4 Cyl Conrods side oil holes

[Cumbria Graham]

I'm having my 3A engine rebuilt and the is a mixture of parts with cod rods from different cars. All have lateral drillings through the central oil way three are so fine that its almost impossible to feed a fine wire filament through them but the other is about 1.5mm or 60 thou. It has run happily for 6000K without bearing damage so I presume its Ok but any advice would be welcome. The rods have the following markings as far as we can make out.

201488-13330P2

210446-1333901

210446-13339R

Thanks Graham

 

[Motorsport Mickey]

Hi Graham,

The small hole midway up the conrod, is a blasted nuisance.

I like some other race minded individuals have broken them there, even with full race prepared rods, shotpeened and balanced. The breakages normally happen at revs where over 5000 revs are used for a time, mine happened on the 14 second full bore straight at Snetterton, about 1/4 of the way down it, where you enter the straight close to 5000 revs. So I would not be bothered about running on rods without the hole, it’s worthwhile having a rod without it,  the idea that the oil can be squuuueeeezzzzeeeddd out of there and help lubricate the cylinder liner walls is overrated against the possible failure opportunities it gives.

The Chinese Maxpeeding rods that are sold are very nicely and accurately made, dimensions on them are mostly within a couple of 1/10s of thou and are a matched set on weight, and they don’t have this small stress raising hole produced in them, and as far as I’ve heard have no down side in them, with no reports of lack of lubrication because of it.
Think about it, at even low speeds, the inside of the crankcase full of spinning crank and thrashing conrods and pistons pulverise any oil dropolets into a lubricating mist which covers everything. These Chinese rods are used as “ budget” race rods by many now in the racing fraternity.  I have a set put by for my next engine build and bought them at £175 for a set of 4 ( free delivery) the costs will have risen since, I haven’t checked. They are a country mile in front old original rods which after cleaning checking new bush honing, lightening, shotpeening and balancing ( but still with the engine destroying side oil “ spitting” hole where the fractures occur), will cost likely over £400 to do.

If you wish to continue with your existing rods I would sleep easily on the idea. The conrod without the oil way drilling midway along the oil passageway to the conrod little end bush will likely be the strongest of your conrods, Good luck.

Mick Richards.

[james christie]

My long term winter project is rebuilding the original engine for my 3A. My first purchase was a set of MaxSpeeding rods last week after much useful advice on these fora.

Nice looking rods. Cost here in France was 377€ delivered. Three are at 647g and the fourth at 648g (!) I weighed one of the old rods - 965g.

james

 

 

[Lebro]

+1 for maxspeeding rods

Bob

[Hamish]

+2 MaXpeeding rods

ive had mine out after about 4 hard years of sprint and hill climb abuse. ( due to piston issues)

and they were in great condition. Just changed big end shells not that they needed it. 
 

real fit and forget parts. 

 

 

Edited September 2, 2025 by Hamish

[Andy Moltu]

The Maxpeeding rods even come with ARP bolts.

They strike me as over engineered- erring on the cautious side so are heavier than Carillos but at a fraction of the price. Way lighter than the original rods and way stronger and better balanced.

[Drewmotty]

I fitted a set of Maxpeeding rods to my mildly tuned TR4 when the small ends started to rattle. At less than £200 at the time it wasn’t worth working on the standard rods. 
I was surprised to find that I could notice the difference from the driving seat; the engine spooling up more smoothly. 

[John Morrison]

Is there a preferred supplier folks for these maxspeeding con rods?

John

[Motorsport Mickey]

I got mine via e bay, about 2 years ago. try a search John and see what comes up.

Mick Richards

[Chris Hale]

8 minutes ago, John Morrison said:

 

Is there a preferred supplier folks for these maxspeeding con rods

 

Here you go John

https://www.maxpeedingrods.co.uk/

[james christie]

Yes, they sell direct to the end user, no middle man😁

james

Edited September 3, 2025 by james christie

[Lebro]

https://www.maxpeedingrods.co.uk/category/h-beam-connecting-rods.html?car_year=1956&car_make=Triumph&car_model=TR3

Sale on at the moment
https://sp-ot.smartpushedm.com/api/viewInWeb/v1/PviVyESMH_hvptViqGlhT9CF1tdy2zzTIw_iGR1-eZUgHC7yy-rJsQ==?sd_id=6192449570816240

Bob

[Chilliman]

Still cheaper to get them on ebay (£336) & also have the buyer protection.

[Chris Hale]

Currently on sale direct from maxspeeding 

https://www.maxpeedingrods.co.uk/product/high-performance-triumph-tr3-tr4-4340-en24-chrome-moly-forged-h-beam-connecting-rods-conrod-with-arp-bolts-x4pcs.html?search=Connecting rods&car_make=Triumph&car_model=TR4&car_year=

 

[John Morrison]

Thanks guys

John

[Cumbria Graham]

Thanks to everyone for your advice. At just under £400 a set, they're great value.