Joe:
You will need to do some measuring to determine for sure, but I
suspect you will be fine. I recommend that you upgrade your springs to
the PI springs (available from Moss).
The only downside to higher ratio rockers (assuming you have
mechanical clearance to install them) is that they increase the wear on
the lifters and cam lobes slightly, by virtue of the increased pressure
on the lifter. If you have a situation where lifter life is marginal, it
could be a problem. In fact, I have never heard of it being an issue,
but something of this sort would really only shorten the engine life
over the long haul (Say, from 120,000 to 100,000 between rebuilds.)
Higher ratio rockers also effectively increase your overlap, giving you
a rougher idle but they also give you more power by virtue of the higher
lift, and because the valve overlap effectively increases.
If you are going for a cam longer than say 270 degrees, and/or
your lobe center spacing is less than say 110 degrees, you might want to
reassemble your motor with stock rockers first, then see if you want
more and don't mind a bit rougher idle and lowered fuel economy. Bear in
mind that the higher ratio rockers are a fairly modest change, and one
that is easily added later, or removed if you don't like the results.
As a calibration point, I installed a 278/288 degree cam (112
degree LS angle) in my 350 Chevy with 1.6 rockers. I ended up going back
to the stock 1.5 rockers to smooth the idle and get back some low end
torque. The cam was beastly enough that I didn't like driving it in
traffic, and changing back to a stock ratio rocker made a very
pronounced difference. How noticeable a difference it makes to
drivability depends on a host of factors, but foremost the cam specs.
Cheers,
Vance
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Lizirbydavis@cs.com
Sent: Sunday, November 21, 2004 6:44 PM
To: 6pack@autox.team.net
Subject: 1.65 roller rockers
Has anyone had any problems with valve clearance or stock double springs
binding using a GP2 cam with 1.65 roller rockers? My head is about
9.5:1 Is
there any significant performance advantage with the 1.65 vs. the 1.55
ratio
rockers. Is there a reason to avoid the greater ratio? (i'll have cam
bearings
installed if I choose to go this route)
Joe Davis
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