11 replies to this topic

[analogue_radio]

Clarifying something on behalf of my Dads friend, to convert from Leaded to Unleaded you only need to change the head, anything else involved?

[wile e coyote]

No thats all it needs - timing may have to be altered a couple of degrees though.. if its a 998 I just happen to have a pristine UL head surplus to requirements....

[998dave]

all gaskets, reset tappets & timing, and depending on source of the head poss. drill/replace thermostat and bypass hose.

Dave

[Dan]

Is your dad's friend asking about a Mini? Unleaded fuel is more corrosive than leaded and in some older cars there are many parts of the fuel system made using materials that will not survive for long using unleaded fuel. There are very few Minis that this will affect (luckily the Mini was always sold in Japan where lead was never used in the fuel so BMH/BL/Rover always used unleaded compatible fuel system parts in Minis) but other makes can be affected quite badly. Anything using Lucas Petrol Injection for example must have the metering unit and pump reconditioned using new seals and many cars need a new fuel pump or hoses.

[TheBIGGERimage]

No thats all it needs - timing may have to be altered a couple of degrees though.. if its a 998 I just happen to have a pristine UL head surplus to requirements....

How much for your pristine head? (That is the mini head not yours!)
(the IMAGE's dad)

[wile e coyote]

will send you a PM later...

[wile e coyote]

You have mail -
a couple of snaps (apologies for poor quality) can be found here:

http://www.esnips.com/web/998ULhead

[philc]

I run mine on unleaded have done for ages, never had a problem. You could have your own head converted, I am not sure on the process, but i am sure someone on here would be able to advise you

[TheBIGGERimage]

You have mail -
a couple of snaps (apologies for poor quality) can be found here:

http://www.esnips.com/web/998ULhead

Many thanks wile e coyote - could be of interest, need to expore further before making decision, so please bear with me.

[T.Harper]

I run mine on unleaded have done for ages, never had a problem. You could have your own head converted, I am not sure on the process, but i am sure someone on here would be able to advise you

An unleaded head has the exhaust valve seat machined out, then a hardened seat (looking a bit like a ring) is fitted (normally interference fit from heating head and cooling the inserts) the advantage is that you will have nice new seats to seal, and that the seats won't recess into the head so quickly - the valves normally pit themselves instead!

[TheBIGGERimage]

I run mine on unleaded have done for ages, never had a problem. You could have your own head converted, I am not sure on the process, but i am sure someone on here would be able to advise you

An unleaded head has the exhaust valve seat machined out, then a hardened seat (looking a bit like a ring) is fitted (normally interference fit from heating head and cooling the inserts) the advantage is that you will have nice new seats to seal, and that the seats won't recess into the head so quickly - the valves normally pit themselves instead!

Thanks T.Harper - anything more than that? What sort of cost?
Cheers.

[T.Harper]

That's the procedure, but it's a bit more involved than that as you may have guessed - best left to a machine shop. The inserts themselves are relatively cheap and can be found on minispares, but I think the procedure will cost you around £100 to have done to the head.

I have seen the seat machined out with a cutting bit on a pillar drill, using the existing guide as a pilot hole. This has to be measured and cut exactly to make it slightly smaller than the seat 'ring' that is fitted in its place. The actual fitting of the insert is something I haven't seen but as I mentioned it can involve extreme cooling of the insert in a freezer or liquid gas and heating of the casting so the insert drops in easily.


There are many 998 unleaded heads around so it's probably best to try to find a low mileage one as this will most likely have the good condition seats - you can pick one up for about £30. I would then definitely recommend stripping the head down and having the valve seats recut to remove pitting, then you can lap the valves in yourself with one of the £4.99 kits from halfords to produce a good seal. MlMotorsport has these standard heads on the shelf ready for exchange. I think they go for about £150, with unleaded seats cut, oil seals replaced - ready to drive. Check their website www.mlmotorsport.com