23 replies to this topic

[Cooperman]

This is how I fit new guides and have done since the days of the 850 in the 1960's.
I get a 1/4" bolt about 3/4" long. I lightly tap the valve guide with a wooden mallet to just get it started into the top of the head. Then I place the bolt into the guide - that is a bolt, not a screw as a bolt has a plain section and a screw is threaded all the way up.
Laying the head on its side in a vice I use the vice to push onto the bolt head, thus sliding the guide into the head. A little bit of light grease on the outside of the guide helps. The correct height above the head top face is quoted in the manuals.
I do No. 1 first to the correct height, then No. 8 to the correct height. It's then easy to do the other 6 without having to measure each time as a straight edge will do the job when placed across from 1 to 8.
Once all 8 are in at the correct height, I take a new valve to see if it runs smoothly in the guide. With iron guides most times all 8 are OK. If they are not I use a 9/32" reamer by hand (i.e. not in a power drill) to clear the tight ones.
Then I try each valve to see if it is seating fully 360 degrees. If any don't have a 360 deg seat, I re-cut those seats - just a light 'kiss' with the cutter is sufficient. The concentricity is normally OK, but sometimes a re-cut is necessary
Finish the lapping in, thoroughly wash the head out and re-assemble.
I now always use iron guides, even for high-performance engines, following a few problems with the phos-bronze ones.
Re-fit head and enjoy.

[MRA]

If yo uuse a reamer you will cut the guide oversize this is why you won't need to recut the seats correctly...... there is no such thing as a tolerance free engineered part there will be some out of concentricity within a valve guide, however when you use a reamer the internal hole is now no longer round or within tolerance, what this means is that if you remove a guide that is 0.002" off centre and replace it with another guide that is also 0.002" off centre but you put it in at a different rotation your valve is now potentially 0.004" out of position, this will mean that your valves will never seal properely.

Banging of any kind on a part that is manufactured to microns (millionths of a metre) means that it will distort, you have now way of measuring the damage that you have done it is a bodge and will lead to tears in the long run.....

Or simply put machine shops spend thousands of pounds upgrading their machinery....... when according to BMCECOSSE all trhey need is a hammer and a scraper

[Bluenose]

So in reading all the comments ive come to a conclusion.i wish id never started,!!only kidding.seriously though,im gonna replace the guides with some new steel ones using a vice.cross all my little pinkys that the valves fit beautuflly,thus not needing any work.out it all back together without banging a single knuckle....

Oh is that a pig I see up there?

[Turbo Phil]

Where abouts are you mate ? If you're nearby I'm more than willing to give you a hand.

[Bluenose]

Deepest darkest Wales turbo.not a boyo though sheep aint my cup of tea:-P .so atleast 5 hrs from the lakes,i know this cause ive come abit of walking up there,bloody lovely too.thanks for the offer mist kind of you,but sometimes a mans gotta do what a mans gotta di;-)

[bmcecosse]

Well - we don't all have a nice press or even perhaps a large enough vice to do the pushing. I used 'banging' in a slightly cavalier fashion - and advised heating the head in an oven and the guides in the freezer. They really do almost slide in by hand then........... And I use a proper stepped drift that snuggly fits the guide bore - and is only very slightly smaller diameter than the guide O/D to get the old guides out. They DO need some serious 'banging' at times to get them out. I also tend to remove/renew the exhaust guides first - and then the inlets in a second session. This way the old guides provide the depth gauge for the new ones.

In general my advice is of the low cost/DIY brand - since most of my own A series work has had to done over the years with extremely poor facilities and very limited cash......... My engines have always worked well and never suffered any serious problems. Follow or ignore the advice as you wish. It worked for me.

Edited by bmcecosse, 13 January 2011 - 11:34 PM.

[Bluenose]

Bmc;low cost/diy is my route too,cheaper and easier the better imo.i personally have very few tools and facilities too,but thankfully a lad who works for me p/time is doing a mechanics course,so its his tools,facilities and sparetime im using;-) and of course my/his cheap labour.fingers crossed that this will cure the prob and its not oil coming up past the pistons as you suggested earlier

[MRA]

BMCECOSSE, I think that you have hit the nail on the head...... You are doing it to a budget, the problem is that this topic will have been read by any number of people, when they see comments on here some will see it as open season to go and build loads of heads and then sell them as "professionally rebuilt" what then happens is the unlucky person who buys a head for £400 instead of the £500 normal price thinking they have a bargain then wonders why after only a short mileage it starts to smoke etc. These customers then go off Minis as they are "unreliable" and expensive to repair.....

Please try to remember that most of us on this forum are trying to keep Minis on the road for the long term future, if your ideas are done to a budget then if you say that then other users will be able to determine whether the quality is at a level they wish to aim for.

We can't all spend £000's on a nice new engine, and your "budget jobs" are no less relevant, however we need to let people know before thay spend their hard earned money on something they wished they had added some extra money and purchased a quality job, such as Swifttune or MED, etc..

[PhilipGCaldwell]

when I did my head I did the porting out myself and the cleaning of the chambers, drifted out the old guides and lapped the valves

I got a headshop to put the new guides in, skim it and recut the valve seats, this work comes in at about £100 which is worth it imho