At 10:25 AM 5/10/2000 -0400, McCarroll Edwin wrote:
>.... improving the acceleration/overall response for the MGA:
> 1. Install Judson suoercharger (how much should be paid for one?)
Advertising clains of 50% increase in power are greatly exagerated. You
would get more low end torque, only a small increase in top end torque,
worse fuel consumption, more noise, great sex appeal, and a much flatter
wallet. Used kits needing some repair and often missing a few parts can
sometimes be had for about $500. Complete kits in good condition would be
$1000 and up. Professionally rebuilt units with a warrantee are about
$1500 (when they are available).
> 2. Replace current sponge filters with K&Ns . Are there K&Ns that will
insert easily into the holders or do you reolace the two filter units
entirely?
I just did this, initially on a trial basis to see if it would work. I
personally don't like chrome under the bonnet of my MGA, but I dearly
wanted to fit up K&N air filters. Kelvin Dodd from Moss Motors volunteered
a K&N filter insert from the swap bin for the trial fitting. It turned out
not to be particularly difficult. This filter element came from the
"222-935 Chrome Filter for 1-1/2" SU carbs 1-3/4" deep".
Start by removing everything inside the original MGA filter housing. The
K&N element will just fit inside of the surrounding expanded metal screen
with some firm encouragment by hand. The central standoff spacers and the
surrounding screen are a bit too tall for the height of the K&N filter, so
they need to be shortened to a height just a tad less than the thickness of
the filter element so it fits snug on the seal surfaces. A bench grinder
makes quick work of shortening both the side screen and the central
standoffs. Keep measuring the height of the parts with a caliper as you
go, ending at about 0.020" less than the filter thickness. All of that
should take less than five minutes at the grinder. Then run a tap down the
holes in the standoffs to make the threads a little deeper so the cover
bolts don't bottom out on the tips of the threads, and finish with
deburring the parts and a fresh coat of paint.
The finished result is a near stock appearance for the filter installation
with nice K&Ns hiding inside. The small reduction of thickness of the
assembly (about 3/32") is not noticeable (unless you point it out to
someone). Now if I can just get Kelvin to dig up another K&N filter
element I could get back to the gravel roads again. I think Kelvin is
trying to source and get a stock number assigned to the replacement filter
element, in which case MGA owners will have available the K&N option
without the gaudy appearance of chrome fittings. So how ya doin Kelvin?
>3. Re-do the head with step grinds and go to bigger valves?
For the 1500 and 1600 engine you can use the MGA 1600 MK-II "16" head or
the early MGB "18" head. These already have 1/16" larger valves and
slightly better porting than the "15" head. The "16" and "18" heads are
nearly identical except for the shape of the Westlake promentory in the
compustion chamber (the heart shape protrusion between the valves). The
combustion chamber is larger than with the "15" head, as it intended to be
used with flat top pistons in the 1622 engines or with the larger
displacement of the 1800 engines. Reducing the chamber volume to be
similar to the "15" head requires milling about 0.045" from the bottom
surface. The "18" heads are more readily available and somewhat cheaper
than the "15" or "16" heads.
You can also use the "L" head from the 1972-1974 MGB. This has intake
valves 1/16" larger yet and even better porting for better breathing, but
it also has air injection ports (at least the US version) that can be
plugged but may be objectionable on the MGA. Watch out for a different
location of the oil feed hole under the rear rocker pedestal.
For a nice improvement in zip for a street engine I can personally
recommend the Crane "Mechanical lifter camshaft for non-emissions
controlled vehicles". This is NOT the factory blueprint cam but a mild
upgrade for street use, giving some torque increase while maintaining an
acceptably smooth idle. Moss sells this one as "222-270 Camshaft, high
performance". Be aware that this cam wants to be installed with a 5 degree
timing advance at the cam, so some offset key or adjustable cam sprocket is
required to optimize performance.
With stock cam and rockers you can get away with shaving the head up to
1/16". With a head not shaved more than .010" for cleanup you can get away
with the increased lift of the mild street cam. for more lift or more
shaving or some combination of both you will need to add eyebrows in the
top of the block for adequate clearance for the valve heads. Check here
for more information:
http://www.ntsource.com/~barneymg/mgtech/engine/en1.htm
I would not recommend building a full race engine for street use, and if
you're inclined to ask, that would be beyond my area of expertice.
Barney Gaylord
1958 MGA with an attitude
http://www.ntsource.com/~barneymg
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