New big end shells, hole or no hole?

[steve briance]

Hello all!

I have just been out to my garage to plastigage my freshly reground/polished crank with new main and big end shells. Mains are good with 0.0025 thou' running clearance.

I checked one big end bearing and got somewhere between 0.0015 and 0.002 thou' which was also good.

I then noticed the new shells do not have the holes which align with the oil drilling in the con rod.

The 7A con rods are hollow and theory is that oil finds its way through the hole in the bearing and up the rod to lube the gudgeon pin but with no hole in the new shells, there is no way that will happen.

My research online seems divided but perhaps settling more on not needing the hole as splash lubrication and the oil coming from the piston squirter jets is sufficient for enough oil to find its way onto the pin. Someone raised an interesting point on another forum for a different marque of car that; aftermarket high performance rods often don't have the oil drilling anyway so there is no need for associated shells with holes. Fair point!

As the pin is not a pressure fed bearing, it can't need much but i was wondering what experience the forum has with replacing big end shells - do you find they come drilled or not?

I have Mahle std size shells p/n 029PL19903000.

[Thuppu]

All sputter shells I have been using(OEM, KS, Glyco) has have the holes. I would use ones with holes as the rods has riffle drilling. Maybe just drill holes on the upper shells..?

[SteveH]

If you have rifle drilled rods I would use the correct mains shells to supply the oil feed, as you're not making use of any benefits of rifle drilling if not. However, I've been using Carrillo H beam rods in my motor for years and they aren't rifle drilled and I've seen no wear in the little ends. The oil squirters provide more than enough feed on our motors, so I doubt you will notice any difference either way!

[steve briance]

cheers both, seems the difference in opinion continues!

I'm inclined to use the oil hole but when you think some aftermarket con rods don't have the drilling and Mahle supplied the bearings with no hole, it makes you wonder!

I will go back to the supplier and ask if there is a different part number for shells with holes, the labelling specifically says 'no holes' which makes you think there is a holed option...

If there isn't, drilling the shell - a simple job of drill and debur?

[SteveH]

There are certainly shells with the holes in the correct location. I have them in my motor, but no rifle holes in the rods

[Error404]

What bearings do you have? I have never seen sputtered rod bearing sets without the feed hole for the drilled rod.
Like Steve I'm running non drilled rods which are fine. The forced oiling to the small end will give you longer life on paper. Will anyone run a performance build for enough time for it to come into play? Unlikely but I would go with forced small end oiling given the option

[steve briance]

The bearings are standard spec. I am rebuilding a 7A back to factory fresh (as far as possible) and with no turbo, sputters are bit overkill.

My only concession to upgrade is that I will be giving Bassett Down Balancing a call once I've finished checking my running clearances, a balance and minor flywheel diet is on the cards

[Error404]

7A uses drilled rods, so the bearings should have the oil supply holes

[LHD_Kid]

I will be giving Bassett Down Balancing a call

Good luck with them... I was extremely disappointed with the quality of the work they did for me... (around 3 years ago)

[SteveH]

Good luck with them... I was extremely disappointed with the quality of the work they did for me... (around 3 years ago)

They were always very good in the past. I know the old chap that ran the place for years sold the business, so perhaps it was the new owners? They moved away from Swindon too, was this whilst they were still there??

[LHD_Kid]

They were always very good in the past. I know the old chap that ran the place for years sold the business, so perhaps it was the new owners? They moved away from Swindon too, was this whilst they were still there??

It was after it was sold, but while still near Swindon. I was doubly disappointed as I went through Aelred, so expected to have a nice job done...
I only found out when I got the stuff back that the old guy had sold up...

[steve briance]

Bearing supplier agreed that the big end shells should have had oil holes in them and a fresh set is arriving tomorrow. the weird thing is -the numbers on the packet didn't even appear in the Mahle catalogue so he couldn't even say what application they were for!

Just for info in case anyone else is planning similar:

Kolbenschmidt big end bearings for 7A (STD size) are p/n 77 206 600
Mahle main bearings for 7A (STD size) are p/n 029HS18815000 (note last 3 digits show the size 0.25, 0.50 over etc)

cheers!