NS Dev
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| posted on 23/3/05 at 01:04 PM |
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Vauxhall XE valve guide removal/refitting
Don't know if anyone can help me on this one (Dave Walker?) but I am currently gearing up to rebuild one of my Vauxhall engines and need to
replace the guides.
I am getting some Colsibro guides (from Mark Baines) to go in the Coscast head, but obviously need to remove the old ones and fit the new.
I have read about various ways of acheving this, mainly knocking out the old guides and then heating the head to 180 deg C, chilling the new guides in
the freezer compartment, then knocking them in.
I have some tool steel to make various bits and pieces to do the punching, i.e. a punch, sleeve to go in the lifter bore to centre the punch, and a
spacer sleeve to set the depth on the new guide, but I want to verify the fitting procedure.
Can I get away without heating the head up. I am concerned because I though Coscast heads were "precipitation hardened" and this hardness
will be lost over 150 deg C. Also knocking 16 guides in before the head cools will be tricky!
Can I just chill the guides and press/punch them in?
How much do I need to chill them by if I don't heat the head. I can get -50 deg C with solid CO2+Acetone mixture.
Or can I do it all at room temp?
Lastly, if knocking them in is too agricultural, I have an arbor press big enough to get the head under, but I would then need a Jig, so if this is
needed, what is the valve angle on the head, for making the jig??
Sorry so many questions!
I know an engine builder will do this for me but at £5 per guide to fit them, I fancy some DIY seeing as I have the facility to make the tools
necessary (I think!) and can get the tools hardened etc at work, and can then do it myself on the next engine too!
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rusty nuts
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| posted on 23/3/05 at 06:30 PM |
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Not sure of the correct procedure with your engine but it's normal to recut the valve seats when guides are replaced and if the £5.00 per guide
includes seat cutting that seems to be a reasonable price . Have replaced guides on several heads myself after putting guides in freezer and head in
an oven . After doing the first one they get easier.
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NS Dev
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| posted on 23/3/05 at 09:32 PM |
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No, it didn't include the seat cutting I'm afraid. I am toying with doing that diy as well, though not sure yet, depends whether I have
time to make a rig to do it.
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david walker
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| posted on 23/3/05 at 10:38 PM |
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Nat, forget the heating up, freezing etc - another one of those ideas put forward by the expert in the pub....
Make up your drift, pilot diameter about 6.5mm, then a stepped up diameter a little less than the valve guide od, say about 10.7mm diameter, for about
30mm in length and then go up to the nominal dia of your bar, ie 13mm for the rest of the length of the drift - taking it to about 150mm in total.
You'll need to get the head under a hydraulic press. A small workshop type, even a bench press. Mine is 12 ton rating and well up to these jobs.
Pack the head to the right angle using hard wood blocks. With the drift in the guide, eyesight is adequate for ensuring the press action is aligned
with the guides. Any damage you do to the head, which will be very minimal, will be rectified by skimming the head face anyway. Press the guides
through from inside the head - under the cam buckets, outwards. Try it the other way and you'll have problems with the carbon that will have
built up on the guide od.
Fit the new guides in the same way, Use a couple of copper washers between your drift and the top of the new guides to minimise peening over the top
of the guides. You'll probably have to ream the bores of the guides anyway when you have fitted them.
If you are doing any porting work on the head you should have the valve throats machined out whilst the old guides are fitted. Remove the old guides,
port the head, fit the new guides and then cut the seats.
Dave Walker, Race Engine Services - 07957 454659 or 01636 671277
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NS Dev
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| posted on 24/3/05 at 08:24 AM |
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[Edited on 24/3/05 by NS Dev]
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ned
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| posted on 25/3/05 at 07:46 PM |
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NS Dev,
as I've not done guides myself I asked a friend of mine who has built several 240bhp spec xe's.
Contrary to what David Walker says he puts the bits in the freezer and leaves the head by the fire. He recons it does make it easier.
The rest of the process he described was as David's description ie using a drift etc.
Not wanting to cause an arguement, just stating that it can be done this way.
Ned.
beware, I've got yellow skin
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