Converting to unleaded petrol

[Pursyluv]

A friend of mine is rebuilding a '71 Spitfire and has asked how this can be done. I've done a quick search and can't seem to find any previous threads on the subject, therefore I'd be grateful for any pointers my fellow PHers can give.

[Richard Moss]

If you get hold of the current issue of "Classics Monthly" (it's the July issue) there's an article in there about an unleaded conversion on an MGB engine. The process is identical for a Spitfire and there should be some pointers on who to send it to.

It's basically: cylinder head off, strip head down, have hardened inserts fitted to the valve seats, new (hardened) exhaust valves, reassemble, refit head (new gasket) and retard the timing a couple of degrees.

[Pursyluv]

Thanks Richard

[//j17]

Unless he's getting head work done already then do the following - nothing.

Triumph engines didn't have especially soft valve seats out of the factory, so don't tend to suffer from seat regression as much as some others. Add to that 30 years worth of lead coating the seat and there's a very strong chance he won't get any seat regression for years.

You'll know when the seats start to wear as you'll need to adjust the rockers more often and the only damage you can do is to eat in to the material of the head...the exact same material the machine shop will be drilling out in order to make space for the hardened valve seat to make it unleaded.

[spitfire-ian]

//j17 said:

Unless he's getting head work done already then do the following - nothing.

Triumph engines didn't have especially soft valve seats out of the factory, so don't tend to suffer from seat regression as much as some others. Add to that 30 years worth of lead coating the seat and there's a very strong chance he won't get any seat regression for years.

You'll know when the seats start to wear as you'll need to adjust the rockers more often and the only damage you can do is to eat in to the material of the head...the exact same material the machine shop will be drilling out in order to make space for the hardened valve seat to make it unleaded.

Or just chuck in a lead additive when you fill up

[Richard Moss]

spitfire-ian said:

Or just chuck in a lead additive when you fill up

Which is what I do on my MGC.

[caziques]

//j17 said:

Unless he's getting head work done already then do the following - nothing.

Triumph engines didn't have especially soft valve seats out of the factory, so don't tend to suffer from seat regression as much as some others. Add to that 30 years worth of lead coating the seat and there's a very strong chance he won't get any seat regression for years.

You'll know when the seats start to wear as you'll need to adjust the rockers more often and the only damage you can do is to eat in to the material of the head...the exact same material the machine shop will be drilling out in order to make space for the hardened valve seat to make it unleaded.

Could have written this myself!

Although Triumph fitted inserts to exhaust and inlet for late US cars - only exhaust inserts are actually needed if working on a head. Exhaust valves from 1967 are usually OK on unleaded - earlier engines tend to suffer.

[mgmrw2003]

Richard Moss said:

spitfire-ian said:

Or just chuck in a lead additive when you fill up

Which is what I do on my MGC.

And what as of Saturday, I shall be doing on our Austin 1300

[300bhp/ton]

//j17 said:

Unless he's getting head work done already then do the following - nothing.

Triumph engines didn't have especially soft valve seats out of the factory, so don't tend to suffer from seat regression as much as some others. Add to that 30 years worth of lead coating the seat and there's a very strong chance he won't get any seat regression for years.

You'll know when the seats start to wear as you'll need to adjust the rockers more often and the only damage you can do is to eat in to the material of the head...the exact same material the machine shop will be drilling out in order to make space for the hardened valve seat to make it unleaded.

+1 unless they'll be doing big miles in a short time period I'd just wait until it needs doing. Lets face, most classic could take 5 - 10 years+ to show any issues if they are only an occasional use weekend toy.

[Steffan]

I entirely agree with various comments that generally this is an unusual problem with classics, particularly the Triupmh engined variety.

I have driven over 13.000 miles in my MG Midget (1500 engine) without any sign of trouble with the valves.

If you are driving hard or seeking more power maybe: otherwise given the mileage and the type of motoring (gentle) most classics enjoy I think this is an unlikely problem.

If yo do get it then upgrade as others have suggested.

But as the Yanks said 'If it ain't broke don't fix it'.

[cpas]

300bhp/ton said:

//j17 said:

Unless he's getting head work done already then do the following - nothing.

Triumph engines didn't have especially soft valve seats out of the factory, so don't tend to suffer from seat regression as much as some others. Add to that 30 years worth of lead coating the seat and there's a very strong chance he won't get any seat regression for years.

You'll know when the seats start to wear as you'll need to adjust the rockers more often and the only damage you can do is to eat in to the material of the head...the exact same material the machine shop will be drilling out in order to make space for the hardened valve seat to make it unleaded.

+1 unless they'll be doing big miles in a short time period I'd just wait until it needs doing. Lets face, most classic could take 5 - 10 years+ to show any issues if they are only an occasional use weekend toy.

+1 more. Just fill with unleaded and retard the ignition if the engine pinks, or use some octane booster or super plus unleaded.

[ccgoose]

i've just had my dad's herald engine converted to unleaded and to be fair, it's made no difference. Other than having the head gasket done and a general good service, not really sure there was much point, but because my dad is no longer around to tell me about the history of the engine, it seemed like a safer option to do and only cost £250.

[cpas]

ccgoose said:

i've just had my dad's herald engine converted to unleaded and to be fair, it's made no difference. Other than having the head gasket done and a general good service, not really sure there was much point, but because my dad is no longer around to tell me about the history of the engine, it seemed like a safer option to do and only cost £250.

As has been said before, the only thing they do is bore out the valve sets and put hardened ones in (which could possibly fall out anyway if you're a pessimist!!) and replace the 8 valves. As these are the only areas that could possibly be damaged by running unleaded, it seems pointless replacing them anyway. There will be absolutely no difference in the way the car drives.

[vitessesteve]

I agree just run it on unleaded. Fix it later if you need to do any other work on the engine.

You may be interested to see what Canley Classics a well known trader has to say on the subject: http://www.canleyclassics.com/?xhtml=xhtml/infodat... - run it on lead free.