mk1-forum.net

HI all, hope some one can help

the dilemma I have is , conrod casting No's, I have what is suppost to be a 970 engine built into a solid block 1275 engine with a large amount take off the top,
the crank looks to be (from the casting No') correct, 970, AEG 330 can just make it out on the crank

now the rods are a mix of 3X AEG177 and 1X AEG521, the AEG521 rod needs to be replaced as the bearing has spun and both the rod and the cap are damaged where the locating tab from the bearing has badly marked the inside of the rod/cap and from what I can find on the net (as I have no paper work to put me right) both No's should be from a 1071 or a 1275,

I have a parts manual with the 970 rod listed as a AEG309,

also found on the web (USA mini specialist's parts list) with the rod No's and sizes, 1071/1275 at 5.75" and the 970 at 5.875",

could some one confirm the sizes to part/casting No's, as the rods I have hear check out at 5.875",
I have found rods for sale and have a casting No' of AEG 521 with a discription size of 5.75"??

thanks for reading, mike

Mike, from memory the AEG177 connecting rod was used in the 1275cc / 1071cc and 970cc engines. It was also used in the 948cc Morris Minor engine. From what I recall the 1275cc / 1071cc rod length was 5.75 inch and the 948cc / 970cc connecting rod was 5.875 inch in length. The extra length was achieved by having the gudgeon pin machined further away from the big end journal. The AEG177 rod is lighter than the AEG521 rod and has less material around the journals where the studs go through.

You can't go by part numbers on these and need to work on measurements.

Maybe someone else on here can explain this more clearly

Alan

HI Alan

thanks for the reply I will remove the pistons and see what the small end on the rod is like,

was the AEG177 and AEG521 rod actualy made for the 970 engine? or just for the 1071/1275 or have I a set of modified rods

I take it the rod for a 970 should be 5.875" long and should have AEG309 on the casting possibly? or have I it wrong

regards mike

Hi mike,

I don’t know and I’m sure nobody now alive knows in all honesty what connecting rod was designed as a one-and-only for the 970cc short-stroke engine. Whilst this connecting rod has the same AEG177 marking as the 948cc large bore, the centre-to-centre length is the same as the 970cc and the 1275cc is shorter at 5.75 inch.

Alan

The Original Rods fitted to all 970 Engines were on the AEG 177 Forging, and machined to suit. It's possible / likely that later replacement Rods were machined from AEG 521 Forgings.

Keep in mind here, all these numbers you find on these parts are not part numbers but Casting or as in this case, Forging Numbers. A very small few align to Part Numbers, but on the whole, they don't.

If the Bolt Holes in your Rods haven't been flogged out and the cap location is still positive, it's quite possible to have that in which the Bearing spun in, reconditioned. As a matter of routine, in every engine I do, I always have the Rods reconditioned.

Spider wrote: ↑Wed Dec 30, 2020 6:46 pm The Original Rods fitted to all 970 Engines were on the AEG 177 Forging, and machined to suit. It's possible / likely that later replacement Rods were machined from AEG 521 Forgings.

Keep in mind here, all these numbers you find on these parts are not part numbers but Casting or as in this case, Forging Numbers. A very small few align to Part Numbers, but on the whole, they don't.

If the Bolt Holes in your Rods haven't been flogged out and the cap location is still positive, it's quite possible to have that in which the Bearing spun in, reconditioned. As a matter of routine, in every engine I do, I always have the Rods reconditioned.

Chris, I fully understand what you said above, what I referred to was cast or forged numbers which do not relate to part numbers. Sorry if I did not make that clear.

Thank you for helping with this question.

Alan

Mike,

The question I forgot to ask you, why do you need to run a short-stroke crank in a solid wall 1275cc block? The 970cc motor is useless and would never compete with any 1275cc motor well set up.

Only asking?

Alan

Supersonic wrote: ↑Wed Dec 30, 2020 10:22 pm
Chris, I fully understand what you said above, what I referred to was cast or forged numbers which do not relate to part numbers. Sorry if I did not make that clear.

Thank you for helping with this question.

Alan

Hey Alan,

Happy New Year to you mate

Mate, yes, you were clear on that and I guess I probably more or less repeated that, but worded differently.

Thanks for your insight here too

Chris

HI All, thanks for the replys

Spider:
thanks for the info on the rod No's to part No's, I was thinking that way but just checking, as for the rod with the spun bearing, it will take a lot to clean it up, the marks are pretty deep, I do get rods re-sized and will take it to see if it is salvegable

Alan:
the Terrapin I have, ran a 970 "S" engine when it was on the hills/sprints back in the 80's and I had no prob' pulling 1G of the start line at Prescott, as the car is now in the historic's class, I was looking to put it back to as it ran then in the 1100cc class, even with the super charged/Methanol bike engined cars around then, I have taken 1St in class at Harewood (in the wet), would like the original engine/box back in the car, but?? I would prob' have more chance finding a replacment 970 rod than the original engine/box

regards mike

Hello

Interesting project you have there .
Just to add

All A series and A+ rods have 5.750" centres except 970,a that are 5.875"

970 rods were produced from 177 and 521 forgings

1071,s and early 1275 S engines used AEG 177 rods , later 1275,s used AEG 521,s , Mk3 cooper s used AEG 625 rods

Some 970 rods have the original number ground off and restamped with 970 part number, also some rods have number etched on side of little end . Most 970 rods appear to have no 970 part number

Rods can be resized on big ends but this will shorten the rod centre size

I may have an odd 970 rod available

Email me on orx77@yahoo.co.uk

HI 251 ENG

thanks for the repy, I have sent you a E-mail about the rod you may have for sale

regards mike