What might cause exhaust valve guides to break?

[zeppelin101]

This one has me baffled. First it was cylinder 4 exhaust guide that broke pretty much at idle.

Today, it's no. 1 that's broken in exactly the same way after I took it for a drive down the road. I must have gone up to 3000rpm or so with a bit of load on to see if I had fixed an air leak I had yesterday.

1 going is odd, 2 going there is clearly something wrong.

Any thoughts?

All of the shims were the same size coming out of the engine so I don't think it's that...

[Mark]

Is this on a head thats recently been re-guided or an old well used one?

How/where are they breaking?

[zeppelin101]

Old head, I haven't touched the guides and it was perfect before. It has been a little noisy since I put it all back together but I assumed that was the lifters and was going to bleed them again to check.

They are breaking on the rearmost edge looking at it from the front. Basically they break and then the rocker flips off the lifter.

[Mark]

You have put the shim and the rocker locator round the right way as the rocker fingers are different thicknesses

[zeppelin101]

You have put the shim and the rocker locator round the right way as the rocker fingers are different thicknesses

Thought I had - which side is correct?

I'll measure to be sure tomorrow...

-edit- Looks like they are supposed to be closest to the front of the engine? Mystery solved in that case. I'm a dickhead.

[hooky]

Thought I had - which side is correct?

I'll measure to be sure tomorrow...

-edit- Looks like they are supposed to be closest to the front of the engine? Mystery solved in that case. I'm a dickhead.

The Guide shims are closest to the FRONT of the engine on the EXHAUST side,
But closest to the BACK on the INTAKE side!

The reason being is that all 8 rockers are identical (Left finger machined), but obviously they face opposite ways on the intake & exhaust side

[zeppelin101]

Great, thanks. Can't believe I missed that taking it apart...

[Mitch]

Don't beat yourself up mate, you're not the first and won't be the last to do this.

[Mark]

Don't beat yourself up mate, you're not the first and won't be the last to do this.

Nope although I only broke 2 rocker locators before working it out

[zeppelin101]

Nope although I only broke 2 rocker locators before working it out

It's a tie then

I also meant rocker guide not valve guide. Duh. Had a barnstormer of a day yesterday

[zeppelin101]

Is there anywhere these can be bought in a hurry? I should have checked them all as I've smashed all but the first one I replace and only ordered one...