K-Head exhaust valve pitting, acceptable?
Turbo Mini Forums

Torn down the K-head for machining and although its fine, noticed a bit of pitting to the ehaust valves, I lightly lapped one in and its cleaned up for a decent seal.

Would anyone have any concerns using them? On the other hand SC do a nice set of large valves.

Thanks.

http://www.turbominis.co.uk/uploads/i/wh40...mole23-4158.JPG

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http://www.turbominis.co.uk/uploads/i/wh40...mole23-4157.JPG

Edited by minimole23 on 3rd Feb, 2018.

What about getting the valves lightly dressed to remove the pitting ?

Phil.

WWW.TURBO-MINI.COM

If it comes to it, I will have to look into it, Theres still a good seal, just not perfect valve faces. I'll lap the 8 exhaust valves in and see how it all looks.

I have a machine for doing it should you wish.

Phil.

WWW.TURBO-MINI.COM

Thanks Phil, I'll get everything properly cleaned up.

The head I currently have on the metro is pretty bad but it doesn't seem to hurt it too much.

The problem is as soon as you have to start cutting seats and refacing valves the cost of your conversion will rocket. Even if you can do all the work yourself you still have to start faffing with shims and buckets etc which in itself can be an expensive game. I never bothered doing mine as I will likely swap it one day anyway and I will fit the bigger valves in at the same time..

but of course if you really want a decent engine you should bite the bullet.

or as somone mentioned elsewhere (probably sprocket) take a bit off the stem and use lash caps

I don’t know how cheap you can buy lash caps over there, but by the time you’ve bought four sets of different sizes, you’re still paying a lot of money.

I went a different route and had my valves and seats re-cut, but first measured the gap of each valve to the cam lobe without the bucket installed to get a baseline (this part wasn’t technically needed but was good practice), then did the same again after cutting them.
I then took the valves back to the shop, and he trimmed the valve stem down (on the same equipment used to recut the valves) by the amount needed for each valve by putting a dial indicator on the stem grinding attachment, and touching off and zeroing the readout, then grinding off the exact amount.

It worked first time on 15 valves; just one needed tweaking again.

Edited by TurboDave16V on 6th Feb, 2018.

My machinist did what Dave suggests above, re cut the valves and seats, then trimmed back the stems for the original buckets.

Funny really as I've just dropped the head off for valve seal testing and we discussed the lashcaps

Lots of options, I'm leaning towards the large valves, as if they just drop in and can be ported to suit, with 4 heads to pluck buckets from I can hopefully come up with a combination that works, (or sell a head to pay for them)

Edited by minimole23 on 7th Feb, 2018.

Is this a Normally Aspirated or forced induction engine?

Larger valves I can understand if your building a Normally Aspirated engine, but there is more than enough valve in the 16v head in a forced induction application that nets HP gains that would scare you, if not kill you. Without considering larger valves, you need to think more about the rest of the car and what you are going to do with all that HP and how you'll get it out of the drive train onto the tarmac.

I'm not really sure what you mean by "drops straight in" as the larger valves would need a whole load more machining than just having the valves and seats re cut and a few new buckets.

Any decent head shop should be able to re cut the valves and seats and shave the stems back to the original clearance using your original buckets. If you have a load more buckets, I would try and put a full set of 16 buckets of the same size together and work back from there.

Big is not always better

Large valves would be dropped in the head for a normally aspirated engine, well ported and with a set of sprint cams, plonked on a sorted bottom end

I've been debating what to do for a while now, but this may be the final straw in terms or project direction. Just cant see that I'll have the time to get a turbo engine together in the next 2 years, with all the additional fabrication involved.

Edited by minimole23 on 7th Feb, 2018.