Conrod movment...

[jake_smith]

sorry about anotheerrrrr thread haha but good for the future when people search

Anyway, just removed my sump and the crank seems fine.. no play in it what so ever.

BUT the conrods have movent side to side about 2mm im assuming this aint normal!?

There is no movment up and down though.. so im have no idea.

[Richg40]

So you're saying that when you grab the big end it moves 2mm side to side in each direction??

[cheys03]

I'm certainly no expert with this, but as the pistons&rings have a small gap between them and the cylinder...could the movement of the conrods not be due to this gap?

[jake_smith]

no not when i grab tyhe big end. When i grab the bottom of the conrod.

And i always thought the piston moved on the gudean pin or whatever its called.

[Richg40]

The big end is the bottom of the conrod.

[jake_smith]

ohh i always thought the big end was the crank bearings? or is that the main bearings haha.

Anyway yeahh back on track.. any ideas people ?

How much oil are they ment to hold?

[Yoof]

If it has a small amount of play side to side on the crank (and therefore gudgeon pin) this is nothing to worry about.

[jake_smith]

hello youth , the movment is aboutttt 2mmm either side and if i move it really quick i can hear it taping the sides.. so im thinking if a engine is running while its doing this will it not make a noise?

But there is no movement up and which make me think there fine!

[scotsjohn]

You'll see this play of this amount on most engines. It allows for crankshaft flex if I remember rightly.

[jake_smith]

ahh ok then sound. Ive been woried these past few days that its fucked haha. Ill put the sump and and fill her back up with oil.

Just out of curiosity what amount of oil do they hold?

[Yoof]

You'll see this play of this amount on most engines. It allows for crankshaft flex if I remember rightly.

Endfloat... I'd be worried if you managed to get a crank to flex 

[scotsjohn]

Basic physics Yoofy;anything that takes explosive forces flexes. A couple of thousand explosions a minute spread over the length of the crank has an effect. You can minimize it with attention to balance and tolerances but it wan't dissappear entirely. Conrods shimmy to and froe on the journals for that reason.

[Yoof]

Thanks for the lesson.

[scotsjohn]

I don't suppose it's something that folk consider any more. I'm from the era of the four cylinder,three bearing crank which says it all. As for lessons,I'm pretty sure if I need to know something about G's then you're the man.

[Yoof]

The 'flex' as you call it of a crankshaft is minimal- especially in a Polo Block, granted on A series engines of old you'll have issues, this isn't why a con-rod is allowed movement on the crank thought is it.

The real reason is to allow a clearance for the oil film to be expelled and thus have oil flow, besides the fact that engine built without endfloat is siezed solid, ergo to have endfloat you also need clearance on the rod laterally- imagine it as a self centre with the gudgeon pin (also floating).

The reason for the movment isn't to allow for 'crank flex'.