Lotus Elan

Sprint Airbox bolts

PostPost by: silverlink » Thu Jul 23, 2020 11:34 am

Does anyone know the size of the three bolts that holds the airbox to the backing plate on my 71 Sprint, if it helps its on Webers. Each one is of a different length.
Thanks
Ian
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PostPost by: 512BB » Thu Jul 23, 2020 1:24 pm

They are 1/4 UNF Ian. Or is it the length of the bolts you are after?

Leslie
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PostPost by: lotusfan » Thu Jul 23, 2020 3:16 pm

I always found it very difficult to line the bolts up with the tapped pillars on the back plate so I fitted some 1/4 UNF studding in the pillars, locked in place with a nut and then fitted the airbox cover much more easily. Retained the cover with a washer and nyloc nut.
Mike
72 Sprint DHC
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PostPost by: mbell » Thu Jul 23, 2020 5:46 pm

I did something similar to Mike. I made up some 1/4" studs out of 1/4" aluminum rod and secure the box with metal+rubber washer and nylon wing nuts. It a little tight to get the box on over the studs and past the top of the pedal box on +2 much much quicker/easier than getting the bolts into their holes.

I don't remember the bolt lengths but if you size them the right length for the depth of the airbox they should be about right, as the post on the back plate protude ~1/2" past the seal face.
'73 +2 130/5 RHD, now on the road and very slowly rolling though a "restoration"
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PostPost by: silverlink » Thu Jul 23, 2020 6:39 pm

Thanks all,
I like the idea of studding the pillars I'd not thought of that and yes Mike you're quite right in that its difficult to line up the bolts. I'll have a look for some rodding and have a go.
Thanks
Ian
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PostPost by: sprintsoft » Sat Jul 25, 2020 11:21 pm

Hi Ian,

I was in the garage this evening and remembered your post, I measured the 3 air box bolts on my Sprint (Webers) :

55 / 48 / 42mm

measured from top of the bolt head to end of the thread.

Deduct 4-5mm if you don’t want the head included.

For what it’s worth I don’t have a problem getting the bolts started, I tilt the box slightly so it’s just open along the top and I can see each bolt to line it up.

Iain
72 Sprint - 0363E
74 S130/5 - 1931L
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PostPost by: pharriso » Sun Jul 26, 2020 4:32 pm

My bolts are off....

All 3 bolts are 1/4 UNF, 1 1/4", 1 1/2" & 2" long, threaded for last 3/4"
Airbox_bolts.jpg and

Ideally the centre one would be 1 5/8" long.
Phil Harrison
1972 Elan Sprint 0260K
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