Triumphrat

I put a 8 bolt cracked head ( typical, valve seat to bolt hole) on my 59 without a top end rebuild. I just wanted to see if the mag was timed right and the bike rode straight, with the intention of rebuilding the top end, or replacing it with a latter top end if all was ok. To my amazement it ran great and the top end does not seem to be a problem either. Will replacing the valve seats cause more damage to the head? Will new seats stay in place without fixing the cracks? How dependable are these old heads as is, meaning compatible with todays fuel? I retarded the spark a couple of degrees and lowered the compression. Anyone been through this please comment. Thanks, Martin, Dayton 0hio

Slinky

I think you would be wasting your money fitting new seats unless you get the cracks welded up first. The pressure inside the combustion chamber is enough to do some serious damage to a weakened head.

__________________
"You can't fly with the eagles if you keep scratching with the turkeys."

panda

you might find a better solution to get a good second hand head. i wouldn't change the seats until they start to wear.. the originals were good even if not specifically designed for lead free.

lowered comp by extra cylinder base gasket ???

__________________
A wise man learns from his mistakes..
A genius learns from other peoples mistakes.

Panda, I put two head gaskets on it. It could use longer push rods, it was close. It still has a healthy kick and bark. Good idea? Bad idea?

panda

preunit
extra head gasket will lower it a lot.. problem is with two head gaskets you now have twice as many places for it to leak where the pressure is high. by raising the cylinder barrels the extra place for teh leak is at a low pressure point ( cylinder base joint) This has the advantage of not changing pushrod tube requirements... ( but check the cam followers have pleant meat between them and follower bearing surfaces in teh barrels)

__________________
A wise man learns from his mistakes..
A genius learns from other peoples mistakes.

papereng

Well, I have had my 1961 T120R since 1970. It had the same cracks from the valve seat out to the bolt holes that yours has. It ran when I bought it, but blew oil out the the cylinder base gasket, so I had to pull the top end and that's how I found the cracks.

I was lucky enough to live in Mass. at the time, and I met Don Hutchinson. He knows his Triumphs, and still rides a '62 with a reversed head (a cool trick you can do to a preunit). Anyway, his advice was to replace the casting, which I did. I have not had any more problems with cracks since putting this head on back in 1972. I think you need to take care when torquing it down to go up in stages, and to re-torque after a few heat cycles.

I have seen repaired cracked heads, and I even know a very precise welder who can make the repair, but I still would go with a new head casting.

If the seats are worn out, there's another good reason to replace it. I don't think you should have to pay more than $150.00 for a new casting w/ seats, but I might be low on that. We can find out easy enough. I see used heads on EBay for less than that pretty regularly, but how can you tell if they are cracked or not? I'd get a new one and transplant your valves, springs, retainers, keepers. Replace the valve guides. Lap in the valves, and away you go.

By the way - I'm also in Ohio - Lancaster. Shoot me an email at papereng@sbcglobal.net.


[ This message was edited by: papereng on 2005-01-06 09:00 ]

__________________
Lee

papereng

Well, I have had my 1961 T120R since 1970. It had the same cracks from the valve seat out to the bolt holes that yours has. It ran when I bought it, but blew oil out the the cylinder base gasket, so I had to pull the top end and that's how I found the cracks.

I was lucky enough to live in Mass. at the time, and I met Don Hutchinson. He knows his Triumphs, and still rides a '62 with a reversed head (a cool trick you can do to a preunit). Anyway, his advice was to replace the casting, which I did. I have not had any more problems with cracks since putting this head on back in 1972. I think you need to take care when torquing it down to go up in stages, and to re-torque after a few heat cycles.

I have seen repaired cracked heads, and I even know a very precise welder who can make the repair, but I still would go with a new head casting.

If the seats are worn out, there's another good reason to replace it. I don't think you should have to pay more than $150.00 for a new casting w/ seats, but I might be low on that. We can find out easy enough. I see used heads on EBay for less than that pretty regularly, but how can you tell if they are cracked or not? I'd get a new one and transplant your valves, springs, retainers, keepers. Replace the valve guides. Lap in the valves, and away you go.

By the way - I'm also in Ohio - Lancaster. Shoot me an email at papereng@sbcglobal.net.


[ This message was edited by: papereng on 2005-01-06 09:00 ]

__________________
Lee