Morris Minor Owners Club

Hello,

I've got a couple of heads which I want to give the basic 'stage one' Vizzard treatment too but have come to a bit of a dead end in trying to source the correct bits to fit to my grinder...

I have an air powered die grinder which takes 1/4" shank bits and runs at the reccomended 22000rpm, it's fitted with some form of metal, conical grinding bit which I tried out today but whilst it does remove some material it is definitely not up to the job of major reworking of cast iron. So I wonder what anyone else uses if they have done this sort of thing... I read that TCT bits are good for the job but only come across wood routing bits when I search for them.

I also see lots of 'porting kits' that have grind stones and snadpaper rolls, but from using similar things in the past for engraving I don't think they're quite up to removing lots of material and probably only just fit for polishing the ports.

Any ideas about companies, type of bits, ebay links or anything would be much appreciated.

Thanks very much
George

I just used cheap mounted point stones from the Pound shop - in an old electric drill. They don't last long - but they are cheap! Use an old vacuum cleaner to suck away the mix of stone and cast. beware - I don't think they would be safe at 22,000 rpm!

PM sent.

Thanks both for replies and PM, I have infact found something that looks the trick on ebay... http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... K:MEWNX:IT

I've bought just this one for the time being to see how it gets on, so if it does the trick I'll get some more shapes - balls, cylinders etc... very exciting, I feel like a real power tuner now! hah

It's a long hard grind......... That won't get down the valve throats very well - which is where most of the metal has to be removed.

yeah, it's the valve bosses mainly that i'll be working on, i thought this would fit down quite well... will have to suck it and see, pretty cheap so can always get another if its not quite right

You need more of a ball shape.

ah well, only another £7, can't wait to crack on with it - I've been reading so much theory I want to put it into practice!

I picked up a bunch of different size burrs from an amazing old tool shop today and had a crack at an exhaust port this evening. I'm quite pleased with the results and pleased that it is relatively quick with these burrs.

Can anyone advise about how to treat valve guides? Vizard states that the guides should be replaced by 'bullet nosed' guides, but is it possible/advisable to simply the grind the guides down to the same profile as the reshaped port?

I'm finding that I can make a notable improvement in the smoothness of the shape of the port by grinding down the guide boss, but can only go so far as I risk attacking the guide. Is it essential that the guide should be a certain length, or can it be ground down somewhat to get the most out of the port?

Cheers
George

You must remove the guides and grind away the boss. New guides should remain full length - and indeed should be bullet shaped! The biggest improvement of course is to enlarge the throat diameter - so only a minimum narrow seat is left for the inlet valve. Don't over-do that on the exhaust valves although some thinning of the seat can still be done.

Thanks Roy, I've a big valve 940 head now so the throats (I think) are as large as they can get - plus I am working on the short side radius.
Do I just hammer the guides out with a drift? Presumably I have to use new guides when replacing them, but do I then need to have the seats recut to match the new guides?
Minispares don't seem to sell the bullet guides, can I just reprofile standard guides with a bench grinder?
Cheers
George

The throats on the big valves can be opened up usefully too. You need a stepped drift - especially to fit the new ones - and yes - just bullet nose the inlets (not the exhausts) any way you can. Don't take them to a knife edge! Some say the easy way to fit new guides - is to heat the head in a domestic oven - guides in freezer - then they supposedly just tap in. I haven't done this - so try it at your own risk.

yes, i'd read that infact, seems like a logical approach!
will the seats need recutting to match the new guides though?

Hi
You will normally need a light recut of the valve seats after replacing the guides.

thanks Taupe. I've been on the phone to a few local engineering companies today to get an idea of price and they've quoted between £50 and £80 for cutting the seats - sounds like alot as it is only a 45 degree cut.
Roy, I've heard you mention just doing it on a pillar drill with a countersink - how does one align the countersink to the new guide? My neighbour has a pillar drill I could use which would be far preferable to shelling out for someone else to do the work

Or can I get away with drifting in the old guides to avoid recutting the seats? - the guides don't appear worn

They will be damaged on removal. Indeed - even the new guides will likely need a light reaming when fitted - or at least - remove any burr at the top face. The only reason to have to cut new seats - is if the holes in the guides are for some reason not central and parallel to the guide OD. Otherwise - it's a mystery to me why the universal feeling is that new seats must be cut! It's really not necessary - just grind in the valves.

Hello George,

you'll be very lucky to get a decent seat with a countersink, especially on a light drilling machine.

You could try E-Bay to see if you can find some seat cutters as an option but I doubt if you'll save very much in cash?

Alec

Thanks both for the comments - good to hear the seat cutting isn't a necessity... I'm more than happy to spend hours porting, banging in guides, grinding in valves etc - just not shelling out loads of cash!
I did have a look on ebay for some valve cutters but like you say Alec there is minimal saving to be made...

Crazy price for cutting valve seats - don't do it! Yes -the head I'm using had the exhaust valve seats sunk down 40 thou using a large countersink in a pillar drill. Slow speed - self centering on the original seats. The head was not clamped down - the cutter was brought in to contact - allowed to self centre - the stop was set to allow 40 thou of cutting and then it slowly cut the seats down. Perfect seats were formed - took very little 'valve grinding' to give them a smooth grey finish. But if all you do is fit new guides - and then shell out the throats so a fine/thin seat is left -it will only take minutes to grind in the valves. Don't worry about it!