Worn valve guides

[Fungus]

Hi, me again with yet another question.

I've just head a polo head skimmed by a local engine builder, who is highly regarded in the mini scene.

I asked him to see what he thought of the valve guides; there's a good 1mm of side-wobble when the valve is slide into the guide (with the end of the stem flush with the end of the guide).

He said that it was acceptable and that VW's usually run fairly large valve guide tolerances.

My worry is that the guide wear will cause premature stem seal wear. My previous engine used to chuck a load of blue smoke out the exhaust when I let-off the throttle after heavy load, and the guides in that weren't great. I'm not sure If the guides were causing the problem (could be rings?) but it's worth a mention.

I want this engine to last, but I don't want to waste money getting the valve guides done if it doesn't need it. As I said, the valves wobble side-to-side in the guides about 1mm, maybe 1.2mm (measured with a straight edge on the head and feeler gauges). The valve stems themselves have no wear and are spot on the factored tolerances.

What do you guys reckon? Will guide-wear cause huge problems or will it be a case of topping the oil up every now and then? I don't want it to eat through stem seals as you can imagine.

Thanks in advance.

[MrSpeedy]

1mm is a hell of a lot of play imo. I tend to change guides if they're anything over 0.015" wear on the old diesels we do.

With that much play you'll get poor valve seating and increased oil consumption down the valve stems.

I'm surprised at your engine man saying that's ok, as all the other engineering shops I know would all recommend changing the guides

[breng]

Far too much play - fit new ones.

[boom666]

if you want the engine to last without having to strip it down just replace them. 1mm does seem a lot. cant you get valves with oversized stems for these ?

[Fungus]

Thanks guys.

The engine builder is really good at what he does, all of his work is excellent. It would just seem that he is wrong in this case.

I'll get the guides changed, might go for three angle Seats too.

I can't seem to find oversized valves but the guides are cheap enough. It's just a bit annoying that it's got to go back to the builder, as I spent ages on the prep and primer and it's now gonna get all oily

Thanks again.

[Fungus]

One last thing... The exhaust valve heads seem ever so slightly warped (the don't spin true to the valve stem). I have had these valves recut, does this mean they are okay to use?

The seating area that was re cut was obviously cut true in relation to the valve stem, so even though the valve head may fluctuate when spun, the seating area is surely still going to spin true?

Thanks

[colnerov]

Hi, if you putting this engine together to get it to work for as cheap as possible to get you out of trouble then the guides and re cut valves would be OK. But as you want a reliable engine to last as you put it, then change the guides and valves.

Colin

[Fungus]

I want it to last, so as you say i'm going to have the guides replaced, the seat re-cut (3 angle) and i'm going to get new exhaust valves (inlets are fine).

Might get the head gas-flowed while i'm at it.

[colnerov]

Hi, you might be better off getting the head gas flowed by someone who knows VW,s rather than a Mini specialist. Because they will know where they can and can't take metal from and what works best. You don't want them going through the port wall into a waterway and scrapping the head.

Colin

[slater]

1mm clearance is just silly, I'm sure you cant be measuring it right. If they are worn they will usually be worn oval at the top tho so easy to spot. Valves will be fine if reground, if they have been done wrong/are bent they wont lap in..

[Fungus]

Not 1mm clearance, 1mm deflection (side to side).

I've found new valves for £7 each so I think I'm gonna do that anyway, at least the exhaust ones.

I'm tempted to go all out and get the head gas-flowed, but it's gonna get expensive so I think I'll just go with new valves, guides and 3 angle seats.

[Fungus]

And the problem in having with the exhaust valves is that I can see light through the saying area when they're slid down in the guides. They've been re ground so they're either bent or the seats are oval