Is there something I need to know about screws and bolts in BZP?

[ajlelectronics]

I need a dozen exhaust manifold fixing screws or bolts in 5/16" UNC 1" long with Allen socket heads. I want BZP and not stainless nor "self colour". Even Namrick appears not to stock them. I will give my local emporium a call on Friday to see what they have, but is BZP out of fashion now perhaps?

 

[hotponyshoes]

Pardon our interruption...

 

[ajlelectronics]

Pardon our interruption...

Thank you kindly, not sure why I missed that unless it was listed in yank sizes maybe.

 

[hotponyshoes]

You might find them locally at a hydraulics or agricultural supplier.
Fairly common on hydraulic rams

 

[Agroshield]

Another one or two:

5/16" UNC Socket Cap Head Screws - Zinc Plated Steel

5/16" UNC Socket Cap Head Screws - Zinc Plated Steel | FRANKSFASTENERS.CO.UK

www.franksfasteners.co.uk

5/16 inch UNC Socket Head Cap Screws ASME B18.3-2012 in Bright Zinc Plated (BZP) Steel - Westfield Fasteners Ltd

5/16 inch UNC Socket Head Cap Screws ASME B18.3-2012 in Bright Zinc Plated (BZP) Steel. Also know as Allen Screw or Allen Bolt. Purchase in box or sachet quantity.

www.westfieldfasteners.co.uk

5/16" UNC 8.8 Grade 5 Zinc Plated Steel Cap Head Set Screws

5/16" UNC 8.8 Grade 5 Zinc Plated Steel Cap Head Set Screws

www.spaldingfasteners.co.uk

UNC Socket Cap Screws - Arun Fasteners

UNC Socket Cap Screws. From 2/56 UNC - 1" UNC, zinc and unplated, in stock for next day delivery. Great prices for singles and bulk.

arunfasteners.co.uk

https://www.zoro.co.uk/shop/fasteners/cap-screws-imperial/5-16uncx1-skt-head-cap-screw-1936ser-bzp-12-9/p/ZT3303707S

 

[carbonarc]

 

[ajlelectronics]

Stainless, prone to galling and snaps when trying to undo a galled fastener.
"Self colour", rusts especially when heat cycled constantly.

BZP, the least problematic for exhaust manifold fixings into cast iron heads.

 

[Agroshield]

Stainless, prone to galling...

As you know, there is a galvanic corrosion scale for different metals.

Have you ever seen something similar for galling? In my head, stainless into cast iron seems like it would be low on that scale given the self-lubricating properties of cast iron.

 

[Ubique]

Stainless, prone to galling and snaps when trying to undo a galled fastener.
"Self colour", rusts especially when heat cycled constantly.

BZP, the least problematic for exhaust manifold fixings into cast iron heads.

Most of the current model exhaust manifold nuts across various brands (they don't use bolts, but studs) are copper coated and crushed to create an interference fit, the studs tend to be 'self colour' or Nickel plated.

 

[frank horton]

sounds like this job is for decoration.......
I'd go brass studs and dome nuts.....Jag's did it for years....
both of the above are available....from stockists....
I replace all manifold studs on antique vehicles this way.....often custom made....
they are pretty much forever once done....

 

[Cobbler]

BMC used brass nuts on the manifolds in the 60’s, I remember they used to squeal when you undid them.

 

[bricol]

Yep, self colour studs and brass nuts. Used with great success for the last 20 yrs on my turbo Lancia - gets pretty hot.

I didn't find BZP screws stayed BZP for too long on N/A cars in the past. And cap heads a right pain in the bum getting undone after a few years when the socket rounds off when trying to undo it, due to the heat cycles accelerating corrosion.