Engine problem - any ideas?

[dp]

Been poking about on a mate's Minor van. The engine is making an odd noise - like only firing on 3 cylinders but when I remove the plug leads in turn, 2 and 3 make no difference at all. I can't believe the engine is only running on 2 cylinders (1 and 4) . The owner has had head gasket problems in the past and thinks the gasket has failed between cylinders 2 and 3.

Does this sound like the cause?

Thanks,

dp

[MoggyTech]

Yes, confirm with a compression test, state of plugs, and make sure HT leads are OK

[mike.perry]

A cracked distributor cap can do funny things to the firing order.

[bmcecosse]

Almost certainly head gasket - but it could be a valve gap closed up - or a burned valve. Off with it's head!

[Grahmo]

I concur, sounds like head gasket to me. The only way to be sure is with a compression test.

Changing a head gasket isn't difficult (find a workshop manual), however your head might be warped so you need to check this with a steel ruler or something. If isn't flat it will need to be machined, or if you aren't running unleaded, this might be a good time to change to a reconditioned head.

[dp]

Thanks everyone.

I checked the leads, plugs, rotor arm and dizzie cap, all looked okay. There's a history of head gasket problems and I suspect botched repairs by garages in the past.

In terms of a possible warped cylinder head, is it also possible the block would warp or is it always the head?

If replacing the head, are there any particular ones to look out for: MG 1100 ones or special mini ones that give a free economy or power hike?

Ta

Darren

[Grahmo]

I am sure it is possible for the block to warp, but in my experience it is always the cylinder head that goes out, normally as a result of overheating.

I am sure lots of people have advice on alternatives that will give you a little extra power, what type engine is it 948cc or 1098cc?

[dp]

Should be 1098 as it's an F reg van

[MoggyTech]

Continued head gasket failure is likely to be due to warping of the head, or worse, etching of the block/head due to gases eating away the metal. Head should be checked and if need be skimmed, and same goes for the block.

[MarkyB]

It would take a LOT of heat to warp a cast iron head.
Etching of the block/head due to gases eating away the metal gets my vote.
Head and or block will probably need skimming.
You won't know till you take the head off.

[bigginger]

The kind of heat that's generated by burning petrol in a confined space repeatedly right next to it, I've heard... ;)

[MarkyB]

The kind of heat that's generated by burning petrol in a confined space repeatedly right next to it, I've heard

The internal combustion engine wouldn't be very viable if this was an issue.
Warping an alloy head is very easily done. Much less common with cast iron.

[bigginger]

Less common, certainly, but it does happen

[bmcecosse]

If it's ever allowed to run short of water - expect warped head to follow! It certainly happens. If the block is scoured then it's an expensive business to strip it all down and skim the surface. May be better to find another block! Or -consider a complete overhaul with rebore and crank grind, along with surface skim. Unfortunately that's not going to be cheap.

[Kevin]

It would take a LOT of heat to warp a cast iron head.
Etching of the block/head due to gases eating away the metal gets my vote.

Well all the moggie ones I have seen over the years have been the head I have not actually seen an A series block affected like you suggest on a running engine although its possible.

[bmcecosse]

It does happen Kevin - if the engine is allowed to run for any length of time with the gasket blowing. Have seen it on Mini blocks - between the bores - more so on the larger bore engines certainly where the 'land' between bores is less. If the engine has a 'history' of gasket problems then the block should certainly be considered suspect.

[dp]

Any suggestions as to a suitable cylinder head to scout in breakers or Ebay for?

I'm guessing something from a Mini is going to be easiest to get hold of but any particular model/year or other caveats?

Thanks

[bmcecosse]

The 1098 head (12g202) has the slightly larger inlet valves and better inlet ports - but needs skimming 60 thou for use on a 948 engine. The MG/Cooper head (12G295) has even bigger inlets and better ports - also needs skimming 80 thou for 948 engine - 60 thou for 1098 engine. The head from a 1275 engine (12G940) has much larger inlets and slightly larger exhausts and far better ports - it needs no skimming for either engine, BUT - it needs the exhaust valves sinking into the head by 40 thou on a 1098 engine - you 'may' just get away without (but I wouldn't chance it) sinking the valves on a 948 engine - but that's only because that engine has such a miserable camshaft with poor lift on the exhaust valves ! Also must be used with 1275 head gasket and 1275 rocker gear - or you can re-space the original rockers so they line up over the exhaust valves correctly. It's by far the best performance improvement per £ you can fit to either the 948 or 1098 engines.
If you want a very simple direct fit head - then yes - a head from a 998 Mini goes straight on - may even be 'unleaded' if that bothers you, same performance on 948 engine - slight loss of performance if used on a 1098 engine. And NO - it won't fit a 1275 engine ! Well, actually it will - but the performance will be terrible!!

[Kevin]

Have seen it on Mini blocks

Well that explains why I havent seen it so far, but what I was puzzled by was MarkyB's reply that he felt etching of the block/head was more common than a warped head.

[bmcecosse]

Certainly not 'more common' in my experience - only happens if car is driven home with gasket blowing. I only say Minis because i have worked with them far more in the last 30 years than with Minors! but they are in essence the same engine.
Any joy with your head yet Kevin?