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MG Midget and Sprite Technical - Leaded Cylinder Head

Hi,

My '67 1275 has not had the head converted to run on unleaded fuel.
What are the benefits and disadvantages of a) doing the conversion (cost?), and b) using a lead additive (brands?)?

I couldn't find any threads that answered this directly, so here's the new one!

Thanks!
Josh 'Midget Mad' Spooner

Josh, personally I just use Castrol Valvemaster additive which adds about 3p per litre to the fuel cost - hardly a huge percentage increase given UK fuel prices! If I were rebuilding the engine anyway then I'd get hardened valve seats fitted at the same time. So it's probably down to the mileage you do & the depth of your pocket. Then there's also the proposed increase in ethanol content which might cause other problems, or so I've read....
mgpete

If you chose to do nothing (simply use unleaded 95 octane fuel) then perhaps in a good few years time you MIGHT have to "put new valve seats into you cylinder head".
If you want to convert now you will have to "put new valve seats into you cylinder head".

So it makes sense not too worry too much.

The cost out to be about 50 to 100 quid to modify the head with new seats. Removing the cylinder head is simple although if you can not do it your self ought to be another 50 to 100 quid!
Robert (Bob) Midget Turbo

Hi Bob

I think your prices are a little low, think about dissassembly, machining, cleaning reassembly times and what about some new valves, springs and guides? As for removing and refitting....takes a fair time even if all the carbs and bits have been removed recently, usually a bit of a nightmare when all has been together for years.

Peter
P Burgess

Maybe. :)
Robert (Bob) Midget Turbo

I agree Bob's logic. The A series engines run fine in standard form with modern standard 95 octane fuel. Don't worry about getting the head "unleaded" or using additives. I didn't, and ran my engine for another 35,000 miles, and that was with a raised compression too. At worst, I might have needed to redo valves, guides and seats but you can do a lot of miles before that is necessary. I eventually got round to swapping the head completely, and that was for a big-valve MG Metro head anyway, and not because of any problems.

But do check that the ignition timing is correct - not necessarily to retard it a bit, but just as you would with any engine.
Guy

I too think that there is no real point in converting a cylinder head as you are not really gaining anything when it goes then get it converted or just use additive and all will be well. I like your estimation Bob maybe a tad on the low side would probably say you are looking at more like £200 + for the cylinder head to be converted and around £150 + for fitting.
C Carter

I had 4 new valves supplied, 4 valve seats inserts and cut and 8 valve guides plus a surface skim all done for £100 last summer. I removed and stripped the head first, and rebuilt it with new springs so that wasn't included.
Guy

Cheaper than I thought to be honest I suppose if you hadnt stripped the head yourself it would be round the £200 mark.
C Carter

Hi Guy

For our £200 plus vat we strip the head, check it for cracks and untoward damage. Caustic tank or acid dip the head, hot slightly caustic wash, grit blast all over including waterways and ports. Remove old guides fit new bronze guides, fit inserts, cut three angle valve seats, fettle any sharp edges in the chambers and ports where the seats have been cut. Replace the head face plugs if required. Skim the head, deburr all the holes, chamfer the combustion chambers, helicoil any poorly threads. Hot wash again. Lap all the new valves in. Assemble head with new valves and double valve springs (heavy duty) then paint the head with Moss engine paint, either black or the Morris green. We then warrant the head and sort out any problems if they should occur, my goodwill goes a long way....see the MGB Tech thread on 10.5:1 CR....we sold David vlaves, inserts and guides which he had fitted. He had a problem with seized guides. When he rang to order more guides I asked if he could send me the old ones so I could check the problem. He brought the whole head in. We ascertained the guides were tight from insufficient reaming. The guides had also been hot due to the ex valves nipping now and again. We also noticed a crack inlet to exhaust seat, this can allow the insert to ease out when hot. We put a little 99% nickel weld to pin the seat in. We reamed the guides, recut all the seats, deburred the chambers, seats and valve throats and reconditioned then lapped David's valves in....NO CHARGE as I like my stuff to run right even when someone else mucks up the job....that is what you pay for when I do work for you. For a £100 more than you paid for a complete leadfree head I reckon this is quite good value.
Occasionally we are arm twisted to do what I call a 'minimum' job, supply and fit guides and inserts, cut seats and skim head. We would take £70 for a 1275 and if we supplied 4 ex valves an extra £14.

Peter
P Burgess

For £200 it is goof value!
To bad postage on a head is so high ;)
Onno Könemann

Hi Onno

£30 plus vat to send to EEC country....with the £ being crap against the Euro you are laughing all the way :)

Peter
P Burgess

LOL Peter!
I wasn't saying that I thought the figure you had quoted in your earlier post was expensive! I was saying that I had got what I thought was a particularly low-cost deal locally, although that required me to do all of the stripping down and re-assembly myself.

For all that you do for the price, it would be a very good option. And I will bear you in mind for next time!
Guy

For that price....it would well be worth seeing if peter has any spare heads or at least pick one up on evil bay and having them worked over and sticking it in the back of the coat closet for that rainy day when yoou need a rebuilt head
Prop

Funny you should say that Prop...we had an mga twin cam on the rollers today, it must have been at least 12 years ago we prepped the head, taken all that time to get round to finishing it, sounded good and went well on a pair of Dellortos :)

Peter
P Burgess

There is another option I’d been looking into and that is Tetraboost. Which is NOT an additive (according to their site) but the stuff to actually make proper 4* fuel or higher if you mix in more.
http://tetraboost.com

Only slight downside is you have to buy a whole case at a time, I would be prepared to go halves or something with people if there was enough interest??

Thoughts??

But I'd agree with most folk and probably not bother paying to convert the head unless you’re either doing massive mileage or doing engine work anyway.
M Slater

Why do you believe it is not an additive?

You ADD it to the fuel that must be an additive? and an expensive one too.

Don't you think?
Robert (Bob) Midget Turbo

I think Bob has logic on his side here :)

The tetraboost is most effective but note the poison label and instructions which more or less say get some poor unsuspecting soul to add it to the petrol on your behalf :)

Peter
P Burgess

Well thanks to everyone for helping me out on this! I think I'll keep her going on additives for a while, until I have the funds to have her machined and put my mind at rest! Thank you, too, Peter, for making me aware of what sounds like a stunning deal!!! Can I take your phone number/postcode/e-mail so that when I decide to bite the bullet in a years time or so I'll know who to come to?!

Thanks again everyone!

Josh
Josh 'Midget Mad' Spooner

Josh, use the dropdown menu in the black header bar on this page, choose Advertisers, Pete B is listed in there. Or just put Peter Burgess into a google search box, he comes up top of the list.
David Smith

This thread was discussed between 16/04/2011 and 19/04/2011

MG Midget and Sprite Technical index

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