PDA

View Full Version : Do Con Rods hold size?



Rori
30th December 2007, 12:15 AM
Hi Folks, this is my first post. I have a 300 tdi I bought just over a year ago with reconditioned head and trans, now done 228000 klm, I put it on gas and very pleased with the result. Now I have a problem, a knock has developed at start up, it goes away in a couple of minutes but now the oil light comes on at idle in hot weather (I live in WA). To me this adds up to a big end bearing on the way out.
If I could get a little info from your collective wisdom it may make it easier for me to decide just how mush work I need to do.
My two main questions are; Do the con rods hold their shape/size or not? (If they usually need to be resized then I won’t be able to get away with just dropping the sump).
What kind of wear would I expect to find in the bore having done this amount of Klm’s?
Hope some of you can help
Regards
Rohan

BMKal
30th December 2007, 12:58 AM
Hi Rori.

Suggest you PM Richard (kie4) or you can e-mail him at LRM@LIVE.COM.AU

He's a Landrover mechanic based in Perth - have heard very good reports of his knowledge and ability.

Cheers ............ BM

Bigbjorn
30th December 2007, 09:59 AM
The short answer is no, they don't hold size. This is why engine reconditioners have con rod resizing machines and jigs for checking alignment ( straightness and twist).

Rori
30th December 2007, 06:37 PM
Thanks BM & Brian, I will have a chat to Richard, he sounds like someone I should get to know.
I used to do most of the machining in a engine recon jobbing shop so I've re sleeved/rebored my fair share of Rover V8 blocks as well as the other related machining, but I've not come across a tdi so I need as much info as possible.
Brian, I checked your profile, I can't believe how many posts you’ve made, 1,847. You probably know this already but there is a lots of variation in the characteristics of con rods, some makes/motors the rods regularly hold size and don’t usually need the big end machined while others are so bad that you hardly ever find one that is true.

Thanks again.

Bigbjorn
30th December 2007, 07:50 PM
What your engine man should do is to ensure big and little end bores are round, on dimension, parallel to each other in both the horizontl and vertical planes and their centres are on the centre line of the rod. If you can obtain access to a toolroom quality horizontal borer and semi finished bearings then machine your big end bearings to finish dimension on one of these machines.