Nick,
When I was replying to Ryan's question the idea of suggesting any
modification to the cam timing from stock was not appropriate as I didn't
have any information on which cam he was using and what other modifications
are done to the engine so I took the safe route as I always try to do.
Dialling in or degreeing a cam is a fairly complex science that you have to
know exactly what you're doing and base your decisions and compromises on
the application of the cam. You can do this by trial and error but I prefer
to plot the cam specs to know exactly what I am doing. There are a few
little known things these days about a stock L series factory cam and chain.
The standard guides and adjuster are far different to the Nismo variety
which are far better designed to cope with modified cams and timing. On L
series production engines, "degreeing" is built into the production cams in
the factory and this is usually the case from the aftermarket cams as well.
You can tell by how much from the stamping on the end of the factory cam. eg
B2 has 2 degrees advance over a B, but it was never the intension to use the
standard sprockets to degree the cam on the standard engine. OK, we do it
but I'm saying you have to have a chain and guides that are in perfect
condition to use position 3 safely, otherwise when the chain catches the
long guide on overrun whole thing turns to scrap very quickly. I've found
that there are no problems with using position 2 and it actually works quite
well with a solid letter cam eg C on a L20B will give you 4 degrees advance,
this even gives very good results with 2xSU's but much better with big
2xDCOE's 50mm and above, pretty flames on gear changes on avgas too.
The Nismo adjustable wheel that goes to 9 degrees was designed to cope with
the various combination of cams that were offered back in the 70's. Some of
these cams even had static retard as the lobe separation was above 110
degrees on a typical 270 degree cam so you could tune the cam for more top
end performance if that was appropriate, i.e. good for dirt racing. Also
fuel consumption is an issue with a production engine, so if you advance
your timing by 4 or even 8 degrees for mid range performance but as the
amount of new charge is pushed out of the exhaust increases then the
efficiency of the engine naturally will suffer. Most good manufacturers will
recommend a centreline point of their products for this reason.
regards
Terry
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of abrahamk
Sent: Tuesday, 10 October 2000 9:13 PM
To: [EMAIL PROTECTED]
Subject: Re: Cam Question -Terry (long)
Terry,
I have just set my cam up on the 3rd setting, 8 degrees advanced (in
theory...not taking into account milled-down head and chain stretch)
Why shouldn't you run the cam this far advanced?
The NISMO option cam sprocket goes to 9 degrees advanced and 12 degrees
retarded, and the works engines use stock timing gear and tensioner.
Unfortunately I don't have a dial gauge to find out exactly how much advance
I am running, but I thought is would be a pretty common modification to get
extra mid-range grunt out of the L-series engine
I haven't run the engine yet, it is due to go in very soon though...
Regards,
Nick
P.S I found a cam-sprocket on a very stock looking 200b at a U-pull type
place . It has about 10 machined holes instead of the standard 4 cast-in
ovals. It looked 'all shiny' so I took it home.
It turned out to be about 10 or 20 grammes lighter than the stock one, and
looks like a quality item, so I used it.
What is it, where is it from originally? Any ideas?
----- Original Message -----
From: Terry Rudd <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, October 09, 2000 11:00 PM
Subject: RE: Cam Question -Terry (long)
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