VALVE TIMING

[Moises]

About valve timing. At 12 degrees before TDC, the intake valve of the
No. 1 cylinder, should it open .014" (Jowett Manual pg. 21) or .013" (pg. 26). ?. I will appreciate your comments
Thanks

[Forumadmin]

Hi Moises,
This describes my way of setting valve timing using 21 thou feeler gauge method. It is easier and more accurate than using a dial gauge.
viewtopic.php?p=46717&hilit=timing#p46717

Yes it does seem the manual writer did not get a consistent answer from the shop floor. The one thou difference will make little difference to breathing as acceleration is high at that point on the lobe. It might also be that a different set up was used for different engines such as the hydraulic and solid cam follower versions. Different cam profiles also require different valve timing.

[Moises]

Very interesting. I will follow your advice. Thank you.

[Mike Allfrey]

Hi Moises in Madrid,

There is one important point related to valve timing on a Jowett Javelin engine. The 0.014-in. movement must be measured at the push rod end of the inlet valve rocker arm, not at the valve end.

The book shows a wedge inserted between the valve stem and the tip of the rocker arm. The wedge holds the push rod and tappet firmly against the heel of the cam to ensure that the actual cam ramp commences without any clearance between the cam and the tappet face while rotating the camshaft until the timing point dimension is reached on the dial indicator.

As Keith has mentioned, whether the dimension is 0.013 or 0.014-in., at that point on the cam ramp, it will not affect the engine's intake of fuel/air mixture by any noticeable amount.

This is a bit late, but . . .

Regards,

Mike A.

[Moises]

Thanks, Mike. It is never too late.
Greetings