[Roadsters] u20 cam timing

[Tom Hendricksen]

Jon,

I had an upper chain stretch and jump a tooth in my '70 2000 sometime around
1972.  Back then I had no idea what the death rattle meant.  I think at that
time it cost me about $30 for a couple of new valves, gaskets, and timing
chains.  I can't remember if I changed any of the gears, but I remember
correctly I did change the upper tensioner because the Datsun mechanic
recommended it.

If your not pulling RPM's I think I would look somewhere else.  There have
been a few discussions about carburetion, or ignition systems that could be
doing this to you.

Tom
69 2000 - Mr. Hyde
Portland
http://www.datsun2000.com
http://www.nowroc.org


On 6/18/2010 9:25:01 AM, shas1983 at netzero.net wrote:
Does anyone have any experience with a u20 cam timing being off 1 tooth or
less? I have aligned the cam with TDC and counted chain links per the
original
service manual. The engine cranks easily and runs pretty well at lower
rpms(under 3000), but seems to loose power and not readily want to climb to
higher rpms under load at speed (free revs easily). The odd thing is I had
to
advance the distributor timing well past the std 16% to get the engine to
run
well.

When I turn the engine over and stop it on #1 TDC per the crank the lobes of
the cam on #1 appear to be silghtly advanced past 10 and 2 and the intake
vale
on #4 appears slighlty compressed more than #4 exhaust. It looks like they
are
advanced at most less than 1 full tooth (15% on 24 tooth sprocket), so I am
wondering if the combination of a resurfaced head and cam tower shims could
have changed the chain length enough to account for this?

I have an adjustable cam sprocket that I can try (+- 6 degrees), but I was
wondering if others have seen this before I change the sprocket.  I would
have
expected the engine to run far worse than it does, but I have just about
ruled
everything else out. Seems good at lower rpms but just does not pull past
3000
rpms like it used to.

Jon Carlisle