Morris Minor Owners Club

I am having problems with my valves floating (or whatever that is called, they stop doing what they should) above 4500 rpm. Not the area I use most of the time, but well.

Would the solution be to replace the valve springs, either by new ones, or upgraded new ones?

Any advice greatly appriciated

Onne

Do you mean bounce? I know new (if yours are worn) or stronger valve springs do help to prevent the bounce at hight revs. Are yours old and worn?

drive slower?

You could fit double valve springs.

What makes you think you have valve bounce ? 4500rpm seems very low for valve bounce.

Are you sure your points are correctly set - too wide & they can bounce.

If the valves are indeed floating at those revs, and it's not just one or two (which could be broken springs, unlikely every spring is broken), then too tight clearances or just old and weak springs might well be the problem.

You shouldn't need uprated ones for anything up to the factory red line, which was a little over 5,500rpm, not 4,500!

I can do a visual check. Points can't be the problem, haven't got those anymore. It sounds more like a rattle at high revs

What engine is this ? Valve bounce is accompanied by dramatic power cut - it's like running on a limiter. If the springs are very old - then new standard springs must take it back to the original spec. Doubles are certainly available - but you need different valve caps and also little retainers for the bottom end of the inner springs - but these things are for folks looking at going to 7 or 8 thousand revs ! How do you know it's at 4,500 revs ?? I ask because so called 'rev-counters' (why is it not Revometer ??) are notoriously inaccurate - better to measure speed with gps - then calculate revs back through the gearing and rolling radius of the tyres.

it's an 1098, and it hesitates to go above 4500 rpm. There was a schedule in another thread, and that confirms my rev counter.
So it will do more than 4500, but reluctantly.
Can my cam be worn?

Onne, did it go past 4500rpm with the original ignition system ?
(I'm assuming the ignition has been upgraded recently)

Yes - cams do wear - but you can check the valve lift easily if you take the rocker cover off.

why is it not Revometer ??)

Because engines don't turn over in meters.

nah, it should be a revolotionerer

Scott, it was worse before I changed to electronic ignition

I can't see the point in points now! Wouldn't nae want to turn back to points!

paul.kissick wrote:

why is it not Revometer ??)

Because engines don't turn over in meters.

Hang on - the speedometer doesn't measure speed - or distance - in metres either It's also a homonym, BTW - the gauges are meters and the units of length are metres. If you're British.

Onne wrote:I can't see the point in points now! Wouldn't nae want to turn back to points!

You would if your electronic ignition had just packed up like mine has. Actually, it's the wires entering the unit. They have finally given up and are too short to be reliably repaired so it's back to points for me on the old 1380.

Onne wrote:I can't see the point in points now! Wouldn't nae want to turn back to points!

Agreed, although I carry a points distributor with me if I'm travelling in the middle of nowhere. The only cars I run with points are my original & restored cars.

Have you tried changing the ignition coil for this problem ?
If the situation has improved with the ignition system change, then I can't see it being a mechanical fault like valve bounce.

Could be air flow restriction - carb too small/throttle not opening fully ? Get someone to press accelerator pedal to the floor (engine off!) while you lift the piston and check if the butterfly is fully open. More likely - ignition timing not advancing with the centrifugal bob-weights - twist the rotor arm - does it spring back ok ? Could also be cam wrongly timed - you can check this by checking the lift on the inlet and exhaust valves on #1 cylinder when at TDC with valves rocking - they should have exactly the same lift. If one is more than the other (by any significant amount) then something wrong. Other possibility is that later longer valves have been fitted in the head but with the original shorter springs - is this possible or likely ? It's the only way I can see 'valve bounce' at such low revs.

Onne wrote:I can do a visual check. Points can't be the problem, haven't got those anymore. It sounds more like a rattle at high revs

It could just be signs of wear in your A series engine (is it a 1098??). A slightly worn A series will go on for many thousands of miles and/or years if treated gently and not thrashed and the oil and water are kept topped up.

Just drive the car normally, keep the engine serviced, and if it makes a noise above 4500 rpm, simply drive below that rpm and the engine will last a lot longer. A 1098 has more torque than power, and at lower revs so you might find keeping the revs a little lower you don't lose much in performance.

True John. But motorways are a bit hard to do now. She doesn't sound that good at 60+mph .

Roy, you do remember me about the rotor bits and bobs. The securing screw in the middle is really really stuck. Any ideas how to get it out? So there might not be a lot of oil there.

Hmm - I can only suggest penetrating oil - or just try another dizzy. But if you twist the rotor arm you should feel the bob-weights moving and then when you release the rotor arm should twist back again. You can squirt some thin oil down into the weights without un-doing the screw - but don't over-do it ! May be worth try new points and condenser - a weak condenser could mean the sparks die off at high revs because not enough charge in the capacitor.

May be worth try new points and condenser

he's not running on points and condenser anymore.
Personally I'd be inclined to recommend same as ECOSSE regarding substituting far another dizzy (preffereably with a known good one) if you don't want to follow my/chickenjohn's advice of just driving a bit slower to avoid the rough zone.