Morris Minor Owners Club

will all the mods to the sr's trav it is likley it would be a 1300? manifold looks like a later 1 3/4 4bolt one?

Am I confused or summink?
Which engine is shown? - is it the one in the saloon or the traveller (I didn't figure you were working on the traveller)?
The manifold looks chunky but based on the thermostat bolt alignment, it is a small block head (I think)... Erm darn!! I think I've forgotten how to tell the difference without seeing one next to the other.

The manifold is for a HIF carb, also the head is for a large block unit (1275), so it might well be a 1275.............

based on the thermostat bolt alignment, it is a small block head (I think)

definatly a large block head, just checked it against my spare head

Well done steve you may have a 1300!

The manifold looks chunky but based on the thermostat bolt alignment, it is a small block head (I think)... Erm darn!! I think I've forgotten how to tell the difference without seeing one next to the other.

I had to look at a head to remem,ber which is which and yes - like everyone else already said, it is a big block head (most likely a 12G940) and with those billet rockers it could well have been off something fairly late like a Mini 1275GT (Cam will probably know the mini stuff far better than me).
Anyway - the head doesn't mean it is a 1275 as I have run those on my 1098's in the past, but the head is worth hanging on to as it makes a nice improvement - even more so with the bigger manifold / carb etc..

turbo is thinking like me with all the mods on the car, peetee mentioned something about a number on inside of head ,is there one i can check for?ray ,not working on trav,but hoping engine/head is good enough to go in saloon,theres not much else good about it,steve,CLEARER PIC ON WEBLINK

I'm lost now - but if it's a 1275 head then you really should pocket the block on a small bore engine before fitting this head.

BMC, im thinking u may be right about old c.tester ,so got new gunson one , on weekend will try to fire up trav engine [BIGHEAD] test it and report back, hopefully its ok, what does [pocketthe block] mean mate?,steve

I'm lost now - but if it's a 1275 head then you really should pocket the block on a small bore engine before fitting this head.

not always

rayofleamington wrote:with those billet rockers it could well have been off something fairly late like a Mini 1275GT (Cam will probably know the mini stuff far better than me).

Those are just A+ solid rockers. They were used on Itals, Metros, Minis, Maestros, etc. From 998cc to 1275cc

what does [pocketthe block] mean mate?,

The 12G940 valves ovlerlap the edges of the bore on a 1098. Therefore if the valve lifts higher than the space available it will hit the block.
With a standard Cam and rockers, you just need to check that the distance between the valve and the block is bigger than the lift. If it isn't then you can cut the valve and seats a bit to make the valve sit further from the block, or have some pockets machined into the block.
Pockets in the block is the superior way to do this as it allows a little better gas flow but unless the engine is race tuned you are unlikely to notice a difference. Seating the valve a bit deeper is the easier way to acheive this, and if the head is well used and already has a few valve grinds done thenyou may not need to do anything.

right lads ,an update,numbers in side head are, 12G940 55, and also 03D ,cheers boys

Yes indeed - you MAY get away with without pockets but it's a bit dangerous !! They can be done with leccy drill and mounted points - just seal up the engine to keep all the crap out !!

well hopefully the engine will run nice,and i can leave the head where it is

well hopefully the engine will run nice,and i can leave the head where it is

If the engine runs well, then I'll buy you a pint!! Getting anything useful from the car deserves a round of applause... ;-)

I checked a spare 12g940 head this afternoon. The ex valves are 6.6mm down from the head face = 266 thou. Allow 20 thou for a head gasket = 286 thou. Now the cam lift (1098 engine AEA 630 cam) is 250 thou and the rocker ratio is 1.25 - so the valve lift will be 310 thou - less the valve clearance of say 12 thou = 298 thou. So without pockets - or cutting the seats and bedding the valves down into the head - IT WILL NOT GO ! It's only short by 22 thou - but it is short. The older 948 engine had a little less cam lift - so on a 948 you may well get away with it - but it must be a bl**dy close thing !
Edit - It seems in some circs the rocker ratio could be slightly more - giving a toatl lift of 318 thou - less 12 thou clearance = 306 thou. So it could be short of space by 30 thou !! hence the need for 'pockets'. This si not a bodge by the way - BMC did it with the MGB engine ! The 948 engine has a camshaft with only 220 thou lift (actually early ones may only be 200 thou !!) and so they will be ok with the big valve head - UNLESS some bright spark has fitted a 1098 camshaft (good move actually) in the past - so it needs checking !!

IT WILL NOT GO !

It is however commonly used and I've done ~25,000 miles with 1098 engine and 12G940 head and no pockets. I only stopped using that head because I'd picked up an unleaded one.
Andrew (Winger300) fitted his 12G940 last year without pockets but had the valves/seats cut to make sure there was enough clearance.
I wouldn't take the tappet clearance into account as this allows for temperature changes and also for a few thou of oil film on the cam.

Gents. I have the same problem. 1098 cc with great psi on 1,3 and 4 (150 to 160 psi) but piston 2 is down to 70 psi, with minimal increase when oil added. All valves set to 12tho. I note the tip about 15tho on the exhaust side, but that wouldn't make piston 2 stand out like this. Could it still be a valve and not the rings? I can't make my mind up what to do next. Any advice? Steve

Steve, what an odd name you use... I sure hope there won't be any Germans offended.
Back on topic again..

If there was no increase with oil added - then it's almost certainly a valve burned out. Off with it's head!

Having replaced the head I have achieved almost 150psi on all four cylinders, great!

Now on to the next problem.

Thanks