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MG Midget and Sprite Technical - A little something for the weekend?

It's a nice weekend, even if it does rain tomorrow

So shall we have a technical one for our amusement.

A couple of months ago I got tired of the usual ear splitting bark of exhaust pushing past ill fitting manifold gaskets

SO I bought a new gasket and addressed the reason for the racket, the mis-match of thicknesses on the two manifolds. I made new "half-washers" to mhe manifolds level when tightened and patted myself gently on the back (gently 'cos I am a poor old weakened old man of course...)

Then I set about using the old girl as I always have, with spritely abandon and possibly an excess of bravado

But all has not been well

in the ensuing weeks Lara's almost legendary turn of speed has been wafting away, a recent run to Swavesey returned only a max of V-legal+10

Lorries were looking down at me with disdain, their drivers chuckling manically as they passed me again in the inside lane just after an uphill overtake

I have not been using more petrol than usual though

Yesterday I decided I'd had enough and after wondering if I maybe had a serious problem I checked the tappets and plugs. All tappets readjusted even though there was little deviation from 0.012" on any of them

Here's a picture of the gasket, both exhaust ports were like this

Yesterday I found out what was my bugbear (not on the gasket!)

unexpected

and more than just a tad embarrassing

who has a theory?


[I expect one of our detectives will have the answer in the first six responses, am I right?]

bill sdgpm

Bill.Has the head burnt away behind the gasket, so no matter how well you tighten the manifold bolts it's still going to leak? Just a thought.

Bernie.
b higginson

Well,
Maybe the flanges on your manifold are too thin and the nuts are bottoming out on the unthreaded part of the studs and not clamping the gasket up tight.
(Which come to think of it may be why mine "barks" as well!)

Guy
Guy Weller

both good ideas... id take a straight edge across the face of the ports on the head and Id drop a straight edge across the exhaust manidold

my guess is like bernies but Im wondering also about warpeage and twist

theres clearly a lack of contact taking place where the metal meets the gasket esp for that gasket to be so new

is that kind of damage on one port or all 3

Prop
Prop

Run a straight edge across your manifold / head & see if it is out of true.
I would fit new studs & nuts anyway, the brass nuts are consumables in my book.
Brad (Sprite IV 1380)

I know :)

You're getting old!!!!!!!!!!!!!!!!

Ducks - low - very very very low :)!!!!

So low - she RUNS out of this thread - fastttt .....
rachmacb

well

all good ideas

but I fixed the manifold issue with the half washers, I thought I told you that...

No folks

look elsewhere

This is a "I know what I did, can you work it out?" thing

he he I suppose the gasket picture is a kind of red herring, just thought I'd use the picture

the pictures are to show how bad the discrepancy is between the Peco and the Titan manifolds which caused the burnt gasket

I dont have pictures of the "found problem" and when I fixed it I forgot to scurry off for the Box Brownie

:(

bill sdgpm

Then I set about using the old girl <<<< obviously your first problem - SHE is now a HE - and needs to be treated like a gelding - you can TELL it what to do, not treat it with respect ;)!

Rach - is obviously in dire need of sleep, so is going to go find somewhere cool ...!
rachmacb

Misunderstood. Thought the photo of the gasket was to illustrate that the blowing gasket hadn't been fixed by making the half washers. Didn't take account of your deviousness in casting red herrings and wild geese around like that.

The only other thing you say you checked were the plugs but it can't have been a loose plug lead as you would notice a misfire. Maybe you got the throttle cable snagged on summut when you refited the manifold?
Guy Weller

Im still not understanding?

So you fixed the problem, and want us to figure out how you fixed it?
... step down washers

or do you want us to figure out what the problem was?
....blown intake/exhaust gasket

Prop... that was easy
Prop

"still not understanding?"

OK

Prop please go and fix that pretty engine

I fixed my problem and posted this as a practise exercise

so we could all laugh at my mistakes and maybe learn not to over elaborate

oh


however I fixed my problem and found it wasnt as awful as I had expected.

I realise I should have posted in General but thought as it was a mechanical answer this would do it, especially as half the Brits* were at MGLive today and the rest of us could do with the exercise

* seems like even more than half the Brits went and they had a damned good time
bill sdgpm

How did you make a mistake???

I think you did well, you got the manifold and carbs off then on a new gasket, made some half washers and reassembled and now runs good


you did well

Prop
Prop

mistake Prop?

easy

I spent half an hour or more adjusting tappets that were "near enough" anyway

I'd even tried swinging the dizzy the last time I drove to Swavesey

I drove miles all over middle England with too little power from a normally very fast engine

And I stood for it for weeks

Guy is very close

Now get on with your engine, mine's fine

bill sdgpm

Forgot to re-connect the vacuum advance pipe.
Guy Weller

Choke cable?
Dave O'Neill 2

still no cigar folks

tantalisingly close though

:-)
bill sdgpm

Air cleaner gasket blocking transfer port ?

R.
richard boobier

All good puzzles have a clue, hanging there like low fruit right in your face.

<< "I have not been using more petrol than usual though" >>

Kinked fuel line?


R
R J Reeves

Aw c'mon Bill, red herrings are not fair. I, like Guy thought that the pic of the manifold gasket was after you "fixed it" with half washers. So, another guess from me would be maybe a loose plug, half in half out, still firing but blowing alot of its energy back out past the plug. I had a Transit like that. Scared me to death.

Bernie.
b higginson

You have an HIF carb - right? On those the throttle cable is supposed to sit within a groove on a quadrant. If it wasn't "in the groove" the throttle would still operate, but never open wide. But then that wouldn't be a progressively worsening problem as you describe.
Guy Weller

oh that's close Guy

the cigar may have been rolled along the thighs of...

I can almost smell it

sorry Bernie, plugs new and fine (if I'd done that I'd walk away in shame...)
bill sdgpm

connected the throttle cable to the choke, and vice versa?
Tarquin

Matt

you're just weird...

:D

no not that, blimey that would run funny but I doubt I'd get more than 15mph that way

:-)
bill sdgpm

Is the throttle cable at the carb slipping through the securing nipple just enough to not fully open and slipping further and further each time the pedal is pressed?
I'll get me coat. Wait for me Prop.

Bernie.
b higginson

Bernie

it is the finest Havana ceegar YOU can afford

(well I can't afford it, I'm just an old pensioner)

And you won it

When I was wrestling with the Peco "manifold from hell" I was wrangling the carb manifold all over the place. I think that when I did I must have strained the cable against the screw in the peg and loosened it a fraction to start it on its loosening journey

When I finished setting the tappets and popped the alloy cover back on I tried to start the engine from over the screen using the throttle cable. When I did the outer cable slipped out about an inch or more from the cable end. Pennies dropped and tinkled all the way down the drive.

I adjusted over an inch and a half of cable back down into the "peg" and still had a fraction of an inch free play in the outer...

The Peco manifold has to be strained like mad to get the six holes to line up when assembling

this is my excuse

I'll patent it

bill sdgpm

Well done Bernie!
The progressive nature of the fault was both the confusing thing and the tell-tale clue! Genius!
Guy Weller

Bill.Just as well that THIS old pensioner doesn't smoke then. Can't take full credit though. Guy alluded to the throttle cable twice, so I suppose it was just a matter of time before someone twigged it.
So. Back to full power then Bill. Be careful if you go near Preston. I picked up a speed camera flash for 36 mph last week in my Sprite! The ironic thing was that I 'd just been at BAE Systems Salmesbury, attending a presentation of the "Bloodhound" 1000mph car with Richard Noble speaking and a real rocket scientist who had the most wonderful handlebar moustache I've ever seen. It was really interesting, but not worth 3 points on my licence. 30 years clean sheet down the drain, right there. Ho Hum.

Bernie.
b higginson

Thanks for the timely warning Bernie

well, not timely 'cos Preston isn't on my immediate horizon but a warning of locally nasty conditions is always worth while


Quite sure not even a magnificent handlebar makes up for your pain though :(

How's it going for Bloodhound, [rolf]does anybody know what it is yet[/rolf]

I had it as a bookmark for a while then it all slipped off my radar, must get nosy and look inside again

Anyway

did we like a little intellectual effort for the weekend then chaps and chapesses?

I thought we might do it again some time

Your go anyone!
bill sdgpm

The camera is on the A6 heading south just after the junction with the A59. Must be set at a very low trigger point. Be careful out there.

Bernie.
b higginson

This thread was discussed between 05/06/2010 and 06/06/2010

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