521 “ S “ con rod

[swifty]

I am rebuilding my 1275 S engine and it has 521 rods . One of these is oval (damaged) . I have a 1071 S rod but it’s a 177 . Can I use three 521 rods and one 177 rod ? . I have noticed that the con rod bolts in the 521 rod is longer than the bolts in the 177 rod . I have the 177 bolts . Would this unbalance the engine by mix and matching rods in this way . …. Shirley

[251 ENG]

Yes if you want a rough unbalanced engine.

It is quite common for the engine,s we build to have rod sets " made up " of various rods .

All will be measured, of the same AEG number , balanced to 0.1g , fitted with new ARP bolts and have big end resized.

At the moment at least 50% of AEG 177 rods we see have stretched, oversize or damaged little ends so are rejected.

AEG 521 and 625 are normally in much better condition

You can have the little ends bushed to suit floating pins , but that's just more expence.

Alternatively just forget 50+ year old rods and buy a new set of maxspeeding rods for about £350

[swifty]

Thanks Simon , I will take your advice . Where do I buy these maxspeeding rods ? … Shirley

[251 ENG]

Max speeding rods are for sale on ebay .

You will need to have floating pin pistons to suit them , not press fit

Make sure you get the cooper s ones not 1300 type .

Depending on block bore size you may have to put a small clearance chamfer on bottom of bore

[Spider]

The Rods should be reconditioned as part of any engine rebuild. If it's the Big End that's oval and that's not uncommon on most rods, they'd be closed and honed back to size as part of the reconditioning process. If you ask nicely, your machine shop will get all Rods the same ctr to ctr length for you.

[swifty]

Getting a good machine shop in Essex is getting problematic. …. Shirley

[CooperTune]

I have been removing con rods and tie wrapping them in sets as removed. Some are 177, more are 521 and 625 sets. Some from Sprite/Midget, others from AA autos found with small journal cranks the rest Cooper S. Having access to a Sunnen rod machine I had considered reconditioning with new bolts and balancing in sets. The bulk of my cores now are A+ with just a couple of Cooper S blocks. I'm not sure with shipping, cost of quality bolts and machine shop labor they are worth anything.

As for machine work, I spent 25 years working 50 plus hours a week in an auto machine shop. I retired in 2000 and since then 5 shops in the region have gone out of business. The shop I retired from has passed though 6 owners since 2000. I expect to see it close its doors anytime. Steve (CTR)

[Jason]

Nice set of 625s if you fancy splashing out:
EBay item number 126066058664