unleaded conversion

[Bill4342]

Hi,
Question. If cyl head has been converted to run on unleaded, do tappet clearances need to be increased? Engine run slightly hotter?
Regards,
Bill. 54 ser 11

[bmcecosse]

Don't waste money on 'unleaded' conversion - it's absolutely NOT necessary unless you are thrashing up and down a Mway regularly even then - one of the biggest con-tricks out there. And no silly additives either... Set teh exhaust valve gaps to 15 thou Inlets can stay at 12 if you wish, and check/adjust every 3000 miles. That's all you need to do.

[amgrave]

If you have already got an unleaded head then inlets 12 thou and ex 15 thou. The exhaust gasses are hotter than leaded fuel so the valve gets hotter and expands that tiny bit more (that’s the theory anyway).

[Bill4342]

Thanks for replies, head converted prior to my purchase last year. Had rocker cover off to repaint and found clearances well above stated. Original hand book states 12 thou for all so i reset them. After all back and running when i had this thought re hotter running.
Regards,

Bill

[bmcecosse]

With unleaded fuel you need 15 thou on the exhausts or you risk burning the seats. MG Rover made that change way backin the 1980s.

[Bill4342]

Thanks for that. Will increase exhaust clearances to 15 thou.
Cheers,

Bill

[n0mad576855]

Hi, This may be a little unusual, but in my boat, Elysian 27, the year is not quite clear,
aprox 1975 onwards
The engine is a Morris 1100 unleaded, fitted with electronic ign, when purchased aprox 6 years ago the cylinder head was being removed to replace burned out valves, she has run fine since this,
apart from the old mechanical fuel pump valves becoming sticky if not used for 6 months or more,
The cyl head has no by pass hose fitted, I am also thinking about fitting an electronic fuel pump, because the AA or RAC do not do a breakdown service for the Norfolk Broads, lol
Now should I leave the engine as it is, or fit an unleaded head, if I can find one without a by pass hose, but I will certainly open up the valves, to the recommendation, you have supplied,
By the way I have just joined
Thank you

[simmitc]

the AA or RAC do not do a breakdown service for the Norfolk Broads

No, but if you don't feel confident in your own abilities then you could investigate an organisation called "Canal and River Resuce" about whom I have read many good reports.

[panky]

You could use a head with a by-pass fitted and blank it off with one of these

http://www.ebay.co.uk/itm/Auto-Silicone ... hash=item0

[bmcecosse]

You certainly DO NOT need an unleaded head and I would avoid the electronic pump too. Just set the gaps to 15 thou -all will be well.