On Wed, 25 Nov 1998 03:13:13 -0500 Trevor Boicey <tboicey@brit.ca>
writes:
>Rick Morrison wrote:
>> ANYTIME you up the HP output on ANY engine, it needs to be
>strengthened.
>
> I don't think this is universally true on a couple of
>levels.
>
> First of all, it should be cut with the line that it needs only
>to be strengthened if longevity is a concern. Most engines will
>survive well about their rated specs, at least for a race or two.
Like I said. If you don't mind a hand grenade looking for a place to go
off.
The racers I tend to go around with don't have the mega bucks budgets to
build engines to explode. Longevity to us is at least one season. There
are a couple of guys I can name who do have more than one spare engine.
But even they don't look to waste them.
Granted, the NASCAR boys and the F1 teams can afford to go through
engines like Sherman through Atlanta, but in the real world, it just
ain't so.
> As well, it has to be said that the possibility always exists
>that an engine is overbuilt. I am not suggesting any models,
>but it is quite likely that many engines out there are overbuilt
>and could happily deliver 50% more horsepower or better. Probably
>less likely in modern computer designed engines where every
>component can be caracterized, but likely true.
Just because an engine is overbuilt, is no excuse to reduce the
reliability just to avoid a little work and expense.
There is always a safety margin in any design. Modern engines probably
have less because of the increased technological ability to predict
stresses, etc. Older engine have more, cause of the fudge factor. (If in
doubt, make it stronger)
Besides, in the case here (MGB engines), we are talking about engines
that are 20+ years old. They ain't exactly as strong as they once were!
> I would actually predict that our LBC engines have a good
>chance of falling in this category. For example, it's a fact
>that MG's monocoques (such as the MGB and especially the Z Magnettes)
>are EXTREMELY overbuilt. At the time, monocoque was not fully
>caracterizable in CAD like it can be today, and many designs
>erred on the side of caution.
Body, having nothing to do with engine design, I'll pass on this.
>> For a street engine, reliablility should
>> be foremost in the builders mind.
>
> Not foremost, but certainly a consideration. REASONABLE
>reliability being the key.
I would say foremost if the car is to see any kind of regular use. And
that's what they were built for, both originally and subsequntly.
Reasonable is a relative term. If you only drive your car 5000 miles a
year, then a
20,000 mile engine is reliable. But if (like me) put 12-15,000 per on the
car, then the same engine IS NOT reasonable.
> I have a sort-of-wild MGB with aeroscreens and fiberglass
>panels and some tuning and so on. It's a load of fun but
>because of the practicality I seem to be lucky to get 2000
>miles a year. (I have other MGs to choose from and if the
>wife gets a vote it's always the Midget 1500)
I have a built Midget which dyno'ed more HP than my B is rated. Granted
that was with only about 2500 miles on the build job, after having been
"run in". I doubt it would pull that much today. You see, the engine is a
bit over 9 years old and has 110,000 miles since the rebuild. But, it's
still faster than the B
At the time, I used all the things I suggested in my original post. It
cost me a bit more initially, and took about half again as much time to
do it right, but the fact it is still going and reliable says that I got
a bargin.
> A B engine might get 100,000 miles typically. If I
>built it hot and could still get 20,000 miles between
>rebuilds, that might be worthwhile for me. I'd get more
>smiles out of the car and still only need an engine
>once a decade.
See the above paragraph.
Rick Morrison
72 MGBGT
74 Midget
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