Unleaded Head

Post by **billlobban** » Fri Oct 09, 2009 3:13 pm

Now that Matilda has passed her MOT thoughts turn to oiley bits. Thanks to BMC , PSL and others my oil leak has recended from a torrent to mearly a flood (well a continual drip to be honest) but I have the feeling an engine rebuild is in the offing. Owner-2 (the artful bodger) sold her to owner-1 converted to unleaded. Now she came with piles of paperwork, old MOT's, invoices for parts etc going back for years. BUT there is no mention of an unleaded conversion despite the considerable cost. Owner-1 only did a couple of hundered miles in the 2 years he owned her.
? with the head off is there any way of telling if its been convered to unleaded or do I just have to wait until the valve seats burn out

Post by **bmcecosse** » Fri Oct 09, 2009 3:29 pm

You don't NEED an unleaded head, unless you plan on hammering the engine at full throttle for miles on end - just set the exhaust valve gaps to 15 thou - and keep an eye on them. If/when you take the head off some day - you may find some pressed in hardened seats under the exhaust valves - but I doubt it!

Post by **billlobban** » Fri Oct 09, 2009 4:09 pm

Why do people spend hundreds of pounds on the conversion? I doubt it to by the way especially having seen some of his other bodges

Post by **bmcecosse** » Fri Oct 09, 2009 4:26 pm

Because they have been 'conned' into thinking they need to do so! My car does not have an unleaded head - neither does it get any 'additive' - and in 10 years so far it hasn't given the slightest hint of a problem. The Mini 998 engine (from early 80's on) has a so-called 'unleaded' head - which does not have any seat inserts - it just has slighty better quality exhaust valves fitted. These better valves will directly fit the 948 and 1098 cylinder heads (need matching caps and cotters) - and indeed the complete head (often given away free by Mini lads) is a direct swop on the 948 engine - and could be used on the 1098 engine with some slight loss of power. But I see no reason to do so!

Post by **billlobban** » Fri Oct 09, 2009 5:36 pm

Thanks again BMC I'll keep my money for other bits. I've got lots more quetsions by the way I hope you wont get fed up answering

Post by **eastona** » Fri Oct 09, 2009 5:40 pm

do I just have to wait until the valve seats burn out

unless you plan on hammering the engine at full throttle for miles on end

Both work for me! (OK, not quite full throttle though).

if you've got an unleaded head, it's going to be fine. (touch wood)

If you haven't and you thrash the living daylights out of it and are unlucky enough to burn/pit a valve then you'll need new seats cut/valves/head job(delete as applicable). But you'll have got a few more miles out of it on the way and just hope it doesn't strand you in the middle of nowhere with a warning free failure.

Just my thoughts on the matter and what I've done for the last 40 000 miles. With one burnt valve incident on the way.

If you want to tear it apart to check, as BMC says, look for the pressed in seats.

It's personal choice really and depends I suppose on how you intend to drive it.

Andrew

Post by **Pyoor_Kate** » Fri Oct 09, 2009 7:08 pm

It does, indeed, depend on your driving style, what you're going to use the car for, and your luck. Valve recession can / does occur - some people are lucky and get none. Some people aren't and get stuffed.

Because my minor is my main car (well, it's off having lots of work done at JLH, but normally it's my only car), I got the unleaded conversion. I can't afford to have it taken off the road waiting for parts (because I can't get to work without it).

As with virtually everything in minors, and indeed life, YMMV.

Post by **ssnjimb** » Fri Oct 09, 2009 7:29 pm

I drive my minor hard i dont hammer it but it gets used on the motorway regulary.

I dont use additive and i dont have an unleaded head.

I set the valve clearances to .12 as per the book. there is no sign of valve seat reccession the tappets open up not close up.

I have done nearly 6 thousand miles in my moggie since buying him in feb

Jamie

Post by **bmcecosse** » Fri Oct 09, 2009 7:56 pm

The reason I say 15 thou for exhausts - is to allow for additional expansion of the exhaust valve which obviously heats up far more than the inlets! If the gap EVER closes up - the seay and/or valve will burn - so by keeping that little bit of extra clearance - you have that little bit of extra safety. In fact - later A series engiens were specified by MG Rover for 15 thou anyway! Guess why!

Post by **ssnjimb** » Fri Oct 09, 2009 8:07 pm

when i re do my tappets on sunday i will check the clearance of the exhaust and then adjust accordingly.

Does the inlet stay at 12 thou

Is there any difference in power etc

Jamie

Post by **bmcecosse** » Fri Oct 09, 2009 8:08 pm

May as well hold inlet at 12 - and no -you won't notice any difference!

Post by **ssnjimb** » Fri Oct 09, 2009 8:13 pm

Slightly off topic but water leaks from the sparkplug side of the cylinder head. When i say leak its very slight and its more of a sweat mark. when i changed the head gasket i had to take the head off again would that be the cause.

Jamie

Post by **bmcecosse** » Fri Oct 09, 2009 8:18 pm

Don't worry about it! But won't do any harm to torque the head down before you re-set the valve clearances. Torque to 44 ft lbf. - in the correct order of course!

Post by **ssnjimb** » Fri Oct 09, 2009 8:36 pm

will give it a try.

Jamie

Post by **eastona** » Tue Oct 13, 2009 5:02 pm

With one burnt valve incident on the way.

Make that two

Car was running like a trail on the M5 last night, pulled off the MWay and it was slightly misfiring. got home and it was like a "soft" misfire.

Ignition was all fine, so suspected a head gasket or valve.

pulled the head this morning before work (if it was a gasket I carry a spare so would have been fine) and it was definitely a valve.

The last time (about 25000 miles ago) I recut the seats (presumably cutting out any lead memory) and fitted\lapped in 2 valves but I think the time has come for an unleaded head.

It *may* have been that I was running slightly too far advanced. "Super" petrol was fine as it didn't pink, but I filled up with regular in yeovil yesterday and it didn't like it so much. Should have notched back the timing, but was too lazy and paid the consequences.

I know a u\l head won't help that, but I think it' sbetter in the long run. As with Kate, it's my daily driver and gets a fair bit of use. (well, not today it didn't

).

I've had 40K out of it since I got the car without changing, so it eeked it out a bit longer.

Andrew

Post by **bmcecosse** » Tue Oct 13, 2009 5:55 pm

New valves- grind in the seats - get another 40K no problems! the important thing is to set the gaps at 15 thou - and KEEP AN EYE ON THEM ! If the gap starts to close up - then adjust it back to th 15 thou. The valve will only burn if the gap is allowed to close up.