272, 276 cams

[Bruce Bell]

Check the archives for " Schrick 272 camshaft review - Updated (long)"
Lots of information there. 

Overlap refers to intake and exhaust valves open at same time. As this
gets bigger the power band moves up in the rpm range. 

Lift is how high the valves open. This is good for gains throughout the
rpm range; however, it is usually difficult to increase lift without
increasing the overlap.

Advance could refer to either ignition timing or Cam timing. Cam advance
opens the valves earlier in the cycle. Advancing the cam can help a poor
idle caused by a radical cam - what you gain on the bottom is lost on
the top end. Dyno tests with advanced and retarded cams done by
tectonics in the 80's indicate the power differences gained or lost is
quite minimal and only at the tails of the power curve. 

Keep in mind that there are no "radical" cams for CIS because they would
upset the air metering plate.

For those running exaggerated ignition timing, test a third gear run
with a stopwatch you may just find as I did that factory settings are
pretty hard to beat. Those with a knock sensor may gain a bit going to
12 or so degrees initial advance. Keep in mind that these motors don't
generally like more that 36 degrees total advance. To do it right you
need to change the advance curve in your distributor. 

The Schrick 272 is very smooth even at Colorado elevations where I live
and drive. I have no knowledge or experience with copies of the Schrick
made by other companies. I wonder if they maintain the 110 deg lobe
centers?

I always ran regular unleaded in the 4kq. Cams, in themselves, don't
demand more octane.

Bruce
'84 Urq 50K
'87 4kq 300+k
'89 200tq
'95.5 S6 RS2'd
'98 A4 2.8 Q


-----Original Message-----
From: Tessie McMillan [mailto:tessmc at drizzle.com] 
Sent: Friday, July 16, 2004 10:29 AM
To: CS_Rally; jeg1976 at yahoo.com; j.d.larson at verizon.net; Hoffman Anthony
J A1C 552 CMS/MXMVC; Bluemaxww1 at aol.com; Alan Pritchard
Cc: quattro at audifans.com
Subject: Re: 272, 276 cams 

OK, so you remind me I had another dumb question. Pardon my technical 
inexpertise, but what is "overlap", and what is "advance"? I'm guessing 
at least the latter might be related to timing, but I don't really know.


If I put in a .... higher lift, right? ... cam, what am I doing to
improve 
the performance? Do I take more advantage of combustion/compression in
the 
pistons, and why? Would I need to run a specific octane gas? 

Tess

On Fri, 16 Jul 2004, CS_Rally (Carlos) wrote:

> I have a 272 installed in a modified NF code engine that I'm about to
go
> through inspection and I'm also curious to see the results.
> As Jim's car, mine is not exactly a standard NA car, but it might be
close
> to your case. BTW, I'm running 30 degrees of advance with no idle
control.
> I also have collecting dust in my garage a 276 that I plan to install
after
> the smog test.