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MG Midget and Sprite Technical - Wrist pin pain

So... it looks like I have a wrist pin going out- '70 midget, 1275 engine. A couple basic questions:
- can I pull the head and oil pan, and pull the piston that way?
- Does anyone sell one piston, or do I have to buy the set?
- anyone got a good used 1275 for sale?

thanks!
Don
don g

You'll have to pull out the engine.
Jon Saylor

You could, but wrist pin is not a common fault, so it's either not a wristpin or there is likely to be accompanying damage. Much easier to pull it.

FRM
FR Millmore

The wrist-pin, or little-end is a press fit on 1275s (at least on my '73); best pressed out (and in) by machine.

You can extract the 1275 piston out of the cylinder with head removed and big-end split (sump pan dropped).

Watch out for the oil drop straight into your eye; there's always one waiting for you.

As FRFM says, more likely to be big-end (what are you experiencing?).

I've done several refurbishes in situ (shells, pistons) with no problems.

A
Anthony Cutler

Thanks Anthony - I was wondering what a wrist pin was.

In damp weather, it's my ankle pins that give me pain. No problem in the snow, though.
Nick

heres a clip of it being done.

http://www.mlmotorsport.com/index.php?option=com_wrapper&Itemid=57
Brad (Sprite IV 1380)

Gudgeon pin in Englishese... Wrist pin is more elegant I think...

All 1275 (A and A+) rods are inteference fit unless modified for racing use when sometimes a bush and circlips or teflon buttons are fitted instead - I have never seen a wrist/gudgeon pin failure on a 1275 that wasn't terminal so it may be that you have a different problem...?
James Bilsland

Could be a different problem- i get a tappity-clinking noise when the engine in under stress. It's not quite as bad when the engine is cold, but very noticible when warm. "stress", for example- being going up a moderate hill in third gear when it shouldnt have a problem. The noise has been there for several hundred miles, and seems to be getting worse. My mechanic friend who has far superior knowledge than me listed to the cylinders and wrist pin was his best guess- he's heard it before, at least on B's.

any advice appreciated! at this point i'm thinking i need to pull the engine and check things out.
don g

Sounds much more like a detonation problem - timing, stuck advance, lean, or overheat, possibly local - carbon buildup from oil burning or waterpump failure. You gave the textbook description of detonation.

FRM
FR Millmore

Agreed!

You could try winding the dissy back say 10 deg and testing.

A
Anthony Cutler

Could be a number of things with little end bearing (Thats cos its at the little end of the con rod! :-) as opposed to the big end which is at the big end of the con rod.. :-)) being at the very bottom of the list.
I would want to eliminate detonation first by the means described by Anthony but I think that too is way down the list.

Is it exhaust manifold blowing?
Is it a badly adjusted tappet?
Is it a bad rocker shaft?
Is it a broken ring?
Our engines are noisy, is it simply that it sounds different to your everyday car?

By the way if the little end is called the wrist is the big end called the elbow? and the crank journal the elbow pin? :-)
Robert (Bob) Midget Turbo

Piston slap......

That's my guess.

Mark.
M T Boldry

Don,
I was amazed at how mechanical and "clackety" a noise is produced when the exhaust manifold gasket goes - especially if it is blowing on the underside of the manifold to head flange. Also much more noticable under load as you describe.

Check the easy things first!

Guy
Guy Weller

thanks, all.
I've had my car for almost 10 years, so i'm familiar with it's noise and, of course, past problems. the noise is more metallic and louder than a detonation problem. coupled with a "second opinion" by the local MG Doc, i'm fairly confident it's somewhere inside- so piston slap, rings, etc-
i'll listen for the exhaust manifold, but the noise wasnt coming from that area of the engine. I had a head gasket blow a couple years ago, and that was actually a similar noise if i remember correctly, but was pretty easy to find as you could see and feel it.
of course, it makes sense to double check all the suggestions before pulling the engine, so thanks for all the advice. merry Christmas!
don g

Don,
I hope it's minor, but knowing how long it takes to do a proper engine rebuild in Missouri(ask Prop) you better get started soon.
18 months till Midget 50!!
Phil

Hey DonG.

Id look into the exhaust situation esp. the dounut, an exhaust leak can sound matalic, just listen to my truck, down hill it sounds smooth, up hill it sounds like the crankshaft bearings have turned to dust.

Im comming back up to St. louis on sunday evening for several more days of work, You welcome to my engine lift and engine stand, let me know And Ill get it loaded before I leave your welcome to it as long as you want.

You might try dropping by harbor frieght and getting a pointy stetoscope like $5.00 and having a listen sessesion to pin point the problem...Just make sure you dont need to hear anything for the next 5-8 days as deafiness follows.


Now that im on the backside of this job and have a bit of breathing room with out flooring and cabinet guys breathing down my neck, Im hoping we can get all the St. louis guys togather and checkout bruces frogeye, and have a listen to your ride...maybe burn some steaks in honor of the new year.

Prop...Half past dead on my feet
Prop

Prop- thanks for the offer. I wont be doing anything until spring, at the earliest, so I'll pass on the offer. Let us know when you're in town though!
don g

No problem Don G.

Ill do, Ill be in town on this comming sunday evening.

looking forward to seeing you guys

Prop

Prop

Don,
Bring it John's on Monday. You know how he loves Midgets.
Lee
Lee Fox

This thread was discussed between 23/12/2009 and 27/12/2009

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