Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Lightened Flywheel

Phil, sorry to read that plug has failed, I`m guessing perforated as the result of corrosion as opposed to pushed out by frost. If corrosion I suspect all are best replaced at the same time, which is hopefully some consolation for if it had been one of the others, you would be left wondering if/when the one behind the flywheel might fail...

John.... David Vizard, that is a name from the past, I bought his book in the early 70`s Tuning for Speed, having seen it advertised in Car and Car Conversions magazine at the time..I had just roughly re-built what was to be my first car, a 59 MK1 Austin Healy (frogeye) Sprite, over carbd over cam`d and a steep learning curve having got it wrong in terms of balanced modification...Duh..!

I think it's been gradually failing for some time - ever since I've had her (14 months) I've had an undetectable water leak - using 1/4 of a litre every couple of hundred miles or so. I imagine it's been dripping out the bottom and scattering as I've been driving.so not leaving any visible mark.

At least the mystery is now solved!

TBM,
Your problem has reminded me of when I cleaned out my Lotus block (pre cross flow Ford block) in 1979. The crud in the water ways was half way up the core plugs. So while you've got the core plugs out you need to give the water ways a good flush out.

Luddite, Yes it is a name from the past but some of the info is still usefull. I also have his books on the Twin cam and the pre crossflow engines.
"over carbd over cam`d and a steep learning curve" yes but thats what you did when you were young!!!! I did the same thing when I was karting. Two strokes with power curves like a needle.
Cheers
John

I had a friend that had a race bike like that. One fine day he started a race at Surfers Paradise (a circuit around an unused airfield) on one cylinder hoping that the thing would get going on two as he was under way. It fired on both cylinders at the start of the straight while he had the throttle wide open. The damn thing nearly rocketed out from under him and he did most of the main straight on the back wheel, totally out of control and hanging on for dear life. The crowd were most amused and the race leader who was in the process of lapping him was left wondering what the hell he was up to.

On the way back to Sydney I learned the importance of making sure the trailer had weight at the front; but that is another story

I wouldn't do it on a road car. Yes it's snappy, but it's more difficult to drive. You can no longer use flywheel inertia to start moving.

Years ago I had mine lightened at the same time that I had the engine bored out to 1700cc, replaced the cam with a fast road item, put twin Weber 40s on it and a big valve head. Consequently it would be difficult to say what difference the lightened flywheel made in isolation but it's very drivable and I've never thought of going back to the heavier item.

I think Dave Vizards figures relate to the early crossflow engines.

The flywheels on a 711M block crossflow are 14lb

Arwyn

Good point, the book was published in 1970.
Cheers
John

Fascinating, I've just been reading my Vizard book again.

On page 57 he reminds us that it's not the weight that matters as much as the Rotational Inertia so it's not just how much lighter it is but where the material is removed from.

He also reminds us that one of the downsides of a significantly reduced flywheel inertia is the tickover. Not important on a competition car but I think a road going Morgan should retain some level of refinement in this respect.

On a road car I always think that a smooth tickover is a measure of a well tuned engine.

John07's comment about his 2 stroke kart engines having power curves like needles reminds me of my 100cc International kart engines. Fixed gear, no clutch, no gearbox and it would pull out of a tight hairpin and still rev up to about 12,000 rpm (no rev counter) I.e a very wide torque band but still with good top end. Horses for Courses.

We tuned all our own engines and Cesare Bossaglia was our Tuning Guru with his book, Two Stroke High Performance Engine Design & Tuning.

BTW, Vizard's book was written in 1970 and the 711 engine was released in 1970 it think so he could have been writing about the later engine but more likely the earlier engine as Arwyn suggests..

From a dull memory... with my large carbs and polydine cam in my A series Frogeye, the issue was that it climed up on the cam at circa 4k rpm to the rev limit at 6k, and not having the benefit of a close ratio gearbox, in changing up to the next gear, you dropped right out of the rev band and back into a very dead zone, which was very embarrising when the old dear in the Hillman Imp would leave you for dead in the traffic light GP..!!!

The thing about tuning would seem to be that out of the box vehicles have a broad power band to cover all types of driving, the same goes for suspension steering brakes and all that makes up a standard machine, be that a delivery van or a sports car, as soon as you change one thing in the package it can have a knock-on effect on other aspects of all important balance of the machine`s initial design strategy, and imbalance tends to be less than ideal..as in the case of my Frogeye.... but I did see 100mph on the clock...once...honest..(-:

The thing about tuning it can totally spoil a machines overall usability, and I suspect there is many a Morgan out there running poorly as the result of "tuning" sold on and it`s new owner trying to get it to run reasonably with by the book ignition timing spark plug choices that may not suit the high compression pistons fitted some time in it`s past or the race cam etc.etc.etc.

A well tuned engine for road performance will hopefully retain a degree well of balance and still be reasonably comfortable in heavy traffic and as such may still idle reasonably given the care and expence of fitting the upgrades, were the same engine taken to full race spec it drivability and fuel consumption would alter, and if it is highly tuned perhaps the race clutch might be a real pain to live with in traffic the engine also overheating in the same situation,,,etc. etc. etc. Having been there and done that more than once (sigh), is one of the reasons my +8 engine is standard, and has served me well having never overheated even while touring in a very hot southern Europe.... touching wood..!!!

Peter your tale of your friend on the two stroke race bike caused me to laugh and brought back memories of a full race two smoke Kawasaki 750 triple that would fire on this and that or the other cylinder as and when it chose, and all H*ll would brake loose when it fired on all three without any warning, the rider was a very nervous guy who regularly dissappeared off track and into the weeds as the result of it`s foibles. It is one thing to have the two stroke riders nervous clutch pinky, but when that thing fired up fully everybody got outa the way... (-: