left hand conrod

[Rich]

can anyone identify this part number 67 1160 R4Z?
this is quite urgent for me to know as I may have purchased the wrong type
Thanks
Rich

[Brian]

Rich that is a large journal A10 rod.

The only thing that is a little confusing is the 4 in the R4Z. I have two spare sets of rods and one set has R1Z and the other R2Z, both sets are identical. The numbers on the rods are the same for both sides, if it has the oil hole then its a left one.

[Rich]

Thanks for that Brian, I have just purchased two left hand rods one new, one second hand, from ebay, I took the chance they were large journal but only had the small journal spares book.
I take it, it will be ok to use two left hand rods (both with oil hole) in an engine?

[Brian]

That I'm not sure about. There has been discussion on the forum before about using two left hand rods. Some seem to think it is ok but personally I wouldnt, I would plug the hole in the right side.

[LJ.]

I take it, it will be ok to use two left hand rods (both with oil hole) in an engine?

Not really a good idea Rich as this will then allow less oil pressure to the left side, this is the side that usually goes bang when oil starvation occurs. There is more information on this in the forum archives.

[Goldy]

Rich have a read through this http://www.audioworld.net/BSA/forum/index.php/topic,2612.0.html

[Rich]

many thanks, I have read the post and providing they are both ok, I will block the hole and get the rods the same weight prior to rebuild

[trevinoz]

Didn't the A65 have both rods drilled some time during production?
If so, having both rods drilled on an A7/10 would not matter as they are virtually the same design as the A65.

  Trev.

[MG]

Dunno if this was at the same time, Trev, but the last A65 models used wider gears in the oil pump to improve lubrication.

[jjbsa]

In the mid 60s I was buying a pair of large journal rods from Eddie Dow's.  They only had the ones with the oil hole in stock and they told me to block the hole in the rod that was to go on the timing side.  I did that.  I have heard of people running pairs of undrilled rods OK. 

[kiwipom]

hi guys, i have read all the posts on this subject. I ordered a set of billet rods from SRM and when i received them i noticed that the hole was not there, i contacted srm and sent the relevent info from my manual and asked for thier opinion. They informed me that the hole was origonaly there to promote oil flow through the sludge trap and was now unnessarsary so i fitted them as per instructions. As a matter of interest where does this sludge come from? is it from unfiltered air or oil? if so once filters are in place no sludge,just my thinking correct me if i am wrong, cheers, Bob

[MG]

Interesting, I fitted a set of SRM rods in September last year (blimey, where has that year gone???). Back then the lh rod HAD been drilled, although I had to prise a lot of polishing compound and muck out of the hole first...
Here's the complete story: http://www.audioworld.net/BSA/forum/index.php/topic,3195.0.html

The sludge comes from unfiltered oil, the idea was to remove it from the oil and deposit it in the sludge trap by centrifugal force.

[Brian]

Only my opinion but if it was me I would be drilling the left rod.

I dont know exactly why BSA did it in the first place but it must have been in response to some problem and they all had the oil hole from then on.

[KiwiGF]

I bought billet rods from thunder engineering uk a short while ago and they look identical to SRM rods (they probably ARE SRM rods) and one rod has an oil hole......

[jjbsa]

Hi Kiwipom,
You photo of the 3 rods is interesting.  The rod on the right, which I take to be the BSA one, has to my way of thinking, an unusual end cap, in that there is lots of clearance around the nut and a rather sharp looking junction between the face the nut seats on and the face parallel to the axis of the bolt.  That junction looks like a stress raiser to me.  All the BSA rods I've ever seen before have had a quite narrow circular section milled recess for the nut, with BSA trying to keep as much metal as possible in that area.  For that reason I have to use a slimmed down socket to deal with those nuts.

While we're talking about con rods, has anyone any experience of the steel Carrillo ones?  Do you need to do a rebalance if you fit them?

JJBSA

[kiwipom]

hi guys/MG, i too have had trouble with conrods. The ones that i was going to use had like yours been cut out with a hacksaw, that is why i got billet ones. The cuts in the ones that i could measure are about .5mm deep do you think that they are still usefull? bored out with oversize bushes, cheers,Bob

[MG]

Hmm, the hacksaw thing seems to be quite common. BA****DS!

0.5mm deep grooves means loosing 1+mm of material in diameter on the small eye, and they are not particularly substantial, so there is an inherent risk of failure involved. If you intend to be going anywhere faster than on a pushbike (your avatar pic indicates so  ), I'd rather replace them.

[chilblayth]

re oil hole in l/h rod ,   i remember reading in a very old publication it was to supply extra oil to the (i think) bore on that side as there had been some incidents of excessive wear on that side     this would have been back in early seventies , i think it was a copy of   `the motor cycle`