What would be the minimum valve lash measurement that can safely be used in
a racing ITB 2000 cc motor? Everything is pretty much stock, valves,
springs, retainers, followers and I will probably wind this motor until the
power tails off or 7000rpm, which ever is lower. The manual specifies .008
and .010 thousandth clearance for the intake and exhaust respectively. Of
course, I'm willing to check the clearances as often as is needed. The
motor will probably be run for about 30 minutes at a time, and I will be
using leaded gas which will reduce valve recession.
71 ITB Car report
I finally got my 71 ITB Capri back together with new/old parts, rebuilt
engine and I drove it yesterday at Sears Point Raceway to test and break the
engine in. I ran the engine at my house for a total of about 2 hours to
break the cam in and pre driving break-in. I drove the car very easily for
two 20 minute driving sessions running up to about 4500rpm 1/2 throttle. I wound it up to close to 6000rpm at full throttle later in the day and the car pulls very well.
All in all, motor is running good, car is now handling quite well although
it still oversteers in turn 2 and through the Esses (turns 8,8a) at Sears
Point. It understeers a bit through 4. I'll have to do some more testing,
I'm experimenting with tire pressures and I'm already down to 20psi cold in
the rears which significantly improved things with the BF
Goodrich R1 tires How much lower
can I go? I might try stiffening up the front sway bar (it's a slightly
ground 1 1/8") if I can't get close enough with tire pressures alone. I
shouldn't complain too much, I'm sure that the car is already fast enough to
break a couple of track records next year.
Oh, I might also mention that I installed a couple of EGT (exhaust gas
temperature gauges) on cylinders 3 and 4. If you recall on the carbed 4
cylinders, cyls 1 and 4 and fed from one side of the manifold while 2 and 3
are fed from the other side. I wanted a way to determine if one side was
running richer or leaner as compared to the other side. Adjusting the
primary or secondary main jets in the Weber carb should affect each side a
little differently.
Here is what I saw.
During my part throttle runs, I was getting higher temps in cyl 3 than cyl
4.
Cyl 3 ~1250 deg F
Cyl 4 ~1300 deg F
During my full throttle runs, I was getting significantly higher temps in
Cyl 4 than 3.
Cyl 3 ~1375+ deg F
Cyl 4 ~1450 deg F and it was still rising before I had to lift for
turn 2.
I'll have to look how my carb is orientated to see which cylinders is fed by
the primary of the carb which was fully open in both of these tests.