998 rods
Turbo Mini Forums

Right lads I was doing a little thinking (always dangerous) is there any reason [bar the gudgeon Pin Diameter ] why it would not be possible to use a 998 rod in a 1275 casting or has this been done
the reason I ask is at this time S rods are almost extinct so if we want to build stroked motors we must use the likes of arrow rods

I have a few BMC Tec data books here and from every measurement I can get there LBC (length between centre) are both 5.75
the big end is 1.625 (same as S)

the only other difference I see is that the main bearing on the 998 rod is .875 wide and on a 1275 crank the big end is .840

taught on a post card ???

Offsets on the 998 rods are all wrong for a 1275

Also, Cooper S rods are EASY to get hold of. Just have a look on Ebay. Prepare to pay between 100 and 150 for a serviceable set.
THe 998 rods are weak in comparison as well.

Off set I will look into that, Im not convinced there all that week I probly should have said I want these rods to work in a 10 hour motor to do a job,
Ill keep serching thanks for the input lads,
regards,
Paul.

10 hours over several 15min runs

offset mightg be able to be adjusted for if your thinning them?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Ok after a little bit more study today I have come up with the following,
there is no major difference in the offset a mere couple of tho which can easily be adjusted for. There is a small difference in the little end off set but I will be running them in an offset bored 1275 block so no problem there. The only major hurdle is the little end Pin diameter is only 16.34 but after reading a little in the yellow book vizard notes that he sees no problem in opening up the little end to take a 3/4 gudgeon pin he is off course talking in the context of the small bore motor but this suites my purpose well, I have just got off the phone to MED to find if they do the piston size I am after with the full flouting pin i.e. the 18mm one and they do so that would only mean enlarging the little end by a mere 1.66mm or .83mm all the way around from what I can see there is no reason why this wont work Visard also quote High hp figures for some of the small bore motors well inside the kind of hp figures I’m after so I cant see the strength being a problem
Does anyone have access to what material the 12G124 rod is made from I suspect
EN16 ??

Dont forget that a 1275 piston, pin and rings weigh more that a 998 piston, and you want to reduce the metal on the little end. Maybe they will maybe they wont bee up to the job. Austin Rover did ttend to over engineer everything about the A series.

How much will all this machining cost in relation to a good used set of S rods for about £100. The pistons will cost a bob or two.

Not sure I understannd the strategy :/

Edited by Sprocket on 2nd Jul, 2008.

Very good Point there Sprocket,
This is by no means a cheep alternitive I am an expermenter I am going to build a short stroke 1350cc motor If I buy S rods I am looking at ath least 100 - 150 quid then I will have to have them shiped to Ireland another 30 odd quid then i will most likle have to send them back to MED to be worked another cupple of quid on the other hand I have a set of full worked 12G124 rods here as you say rover did tend to over engineer thinks and from what I can work out there made out of the EN16t same as the 1275 rod,
Pistons price does not realy up set me in or around the 300 mark .
I will let you know how I get on thanks all for the advice
regards,
Paul.

could always use the S sized sprite/midget rods as a cheaper alternative. less than half the price of S rods usually.

Why don't you contact Steven Gault in your country. He'll do them!

Gault is a Nordy but close enough .

Ha Lads I was just poking around a friends garrage last night an came across a set of 1275 rods with the casting number AEG 625 MF A1 are these Midget/sprite or cooper S more to the point are they of the 1.62 variety I could not measure them there and then because I was supost to be at a christening not snooping trough his garrage :)
thanks lads,
Paul.

Midget ones, small journal.

Thank you kind sir Ill take the easy option so and grab these the week end he will be delighted with his new set of big bore 1275 rods :)
regards,
Paul.