Big valve head refurb.

[bmcecosse]

You have to remember- 'machine shops' are there to make money..... Your big valve head will be fine with a good clean and valves ground in. If really bothered by the tiny 'ridge' you can take it away with small mounted point in a leccy drill (or perhaps in this case a Dremel) - but take GREAT CARE not to touch the valve seat. Go for it. The head you are going to use on the 1098 - well, he's talking through his @@@@ - it must NOT be skimmed - it's already much smaller combustion chambers than the standard 202 head and so raises the CR nicely as it is - so no skimming - or perhaps the very lightest touch if it's thought it may not be flat - but I bet it is. Before worrying about sinking valves - or pocketing blocks - measure the distance from top face of valve to head face. You need minimum 300 thou. These 'pitted' exhaust valves look quite chunky - so first off I would be taking some metal off the faces to make them more flat. A grinding wheel will do that well enough for what you need. And then if you are short of the 300 thou -decide if it's easier to sink the valves - or pocket the block. Doing the block is messy -but can be done in place with mounted points in a leccy drill - been there, done it 50 years ago - never again... But you MUST of course keep all the dust and grindings out of all the moving parts - and it can expose the top ring to excess heat - and it pretty well ruins the block for any other use.... if you later perhaps decide to go back to a standard head. So - pocketing the valves is by far the better way to go. Let's see how you get on with the valve flattening and measuring....

[bluegrass]

Ok, thanks for this.
I will definately not be pocketing the block. I'd rather get another 1275 if it came to that.
With the valve clearance, do i need to have the head assembled with rockers etc to check that.....I'm not quite sure about that side of it or how to position the valve in the head to measure the correct distance.

With the big valve head, i have some grinding stones i could put on my dremel to carefully remove the ridge, then i am assuming i can use the 'emery' technique to take the valve seat down.....

Its a shame there is'nt a reasonably priced manual cutter, i'd happily buy it and have the facility to cut my own valve seats.
I'm also looking for a valve guide tool to insert and remove guides easily, but again very hard to find.....Do you know if the height of the valve guides protruding at the top of the block is the same for both heads and what that measurement is meant to be?

Thanks

[bmcecosse]

Just sit the head upside down on some wood blocks - and drop the valves in. Don't get too anxious about the guides - they are usually fine - but if you really think they need changing the dimensions of the tool are well know. For the height - simple - just do one at a time and push the new guide in till it's same height as the others - check with a straight edge steel rule , or even the back of a hacksaw blade. I had valve seat cutters - it was hard going.... The emery trick will tidy them up enough.

[bluegrass]

Ok, i'll have a go, and report back. Thanks

[les]

Pretty sure it's 19/32 of an inch protruding.

[bluegrass]

ok, thanks.

Just to clarify, do the guides just knock out, no heating of head required? Do i knock out from bottom of head out through the top. Insert from top of head down, then trim the 4 shorter valve guides once inserted?

[bmcecosse]

Remove from top down - and then insert new also from the top. Removal is fine at any temperature - and you don't care what happens to the guide -just don't damage the head. When fitting new - best with head in oven to say 100 degrees - and guides in freezer overnight. They should then tap in easily - as i suggested - use the remaining guides as the height standard. So -perhaps change all the inlets, and then change all the exhausts if you really feel the job needs doing - that is. Where excess length sticks up in the valve throat - I remove it with mounted points, but don't make them too short. You can 'bullet' shape them before insertion if you think it's worthwhile.

[les]

Be careful not to burr the top of the guides when removing them, otherwise they will bind on the way out and possibly cause the new ones to be a looser fit than they should be. Use a brass drift or something that won't damage the tops.

[bluegrass]

Thanks Les...I'm searching for a commercially available drift to do it with, but can't find one....Maybe i'll have to get a tool made up in a shop, i dont have the gear to make one.

[bmcecosse]

No-one near you who can lend one? This is the sort of thing the local branches should be arranging between members. Or someone lucky enough to have a lathe could churn them out and sell them for a Fiver!

[bluegrass]

I did meet a retired aircraft engineer recently who has a workshop full of lathes etc....Maybe i'll visit and see if he can help. Someone should make them....they would sell loads i'm sure.

[panky]

Here are the dimensions you need for the drift, page 3 and scroll down a bit

http://www.mmoc.org.uk/viewtopic.php?f= ... l&start=40

[ampwhu]

I have a tool for removing valve guides. my mate who has an engineering shop, made one to the exact dimensions on a lathe. anyone local can borrow it.

as regards to cleaning the head, is it possible to bead blast it? the reason I ask, is I am going to have some wheels refurbed and I could get mine done at the same time.

I had a go at the emery cloth cleaning today and it is working fine.

[philthehill]

The problem with bead blasting the head is that there are too many channels/apertures and oil ways where the bead material could get trapped and then become detached and start to circulate throughout the engine once running - therefore my advice is not to bleed blast just stick with the good old emery cloth and then wash down with plenty of paraffin and finish off with a hose pipe keeping all nasty's out of the drains.
Phil

[bluegrass]

Maybe soda blasting would be a better idea, and the media just washes off. I think you should manufacture your valve guide tool Phil, it looks excellent.......I am a little envious......Thats also a kind offer for people in your area "ampwhu".....I like the helpful spirit of this forum very much.

[philthehill]

Whilst my valve guide remover tool (originally made over 35 years ago) is well used the basic tool is not my idea it is featured with dimensions in the Minor Wksp Manual Section AA19.
Here is the complete tool which can be used for removing the guide and fitting the guide at the right height.
I prefer using a press with the tool for removal and fitting and not hitting the end of the tool which may cause the guide to burr.
Phil[frame][/frame]

[bluegrass]

What i like about your version is the ability to use different spacers for different valve guide heights....

[philthehill]

This particular tool is really only suitable for an 'A' Series but could by varying the dimensions be adapted for other engines.
Phil

[bluegrass]

Yes i was thinking 'A' series, but even then some heads seem to require slightly different valve guide heights. That tool together with different spacers could cover them all.

[bmcecosse]

The 'install height' is already specified by the 7 guides you haven't yet knocked out (or have already renewed) - just use a straight edge across the guides !