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A leaking test on my TR6 engine is showing a leaking exhaust valve on cyl n=
o 1 (48% on the gauge of the device) and a leaking inlet valve on cyl no 2 =
(75%). Compression on cyl no1 is 9.5 bar and on cyl 2 it is 8 bar. The comp=
ression on the other cylinders is between 12 and 13.5 bar. This is with a r=
ace cam with a valve overlap of 110=C2=B0 (320-F grind). Because of the hig=
h overlap, the piston has risen a lot before the inlet valve is closed, so =
I did the compression test again, but with a valve lash of 2.5mm/0.1" : com=
pression went from 9.5 bar to 14.5 on cyl no 1 and from 8 bar to 15 on cyl =
no 2. With this valve lash, the compression on the other cylinders went up =
to 16 - 18.5 bar. Of course, when the engine is running at high rpm, a lot =
of valve overlap is necessary for best cylinder filling, but I wonder if 11=
0=C2=B0 isn't too much?? The recommended valve lash is 0.40mm/0.016" when t=
he rocker ratio is 1.45(0.43mm/ with my 1.55 roller rockers). Would it be r=
isky to set the valve lash at some 0.05mm/0.002" higher?=20
PS : is it common practice to set the valve lash at a couple of mm to perfo=
rm a compression test, because it seems that the valve lash has a lot of in=
fluence on the result when testing a race camshaft?=20
Marcel=20
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<html><body><div style=3D"font-family: Verdana, Arial, Helvetica, sans-seri=
f; font-size: 10pt; color: #000000"><div>A leaking test on my TR6 engine is=
showing a leaking exhaust valve on cyl no 1 (48% on the gauge of the devic=
e) and a leaking inlet valve on cyl no 2 (75%). Compression on cyl no1 is 9=
.5 bar and on cyl 2 it is 8 bar. The compression on the other cylinders is =
between 12 and 13.5 bar. This is with a race cam with a valve overlap of 11=
0=C2=B0 (320-F grind). Because of the high overlap, the piston has risen a =
lot before the inlet valve is closed, so I did the compression test again, =
but with a valve lash of 2.5mm/0.1" : compression went from 9.5 bar to 14.5=
on cyl no 1 and from 8 bar to 15 on cyl no 2. With this valve lash, the co=
mpression on the other cylinders went up to 16 - 18.5 bar. Of course, when =
the engine is running at high rpm, a lot of valve overlap is necessary for =
best cylinder filling, but I wonder if 110=C2=B0 isn't too much?? The recom=
mended valve lash is 0.40mm/0.016" when the rocker ratio is 1.45(0.43mm/ wi=
th my 1.55 roller rockers). Would it be risky to set the valve lash at some=
0.05mm/0.002" higher?</div><div>PS : is it common practice to set the valv=
e lash at a couple of mm to perform a compression test, because it seems th=
at the valve lash has a lot of influence on the result when testing a race =
camshaft?</div><div>Marcel</div></div></body></html>
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