Morris Minor Owners Club

Evening all ,
This probably been covered and I have tried to search it
But my basic question is...
My 1098 engine which I'm doing quick refresh too
Has the standard leaded head
Looking at prices I'm going to have to spread about £180
On an unleaded exchange head...
Can I not just fit a late 1000cc mini head
Or will I run into problems
Budget is very tight I'm not trying to cut corners

Thanks Chris

Quick answer is yes - but you will lose some performance because the inlet valves are smaller. The simple answer is - NO NEED to worry about 'unleaded' - just use the head you have - set the exhaust valve gaps at 15 thou (inlets at 12 or 15 as you wish) - and check/reset the gaps every 3000 miles. It will be fine! And - don't waste money on any silly 'additives'.....

bmcecosse wrote:Quick answer is yes - but you will lose some performance because the inlet valves are smaller. The simple answer is - NO NEED to worry about 'unleaded' - just use the head you have - set the exhaust valve gaps at 15 thou (inlets at 12 or 15 as you wish) - and check/reset the gaps every 3000 miles. It will be fine! And - don't waste money on any silly 'additives'.....

thank you for the reply... you seem to be one of very few on this site that will take the time to reply to posts

Glad to help - but I am far from alone in answering posts - it's just that I am sad enough to be on my laptop at all hours of day and night.....

Not sad at all but an asset any club would love to have

As said, a mini head will fit and work nicely with a drop in performance (the later small bore minis used the CAM4810 casting). A lot of people run standard heads on unleaded without issue, the lead memory and the hardening of the seats from the impacts with the valves will take a while to wear off! But, there have also been cases of valve seats being eroded and if you want to use an additive the FHBVC did testing of the various types with an A Series engine! Valvemaster came out on top.

If you are planning to spend time on dual carriageway or motorways I would be looking at an unleaded head or additive. If not I would be happy just to keep an eye on the situation (especially if money is tight!)

I used the additive ,cheap to buy stops the nagging worry etc .Pays your money take your choice

The only additive that will do any good is 'Tetraboost' - and it's not inexpensive - that's because it is the ONLY one to have tetra-ethyl lead in the mix - so it effectively turns unleaded petrol into leaded petrol! The others are various sodium and potassium compounds - and of doubtful use, although most boost the octane number slightly - to save any pinking. The 'tests' have been heavy criticised and were not representative of what happens on the road. Using a 15 thou exhaust gap (as specified by MG/Rover when unleaded fuel came along) and checking it every 3000 miles will keep you motoring for many, many thousands of miles.

The other option, of course, is to fit a 1275cc 12G940 head, and you can get them in unleaded form fitted as standard to late Metros and Minis.

When my Midget engine's original head valve guides wore out, I fitted a Metro unleaded head, which had the benefit of bigger valves, and it's run well ever since.

Only the 'leaded' 940 heads on the early MG Metro and the Cooper S have the larger 35 mm inlet valve, all others (ie early leaded and later unleaded) heads have 33 mm inlets - and all have 29mm exhausts - unless modified of course.