Fitting a Cast Iron Liner into an aluminium Barrel

[John OlsenParticipant @johnolsen79199]

As I recall, there was initially some resistance to the idea of pressed in liners because of fears that the aluminium would expand away from the iron liner. Hence the use by some firms of various processes to cast the aluminium around the liner with the idea that they would be bonded together. Practical experience showed that the differential expansion is not actually a problem, so for instance most of the Hondas during the seventies seem to have had liners pressed into the barrels. I don't have any actual numbers for the degree on interference that should be aimed at. I'm sure I had some forty years ago! I should still have a book somewhere that talks about hotting up various models of Honda, including boring out the barrels of a 175 twin and fitting liners and pistons from I think a 305, anyway it took the bike out to about 240. This involved taking material off the outside of the liner as well as the inside of the barrel, and didn't leave an excessive amount to hold the fins together.

One point of curiousity…what does your Fury use for the valve guides? My 1971 Triumph Blazer SS 250 had aluminium bronze for both. According the the afore mentioned Phil Irving, aluminium bronze is not suitable for exhaust valve guides because it goes hot short, and this proved to be the case because when I checked the state of things not long after acquiring the bike, the exhaust guide proved to be loose in the head. It was replaced with a cast iron guide, made from an old sash weight and fitted with the maximum possible interference. The head was heated in an oven and the guide was cooled with liquid nitrogen. It never gave further trouble. One later amusing incident was when I was discussing the job with a mechanic who worked on Ferraris…he commented that cast iron was OK except it tended to hang up at High revs. So I said that that was no problem, this engine only went to 8000. At that he looked a bit bemused, so I pointed out that my other bike, a Honda 100, also had cast iron guides and went to 11000rpm. I think at that point he decided I was beyond hope.

John

[Bob RodgersonParticipant @bobrodgerson97362]

Hi John,

I don,t have a cylinder head with guides fitte so can't be sure. I will check the spares manual to see if there is any information ther on material.

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