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MG Midget and Sprite Technical - What to do with an old engine

Hi All,
Getting close to finishing the rebuild of the body of my midget..
When I got the car it had no engine.
So bought a 1275 from a Morris Marina..
Now got to the stage of looking over the engine and rebuilding for installation.
Have taken the head off and all looks OK. one of th valves has some light corrosion (probably from standing.
Plan to remove the valve springs and check the valves over, check the guides for wear and then lap the valves.
Then I'll check over the bottom end, the bores look OK, but I guess I need a bore gauge to check whether I need a rebore.
I was then going to check the big end and main bearing clearances with some plastigauge. If it looks OK will replace the bearings, if not regrind.
What make of bearings should I go for?
Then was going to replace the timing chain + tensioner.
Should I replace the oil pump?
Am also thinking about replacing the cam with something more fruity. Needs to be tractable 'round town. Any suggestions. If I change the cam I'll change the tappets of course.
I have a midget back and front plate and flywheel. I know the flywheel probably wont fit the crank, do I alter the crank or the flywheel to fit.
What else should I do?
O yes the car is '70 midget with a new fibreglass speedwell monza front end..
Thanks for any help.
Cheers
tim
T Dafforn

Engine rebuild...
Easiest way to get good parts is order them from Peter May or Burgess.
They will be able to deliver something to suit your needs.

List of things you should change
Oilpump
Bearings
Timing chain
Piston rings

If you change the cam you change the followers

The headwork depends on the state of it.
But as you are uprating the cam the a nice PB head might be a good idea.

No idea about the flywheel never touched a marina block
Onno K

Can't comment on most of the above, but there is no tensioner fitted when fitting a Marina or Ital engine in a spridget, different timing chain cover. I believe that you have to have the flywheel redrilled, not the crank, if I'm wrong, I'm sure someone will correct me!
You could change the oil pump for a high capacity version but make sure it fits under the engine rear plate and a good general purpose cam is probably a 276. To get the best performance without spending a vast amount on new carb/carbs stick with the HIF 44 from the Marina it is supposed to giver better tractability and top end compared to twin carbs, fit it with a decent air filter with an internal stub stack.
The Marina head is supposedly quite well developed, but A series engines do like being properly ported, so get a copy of "Tuning the A Series Engine" by David Vizard and you will learn more than you ever wanted to know about breathing on the engine :+)You will also need a decent three branch exhaust, but don't expect miracles, to make it a real flyer you have to spend serious money. The above would probably gain you 10-15 BHP after a session on a rolling road getting the needle correct and playing with your dizzie advance curve.
Graham.
Graham P

this is what to do with an old engine!


http://www.ebay.co.uk/itm/150707236640?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Mick - still wiring!!

As far as crank and flywheel are concerned, if the engine is apart, I would be inclined to have the crank machined to take a Midget flywheel.
Dave O'Neill2

Hi all
Got vizard, fab book
Timing chain cover... Is it the cover, or the breather?
Have got an HS6 and manifold and the Car came with a 3 branch exhaust.
Re: engine as a coffee table just sold my Elan with spare engine which would have made a great coffee table!!!!
Tim
T Dafforn

T, why sell an elan for a spridget? I'm a sprite owner of long standing, but I think I might well have preferred an elan had it been on offer as cheaply as my sprite. :)

May I ask why you went for a Marina engine rather than look for a 1275 spridget engine?
Lawrence Slater

It's the cover that is different.
But you can use the cover for the tensioner as a template to drill the holes needed and still use a tensioner on a midget front plate.

H6 and 3 branch sound like a good choise for a mildly uprated engine.
Though it does somewhat depend on wether it fits under the bonnet and if the 3 branch design is any good
Onno K

The elan was a +2s130. Very nice car, butnot a soft top and I had finished the restoration. So bought a midget for £150 without an engine as something to play with. 2 years of body work and just waiting for respray. Re: bonnet clearance, I'll have to wait and see. The monza bonnet is quite different to the standard item.
Cheers
Tim
T Dafforn

Tim-
I'm surprised that nobody has answered your question concerning bearings. Unfortunately, Original Equipment type Vandervell VP2 Indium bearings have become increasingly hard to find, but there is a newer-technology alternative which is acceptable for high performance use. These consist of an Allecular material of an aluminum, tin, silicone, and copper-plus alloy that is bonded onto a high strength steel shell. Because this material is an alloy, it maintains its properties throughout its entire depth, delivering consistent and reliable performance. Since King’s allecular bearing layer is much thicker (.015" vs. .0008")than the babbitt overlay of tri-metal bearings, it provides eighteen times more embedability than that of a tri-metal bearing so that it can catch and hold particles so that they do not abrade the journals of the crankshaft. This is especially true for those particles that are over .0004" (.01016mm) in diameter which are the cause of most of the damage to crankshaft journals. Other manufacturers produce bearings whose wall thickness at the crown can vary by as much as +/- .00025" (.0635mm). King bearings are produced to a finer tolerance that permits no more than +/- .0001" (.00254mm) variation of the desired thickness. The Allecular material’s melting/fatigue point is over 1,100 degrees Fahrenheit (593.3 degrees Celsius), which is almost three times that of the thin babbitt overlay in a tri-metal bearing (400 degrees Fahrenheit / 204 degrees Celsius). This means added protection against localized overheating due to misalignment, overloading, low oil pressure, loss of coolant, etc. King Engine Bearings has a website at: http://www.kingbearings.com .
Stephen Strange

Is there a UK company doing the equivalent bearing?
Lawrence Slater

ACL do fine A-series bearings.

And come on we are not talking about a 9000rpm screamer so it would most likely survive fine with county bearings
Onno K

Hi Lawrence

The County bearings are King bearings.

Peter
P Burgess

Hmm then why do I keep hearing don't use them use good acl or NOS bearings?

their website seems to state they are the end all be all
Onno K

When I rebuilt my 1275 lump, I just contacted MINISPARES and bought 1275 cc bearings (whatever they had in), metro pistons (was going for +40 though rebore anyway, higher compression pistons), they supplied the oil pump etc. The chap that did the engineering was GREAT, based in Witney so not too far away and the companies called Garidas Engine Services.

Use new Small end nuts (minispares)and get I think they supply a 'kit' of lock tabs for the engine.

Cam, I used a Kent fast road cam (comes in a kit with new followers and springs).

Get the machining done, put the bearing caps, rods etc in the dishwasher to clean them up and put it back together yourself. Very rewarding!
Robin Cohen

I rebuild a mildly modified (1380) Marina engine a couple of years back. It was already bored out but fitted up for a Minor when i got it

Just to re-iterate some of the above. For a standard or relatively standard UK rebuild just use one of the many mini specialists for bearings. I found MiniSpares excellent.

You can fit the tensioner - but your midget front plate will need modifying to take the different shaped timing chain cover (Mine was already done).

I found a Kent 266 in my old 1275 excellent. noticeable improvement on normal but never felt as though I'd sacrificed anything. The Swiftune SW5 seems to be very well thought of similarly.

I machined the flywheel to fit the crank - I was having the flywheel balanced anyway so seemed easiest.

Pictures of my build here...
http://www.eatworms.org.uk/mg-midget/projects/94-midget-engine

There's one in the middle of the front plate with duplex timing gear and tensioner. You can see the outline of the new shape timing chain cover.

(final advice - if prop tells you to do anything with an engine - do the exact opposite)
Dean Smith ('73 RWA)

Hi Chaps,
Thanks for all the advise..
Anyone know where I can get a new timing cover that can fit?
Also should I stick with the compression of the Marina, which i think is 8.8:1 or should I up it (Am I correct in thinking that I could use the MG metro pistons to get 10.5:1?)
Cheers
Tim
T Dafforn

More CR better!

Though very dependant on cam and fuel used.
Read the vizard book to know.
But a 10.5-1 should be nice
Please do the calculations to know what CR you end up with
Onno K

Onno

Top A series race engine builder here prefers King over ACL any day, swears they are more reliable.
Paul Walbran

This thread was discussed between 02/12/2011 and 07/12/2011

MG Midget and Sprite Technical index

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