New Product - ARP SS Head bolts for new alum cylinders

jseng1 · Mar 5, 2025

For new alum cylinders on the market - High strength ARP SS bolts with fluted shanks so they'll stretch - allowing torque to stay consistant.

New Product - ARP SS Head bolts for new alum cylinders

jseng1 · Mar 7, 2025

Getting a good snug fit in the bolt hole threads is the most important thing with these head bolts for alum cylinders. You don't want a sloppy fit that could strip out the threads. It took a bunch of tests and a custom size thread to find a satisfactory fit.

acotrel · Mar 7, 2025

I would have thought that only the through-bolts would need to be able to stretch to compensate for the expansion of the aluminium barrels - the amount of expansion depends on the height of the aluminium which the bolt holds down.

850commando · Mar 8, 2025

how many pesos? $

jseng1 · Mar 9, 2025

Rod bolts have reduced shanks so the stress is spread throughout the bolt and not focused on one area where it can snap. For the Norton its important that the bolt can stretch when the motor heats up and cools down. That way it doesn't lose its tension.

APRRSV · Mar 9, 2025

jseng1 said:
Rod bolts have reduced shanks so the stress is spread throughout the bolt and not focused on one area where it can snap. For the Norton its important that the bolt can stretch when the motor heats up and cools down. That way it doesn't lose its tension.

Hi Jim,
What about the cylinder through bolts anchoring the cylinder to crankcase as @acotrel alluded to?

Schwany · Mar 9, 2025

APRRSV said:
Hi Jim,
What about the cylinder through bolts anchoring the cylinder to crankcase as @acotrel alluded to?

High Performance Norton Parts

Through years of extensive testing on both road and track, JS Motorsport has developed high-end products in a modern format that will increase a Norton’s performance, reliability and rideability.

jsmotorsport.com

Scroll down to the Bolts.

BTW... I'm using JSM through bolts with my Molnar barrels anchored to my pre-Commando 750 crankcase. No leaks and they stretch quite a bit when the barrels get hot.

Fast Eddie · Mar 10, 2025

APRRSV said:
Hi Jim,
What about the cylinder through bolts anchoring the cylinder to crankcase as @acotrel alluded to?

They are the same for the different types of barrels, not dedicated to the Molnar barrels, Schwany put the link above.

I use JS through bolts on a 1007 with Maney alloy barrels and am very happy with them.

Ron L · Mar 10, 2025

jseng1 said:
For new alum cylinders on the market - High strength ARP SS bolts with fluted shanks so they'll stretch - allowing torque to stay consistant.

Are these 26 TPI (CEI) or 24 TPI (NF)?

jseng1 · Mar 10, 2025

Ron L said:
Are these 26 TPI (CEI) or 24 TPI (NF)?

They are 20 TPI BSF British for Molnar cylinders
I also have them in 26 tpi Whitworth for Stock cast iron cylinders and US 16 tpi for Maney cylinders
3/8"

New Product - ARP SS Head bolts for new alum cylinders

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