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Valve guides

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faeton
Posts: 103
Joined: Mon Feb 29, 2016 9:31 pm

Valve guides

Post by faeton »

After rebuilding my engine many years ago because of blue smoke on start and overrun I have never been entirely happy with the results . Although there was an improvement . Recently whilst going through my spares including remains of 2 dismantled saloon engines. I came across a load of vv guides
I have been threatening to strip my engine for several years but as it is running so well I keep putting it off . I think I may now have discovered the problem . I noticed amongst the 16 or so spare vv guides that there are two different lengths , Although it was many years ago and my memory is not so good I don't remember the modified guides I was supplied with being different lengths, I cant recall who supplied.

As I didn't have a press I got a friend to fit them also warming the heads, He probably didn't notice the different lengths of ex and inlet when removing old guides. Could be that all ex guides were supplied and fitted. These being the shorter ones it wouldn't help the oil consumption if fitted on the inlets

Looks like I will have to strip the heads and check . I also understand that the guides when pushed in and out can score the heads . I was advised to fit with Loctite as oil can be drawn down the score marks , There is a lot of discussion on the Mini Website about the poor quality of the standard black seals . An engine tuner advised the use of Viton seals . These are generally red anyone know where they can be obtained.

tjt77
Wise Man
Wise Man
Posts: 525
Joined: Wed Mar 23, 2016 7:01 pm

Re: Valve guides

Post by tjt77 »

its highly unlikely that anyone would put the guides in wrong position... the inlet lave guides are longer and have a tapered end to help flow where they protrude into port..exhaust valve guides are shorter and almost flush with the head casting in port and hence have no taper at the port end ..
current guides sold today have a provision for a stem seal machined into them .. a competant machine shop can machine the old style guides to take a modern seal..whilst the current production guides come with provision for a stem seal on both inlet and exahaust.. its not neccesary on the exhaust guide.. When the cars were in production there were issues with exhaust valves sticking in exhaust guides in the early saloons causing major engine image.. this was overcome by shorting the guide so it did not protrude into port and increasing guide to stem clearance slightly.. its wise to bore the exhaust guides out and fit a silicon bronze insert if you have a friendly machine shop that can do this for you.

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