I seem to recall that the forged pistons expand more than the cast
pistons (why, I don't know). Thus, they need a larger clearance to allow
them to expand without cracking the block or seizing, or whatever.
On another note, I finally managed to set the decelleration-bypass
valves on my TR7 carbs (twin Strombergs). I did use the method outlined in
the Bentley manual, and it did work. One thing they didn't mention, of course,
is that everything must be correct, or at least very close (mixtures, idle
speed, timing, etc.). Seems kinda obvious, though, in retrospect. One other
thing to note about this procedure, though. I don't know how it is in other
books, but in the section pertaining to me (US twin carbs), the description
of the procedure is poorly done. The procedure is much as follows:
1) gradually screw in (clockwise) the decel/bypass adjusting screw on the rear
carb until the engine revs begin to increase (of course, it may be necessary
to unscrew it, and maybe bump up your idle speed, first)
2) unscrew (anti-clockwise) the screw two full turns (fun with the engine
running and the air cleaner in place ;)
3) at this point the manual says "Repeat procedure 1 on the front carb"
however, they are not numbered like I have numbered them; rather, they start
at 54 (because this is part of the tuning section). Thus the question is,
what is procedure one? Answer: as I have numbered it here. Then, if I recall
correctly, you unscrew the front adjusting screw one turn (just follow the
book from here).
If you can't get your Stromberg(s) to idle properly, or you have little
to no power at low end, try adjusting these. It makes a BIG difference!
Vaughan Scott Rensselaer Polytechnic Institute
scottv@rpi.edu Troy, NY
'76 TR7 (can you say NO CAT!) - racing this weekend
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