Brass Nut Manifold & Down-pipe 5/16" UNF. (Sold as a Set of 6) GHF261-SetA

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Manifold & Down-pipe Brass Nut. 5/16" UNF.  (Sold as a Set of 6)   GHF261-SetA

Brass nut 5/16" UNF standard length for exhaust manifold or combined inlet/exhaust manifolds:

Sold as a Set of six Brass Nuts

Brass nuts on the manifold head pipes minimizes the possibility that the head pipe nut (s) will come loose. The brass nuts expand/contract at a different rate than steel, therefore they are more stable. Regular brass exhaust nuts are thicker than steel, by approximately 1/8", therefore they get a better purchase on the stud.
Good brass exhaust nuts are very hard to find.

It is OK to use Steel washers with the Brass Manifold Nuts

Triumph & Austin Rover  Part numbers 515369  / 10M308 / GHF261

Fits, as well as many others:

Triumph Vitesse 1600 & 2000 Mk2 -

Triumph GT6 Mk1

Triumph Spitfire 

Triumph Herald

Triumph Dolomite 1500

Triumph Stag

Wolseley 15/60 - 16/60 - Hornet

Riley 4/68 - 4/72 - Kestrel - Elf

Austin Mini - A35 - A40 - A55 - A60 - 1100 - 1300 - 1800 - Allegro

Morris Oxford Series 3, 4, 5, 6 - Minor - Marina

MG Midget - MGB - MGA - Magnette

Healey Sprite - 3000

Ford Escort Mk1, Mk2 - Capri - Cortina

GHF261

Jaguar part# C30787

Jaguar 420 Saloon
Daimler 2.5 V8 / V8 250
Daimler Sovereign
Daimler Sovereign S1
Jaguar E-Type S1, S1.5, S2, S3
Jaguar Mk I / Mk 1 3.4
Jaguar Mk II / Mk 2 2.4, 240, 3.4, 3.8 & 340
Jaguar Mk IX / Mk 9
Jaguar Mk VII / Mk 7
Jaguar Mk X / Mk 10 3.8
Jaguar Mk X / Mk 10 4.2
Jaguar S-Type 3.4, 3.8
Jaguar XJ6 / XJ12 S1, S2, S3
Jaguar XJS
Jaguar XK 120
Jaguar XK 140
Jaguar XK 150