something serious...

[phurn]

If its not one thing its another.... heading to imo this morning I developed an awful misfire. It's bumpy and lumpy at idle, but if I rev it under no load it seems to sort itself out. However at load its terrible! I have no power and it makes and awfully metallicy noise. I pulled the ht lead off number 3 and its no worse so I believe that to be the problem cylinder. I haven't taken the spark lead out yet but I know the ht lead has a spark (OUCH) however I also have mayonaisse under my filler cap, but my water hasn't noticeably decreased and Theres no oily residue in there.

[alex_holden]

If the spark plug seems OK when you take it out, the next step is to do a compression test. Could be a burnt/stuck valve. Very crude first check if you don't have a compression tester to hand is to turn it over on the starting handle (ignition off) and see if it gets difficult to turn four times in every two revolutions.

[bmcecosse]

Probably head gasket - if a plug change doesn't fix it - don't drive it till you do a comp check - or have the head off.

[David53]

I agree it does sound like a head gasket blown between two cylinders if you have a strong spark at the lead. Compression check is the way to go.

[chrisryder]

another compression check is to have all the plugs out and turn it over on the starting handle with a thumb over each plug-hole in turn. you will feel your thumb pushed off each one (hopefully!) if you don't then it's either headgasket blowing between bores, or a stuck valve.

[phurn]

Well its defiantly gasket. No compression on 3+4. Ordered a new one gonna get stuck in tomorrow, any tips for best way of going bout it? What size spanners/ sockets will I need?

[chrisryder]

you should be able to disconnect the manifold from the head without taking off carb or exhaust, which saves time and gaskets. for the manifold it's 6 brass nuts that are 1/2 inch heads. 13mm will fit them but it's not advised!

there is a thread in 'usefull tips' i think that gives all the nut and bolt sizes. most of it can be done with 1/2 inch and 9/16 sockets and spanners. you may find that the push rods won't want to fall through the head and stay in the enigne, and it's best to keep them in the same order. if you take the rocker assembly off before taking the head off, you can lift out each push rod in order and push them into a sheet of cardboard with 8 holes poked in, and an F written on for Front.

You can choose to leave the heater tap at the back of the head on the head, in which case just remove the hose via it's jubilee clip (and the heater tap control cable if there is one fitted). doing it this way lets you use the tap as a handle helping with lifting the head up (so long as the tap is strong enough!). the alternative it to unbolt the tap from the head. this means you don't need to disconnect hose or cable, but will need a new gasket for the tap, and the nuts can be hard to get at. they are small too, possibly 7/16 or 11mm ish.

be sure to drain the water down a bit too, or you'll fill your bores and oilways with water! oil won't need draining so long as the engine has been allowed to cool, as the oil sits just below the top of the block.

Good luck, on the MOT last year we changed so many that we got it down to a fine art that took just under 2 hours a time

[phurn]

What about reassembly and timing? Is there as specific order for the head bolts?

[kennatt]

I would also getbthe head checked ,might need skimming,or new gasket will very soon blow again if the head is not flat.

[bmcecosse]

If you can, leave the manifold connected to carb and exhaust. If you don't have a workshop manual - PM me. You should use a torque wrench when tightening up - don't worry about push rod order you will need to reset the gaps anyway. It' seems silly not to grind in the valves while the head is off - but if you need the car urgently I can see the need to just drop it back on. DO however clean both faces well first. Cheapest gasket is from mra Minis http://www.mra-minis.co.uk/classic-mini ... 2506hg.htm and I'm told they are superquick at despatch.

[moggydriver62]

A manual is very handy.Even a haines manual will give you what you need.
It will show you what to look for,what to take off,or not take off.
Every body on here is very helpful,but you can"t remember all of it.
Git er done Git a book. ( and a beer)?

[MarkyB]

If the head hasn't been off in living memory then don't just yank the push rods out, lift each one up about half an inch and give it a little spin between your fingers.
This should ensure that you don't pull the cam follower up and out of its hole at the same time.
If you do pull the follower out you'll have to take the cover off the side of the engine to replace it which is a pain.

[IslipMinor]

don't worry about push rod order you will need to reset the gaps anyway

Sorry, I disagree completely! It's nothing to do with whether the gaps need to be reset, the pushrod will have formed itself to the shape of the cam follower and rocker arm, so why lose that pairing for no reason? No actual harm will come from mixing them up, just need to reset the tappets more often for a while until everything reshapes itself, why do that?

When removing the pushrods, pull the top to one side as you carefully lift them out to break the 'seal' that the oil creates bewteen pushrod and follower. Even give it a sharp jerk to the side - you don't want the follower to lift up and fall on its side. They can be recovered through the side tappet covers, but must be kept in their original location to retain the wear pattern match with the cam lobe.

[bmcecosse]

I used to worry about it Richard - but as I got older and wiser I realised it really doesn't matter. But of course -no harm in keeping them in same order.

[chrisryder]

i just knocked up this drawing for someone else on here, that's the order i do the head nuts up looking from above, stood infront of the car.

[frame][/frame]

i tried leaving the manifold attached to the head and just undoing the exhaust clamp. it didnt work. well, it did, but it was far too heavy to lift. i ended up stood in the engine bay:[frame][/frame]

'er indoors helped by taking a picture!

[Neil MG]

Chris, "i tried leaving the manifold attached to the head..."
Looks like the manifold is attached to your head!

Great picture though!

[ian.mcdougall]

if you had removed the bonnet support you could have tied the bonnet back for more room

[ASL642]

Chris -you should use that as your post pic - that's a wonderful shot - well done Lil!

[taupe]

Classic picture of Minor Dedication!!!

[phurn]

Well the old gasket off... gaping hole in-between cylinders. I'll put the new one on tomorrow, any tips for removing the old gasket residue?