13 replies to this topic

[HarrysMini]

Hi,

 

I am in the process of lapping in the valves on my MG Metro big valve leaded head. The inlet valves are all good and will be absolutely fine until the next rebuild, however, the exhaust valves (mainly no. 1) have some pitting, as below.

 

 

Is this going to be useable? Or can I expect a loss of compression from this?

 

Any thoughts appreciated.

 

Thanks?

[Fast Ivan]

I would say that's shot harry

[Tamworthbay]

+1, I would replace. That pitting looks deep so would take some grinding out.

[HarrysMini]

I thought it would be.

 

Here is a picture of the valve seat if that helps

[Ethel]

I'm  guessing it's still an unleaded head, are you using any fuel additive?  Have a close look at the seat for corresponding damage.

[HarrysMini]

It is a leaded head, with no conversion. I don't know if any fuel additive was used as I bought it with the engine and I'm unsure of it's history. All I know is it is a 35000 mile engine.

[A-Cell]

The valve is not much good now with that pitting. Looks like cause is using unleaded fuel. It would be worth having the head converted to run on unleaded, ie get hardened valve seats fitted whilst it is off. Then new exhaust valves.

[DomCr250]

I get a set of hardened exhaust seats installed (to me i cannot see the inserts?) now the head is off and at least one new valve ...in the long run a lot cheaper than having to pull the head off again.

[HarrysMini]

I thought about getting a conversion, but it's all cost and I was hoping to wait until I fully rebuilt the head in a couple of years time.

 

What are people's thoughts on the seat? Can that be ground or will it need recutting?

[minimender]

Cant loose anything by trying to grind them in, if not, new unleaded seats are not that expensive, ask around and get best price from engine reconditioners, 30/40 quid for exhaust valves and have new guides fitted as well. that will be a recon head and good for many miles to come

Edited by minimender, 15 February 2014 - 02:46 PM.

[HarrysMini]

I have found the valves I need, they're £8 each so that's not too bad. I think I'll get a set of them and try grinding them in. http://www.minispare...px|Back to shop

 

In the near future, I'm hoping to get some porting/gas flowing done and as the same time I'll get hardened seats and bronze guides to make it a full rebuild.

Edited by HarrysMini, 15 February 2014 - 03:24 PM.

[minimender]

I have found the valves I need, they're £8 each so that's not too bad. I think I'll get a set of them and try grinding them in. http://www.minispare...px|Back to shop

 

In the near future, I'm hoping to get some porting/gas flowing done and as the same time I'll get hardened seats and bronze guides to make it a full rebuild.

I would grind the old ones in to see if you can clean seats up first, then lap new ones in , eight quid each seems a little expensive, try shopping around

Give these a ring, very competetive and post next day delivery, best to ring for a better price.

http://www.lymmengin...rmation/contact

 

Also on ebay but again you need to ring for what you want and its probably cheaper to do that

Edited by minimender, 15 February 2014 - 04:58 PM.

[carbon]

Harry,

 

The pitting on the exhaust valve seats looks a bit more than you can easily remove by hand grinding the valves in. Ideally you need to aim for a lack of any pits, and for this the quickest way would be to get the seats reground by a machine shop. There are tools you can buy with cutters to do this by hand, but they can be hard work...

[HarrysMini]

I would really like to not have to get the seats recut if at all possible, as it's all expense and this already expensive engine is costing far too much already.

 

I'll give the lapping another go, it wasn't very well done the first time round as the suction cup on the stick won't sit on the valve very well and keeps coming off.

 

Thanks for the advice.