Author Topic: Valve guide removal  (Read 3009 times)

Offline huddie

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Valve guide removal
« on: 05.09. 2009 12:45 »
I am about to give my head (cast) a complete overhaul and never having removed valve giudes before I am looking at the head wondering which way they drift out?.  I have a suitably sized drift on its way via ebay. Having done a search on existing topics using "valve guides" as the search key my question is still unanswered. Do they come out down into the combustion chamber or up out the top of the head, and is there a shoulder on them to aid refitting?. Can anyone help.  Regards Huddie.

Online bsa-bill

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Re: Valve guide removal
« Reply #1 on: 05.09. 2009 13:42 »
Hi Huddie - they come out the top, knock them out from the underside from the combustion chamber.

others heat the head up in an oven, I hav'nt tried this, probably works fine I just think if the guides are cast they will probably expand the same amount as the head so not much will be gained - instead I used a electric heat gun to heat around the guide area but keeping off the guide.

When the guides arrive you will see straight off how they are located.

All the best - Bill
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Offline muskrat

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Re: Valve guide removal
« Reply #2 on: 05.09. 2009 14:07 »
G'day Huddie,
                  I'm one of those that heat it up in oven. 250 C for 1/2 hour then spray aerostart or catbie clean down the guide to cool it a bit. They come out easier and less chance of damaging the bore. New ones go in by heating the head again and freezing the guides, they fall in or very little force. Most will be right to go but some do need honing to size. Take your time, be gentle with the new ones. I've done hundreds this way and only wrecked one.
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Offline scotty

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Re: Valve guide removal
« Reply #3 on: 05.09. 2009 15:15 »
Huddie

I purchased a tool on evil bay that was made for VW air cooled engines that claimed to be suitable for A10's and it worked great.

Heated up the cast head in the BBQ and gently drifted them out from the combustion side...they came out without any dramas or butchery  *smile*

At a later date I had the auto machine shop install the new guides as they were re furbing the head for me.
They asked me for the bore/tolerance of the guides as they wanted to make sure the clearance was correct with the valve stems.
For this I referred to the data in the Haynes Manual:
A10 Valve Stem dia when new  Inlet 0.3105 - 0.3115 in  Exhaust 0.309 - 0.310 in
A10 valve guide bore 0.313 - 0.314 in
They did end up machining the bore of the guides.

hope this helps

scotty

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Offline huddie

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Re: Valve guide removal
« Reply #4 on: 05.09. 2009 15:53 »
Hi to you Bill,Scotty and Muskrat, Many thanks for your help. I had assumed that any new guides would have been the right size and wouldn't need reaming. I am away next week in Snowdonia, not that far from SRM in Aberystwyth so Maybe I will get my guides valves etc from them. Maybe the respective guide/valve will be matched? Thanks again
Regards Huddie.

Offline muskrat

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Re: Valve guide removal
« Reply #5 on: 05.09. 2009 21:28 »
G'day Huddie,
                  I am sure the SRM kit will be of the highest quality, but they still may need reaming/honing. It also depends on how many times the guided have been replaced in the past. Every time you do you wear the bore a poofteenth, so thats why they make oversize guides. Once it's done you WILL also need the seats to be recut, or use the old valves and a lot of grinding paste to get them close then finish off with the new valves.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7