HDI rod direction

[Ben]

Right, rebuilding the engine and not too sure which way around I should be fitting the rods. Below is hopefully a picture of a page of the Haynes manual.



Basically the picture on the left shows that XUD rods should be fitted with the shell cuts outs at the front of the engine, and the picture on the right shows that HDI rods should be fitted with the cut outs at the back

Firstly I can't understand why they are different, and I can't really see why it would make any difference as there are no holes or channels in the shells?

But it must be quite important else Peugeot wouldn't have had them opposite ways around.

So do I put the HDI rods in XUD way around, because they are going in an XUD block with XUD pistons?
Or do I put the HDI rods in HDI way around because they are HDI rods?

Help much appreciated because I really want to get this engine built!

Ben

[Tom]

I'd personally put them in XUD way round. But i am by no means clued up with this stuff. The whole XUD way round because its an XUD makes sense to me haha

[Ben]

Yeah that's what I would have thought. But I don't know what determines which way around they go. If its the rod itself then they'll go HDI way..

[Tom]

Well its all way over my head, hopefully someone with HDi rods will be along shortly to confirm

[CJ_Derv]

I need to know this also as dont have haynes lol just autodata

[Dave]

They are opposite ends on an XUD, but the same end on the HDI. I placed both the cut outs at the front of the piston - but I did shit that block I highly doubt this is the cause though!

[Ben]

Sorry Dave not quite sure what you mean by opposite ends?

[Dave]

Inspect how the shells fit into the hdi rods, and xud rods you'll see what I mean.

[Ruan]

Youll want them in a certain way as otherwise the bearing can spin easier... That's what the notch is there for...

[Ricky]

I put mine in how it shows the XUD ones should be and I spun a shell soon after..

[darrenjlobb]

You need to put them in so there physically the same way around in the block as they were in the hdi, so valvecut outs at the rear, notchs at the rear, the reason its like it is because the stress during running is on the top bearing shell (rod is under load for compression and firing) which means due to the crank turning clockwise, the stress is on the shell to spin the opposite way, this neesd to be TOWARDS the notch in the bearing shell or else it will round out its notch in no time and spin the shells....

Basically imagine it was a hdi, and put them in the same way, even tho pistons are different, its not that that matters, its the fact the engines rotating the same direction that does

Hope that helps

[Dum-Dum]

You need to put them in so there physically the same way around in the block as they were in the hdi, so valvecut outs at the rear, notchs at the rear, the reason its like it is because the stress during running is on the top bearing shell (rod is under load for compression and firing) which means due to the crank turning clockwise, the stress is on the shell to spin the opposite way, this neesd to be TOWARDS the notch in the bearing shell or else it will round out its notch in no time and spin the shells....

Basically imagine it was a hdi, and put them in the same way, even tho pistons are different, its not that that matters, its the fact the engines rotating the same direction that does

Hope that helps

That makes so much sense. REP!

[Ben]

Very helpful reply ta, rep given

[Dave]

You need to put them in so there physically the same way around in the block as they were in the hdi, so valvecut outs at the rear, notchs at the rear, the reason its like it is because the stress during running is on the top bearing shell (rod is under load for compression and firing) which means due to the crank turning clockwise, the stress is on the shell to spin the opposite way, this neesd to be TOWARDS the notch in the bearing shell or else it will round out its notch in no time and spin the shells....

Basically imagine it was a hdi, and put them in the same way, even tho pistons are different, its not that that matters, its the fact the engines rotating the same direction that does

Hope that helps

The shells would spin the same way as crank rotation if they picked up, the notch for compression/load shell should be at the front.

[Ben]

Really not what I wanted to read Dave! Engine is all built up and hopefully going in this week. Now I dont know whether to put it in or not!

[Matty]

When I did mine a while ago, I put mine in the front way..was fine.

[Ben]

I hope they aren't supposed to go in the front way! I had them in that way and then turned them all round because I thought they were wrong!

[Dave]

I just actually read that page from the haynes manual - it is correct, but dont mix up the valve cutouts on the HDi piston with the pre-cup cloverleafs of the XUD, they both have entirely diffrent purposes, and happen to be located on opposite sides of the pistons, hence being opposite to XUD on the HDi and vice versa in the haynes.

Irrelevant of engine/pistons in use, the notches for the upper shell should be at the front, as said in the haynes.

Bets get your engine stripped again Ben

[zx_volcane]

Bets get your engine stripped again Ben

If it does please get some pics, a thousand words apparently

[Ben]

I am now thoroughly depressed, because I'm pretty sure you're right. The notch for the bottom shell always goes the same side as the upper doesn't it, so they both want to be at the front?

This has really ruined my week! I have no space for engine building now as I've got the car in the garage with its engine nearly out!

And I'll have to buy another head gasket now this ones been squished

[Dave]

Drop your sump off, end caps off, tap rods up slightly, job done?

[Ben]

You got my hopes up there. But no, the rod needs to be turned around doesn't it..

[Dave]

Ah, ofcourse, shit mate, just bite the bullet and get on with it!

[Ben]

Will do. As I'm going to be taking it apart again I may as well ask about my other possible problem.

The pistons don't seem to be quite central in the bores, pic below should hopefully illustrate. I know its a circle! but bottom right has a wider gap than top left..



I didn't notice them to be like this the first time they were put in. Could it be because the piston rings are not worn in yet? Or because the piston rings have been in and out of the block a few times?

[Ben]

Just to clear this up for anyone else using hdi rods in an xud, the rods DEFFINATLY go the same way around.

I think the confusion has come from some of us assuming that the hdi pistons go into the block with their cut out at the front, as is the case in the xud engine. Hdi engines actually have the cut out at the back though, so the rod is actually the same way round.

So in the picture in the first post where you would assume that hdi rods are the opposite way round, there not, its the piston.

[rryan]

I am just doing this myself and was about to start a thread until i saw this one - lucky i looked

just to be clear the con-rod notches faces "forward" but does the and big end cap notch face forward aswell??

[Ben]

Yeah the notches both go the same side, both at the front of the engine.

[rryan]

cheers mate