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CJD
06-23-2014, 03:11 AM
Next offbeat question.

I was browsing the service manual and noticed the material for the original exhaust valves was a "chrome nickel steel stamping with a stellite tip". The current valves available are listed as stainless. Does anyone know how well stainless compares to the original material? Is the stellite tip significant enough to be worth 4 times the cost of a straight stainless tip?

vivdownunder
06-23-2014, 10:28 AM
Depends how much use the car will get. Stellite tips are as hard as billy goat's knees as to defeating flat tappet scuff wear. Softer stainless steel valves, especially exhaust valves, only rate about 40% of the life of stellite valves.

Viv

CJD
06-23-2014, 12:25 PM
Thanks, Viv. It will see little use. I was just worried, as I recieved 3 heads in my Christmas pile, plus the 2 I have been working on for the TR2...and on every head one or two valves are mushroomed out on the tip. I have used straight stainless on many other engines, even with pretty heavy valve springs, and have had negligible valve tip wear problems. I just wondered if the triumphs are harder on tips?

TR3driver
06-23-2014, 07:26 PM
Not likely the factory used Stellite unless they perceived a problem.

CJD
06-23-2014, 09:10 PM
Not likely the factory used Stellite unless they perceived a problem.

So, Randall, I guess you are recommending the stellites?

TR3driver
06-23-2014, 10:38 PM
So, Randall, I guess you are recommending the stellites?
I basically agree with Viv; probably not necessary for an engine that won't see long, hard usage. I'm pretty sure the oversize valves I got from BFE were just stainless, and the tips still looked OK after 10K miles or so. (Wish I could say the same for the hardened exhaust seats)

TriumphantMan
06-24-2014, 10:23 AM
(Wish I could say the same for the hardened exhaust seats)

What kind of trouble did you have with the hardened valve seats. I'm rebuilding my '63 TR4 and maybe I can avoid any trouble.
What would you have done different?

TR3driver
06-24-2014, 11:35 AM
What kind of trouble did you have with the hardened valve seats. I'm rebuilding my '63 TR4 and maybe I can avoid any trouble.
What would you have done different?

I don't really know what the problem was; but I think my mistake was using "racing" valve springs and not checking the seat pressure. Or it might have been the too-high compression ratio and not removing the sharp edges in the combustion chamber. Or even the MMT-based octane improver I used to compensate for the high compression ratio and tendency to knock. Another possibility is that the altered combustion chamber shape (from milling the head) was enough to move the mixture lean during high rpm medium throttle operation.

At any rate, those are all things that I will do differently next time. I probably should have tried running lead substitute to see if that would stop the recession, but I didn't. (I was kind of distracted with other things at the time and driving the TR was a sort of therapy to keep me going.)

Here's a shot of the modified head, after perhaps 20k miles of mostly street driving:
https://i258.photobucket.com/albums/hh260/TR3driver/TS39781LO/th_DSCF0023.jpg (https://s258.photobucket.com/user/TR3driver/media/TS39781LO/DSCF0023.jpg.html)

As you can see, the exhaust valve has extreme recession. It was so bad that I could no longer adjust the valve lash, even with shims under the rocker pedestals and shorter pushrods. The spring retainer was literally hitting against the rocker arm! Less obvious, the intake valve seat (which is still the original cast seat) has recessed a bit as well. At the time, I just threw the modified head in the corner (where it still resides) and installed an unmodified head from another motor (no other changes). It was still running fine (though not nearly as much torque & power as the high compression produced) a few years later when the car got totaled in an accident.