Engine mount type for Spyder stressed skin chassis

PostPost by: lowflyer » Wed Nov 11, 2020 2:23 pm

Apologies if there is a categorical answer to my question, but I've not found it yet after a lot of searching.

The engine on my Elan S4 has a slight tilt downwards on the carb side and as a consequence the airbox clearance is tight and it can rattle against the footwell sometimes. A quick visual inspection of engine mounts doesn't reveal anything too bad, just a little more shearing of the rubber than I'd like so I thought I'd replace the carb side mount anyway.

tilt.jpg and
Slight carb side tilt


The car has a Spyder stressed skin type subframe, not a space frame. It has the circular section front cross member but might be a rejigged original, not sure and there is nothing in the car's history file about it.

The stressed skin unit does not have the asymmetric engine mount brackets of the spaceframe which I'm aware use the same exhaust side (curved) mounts upside down on both sides. Mine has 'curved' mounts in the original "U-at-the-top" orientation on both sides.

exhaust-side-mount.jpg and
exhaust side mount


The tilt is either due to the mount sagging or having the wrong mount.

My question is, should this chassis type have:
a) the curved exhaust side engine mount on both sides?
b) the higher lift engine mount on the carb side like the original Lotus?
c) something entirely different? :)

Thanks!

Andy
Elan Coupe 36/5245
Instagram: @sidney_the_elan
https://www.thingiverse.com/andy_makes_spares/designs
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PostPost by: mbell » Wed Nov 11, 2020 8:42 pm

I think b). You still need the high lift mount.
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PostPost by: oldelanman » Thu Nov 12, 2020 7:13 am

I have a Spyder stressed skin chassis and it uses the same engine mounting arrangement as the Lotus original.
The high lift carb side mount is only used on Elans with Weber/Dellorto carbs not with Stromberg engines which you appear to have, they use the same Ford mount on both sides. The engine should sit level left to right.

The rear carb jet cover is very close to the top of the footbox and contact under acceleration is not unusual ... a sagging engine mount will make this more likely. Some folks slot the engine mount bolt holes to raise the engine slightly or reshaping the top of the footbox to provide more clearance is another solution.
Roger
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PostPost by: Bigbaldybloke » Thu Nov 12, 2020 7:57 pm

On my Plus 2 with a Spyder stressed skin replacement chassis and Weber carbs I needed the high lift mount on the carb side, it lifts the air box about 1/4” or so compared with the standard mount.
Attachments
425EB686-0BB8-41A9-8707-E7320EA6AE15.jpeg and
With high lift mount
0104B5BC-352F-4BF1-88A3-105D7F70D69E.jpeg and
With standard mount
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PostPost by: lowflyer » Sun Nov 15, 2020 1:07 pm

Thank you everyone for your comments.

I can now confirm, as Roger stated, that the Spyder stress skin chassis uses the same engine mount configurations as the original Lotus. So in my case running Strombergs I needed the same (exhaust side) brackets on both sides.

I thought the last mount had sheared "a bit" but after removing and comparing with the new one it was 12mm lower.

mount.JPG and
New Vs Old Mount


The result after replacement is plenty of clearance between the carbs and footwell. The bonnet even fits without fouling the carbs which was a bonus too!

Andy
Elan Coupe 36/5245
Instagram: @sidney_the_elan
https://www.thingiverse.com/andy_makes_spares/designs
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