Head pitting - acceptable limit?

[Stonejag 10]

Got all the valves out of my replacement head and started to clean it up. Had a bit of a moment where I didn't spot a crack in the bottom of the plastic storage box I was using to wash it and spilt over 2 litres of white spirit in the lounge :lol:

 

After a good rinse in white spirit and hot water I was able to get almost all of the carbon off the block side - doesn't need to be perfect as I was planning to get it vapour-blasted before refitting everything. However I've found some corrosion around one of the coolant passages where the head mates up to the block, some of the metal's been eaten away around the oval slot in the block that isn't present in the head, near cylinder 5. What's the wear limit on this section, do I need to get the head reskimmed? The head's only supposed to have done 8000 miles since it was rebuilt so I'm not best pleased!

 

Pic below - the deepest point of the corroded spot is around 1.2-1.5mm deep.

 

Stone

[Stonejag 10]

Nobody? Would like to get this off to vapour-blasting this week if it's usable. I've seen quite a lot that have been worse on here but I don't know what's going to cause a problem or not...

[VR6Pete 0]

Finding a VR6 head these days unpitted is a big job :) I've seen people use liquid metal to fill the pitting, but it looks minor, ive seen much worse.

[P3rks 11]

Finding a VR6 head these days unpitted is a big job :) I've seen people use liquid metal to fill the pitting, but it looks minor, ive seen much worse.

 

Is it a case of filling it with liquid metal then getting the head skimmed or vice versa?

 

or just a case of filling, sanding then putting it back on if it doesn't need a skim?

[Kevin Bacon 5]

Yeah chemical metal it before skimming or just sand it back after it's dry if DIY and not skimming. I would do as many thin layers as possible, rather than one great big thick one. Same on the block.

 

The CM's job is just to press down on the gasket where a pitted hole wouldn't and won't be anywhere near the cylinder, so it's fine.

[Stonejag 10]

Good stuff, cheers chaps! Actually I've just found this hilarious forum thread which puts it in perspective a bit :lol:

 

Vapour blast on Friday, then fill and sand and I'll be ready to start reassembly :)

 

Two further questions:

 

1) Can you check valve lifters outside a fully built engine? The Bentley only provides a method for checking them on a head mated to a block, camshafts installed and full of oil... Got a set of INA ones very very cheap (cheers, Ben!) - they all feel to have the same level of 'spring' when I poke them by hand but beyond that and checking the dimensions I'm not sure how much can be done...

 

2) Are there any decent replacement valves that aren't too dear (I'm thinking of the ones with a dished base, can't remember what that's called!) or just bung the OEM ones in the ultrasonic bath for a bit and stick with those? The local mad scientist offered to chuck them all in the lathe for me, until I pointed out they were sodium-filled :lol:

 

Stone

[VR6Pete 0]

Is it safe to vapour blast a head? I've had a fair bit done but even on things like a cam cover I still had to give it a good washing down after as the stuff that's used is really fine?

[Stonejag 10]

No worries, when I get it back I'll put it through the dishwasher.

 

http://www.youtube.com/watch?v=6qs7qsCPabI

 

---------- Post added at 7:47 PM ---------- Previous post was at 7:42 PM ----------

 

...but more seriously, I was going to give it a degrease, cold rinse, blast with compressed air and repeat a couple of times to be sure. Dishwasher wouldn't hurt, though.

Edited April 23, 2013 by Stonejag