ARP studs/bolts thread fit

General engine tech -- Drag Racing to Circle Track

Moderator: Team

Post Reply
89BLK5OH
New Member
New Member
Posts: 21
Joined: Sat Jul 25, 2020 1:31 pm
Location:

ARP studs/bolts thread fit

Post by 89BLK5OH »

What class of thread fit are ARP head studs and bolts ?
1A , 2A , 3A ?

What is a proper procedure for measuring thread fit into an engine block ?

What is considered too loose ?


Thanks :D
Geoff2
Guru
Guru
Posts: 1980
Joined: Mon Nov 09, 2015 4:36 pm
Location: Australia

Re: ARP studs/bolts thread fit

Post by Geoff2 »

Don't know about thread 'fit', but ARP need to lift their game. I have had instances where their fasteners are either too long or too short.
Not rocket science getting those dimensions correct.
Momus
Pro
Pro
Posts: 307
Joined: Tue Aug 13, 2013 8:38 am
Location:

Re: ARP studs/bolts thread fit

Post by Momus »

There is a lot of detail on thread fit and tolerances in the SAE specs.

Broken down the specs say studs should be a tight screw fit into the female block thread, which theoretically will have been cut with a slightly undersize tap- maybe 0005".
swampbuggy
Guru
Guru
Posts: 1575
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: ARP studs/bolts thread fit

Post by swampbuggy »

Any High Quality Stud / Bolt produced has the threads Rolled into place, not cut with a tap. I really don't know how this process is done, i just know it to be so. Mark H.
swampbuggy
Guru
Guru
Posts: 1575
Joined: Mon Apr 04, 2011 8:54 pm
Location: central Florida

Re: ARP studs/bolts thread fit

Post by swampbuggy »

Correction to the above reply, i meant to type "Die" not Tap. Reminds me of a person calling a Nut a Bolt or vise-versa.
dannobee
Expert
Expert
Posts: 898
Joined: Mon Nov 04, 2019 9:01 pm
Location:

Re: ARP studs/bolts thread fit

Post by dannobee »

Here's how ARP rolls the thread on their studs.

https://www.youtube.com/watch?v=UGqzj0CPx08

You can measure the diameter of the bolt or stud and determine its thread class, but it doesn't tell the whole story because the class of fit requires that the internal threaded part has the same tolerance. In other words, it takes both parts to keep the thread class in tolerance. AFAIK, connecting rod bolts (and some flywheel bolts) are the only class 3A (and their nuts 3B) used in automotive. Anything going into cast aluminum or cast iron will be 2A.

I'd suspect ARP's are no different, but measure and compare to the bolt's thread class tolerances.

https://www.natool.com/wp-content/uploa ... 01-102.pdf
User avatar
BOOT
Guru
Guru
Posts: 2895
Joined: Fri Apr 09, 2010 6:23 pm
Location: Michigan

Re: ARP studs/bolts thread fit

Post by BOOT »

Op did you read this article posted on the 26th, same as your post?

https://www.streetmusclemag.com/tech-st ... -in-depth/
Channel About My diy Projects & Reviews https://www.youtube.com/c/BOOTdiy

I know as much as I can learn and try to keep an open mind to anything!

If I didn't overthink stuff I wouldn't be on speedtalk!
amc fan
Expert
Expert
Posts: 598
Joined: Wed Jul 11, 2012 7:03 am
Location: BETHLEHEM PENNA.

Re: ARP studs/bolts thread fit

Post by amc fan »

My question is: What does the factory use to thread the holes for the head studs/bolts on the engine block?
What class thread are they? 2-3
Are the tapped, rolled, milled?
Betting they are all done at the same time.
When the factory hones the block for piston fit do they install a plate or hone it with no plate.
miniv8
Expert
Expert
Posts: 896
Joined: Mon Sep 11, 2006 5:22 pm
Location: ICELAND

Re: ARP studs/bolts thread fit

Post by miniv8 »

With all the trash bots here clogging Speedtalk, you throw out my reply with a link to https://optitorque.com/

That's funny.
Magnús Aðalvíkingur Finnbjörnsson
Post Reply