A hot cam adds power by optimizing breathing usually at higher rpm where the
engine puts out it's most HP. Longer duration means that the valves are open
longer allowing for more air to move. Overlap means that the exhaust and
intake are open at the same time allowing for a flushing out of the exhaust
fumes. When combined with a good exhaust header, the scavenging can ad a bit
of HP. Increasing the valve lift and the rate at which the valves open (lobe
shape) can also increase performance. All of this is usually at the expense
of low end torque and reliability. The power curve gets narrower and peaks
at a higher rpm. An overlap that produces a lot of power at 5500 can cause a
lumpy idle. Unless you rev your engine a bit during normal driving I think
that you would be disappointed with the less than stellar low end
performance and unaware of the high rpm improvements. There's a lot to be
said for keeping stock. You wont have to worry about the possibility of
degreeing in your cam, dealing with offset keys and the possibility of
having to buy a $100 adjustable cam sprocket to properly degree in the cam.
Stay away from regrinds, I hear they wear quickly. A very mild cam can
increase your performance in a more usable rpm range without the lumpy idle
of the fast street cams. Another thing to think about is that an engine with
a free flow exhaust and big carb and high compression will benefit more from
the cam than a totally stock setup with a restricted induction and exhaust
system. A good cam can complement other performance enhancements but I don'
t think that you're going to notice any "kick in the pants" increases in
performance especially because your not replacing a late model emissions
cam. Kent makes a lot of cams. Try to get their presales number and they can
help you pick a cam.
If you want a little more oomph at low to middle, try using K&N air filters
and install a free flow exhaust header and muffler. And remember that with a
new cam, stock or Kent, you should notice an improvement in HP from the last
time you drove it because your old cam was shot.
Chris Reichle
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From: mgs-owner
To: mgs
Subject: MGB camshaft selection
Date: Sunday,January 26,1997 10:13PM
The time has come in my engine rebuilding process to select a new
camshaft (the original shaft has several lobes/lifters badly pitted and
one lobe worn down ~ .030). I'd like to solicit opinions from the list
on which cam would be best suited for my purposes.
Some background: I'm currently in the process of a full engine rebuild
(usual rings/bearings/valve job; nothing exotic) on my 70 MGB. I'll be
using standard SU's/aircleaners and stock exhaust. I'm tempted to just
replace it with another stock cam, but if I can get a little more hp by
going up a step in camshaft, I will. I'd like to retain a fairly normal
idle, but would like a little more oomph, preferably in the low to mid
range. The car won't be raced or autocrossed, just your usual daily
driver.
I've been looking at the Kent 714 Mild Road cam (same spec's as the
Special Tuning 714 Fast Road cam) as a possible replacement and was
wondering if anyone has used this cam in a stock setup and would care to
comment?
Spec's according to Burgess' "Power Tune..." are:
Duration Valve Lift Overlap Timing In
Ex
STOCK 252 .361 37
16/56
51/21
Kent 714 270 .358 56
26/65
60/30
Special Tuning 268 .358 53
24/64
59/29
Fast Road 714
Burgess' comments on the Kent 714 are less than flattering: "A mild road
cam that's only good for high revs - doesn't seem to deliver anything!".
But I have a feeling he's looking more towards gaining more hp from some
serious power tuning with a more radical camshaft and pretty much
dismisses the less milder camshafts as usless.
Comments and suggestions welcome...
Jeff
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