving out an SV guide in the preferred direction.
Nick H
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