New Cylinder Head - Running In?

[Gareth]

Hi gang!

It's been ages since I asked a technical question, so I thought I'd make a stab at this one.

Over the past few months I've noticed a distinct loss of power. That has been traced down to an absence of compresson on cylinder no.3, and since she's not burning any oil (no smoke whatsoever) it's looking like the valve has begun to break up. So early next week, Phyllis is having an unleaded head fitted!

As an aside, the reasoning behind those pellets (which came with the car and have done sterling service/nothing for four years) is now looking distinctly dodgy, not to say, unseated - sorry to all: you were probably right!

Anyhow, moving on. The rest of the engine *should* be okay, as there haven't been any unexplained noises, so for the time-being we're settled on a new head. However (and here's the point of the question - at last! I hear you shriek), will I need to perform any "running in"? I'm thinking the answer would be "yes", but I'd like a bit of feedback - so what do you all recommend?

Oh, and I've already had a play in Photoshop and made a Running In: Please Pass! sign, just in case... ;) Where's that laminator gone...?

[57traveller]

For just the cylinder cover Gareth I would say it's not necessary. Never heard of the need before.

[Cam]

I have never run a head in either. With an engine it's the cylinder bores, crank shell bearings and cam bearings that need running in, and being as these are not present in the head then don't bother.

Mind you you won't be running at high RPM (5000 - 6000) anyway will you?? So it's not really an issue. Just drive normally.

[Kevin]

I've already had a play in Photoshop and made a Running In: Please Pass! sign

You could still use if you like Gareth ( then some of the others wont go on abour your driving speeds any more )

[Willie]

I would only be worried about new valves running in new valve
guides but they would be polished in very rapidly, and you are
not one of them 'boy racers' are you?

[rayofleamington]

I'm surprised it happened so quickly Gareth, although if you drove like me you'd have burnt a valve in months not years.. . Maybe you do more miles than I'd thought. Before jumping to conclusions it might be worth to see what the valves look like.
As for running in a head - I would guess take it very easy for a hundred miles or so, but then your normal driving should be ok. High revs for long periods would not be a great idea in the first few hundred miles in case any of the valve guides have high spots (= friction = heat = risk of sticking), however if the head is done right it should NOT have any problem like that.

[Chris Morley]

Gareth the iconoclast

As an aside, the reasoning behind those pellets (which came with the car and have done sterling service/nothing for four years) is now looking distinctly dodgy, not to say, unseated - sorry to all: you were probably right!

How long ago was that Gareth? I guess nearly four years ago and on a totally different messageboard?

Also I seem to recall you were casting aspersions on the Federation of British Historic Vehicle Clubs at the time. Luckily you didn't put them off and they continue to add lead-free products to their approved list.

http://www.fbhvc.co.uk/fueladds.htm

[57traveller]

Just to follow on Gareth, I would try to avoid sudden and excessive acceleration and close to max speed/power for about the first 100 miles until the holding down studs/nuts are re-torqued (don't forget to do this and check valve clearances). This will avoid subjecting the gasket to high firing pressures initially. Follow up the exhaust/inlet manifold nuts as well.

[Gareth]

I only do 6k a year, and it's split between steady cruising and town-toddling. It's rare that I sit in traffic, and almost all my driving is done in 4th gear. Haven't investigated the head so far, but she wasn't burning oil and there were no nasty clonking sounds. The only symptom was a very low compression reading on one cylinder, so it sounds like it's connected to the valve gear.

How long ago was that, Gareth?

Barely a few months, when the thread resurfaced! What can I say? We can all be wrong, can't we? ;) In my defence, I never said that it was an ideal solution... (can you see me grabbing at straws? ) When the head's off, I'll get the guys to have a look at the valves and seats and see if they can identify any particular point of failure... Who knows, it could be a spring, or something that might have failed anyway? (Straws again...)

I always said I'd put an unleaded head on when the time came, so you ought to see me trundling around the shire, complete with Please Pass sign for a couple of weeks. In fact, I might keep the sign there permanently, eh Kevin? ;)

I had wondered when to retorque the head nuts, so I shall do the advised after 100 miles. Glad I won't need to stick to any rpm limits for 500 miles or anything like that. If 100 miles should be enough to make sure everything's bedded in, then that ought to be fine.

Thanks all!

[Chris Morley]

Who knows, it could be a spring, or something that might have failed anyway? (Straws again...)

Yes, it could well be caused by something else other than valve seat recession. If you do need to fit an unleaded head it seems wise to make sure it has a good mileage based warranty as even a dodgy one could work for 6k.

[Gareth]

Just an update - definitely VSR... and one valve on no.3 was quite badly chipped.

The new head's on, and she's running very nicely indeed. I had a service at the same time and although I haven't gone over 50mph yet there seems to be more power - she can hold 50 uphill for longer than before.

[Kevin]

Well that was nice and quick Gareth