I think the big question is what are you really trying to do and what
kind of power changes do you expect. An engine is a system. Change one
thing and it affects the rest of the system.
Instead of giving Moss all your cash for a Peco, here's a way to get
about 10% more power (and maybe even more) and a good feeling about your
car for almost no money.
1. Tune up your engine, make sure the distributor vacuum advance works
right, change the points, cap and rotor, plugs and wires. Time the
engine and get it running smoothly.
2. Properly set up your SUs. Look at Roger Garnett's information on
the tech page on Team.Net on tuning SUs. Do that, drive the car, tweak
a little, drive the car, tweak again and then drink a beer.
3. Adjust your valves and do a precise job of it. You'd be surprised
what this will do!
4. Change the air cleaner elements to new ones, K&N or otherwise.
5. Change your oil, flush the cooling system and refill with the proper
mix of coolant and distilled water.
OK, not enough improvement? Then you need to start looking at other
mods, but first understand what the net effect may be. Beware of
catalog horsepower figures, they're usually BS. Whatever power you do
get, you'll likely sacrifice bottom-end for a more peaky engine. This
does not make your car better. I'll agree that the shorty stacks used
with stock boxes and a somewhat less-restrictive exhaust will help all
the way around.
Beyond that, start looking at cams -- and higher compression pistons if
you have a low compression engine. But, stock MG cams are pretty good
and have good bottom end.
BTW, one reason the stock air boxes work well is that they balance the
intake pulses to each carburetor. You may want to stick with these.
YMMV, just my 2 cents.
Cheers,
Andy
DANIEL RAY wrote:
>
> Let's try that again..
> ----------
> From: DANIEL RAY
> Sent: Monday, January 19, 1998 10:59 AM
> To: 'michael j robson'
> Subject: RE: aftermarket air-cleaner assemblies
>
> Ok, well, pardon my total confusion after seeing this go back and forth.
> I had planned on eventually putting on K&N filters and a Peco exhaust (not
>the header but just pipes). Is this a wast of time and money with a stock
>engine? My stock filters are in good shape, but the exhaust needs
>replacement. I just wanna do the right thing, if this "increased hp" thing is
>a myth, than I might as well just stay with the way it was put together in
>jolly ol' England!
> Thanks
> Dan
> '73 B
>
> ----------
> From: michael j robson
> Sent: Sunday, January 18, 1998 7:46 PM
> To: gofastmg@juno.com
> Cc: tboicey@brit.ca; mgs@autox.team.net
> Subject: Re: aftermarket air-cleaner assemblies
>
> On Sun, 18 Jan 1998 17:37:40 EST gofastmg@juno.com (Rick Morrison)
> writes:
> >
> >On Sat, 17 Jan 1998 23:36:59 -0500 Trevor Boicey <tboicey@brit.ca>
> >writes:
> >> I'm not sure I would agree with this.
>
> >> Obviously, improvement to both systems is important. The best
> >>triple webers will not really pay off with a stock exhaust
> >>and stock cat.
> >>
> >> However, I can't see how the intake and exhaust could be
> >>so tied. They aren't part of the same system, like the cat
> >>and the muffler which can be matched for best performance. As
> >>well, they don't handle the same air flow anyways, since a lot
> >>more gas comes out of the exhaust than is drawn into
> >>the intake.
> >>
> > Honeymoon's over Trevor, I'll dis agree with you here
> > The exhaust and intake are so tied. Simply put, what goes in, must
> >come out.
> > If you increase the intake volume (increase volumetric effeciencey),
> >and nothing to the exhaust, the resulting intake charge will be
> >contaminated with burnt gases that cannot exit the chamber due to
> >higher exhaust pressures.
> > Result - little or no increase in performance, and possibly a
> >decrease.
> > (Remember that exhaust back pressure increases with RPM, but in a
> >non-linear maner - ie, the slope of the graph curves upward.)
> > Now, haveing said that, a little disclaimer. On an MGB the exhaust
> >is, in stock form, superior to the intake in flow characteristics. So
> >a marginal improvement to the intake side will generally result in a
> >performance increase (assuming a well thought out and viable
> >improvement), even with no exhaust modification. But a point of
> >dimishing returns quickly sets in where continued intake improvements
> >soon overwhelm the stock system ability to cope.
> > At this point, an exhaust upgrage is in order.
> > When planning induction improvements, one is forced to consider the
> >effect of the intake changes on the exhaust flow, if the objective is
> >to maximize the result of the improvement.
> >Rick Morrison
> >72 MGBGT
> >74 Midget
> >
> Guess we learned at the same school Rick- and in my experience the
> theory is borne out - Skips original point was that the carbs are
> basically too small but having tried all sorts of combinations its still
> a question of balance (obligatory Moody Blues ref)
>
> mike robson
> 69 roadster (stock filters and exhaust, had stock filters performance
> exhaust)
> 70 BGT (K+N filters Monza exhaust)
> 72 roadster (pancake filters and a bloody great stainless steel pipe with
> no box!)
--
Andy Ramm
A silver face in a tweed world.
Remove obvious spam filter from email address when replying.
"What we play is the blues, straight from the delta, and I believe we'll
make it on that," B.B. King
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