Cylinder Head Cracks

[danielsprague]

Hi

I'm rebuilding a 2L non-turbo engine as it was using oil, though otherwise performance was pretty normal, if a little lacking in low end torque.

I've just finished a homemade hot tank and rinsed off the head.

Unfortunately, there are a few very minor surface cracks

On the bridge between the two valve seats, cylinders 1,2 and 4 have a very fine crack.

Cylinder 2 has a very fine crack also from the exhaust valve seat to the combustion chamber hole.

These cracks are very minor, just on the surface by the looks of things. Looks like heat fatigue. None of them run to or touch any oil / coolant galleries, or run to the edge of the head, so in my view it's not a big problem? The fact that they are present on 3 of four cylinders suggests to me they've probably been there some time, and were not causing any problems.

Obviously, this isn't perfect, but unless it's really bad, I don't want to spend hundreds on a new head and having it shipped all the way here.

BTW - I visited an engineering works in town here a few weeks back, and they were re-using a head which had a huge piece gouged out of it, by what must have been a thrown con-rod or a smashed piston... so the guys down here certainly won't turn their noses at it.

Cheers

Daniel

[MAUI]

Hi, If youre planning on doing it on the cheap, i would give it a quick skim,dosent cost much,while its apart,so i guess youre going to put new rings on the old pistons, are you going to use any other new bits ,bearings , shells ,etc?
If it was me i would buy another wrecked engine and swap bits over.

[NiftyNev]

These cracks are very minor, just on the surface by the looks of things. Looks like heat fatigue. None of them run to or touch any oil / coolant galleries, or run to the edge of the head, so in my view it's not a big problem?

How can you be sure without a pressure test?

Nev

[danielsprague]

How can you be sure without a pressure test?

I can't, but, as I said by the look of things they don't look deep, more like heat fatigue. There's no sign of water having entered the cylinders, never any oil or unusual pressure in the cooling system. If the crack hits a coolant passage I would surely know about it. The engine ran fine before, my feeling was there was some lost compression (seemed to loose low-end power), but I'd put this down to the worn rings, pitted valve seats and so much coke on the inlet valves that in cylinder number 4 at least, it didn't shut properly.

I'm doing a full rebuild, new rings, main and big end bearings, reboring with new oversize pistons if necessary, new camshaft bearings, valve springs, lifters and guides, plus all seals and gaskets. Once the new valve guides are pressed in, the head will be skimmed.

Of course, a brand new genuine head would be better, but aside from the cost, the problem is my location, I'm on a long road trip and I'm currently in Pakistan, so there are huge shipping vosts invloved. My plan is to use the head as I reckon it's fine for now at least, and if it goes, it doesn't make much difference if I'm in Pakistan, Yemen or the Congo...

But I may have a look at the breakers up on the Afghan border as they sell used parts dirt cheap, but they're usually knackered.

Cheers

Daniel