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MG MGB Technical - Unleaded cylinder head?

Ok, just stripped my 1980 MGB Roadster. Engine is out, ready for a paint and thought better to get it converted to unleaded. Does anyone know who does this in Surrey etc?

Car only has 49K on the clock and keen to keep the engine etc, so looking at getting existing refurbished.

Thanks
s lewis

Southern Rebore Services at Rowfant.
Alan
Alan Anstead

If there's nothing wrong with the head I wouldn't risk causing a problem by getting it converted, just carry on with using an additive. At 4p per litre (e.g. for Castrol Valvemaster)it's cheap enough.
Paul Hunt

You can't argue with Paul's advice but if you want your head unleaded plus a little more power and mpg - talk to Peter Burgess (he's on the web)
Roger W

Are additives good enough to cope with track days?
c cummins

When unleaded was introduced here, the Valvemaster blurb basically said "no". OK up to 4000 RPM, but by 6000 their graph was showing signifcantly increased effects on the valve seats.
So most people here use leaded race or aviation fuel if they are track regulars.

In my case I have inserted both inlet and exhaust seats, which has also solved the problem of cracks between the two as the two seats intersect (exhaust seat cut into the inlet a bit) and form a figure 8. This results in the interference fit having the seats push against each other instead of just the one trying to be held in by that very thin bit between the seats. (And when the valves get to 1.75 and 1.44 that's not very much!)

It's done 20+ years' work like that, including 3 marathon rallies with approx 800 miles of special stage apiece and countless shorter events, so you could say it's been successful.
But having said that it will probably go BANG tomorrow :-)
Paul Walbran

"Are additives good enough to cope with track days?"

They seem good enough to cope with several hours on a motorway at 70+.
Paul Hunt

That would be consistent with Valvemaster's data
Paul Walbran

Ok, taking some advice on hand I am going to leave it as is and replace when its due. Will use aditives for the time being. saves me money money during the restoration.
s lewis

It would be a wise investment to have the hardened seats and valves, along with the bronze guides, installed while you have everything apart. The cost isn't that much and it will save you the trouble of having to pull the head, at a future date, to have the work done then. I picked up a spare head, in a salvage yard, back in the early '80s and had this work performed to it. I've had that head on three different engines and I've never had to do a single thing to it since. Valve adjustments are rarely required, as there is extremely little wear taking place. The choice is yours, but it's a small investment to make in a car that's worth keeping. RAY
rjm RAY

"I've never had to do a single thing to it since. Valve adjustments are rarely required"

Ditto mine without unleaded vales and seats. Valve adjustment used to be a pain, it seemed to be out every year, sometimes too big sometimes too small. I couldn't even get the clearances to stay the same when turning the engine by hand. Then I discovered that at the strict 'rule of nine point, i.e. adjust n when 9-n is fully down, some of the valves clearances were still changing. So I changed to setting them at the biggest gap, which as well as making them repeatable, and not changing from year to year, also made them a bit quieter.
Paul Hunt

Paul, I've always wondered why you have that particular problem. Maybe your camshaft wasn't ground properly. I've never encountered the problem you've described, but everyday I seem to encounter something new and bizarre. RAY
rjm RAY

Indeed. I helped a pal with his valves a while ago as he was having similar problems, and found the same cause, albeit different valves.
Paul Hunt

Makes you wonder just what happened when the camshafts were being manufactured. RAY
rjm RAY

I noticed what Paul is talking about with the valve lash. When I adjusted with the cam follower directly opposite of the high point of the lobe, I could find an area shortly before lift started where the lash was greater.

It was a fresh Delta grind on a damaged Crane billet cam. I asked Delta about it and was told that the extra lash I was finding had to do with the lobe ramp and that I should adjust it when the cam follower was opposite the lobe high point and ignore the lash at the other location.

Charley
C R Huff

Base circle run-out shouldn't be present, but when it is you do need to work round it as above. The B is particularly sensitive to it, as the book clearance of .015" is right at the end of the opening ramp. As a result, any extra will cause the clearance to be taken up past the end of the ramp at a point where the valve train is accelerating very hard and so is bound to be noisy.
Interestingly, for the same opening ramp form in the A series, BMC specified .012" running clearance. This translates to .013" at the B series rocker ratio, so as it is comfortably on the ramp, it is the setting I prefer to use on B series.

Where base circle run-out is present, I measure where the ramp ends relative to the full lift position and work out a setting to use for the rule-of-nine method, as it makes adjustment much easier if you can easily identify where it should be done.

Have to be careful though. If the base circle run-out is due to the camshaft not being properly centred when the cam form was ground onto it, then the run-out won't be in the same position relative to every lobe so it becomes more tricky.
If the run-out is in the cam form master, it's the same for every lobe - but also the same for every camshaft taken off the master.

But the best solution is to have no run-out in the first place.
Paul Walbran

This thread was discussed between 16/04/2014 and 24/04/2014

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