Valve Guides, Cast Iron Vs. Bronze

[PatGalvin]

OK, more machine shop issues. My machine shop recommends the cast iron guides. They said the manganese silicon bronze guides have been nothing but problems and that the cast iron guides will last as long as anything other wearing part in the engine. Claimed they have had lots of the bronze guides come back as problems. Cast iron expands at higher rate than bronze and the guides would loosen and move in head. This shop has been around forever and done a lot of these british engines so they have some credibility. They are definitely not upselling me.

Any thoughts from the esteemed collective on this?

Pat

 

[TR4nut]

I hadn't heard of that issue - the issue I heard with bronze is that you had to have a little more clearance in the guides otherwise you'd risk sticking a valve. The machine shop I used put in bronze, so we'll see sometime if that was a mistake (assuming I get my 3A going sometime).

 

[TR3driver]

I'm inclined to agree with your shop. The bronze guides are more trouble than they are worth. And the fact you have to ream them oversize tends to negate any advantage they have in wearing slower. In effect, you have to install them pre-worn.

I'll be using iron next time.

 

[TR6oldtimer]

My machinist insisted on cast iron as he too had experienced problems when fitting the alloy guides into older engines. I had a choice, iron or look for another shop. So I have iron. He was able to source the guides through his suppliers, cut them as appropriate for seals, and it was done.

 

[Bremer]

If iron is what your shop recommends, I would go with that.
It seems that both types of guides can be successfully fitted, but the bronze ones require more clearance to the valves. (Again) quoting Kastner: "(When fitting bronze guides) you fit the inlet guides to a .0015'' to .002'' and .002'' to .0025'' clearance for the exhaust valves." He is also not a proponent of valve guide seals. Some oil is required to go down the guide to keep things happy.

 

[Moseso]

The guy that "un-leaded" my cylinder head said the same thing. "Cast iron guides work just fine. Don't get too fancy." So far, so good.

 

[poolboy]

.... He is also not a proponent of valve guide seals. Some oil is required to go down the guide to keep things happy.

Sounds like what a dirt track racer once told me. He said that if it's using oil that's good cause you know things are getting lubricated.