Larry:
So long as you are not floating valves, and are staying within the
stock rev limits, then the stock springs are fine.
Valve springs are like anything else. You want them just heavy
enough to do what they are supposed to, close valves after they have been
bumped open.
Any heavier and they cause excessive drag and loading on the cam
reducing the life of the valve train.
If you run a higher lift cam, or use higher revs, then the valve
springs will need to be uprated. In these circumstances the demand on the
springs is higher than the manufacturer intended, and thus they will need to
be uprated over stock.
One thing that you can do is go to lighter alloy valve caps. This
is a case where you will be reducing valve train momentum by throwing
lighter more expensive materials at the engine. This is a positive thing
with no performance drawbacks.
I'd recomend making minor modifications where you are spending more
money or time than the factory could afford to. Minor head cleanup (not
massive porting, which reduces low end torque), manifold port matching,
smoothing and lightening of components, precise timing, balancing, accurate
timing and fuel adjustment etc.
Changing things like cam shafts, compression ratios, valve springs,
flywheel weight etc. all tend to make the engine less flexible, and less
usable as transportation. KISS will tend to get you more enjoyment out of
the car than throwing on expensive performance bits that may not be matched
to your driving needs.
Using a dyno is an excellent idea. I'm hoping to be able to do that
once I get my beastie back together.
BTW. My vintage race MGB is a perfect example of what not to do. I
have a very hot engine that was built by someone who knew what he was doing.
I dropped it in my car and bolted up a distributor and Weber DCOE carb. The
performance is disapointing. What I need to do is spend a chunk of time
making sure that the carb and distributor are doing what the engine wants.
If I don't do that, the engine is not going to work correctly and something
bad will probably happen. Gee maybe that's why I just had the head gasket
fail?
So when you find a good dyno, let me know huh.
Kelvin.
> -----Original Message-----
> From: Larry Colen [mailto:lrcar@red4est.com]
> Sent: Tuesday, August 01, 2000 12:54 AM
> To: british-cars@autox.team.net; mgs@autox.team.net
> Subject: Re: Race prepping, shock valves
>
>
> I want to thank everyone for the various answers that I've
> been getting
> to my questions. Since I'm only planning on entering my MGB
> in one race,
> rather than campaigning it, I don't want to throw too much
> money at the
> project and I really appreciate the reminders of keeping my
> improvements
> in balance with one another. Since the car has stock spring rates and
> slightly uprated bars (the Hopkinson kit from Seven), I think
> that I'll
> forego throwing money at the suspension. She actually handles rather
> nicely and very predictably. It's my gut level feeling that she could
> use with a little more damping, but I'm probably more likely to make
> her handle worse than better if I go mucking about.
>
> Oldtimers from the list might remember that back in '89-'93 I
> campaigned
> a Ford Cortina (early '68 MkII GT) in SCCA ITC. On a couple
> of occasions
> I took her up to Oregon for the fourth of July double
> regionals. While
> I was there I entered the Conference Production I class and
> my closest
> competion (i.e. the other car in the class) was Bill Thew in
> his MGBGT.
> This is the very same MGB that the Olsens will be driving at
> Thunderhill,
> so I've got some history with that car motivating me to want
> to at least
> be able to keep it in sight for a few laps of the race.
>
> Some more race prep questions:
>
> Reccomendations for valve springs? The cam has stock lift and
> duration,
> and I'm not planning on revving the engine very high. I've
> been warned
> against running over 5500 RPM for any length of time without a cross
> drilled crank. I'll take her up to 6000 or so for brief periods to
> save the stress of multiple shifts. Other than that, the engine is
> basically blueprinted, balanced, nitrided, forged pistons. Solid, but
> not set up for SCCA E Production.
>
> Reccomendations for a dyno tuner? I used to have Charlie
> Rockwell tune my
> racecar, but he closed up shop a few years ago. I definitely
> found the
> value of having someone knowledgable dyno tune the car. I
> usually saw at
> least a 5hp gain. I hear that Frey Racing sold their dyno to
> the Mustang
> Ranch.
>
> Larry
>
>
> --
> I want to have profound thoughts and have other people
> implement them.- T. Bird
> lrc@red4est.com
> http://www.red4est.com/lrc
>
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