New con rods = new bearings as well?

[ianmway]

Hello,

I'm planning on fitting uprated rods to a 1.8T BAM as the power\torque is getting to the point where opinion says that the stock rods might bend.

Should I fit new bearings and gudgeon pins or is it a case of if it’s not broken don't fix it?

PS
Going to leave the pistons & rings as is unless there is something wrong with them or the cylinders need re honing then it will be new rings.

Thanks

[catman]

I would replace the bearings if you're stripping the engine. I can't see a reason not to.

[ianmway]

Cheers,

I thought the bearings might be like cams where they wear into other components, better to ask the question than end up with an expensive mistake.

Any idea on the gudgeon pins?

[320d is all you need]

ianmway said:

Hello,

I'm planning on fitting uprated rods to a 1.8T BAM as the power\torque is getting to the point where opinion says that the stock rods might bend.

Should I fit new bearings and gudgeon pins or is it a case of if it’s not broken don't fix it?

PS
Going to leave the pistons & rings as is unless there is something wrong with them or the cylinders need re honing then it will be new rings.

Thanks

Why wouldn't you fit new bearings?

[ianmway]

As I said,

I thought the bearings might be like cams where they wear into other components, better to ask the question than end up with an expensive mistake.

Any idea on the gudgeon pins?

[Boosted LS1]

It's a good idea to fit new shells and uprated ones if possible. The pins should be fine. How do people bend the rods though? Is it something that happens?

[320d is all you need]

Boosted LS1 said:

It's a good idea to fit new shells and uprated ones if possible. The pins should be fine. How do people bend the rods though? Is it something that happens?

On the 1.8T VW engines from back in the day, AUM, AGU, BAM, etc. Yes absolutely, rods are chocolate.

[ianmway]

Thanks all,

So new bearings it is.

[Boosted LS1]

320d is all you need said:

Boosted LS1 said:

It's a good idea to fit new shells and uprated ones if possible. The pins should be fine. How do people bend the rods though? Is it something that happens?

On the 1.8T VW engines from back in the day, AUM, AGU, BAM, etc. Yes absolutely, rods are chocolate.

Crikey, looks like the OP will need a rebalance as well then.

[320d is all you need]

Eh?
You can put just rods in and be fine to get a hybrid turbo.

No need for further work.

[leigh1050]

ianmway said:

As I said,

I thought the bearings might be like cams where they wear into other components, better to ask the question than end up with an expensive mistake.

Any idea on the gudgeon pins?

Why would you want to use the old ones?

[Tony1963]

OP,

How far do you think you’ll take this engine? If you’re not going for further power increases, you’ll be fine, but maybe now “you’re in there” pistons and crank might. E worth thinking about ‘if’ there’s a chance you’ll want even more boost etc.

[Evoluzione]

Ultimately the correct answer is you do a visual and measure. If there's nothing wrong then put them back in.

Edited by Evoluzione on Wednesday 20th January 10:07

[99hjhm]

ianmway said:

Cheers,

I thought the bearings might be like cams where they wear into other components, better to ask the question than end up with an expensive mistake.

Any idea on the gudgeon pins?

Yes and no, worth asking, the bearings are soft so won't really care, you hear of people 'bedding in the bearings', personally I think this is rubbish. Providing there is tension when you clip the bearings in and little visual wear then they are probably fine to go again.

The bearings can loose their tension that holds them in place in the rod which is almost more critical than any wear, if your planning on running boost that would bend rods then an upgrade to ACL race series bearings or the Mahle Motorsport VP2 range might be worth considering. Would stay away from the King Race bearings as the backings are brittle and I have had the Audi bearings crack at the tag, they also have too much crush deforming the shells. You want to be making regular oil changes at this stage.

The pins are a match for the piston, so shouldn't need to be changed unless they are showing wear, which probably means the piston will be worn somewhere too. Make sure the new pins slide freely through the bushes in your new rods freely at room temp, seeing it more and more where the fit is far too tight and 'shops' think its ok to 'send it', will create its own clearance etc bull poo.

[99hjhm]

Boosted LS1 said:

Crikey, looks like the OP will need a rebalance as well then.

Not on a four cylinder?

[ianmway]

Thanks 99hjhm

OP? I'm sure it's something obvious but for the life of me can't think what it is?

In answer to the question how far do I intend taking thie engine? To about 350hp, the stock rods "might" be OK, but for peace of mind I'm going with the uprated rods.

The plan for next year is to build an all singing & dancing engine on the bench and then swap it with the one inplace at the moment, might even go stroker not decided yet.

Thanks all for your input

[Boosted LS1]

99hjhm said:

Boosted LS1 said:

Crikey, looks like the OP will need a rebalance as well then.

Not on a four cylinder?

Not usually but best to check in case some parts aren't weight matched.

[HJG]

I'm calling out those rods...'power' doesn't bend rods.
Rods are almost exclusively bent by hydrolocking. It's a 2 bar link so the combustion force (cylinder pressure x bore area) travels down the axis of the rod so there is no bending moment present.

Rods can buckle, sure, but the force to cause this is often far bigger than any cylinder pressure the engine can create. Rod buckling is usually only seen from a bad tune with ignition in the totally wrong place.

I have no experience of this specific engine, maybe the rods really are that bad but it would surprise me that they would be so on the edge.

It's usually the piston that fails first when increasing power output.

To answer original question, replace bearing shells and make sure the new rods are correctly sized for the shells or you'll have a much bigger isssue - usually a con rod size hole in the block.
You do not need to change the gudgeon pins.
Maybe get the crank polished, it doesn't cost much.
No crank balancing required on a 4cyl - even if your new rods have a slightly heavier big end, the main bearings will deal with it.

[ianmway]

Apparently these rods are know for bending, the 1.8T related forums are full of chatter about it, with a few examples.

Bending due to torque reallly not HP, but people like to relate it to HP as it's esier to talk HP rather than torque.

[HJG]

Have you got a photo of standard rod vs aftermarket rod?
Correct too many people don't know the difference between torque and power.
In this instance it's technically neither...the crank sees the torque, not the rod. The rod is seeing cylinder pressure.