13 replies to this topic

[WiredbyWilson]

Non-car specific,

Just wondered how easy it is to fit valve guides at home, I have seen on MRA Minis you can buy a tool to do it?

Or i could take the head in and have it chemically cleaned, new guides fitted and checked over.

Other question is the valve seats have to be re-cut don't they

[bmcecosse]

On Mini heads - you should use a stepped drift - although I believe if the head is oven heated and guides in freezer - they can be pushed in easily. Some domestic authorities object to this use of the oven........ may be necessary to clean up the ends of the guides where they are 'banged' in - some say they should be reamed - i have never found this necessary. Seats in my experience have been fine with new guides (can't see why they wouldn't be) - but again others say you 'must' have them recut.

[Guess-Works.com]

Special tool available from MRA minis

http://mra-minis.co....?products_id=46

Opps... re-read and see you've already spotted that.... makes it *yellow human water* easy to install them especially if you have a press, but I've done them in a vice...

Edited by Guess-Works.com, 04 February 2010 - 11:24 AM.

[Guess-Works.com]

The issue associated with seats and guides, is all guides are built to a tolerance, for the valve to sit "perfectly" central to the seat they should be re-cut, even the smallest offset will mean the valve is thrust to one side of the guide when seated which will promote wear and eventual ovaling of the guide and failure.

[WiredbyWilson]

So the belt and braces approach is the have the seats re-cut, at which point I may as well get my mate to fit the guides at the same time?

[dklawson]

So the belt and braces approach is the have the seats re-cut, at which point I may as well get my mate to fit the guides at the same time?

Yes. If your friend has the tools to ream the guides and re-cut the seats it is typically less effort, and in the end more economical, to have a machine shop do all these tasks together.

Roy, I like your comment "Some domestic authorities object to this use of the oven". Fortunately for me, I am the domestic authority in my home so I overrule any objections.

[Guess-Works.com]

On a similar note I was playing with my new toy last night...

A set of valve seat cutters

Edited by Guess-Works.com, 04 February 2010 - 01:30 PM.

[bmcecosse]

Re-cutting the seats recesses the valves slightly - so avoid if possible. I find a good hand grinding is enough.

[WiredbyWilson]

Re-cutting the seats recesses the valves slightly - so avoid if possible. I find a good hand grinding is enough.

What problems would you say that causes then bmc?

Will prob seek advice of my machinest mate as to what to do.

Next question - which valve guides would work best??

[bmcecosse]

Depends on depth of new seat - if it's a LOT - then really need to open up around the seat with a small grindstone - and it will all be dropping the CR. But should only really need a light touch to make the seat ready for hand grinding - so make sure he doesn't go mad!

[WiredbyWilson]

Depends on depth of new seat - if it's a LOT - then really need to open up around the seat with a small grindstone - and it will all be dropping the CR. But should only really need a light touch to make the seat ready for hand grinding - so make sure he doesn't go mad!

He knows a lot about minis, so i think it will be in safe hands, he bored, balanced and built my current high compression engine.

I once asked him how much i would cost to have a head "fully worked" - he said how deep are your pockets.

[WiredbyWilson]

Anyone got advice for which valve guides are the best to use?

[Guess-Works.com]

depends on what material the valves are made of.... nothing wrong with the std cast ones, but not recommended when using EN214N steel valves... use bronze in that case.

[WiredbyWilson]

depends on what material the valves are made of.... nothing wrong with the std cast ones, but not recommended when using EN214N steel valves... use bronze in that case.

Well im guessing the head is still running std valves so std ones it is!