12 replies to this topic

[cjhols]

Hi all, I'm re-fitting the head to the cyclinder block and was wondering whether it is impeartive to have and/or use an alignment stud to align the head and block? To be honest I can't recall the block having one??? Any thoughts???
Thanks Peter

[JonnyBMX]

dont quote me on this but surly the studs in the block used to hold the head down will allign it? this is how i did mine and ive had no problem after many miles...

[Artful Dodger]

the alignment stud is the same as any other stud. it is the front middle stud. the difference is that the hole in the cylinder head is a much tighter fit compared to the others. this means that it will sit in the right place.

[JonnyBMX]

ahh right! this explains things ahah i was wondering how id never heard of it when ive not had any problem alligning them before :)

[cjhols]

Yes but I don't seem to have the stud. Will it align with just the bolts???

[Artful Dodger]

you are missing a stud? if you are missing the aligning stud it may nor go on square. i wouldnt fit the head then.

in fact if i had any stud missing i wouldnt fit the head!

[Tamworthbay]

you are missing a stud? if you are missing the aligning stud it may nor go on square. i wouldnt fit the head then.

in fact if i had any stud missing i wouldnt fit the head!

I think he may be confusing bolts and studs.

OP- do you have any threaded holes in the top of the block which don't have anything in?

[tiger99]

The confusion arises because the K series engine used in the Metro etc has two head aligning dowels which originally were plastic and gave trouble, but I believe were replaced by metal, or an aftermarket supplier made better metal ones. I think that the O series and the diesel variant the Perkins Prima, had a similar feature, but it is ages since I had one of those apart so I may be wrong. To positively align the head you would need two dowels.

If the front middle hole in the Mini is tighter than the others (can't say that I have ever noticed, and I have had heads off more times than I care to remember), it would only locate the head at one point, and it could rotate slightly, depending on the clearance in the outer holes. My general impression is that all of the studs are sufficiently close fitting that there is not a problem.

[cjhols]

Yes Dowells is a better term than studs. And yes the block or head do not have any??

[Cooperman]

The A-series engine does not have head location dowels, just studs.

[Artful Dodger]

If the front middle hole in the Mini is tighter than the others (can't say that I have ever noticed, and I have had heads off more times than I care to remember), it would only locate the head at one point, and it could rotate slightly, depending on the clearance in the outer holes. My general impression is that all of the studs are sufficiently close fitting that there is not a problem.

It is. It positions it roughly, if it wasn't there the head
Would be able to move sideways, putting the chambers off centre to the bore. Can't be good:P

[tiger99]

Well, I see that a single stud will prevent sideways movement, which will help with the most critical bit of the gasket between the bores, although it will not stop the head going on slightly skewed, which will misalign the outer chambers, but not by very much.

I suspect that most people who successfully overhaul and rebuild Mini engines are blissfully unaware of the centre hole being tighter. If it is doing its job you don't have to know.

[Cooperman]

Hi Tiger, I only learned about that centre stud about 10 years ago having been building (or re-building!) Mini and other A-series engines for years. It's not obvious until you look at the head closely. It does, though, prevent the gasket blowing as the inter-cylinder wall on 2 and 3 can be so close. I think you're quite right about any angular mis-alignment being so small as to not matter.