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MG TD TF 1500 - Rod/piston removal

Way back in the past I vaguely remember removing a rod and piston without removing the crank...can anyone verify that it can be done? I need to do it again and donít want to pull the engine if I donít have to.

Thanks in advance.
Gene
Gene Gillam

Gene, there was a discussion of doing that in some old threads that indicated that it was doable. I haven't searched the archives but it should be 2012 or later.

Jud
J. K. Chapin

It's awkward with quite a bit of twisting and turning of the crank and rod, but humanly possible. You may well break some rings getting it out, as well.

I confess I would rather pull the engine!

Tom Lange
MGT Repair
t lange

I recall it can be done. The problem is re-installing as it is nearly impossible to compress the rings with the crank in the way. George
George Butz III

Thanks Jud...looks doable from underneath...push the piston up through the head, remove wrist pin, pull rod out from below. Iíll check in the archives.

Gene
Gene Gillam

George, if I remember correctly Iíve shoved the piston up thru the block from below with the rod attached, installed the rings and then pressed it down. Itís been a long time though!

Gene
Gene Gillam

I can confirm what Gene Gillam has stated. I have done it that way. No. 1 piston is the most difficult due to the web on the block and as far as I know it also depends on the actual piston size whether it is doable. It is a tight squeeze. You can use the jubilee clip from the TD top hose as a piston ring compressor. I don't see any problem breaking rings getting the pistons out.

Regards
Declan
Declan Burns

Yes the piston & rod MUST come out the bottom, yes it can be done without breaking the rings,this is a lot easier than pulling the engine. However reinstalling can be a challenge, # 1 and or #2 when very close to the bottom of the bore, make sure you tilt the piston to 100% vertical, it does take some patience and wiggling!
As most of these engines have been overbored, the chamfer to compress the rings, at the bottom of the bore, is no longer there. This means installing the rings when you push the piston above the bore, it can be done with your fingers below the bore but not with 3 piece oil rings.The piston will not go high enough for the wrist pin to be completely above the bore, unless the overbore is very large. When removing / installing the rod from the piston you must secure the piston / rod assembly by wrist pin, if you secure the assembly by the rod you will twist the rod.
Len Fanelli
914 420 8699
Len Fanelli

I have done it with 66.5 mm pistons but I know it can not be done with 69.5 mm pistons. I do not know where the limit is. It might work with 67.5 mm pistons.
Next time I build an over-bored motor, I plan on investigating the idea of slight chamfering / relieving the crank and smoothing the block in the right spots so that oversize pistons can be removed like standard ones. Of course the "relieving" would have to be done before balancing.

Lots of good advice above. The rings can be put on at the top as suggested above but the piston can not be fitted to the rod in situ. When the big end is up as far as it will go, the gudgeon hole is not clear of the top of the block.
Bob
R L Schapel

Damn...guess Iíll bite the bullet and pull the engine...a lot of work for so little damage.

Gene Gillam

Gene, I've not had much experience looking at an engine from that angle. What's the "little damage" that makes you need to remove the piston? When I sucked a bolt through the rear carb and into the #3 cylinder I was able to repair the damage just by pulling the head.

Jud
J. K. Chapin

Oops, meant to attach this. This is the bolt where I found it.

Jud

J. K. Chapin

Hi Gene, Pretty sweet looking internals. What happened? George
George Butz III

Gene
Nasty bit of damage there,I wouldn't call that minor, how did that happen ???
Just looking at the bottom of the bore I would guess that it is a fair bit over standard size
The aftermarket rods (are those Carrillo's) are usually quite a bit smaller on the bigend than the std. rods
There is a 'chance' that the rod might just pass up through the bore if you have the head off
Maybe measure the rod width and compare it to the bore size--It would be a lot easier to pull the head than have to pull the motor and remove the crank----just a thought
If it will clear the bore it would make it an easier job to reassemble from the top as well
willy
William Revit

Bob It can be done with a 68 MM bore, or .060" overbore.
Len Fanelli

Thanks Len. I had wondered what the limit is.
Bob
R L Schapel

Willy,

Theyíre Saenz rods and the overbore is .080Ē. The rod was damaged when the circlip on the top of the oil pump gear broke and allowed the shaft to be pulled down into the rod. Iíve sent the pump to FTFU for a rebuild and Manley Ford has ordered me a new rod from Saenz. The crank/rods were sized to have MGB big ends.

If I get a chance Iíll pull the head this weekend...thereís no hurry since parts wonít be ready for 6 to 8 weeks.

Gene
Gene Gillam


Gene, have you determined what caused the circlip to fail? I saw a technical paper once that talked about the wrong type circlip hitting the edge of the relief cut out in the pump cover and resulting in damage/failure?
I've worried about this issue because the replacement ones I've seen are usually thinner than the pump shaft groove and the fit isn't the best. I believe most circlips provided for this application by the major suppliers are True Arc type.
Richard Cameron

Cheers Gene
Unlucky but lucky as well with the damage and what could have happened
It's going to be interesting to see if the rod will pass up through the bore
fingers crossed for you
willy
I guess at least it will go high enough to get the rings off and then out the bottom but it would be a whole heap easier if it comes upwards
William Revit

If you look at the different suppliers you will see different circlips for the pump shaft.

The preowner of my car also ran into that troubles. The shaft distroied a piston rod.

What is the right circlip for the oilpump? I got one after waiting a long time because backorder but I'm confused.

W_Mueller

This circlip was provided by Moss in their oil pump rebuild kit. It was extremely thin and narrow...hopefully FTFUís circlip is sturdier.
Gene Gillam

From a MG T-ABC post about this issue: The original circlip was quite substantial, having a thickness of about 1.5mm and a wall depth of around 2mm. Replacement circlips look quite feeble and a few reports of their failure have been made.
Len Fanelli

I sent my broken circlip to Doug Pelton at FromTheFrameUp along with the rest of the oil pump so he could see the problem and Ďhopefullyí provide a stronger item. Len Fanelli (see above) was the first to identify the possibility that the problem was the circlip.
Gene Gillam


Gene, I know from your past posts on this and other forums, your not new to the TD ride. Your experience and input has been beneficial to many of us in the past. Please keep us informed as you discover the root cause and best course of preventative corrective action when you get more information.
Richard Cameron

Len wrote:

The original circlip was quite substantial, having a thickness of about 1.5mm and a wall depth of around 2mm. Replacement circlips look quite feeble and a few reports of their failure have been made.

The picture shows what I've got from MOSS EUROPE.

The thickness is only 0,9mm and the wall depth is 1,15 ... 1,78mm.

I suffer from such quality.

W_Mueller

All,

Peter Edeny seems to have a better circlip, It doesn't look to be 2mm thick, but looks to be made a little stronger.

https://www.mg-parts.co.uk/index.php?route=product/product&path=3_10_13_15&product_id=321

John


J Scragg

Two quick updates:

1.Received this from Doug at FTFU: The circlip was wrong type and caught on the inside of cap recess which caused the failure.
Remember now, this was the circlip that came with the Moss oil pump rebuild kit!

and

2. Well, just tried going up from the bottom...wonít work...Iím about a 1/2Ē short of exposing the wrist pin so it would come out...and the web of the crank wonít allow me to remove the piston from the bottom. Time to pull the engine!


Gene Gillam

Gene,

Have you thought about leaving the rod as-is? I'm not trained in these things, but these rods have a lot of excess strength. What do the experts say?

Jim
J Barry

Further to Doug Felton's advice re Moss's oil pump rebuild kit, and circlip specifically. Should we proactively be pulling our pumps? If so what is the "proper" circlip?
W Worden

This is the part from MOSS which is no longer available. Don't know if it is better.

W_Mueller

The circlip I received in the rebuild kit resembles the upper middle circlip in this photo. Also, I have to replace the rod because this was built to be a Ďraceí engine and all the parts are balanced...although I donít race the car, sometime in the future if it passes to a new owner they may want to race it.

Gene Gillam

W. Mueller,

Believe that's the original type clip used (as I remember it).

Gene
Gene Gillam

Oil pump rebuild complete and itís on its way back. Doug sent the following note:

The rebuild was worse case as all internals needed replacement. The original gears were cut too short, driven gear shaft bent, body housing cracked and welded (everything good and square), new bushings and washers. We put correct circlip on shaft, Moss clips are also bad and we supply a different type perfect for the application.

So, if you have an oil pump rebuilt using the Moss kit I suggest you pull it and, if nothing else, replace the circlip. Itíll be a lot cheaper than a rebuild!
Gene Gillam


Gene, could you find out what the correct circlip looks like and where we can get them.
Richard Cameron

The circlip illustrated by Mr. W. Mueller is known as an inverted external circlip and a 13mm dia. version would be able to fit inside the counter-bored section of the pump's end cap. However, it may be classified as light duty as it only partially engages with the groove in the drive spindle. Looking at the specification of such a circlip reveals that the recommended groove depth is only about 30 thou. which doesn't seem much.
It might be possible to use a 12mm dia. inverted circlip after machining a deeper groove. However, if one's going to do some machining, an alternative might be a heavy duty 12mm circlip with its ears ground down to clear the end cap recess.
The ciclip from Peter Edney doesn't fill me with confidence due to the limited engagement in the groove.
Moss have been informed of the potential problems which are more likely to effect high revving engines with good oil pressure due to an unfortunate design where considerable end thrust is generated by the helical gears on the pump and camshaft attempting to pull the pump's drive shaft into the engine.
Hope this all makes sense.

E A Worpe

This thread was discussed between 18/02/2019 and 13/03/2019

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