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TR6 tr6 valve guides

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pdplot

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I'm planning to replace the valve guides in the near future. Any thoughts as to cast iron or bronze? This is strictly a road car rarely over 4200 rpm or so.
 
My vote is iron,but even more important is to make sure the upper end receives its fair share of the oil. I like the bypass line to the head trick,cheap insurance...
MD
 
I'll second the vote for iron guides, but not the bypass line. IMO as long as the rocker shaft (and passage to it) doesn't get clogged with sludge, the factory metering system delivers just the right amount of oil. But it's worth checking that the passages are clear each time you set the valves.

Note that, if you do go with bronze, they have to be reamed oversize after installation. The bronze expands faster with heat than the cast iron head does, so the guide/stem clearance closes up when the engine is working hard. Without the extra clearance, the guide may gall to the stem or even lock the valve open. To my thinking, the extra clearance pretty well negates any "long life" advantage of the bronze. In effect, you are installing them "pre-worn".
 
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I know there are guys with a LOT more miles on their engines but at 110K miles my cast iron guides were still within spec.
 
+1 for cast iron.

I put cast iron guides in our GT6 head to replace its original cast iron guides. They went in nicely without secondary machining/reaming.
 
I have 103+K miles on car which I believe to be original. Car smokes on startup and on deceleration but compression is strong - 155-160 in all six cylinders. And - what about valve seals? They worked on a Corvair I had some years ago.
 
pdplot said:
I have 103+K miles on car which I believe to be original. Car smokes on startup and on deceleration but compression is strong - 155-160 in all six cylinders. And - what about valve seals? They worked on a Corvair I had some years ago.
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The phospor bronze valve guides are supposed to be "self lubricating".. so I can see limiting the oil with stem seals, but the cast iron probably do better and last longer with a more generous film of oil between the valve stem and guide.
What's your machinist think ? They do more of this kind of stuff than most of us.
 
I haven't pulled the head yet - and am not looking forward to it. Except for the oil, the car runs perfectly, idles well and pulls strongly with no skipping from low speed. Except for the old redlines (which still have quite a bit of tread), a couple of small tears in the drivers seat and the left rear u-joint which has a bit of play, the car needs nothing.
 
Since it seems to be OK otherwise, just adding some seals might be the way to go for now. With a little bit of trickery, you can install seals without removing the head. I used air pressure to hold the valves up while removing the springs and installing the seals, but the rope trick should work too. And if something does go wrong, about the worst chance is that you'll wind up pulling the head anyway.

PS, I'd still lose the Redlines if they are over 10 years old, no matter how much tread they have. Old radial tires can fail suddenly at speed, and do some serious damage. Unfortunately I didn't take a photo of the damage to the Stag, where it not only flayed off the paint all around the wheel well, but took off part of the metal as well. But this gives you some idea:
shreddedtire.jpg
 
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Not that this has anything to do with valves or valve guides, but how's the Oil Pressure ?
With that many miles, if the connecting rod bearings haven't been replaced, they might be about ready..I guess Main bearings and Thrust Washers could stand checking on too.
OK I'll stop.....:greedy_dollars:
 
There was a big discussion about the phosphor bronze guides on the Healey list a few years ago, with some of the guys experiencing or hearing about the valves seizing up when hot. Apparently due to different expansion rates between the metal in the valves and the guides. Some said stay away from them, and some said they were OK as they were reamed to proper clearances, which are different than those for cast iron (and maybe using cast iron specs led to the problems). On knurling, my machine shop guy said something similar to the prior comment, used to be done, not so much anymore, he thought the extra metal "created" by knurling them out would fairly quickly collapse or wear down, I suppose that and the higher costs of labor (pulling the head) has led to the practice of recommending guide replacement rather than knurling when they are worn.
 
Oil pressure is almost 80 lbs/sq.in cold and 60+ hot. Even fine at idle. I'm now using 20/50 Castrol after years of 10W40.
 
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