Lotus Elan

Weber Cold Air Box Mods.

PostPost by: ceejay » Thu Jun 30, 2011 3:40 am

The very first time I was involved with fitting the cold air box
to the Webers I came across the first cause of frustration, IE
the bolts would not readily line up with the threaded
spigots attached to the backing plate, the bolts not
having some sort of guide meant a bit of fiddling
around to find the threaded spigots as shown in Image #1:

Image #2:
So, I set about fixing this problem, first job was to machine
two small hat shape spigots from aluminium, which were
clear-drilled 1/4" ID, these were to act as bolt guides and were
aligned and fixed over the air box bolt holes with F/glass on
the inside of the air box.

Image #3:
Attention was then moved to the backing plate, four small
extra reinforcing straps made from sheet metal were brazed
to each spigot, and to the outer corners of the A/box as shown,
the idea of the straps was to spread the bolt tightening tension
load over a wider area of the air box, also, with the standard
set-up, if the bolts were ever over tightened, the sheet metal
backing plate could possibly be pulled away from the front face
of the Weber, creating a small air gap & allowing a small amount
of unfiltered air into the air box.

Most air box bolts probably wouldn?t be over tightened,
but if the gasket was not sealing properly, the temptation
to over tighten is there.

Image #4:
Provides a close up detail shot showing the alloy spigot
fixed to the inside of the air box.
The set up explained here has been a permanent feature
of the cold/cold air box system on my twink for the past
twenty-six years.

BTW, the sealing gasket also shown here on the air box is
a rocker cover gasket from the early K series
Toyota Corolla, and is almost a perfect fit.

Neither the backing plate nor the cold air box are
original items, they were both fabricated in our workshop
during the early 80s not long after I acquired the basket
case S2 elan.

CeeJay.
Attachments
1-backing-plate-webers.jpg and
2-air-box-inside.jpg and
3-backing-plate-brace.jpg and
4-bolt-guide.jpg and
ceejay
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PostPost by: gjz30075 » Thu Jun 30, 2011 11:13 am

Brilliant! Thanks for showing.

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PostPost by: gordont » Thu Jun 30, 2011 11:35 am

Col
Does the air box then have the normal tube to in front of the radiator?
Gordon
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PostPost by: ceejay » Thu Jun 30, 2011 12:00 pm

Yes, sorry did not show the extra bit, the front of the box
leads down with flexible trunking to a front mounted air
filter which was an air filter canister sourced and modified
from a Triumph 2000.

Also the air box does not taper over the full length as
the std air box does, I may be wrong when I say this,
but I think that all of the ram tubes should have equal
air space to draw from.

If you are interested, there's another story with the
ram tubes too, I also made them way back in the
eighties from some MS exhaust tubing and some
hollow bar to machine the ram tube base's, the
rams were metal spun on some dies in lathe
that I machined up.
I noticed recently in an advert that genuine weber
ram tubes made in this manner are pretty exy.
Ceejay
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Provide land to people who want to grow
things.
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PostPost by: Robbie693 » Fri Jul 01, 2011 9:21 am

Hi Ceejay,

This Mazda 323 seal for the airbox, do you know if it would fit on a Dellorto box too?

Cheers

Robbie
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PostPost by: ceejay » Fri Jul 01, 2011 9:54 am

Sorry Robie, the gasket is from the early series Toyota Corola... K series engine,
probably built in the late sixties? not sure.
If the Dellorto box is same dimension as the weber air box, then yes, probably
would fit, but you would have to check.
I've just been out to the W/shop to get the Dims of my air box.
measurements are:
360mm X109mm (14.173" X 4.291")
See how that stacks up.
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PostPost by: Robbie693 » Fri Jul 01, 2011 1:06 pm

Thanks Ceejay, I'll measure mine later. Although getting one may be difficult - I didn't realise it was from a Corolla of that vintage!

Cheers

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PostPost by: ecamiel » Sat Jul 02, 2011 1:33 pm

All good mods.
The most important mod is to change the shape of the box to allow adequate clearance around the ram tubes. It is too small, particularly at #4 cylinder. This causes rich running and loss of power. Ideal clearance is at least one diameter. I modified a cover to get clearance but someone makes them with increased clearance. Tingle used to have them but he has retired.

[
i]Also the air box does not taper over the full length as
the std air box does, I may be wrong when I say this,
but I think that all of the ram tubes should have equal
air space to draw from.[/i]


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