36 replies to this topic

[topcat]

So I thought I'd run in my MG engine so I drove from London to Bristol with no problems, started out on the return journey yesterday and SNAP! Got about 50 meters and broke down. I havent taken the head off yet, I'm hoping the valve hasnt done much damage. (Do they damage the piston/cylinder when they drop in?)

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So I think I'm going to put my old cooper head on now as its unleaded. I'm just about to take it off the cooper engine, whats the best way to check that it is flat? How much does a head skim cost. Should I re-lap the valves? What would I need to do this? Thanks.

[bert998]

head skim cost me £25 a couple of months ago;)

[The Matt]

You may be lucky and have done no real damage to the piston. But it's gonna have been bouncing on the top of that piston an awful lot. Try pulling the valve up with a pair of pliers and see if the stem is bent at all. You 'may' even get away with replacing the spring if there is no damage anywhere.

Head skim will be IRO £20-35 going on what I have paid in the past.

If you are gonna relap the valves, you can buy a kit from Halfords for around £5ish which will do the job.

Good luck with yer piston

The real issue is why the spring broke??????

[Jammy]

I would imagine it has damaged the piston. Even travelling at quite a low speed the components are moving very quickly!

You planning on taking the head off yourself, and if need be changing the piston yourself? Since labour will be a massive chunk of this repair bill!

Why does everyone always have the head skimmed when they take it off? Surely A series cylinder heads don't warp THAT easily?

[topcat]

Well I'm swapping the head myself. I only put the engine in last weekend so If the piston needs replacing I don't know what I'll do. Getting a bit bored with taking the engine out (second time in 2 months)! I'll probably just give up cars and stick to a push bike.

I wouldnt be supprised if the head has warped a bit because I did loose my water and overheated quite badly. I think the gasket was blowing between the middle two cylinders aswell.

No idea why the spring broke, the valve clearances were fine, weird.

Ive taken my old cooper head off now and it looks ok. The exhaust valves have alot of yellow deposites and the rest is pretty black. What do you use to clean out the chambers around the valves?

Edited by topcat, 23 October 2006 - 11:53 AM.

[TimS]

Can you pull the valve up and down ok? do you still have the cap and collets (sp)?

[topcat]

I've still got the collet. I think the valve has droppped right down in. But it doesnt really matter as I'm gonna swap the head over for the cooper head which has valve, springs etc... anyway. Just so long as the pistopn isn't damaged. Still not sure what to use to cleanup round the valves on the cooper head.

Edited by topcat, 23 October 2006 - 02:40 PM.

[The Matt]

Well, sorry to say it, but the more I think of it there is gonna be some piston damage. If the valve has dropped right in it is gonna have been smashing against the piston. When the piston is coming up to the top of its stroke I don't think there is enough room there for it not to smash inbetween the head chamber and piston crown.

Sorry to be pessimistic, but I think you can expect piston damage.

[topcat]

I know its a worrying thought! Might get round to taking the head off tonight. I'll keep ya informed!

[The Matt]

Yeah, let us know how ya get on mate.

[mini bunnykin]

not good well bristolminimad pistons went on his mini and it was apparently due to not being set up right...

i hope you manage to sort it!

[Brooky]

To clean the valves,remove them and put them in a drill(1 at a time) and clean them with some emery.

To do the conbustion chambers stick a rotary wire brush in the drill and just clean them up.

Good luck with removing the head. i recon there will be quite abit of damage :'(

[fikus01]

when my old 998 broke a valve i drove it for 3 weeks before getting annoyed enough to investigate it, i had been thrashing it hard because above 3000rpm it was fine! took off rocker box and when engine was running and the compression must have been pushing the valve back up into place under compression!!

[biggav]

some people i know are obsessed with having the head skimmed at every opportunity!!!
:'( ... Whenever i have my head off, i strip it and get it checked by a local engineer for about 5 or £10 cash (doesn't take too long and keeps him sweet for if ever i really need hos help) I also use osselli as they are really good and have all the gear set up... bit expensive though. I have a new dtage 4 head from minispeed arriving hopefully tomorrow.......

Good luck, hope the damage isn't too bad!!!!

[topcat]

OK so here's the damage:
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What's the verdict?