Anything and everything GT6.

Engine, cooling system, fuel system, exhaust system.

Hi

Just wondered how you'd go about changing a gt6 mk3 head to an unleaded one, and the cost and difficulty of it?

Many thanks
nic

whip off the head in the standard manner.

pop out the valves.

take the head down to an engineers and have new hardened seats put in and the valves lapped in.

personally i wouldnt bother as unless theseats or valves are burnt out, theres not much difference.

If you go for an exchange unleaded head, the job is really just the same as changing a head gasket. Take old head off, clean up block face and fit new head. Just make sure you identify which type of head you have (with domed or flat topped pistons) so you get the right replacement.
While the easiest, it is not necessarily the most cost effective way of doing the job, although you can be confident (if it comes from a reputable supplier) that you will have no nasty surprises and all necessary jobs should have been done. You also know at the outset what it will cost.
If you choose to do the job yourself, you will need to buy the correct, harder, exhaust valves. (I would expect the machine shop to source the necessary hard seat inserts).
This is the bare minimum work. However it would probably make sense to replace the valve guides (standard ones are quite good enough, you do NOT need bronze ones), POSSIBLY replace the inlet valves if they've done a high mileage, and replace all the valve springs, unless they are known to be low mileage. While not strictly necessary, if one breaks you will probably wreck your engine with a dropped valve!
Apart from fitting the new guides and seat inserts, you can do all the other work yourself. (Theoretically you can pull new guides into the head with a long stud, but I'd leave that job to the machine shop).
BUT, unless the head is already in need of reconditioning, or suffering valve seat recession, I'd leave well alone until seat recession DOES start to occur, and then fit a lead free head.

Only EXHAUST valve seats.
No need for steel inlets.
And not a good idea - two inserts will meet each other in the middle.
John

If the head doesn't need to come off i.e. for a decoke or some other reason and it runs OK then I wouldn't bother, I'd leave well alone but keep an eye on the valve clearances. Some drivers don't even bother with lead replacement additives.

It's not a difficult job to do but the head could be a pain to get off and once its off you'll be very tempted to play about with it. I had terrible 'running on' and that's why I had mine done (also flowed the ports and that was fun...not that I could notice afterward!) but it was expensive, something like Â£400 for inserts, all valves re-cut and a skim. The company said the exhaust valves didn't need replacing, so they weren't, but they did fit the inlet seats as well, which may have been superfluous (and yes, John, it is tight!). I found one inlet valve that was cracked so I replaced that, also the springs...oh yes while cleaning up the rocker gear I scored the rocker shaft so that needed replacing (not too expensive from Canleys). I've done about 7000 miles since then and all's well.

Just had a look at your car...I think I'd spend the money on something else!

Meeeooowwwww!!

You lurk in the background for ages and then you come out with a comment like that Don, It must be quiet at work this week.

You got that fence finished yet???

Cheers

Colin.

[quote=Don Cook]Just had a look at your car...I think I'd spend the money on something else![/quote]

What, like a cover to stop that cat walking muddy paw prints up the bonnet? ^_^

If it ain't broke, don't fix it.

I have several engines running on unleaded and use Castrol Valvemaster Plus additive. No problems.

They are:

GT6 Mk1 - Standard timing with the octane boosting additive
MGB 1800 B series - The old LRP fuel was not as good as unleaded with the additive
Triumph 500cc T100T (that's a motorcycle) 10:1 compression. - Knocks like hell without the additive, OK with it. Really required 5* fuel when it was built.
Matchless G5 350cc. Runs on any old guff!

I also used to have a Metro with an A series engine which was very prone to valve recession but I had no problems.

Did you just put unleaded petrol in with the additive added?

Nick

The Castrol additive I use comes in handy little bottles with a built in measuring gizmo that gives the right amount of additive in 5 litre steps.

Whether you put the additive into the tank first or after the petrol is a bit like the argument with tea and milk. Personally, as long as the tank isnt empty, I put the additive in first then the petrol to stir it up. I use standard unleaded 95 with additive. Runs great.

A few years ago, Practical Classics mag together with the Federation of British Historic Vehicle Clubs (FBHVC) ran some benchmark tests on various additives to find out how well they worked. They used stock A series engines, known for valve recession, with new heads to avoid "lead memory" effects and compared the results for fuel plus additive against unleaded only.

If I remember correctly, It must be said that the additive manufacturers were asked to pay towards the tests so not all products were tested and the manufacturers needed to agree that the results were published so it is not a complete list. Nonetheless, a good range of products were tested and the FBHVC approved list is here http://www.fbhvc.co.uk/fuel/additives.htm

Paul

Thats great, thanks.

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