18 replies to this topic

[Tommyboy12]

So I took the cylinder head off my car tonight thinking that's what was causing the overheating. Good news is that it wasnt! Apart from what looks like a slight blow between 2 and 3 the head-gasket was fine. Turns out its actually the thermostat I've learnt my lesson to check that first from now on!

 

Anyway as ive never had the head off my Mini before I thought I would have a look around and see whats crack-a-lacking. The engine seems relatively healthy but I have a few concerns: The monumental carbon build up and a rather light looking exhaust valve.

 

 

Pistons from rad side to clutch side.

 

1.

 

2.

 

3.

 

 

 

4.

 

I've noticed that piston 3 and 4 look 'drier' than 1 and 2.

 

All the bores still have visible hatching and look in good order with no scoring. However, there is a very slight lip on the top of each bore. Its not much but sliding my finger over it I can just feel it. This picture is poor but you can just about see the hatching as well as the staining of the lip.

 

 

Cylinder head next. This one is piston 1 on the right and piston 2 on the left.

 

 

This is piston 3 on the right and piston 4 on the left. These two have lighter coloured exhaust valves with piston 4 being the lightest.

 

 

From the drier pistons and the lighter exhaust valves I would say that pistons 3 and 4 are running leaner for some reason? I don't know why when I run a single HIF44?

 

My biggest concern is this!

 

 

I have no idea what it is but its made of some sort of plastic and it came out of the pushrod hole when I pulled out the last pushrod on the right (nearest the rad)!

 

Hopefully someone can shed some light on the health of my engine. Also what's the best course of action for cleaning up the carbon build up?

 

 

Thanks in advance!

Edited by Tommyboy12, 24 June 2013 - 08:05 PM.

[leroy26]

old skool method i was taught is lightly scrape it off with a screwdriver taking care not to score it or get the dust down the bores

[Alex_B]

The a-series runs leaner on two of the cylinders due to the port sharing and the nature of the head, thats normal, the lip is because the piston doesnt travel up the bore that far, provided the rings are still sealing well (compression test wet and dry will tell you that with the head back on, but apart from a clean up it looks ok and I dont know what that rubber thing is im afraid

[Tommyboy12]

Im aware of the charge robbing but I thought that affected 2 and 3, rather than 3 and 4.

 

I last checked the comp ratios at the start of the month and they are OK but they are a little high on 1 and 4/little low on 2 and 3. Which may back up the slight blow I am seeing on the old headgasket.

 

1 - 215psi

2 - 200psi

3 - 195psi

4 - 210psi

[KernowCooper]

A couple of those exhaust valves look well pocketed I'd have a look at the vales now you have it apart and put on new valve stem seals

 

I would not be to adventurous  taking carbon off the outside of the pistons or the top of the bore on a worn engine, you could burn oil otherwise

Edited by KernowCooper, 24 June 2013 - 08:20 PM.

[jaydee]

That soot is oil being burnt, probably from a leaky valve

You valves looks a bit too much recessed, i'd consider a srip down and rebuild for the cylinder head

As long as the pistons havent goe side movement i'd leave them as they are

[Tommyboy12]

Pistons seem fine. I will be getting the head done. Im fed up of buying fuel additive!

[Sam14]

A bit of gravel in number 4...get it out.

[Tommyboy12]

Its loose carbon build up. Ive already been fishing other bits out. Ill be cleaning off the loose stuff at least before it goes back together.

[Captain Mainwaring]

A couple of those exhaust valves look well pocketed I'd have a look at the vales now you have it apart and put on new valve stem seals

 

I would not be to adventurous  taking carbon off the outside of the pistons or the top of the bore on a worn engine, you could burn oil otherwise

 

I know a lot of sources mention this, buy do you think that cleaning would make too much difference?

I must admit I have't pulled the head on an engine that has been as cokey as that for a while, but if and when the heads get lifted on the various bikes I own, they get a good clean and they don't use any more oil than normal....

Not doubting you, just wondering

[KernowCooper]

Seen it before when you remove the carbon lip at the top of the bore and clean to the edge of the piston on a well used engine they start to use a drop more oil, not just the A series but Fords Vauxhall and others.

[Tommyboy12]

The engine is a worn unit but is still plenty strong at about 85bhp so I dont want to upset it too much. I would like to clean off any loose stuff though. If the lip isnt a problem it can be left too. The head will no doubt be cleaned while I have the valve seats hardened.

[Tommyboy12]

Ta-da! One nicely refurbished head with new exhaust seats, inlets cut, new guides and a light skim. The guy in the machine shop used to race Minis and said that this head has had some serious work done to it. Apparently the exhaust ports have been really worked on, so much so that it would be impossible to open them up anymore! Im not complaining about the suprise of a well worked head!

 

 

[jaydee]

Looks good, i have to say in the pic looks like theres a hairline between cyl 2 &3 but i soppose its just the pic otherwise you had noticed that

Keep the engine as it as long as you have healty compression and the piston are well seating in the cylinder dont worry about the top cylinder lip

Dont forget to give the deck surface a good scrub so its nice and clean and the new HG can seal at its best

[Tommyboy12]

Its just the picture. Its some of the fluid from the cleaning process that makes it look like a crack. I will be cleaning the deck up properly and removing any big loose chunks carbon from the centre of the pistons. Compression and pistons in general are fine though so im leaving the cylinder bore and the edge of the pistons well alone!