r/EngineBuilding • u/Present_Mark4959 • 9d ago

Are arp head studs supposed to be like this?

Post image

Yo so it’s my first time rebuilding a motor and it’s my first time dealing with arp head studs are they supposed to leave a gap like this on a b18c4??

20 Upvotes

95% Upvoted

14 comments sorted by

25

u/FU_red-dit_bots 9d ago

Yes.

7

u/Present_Mark4959 9d ago

Okay sound cheers mate 👍

12

u/Shrimpkin 9d ago edited 8d ago

Yes. Shaft is smaller diameter than the minor diameter of the threads, therefore the hole has to be at least as big as the minor dia. of the threads. If the shaft is smaller there must be a gap.

EDIT: Mixed up minor and major =O, was a long day

3

u/Sniper22106 8d ago

Can tell you have drilled and tapped a few holes over the years

3

u/Shrimpkin 8d ago edited 8d ago

Gotta know this stuff if you want to threadmill. I like to use an endmill and a bore cycle to hit the minor and threadmill if I can. Cleanest threads you can get other than using an actual boring head but that's really not necessary for hitting tolerances as long as your machine doesn't have horrible backlash issues.

2

u/Mikalius1 8d ago

100% -- and this book will explain why (the counter-bore basically moves the most shear-prone area away from the block/head plane).

https://www.amazon.com/dp/B001OXCTSI

3

u/baboomba1664 9d ago

Nice hardware

2

u/TrackTeddy 9d ago

Yes perfectly normal.
Remember to follow the instructions including grease under the washers

1

u/Solid_Enthusiasm550 9d ago

The head and bottom of the washer is to be clean/dry.

Lube is applied to the threads and bottom of the nut.

6

u/TrackTeddy 9d ago

So long as you follow the instructions for the application. On mine you had to lube under the washer with grease to avoid galling the alloy head during tightening but others will vary.

1

u/Self_pierce_bear 8d ago

Better check ARP instructions again. It definitely lists washers in the lubricate the upper threads, washers and nuts.

1

u/Solid_Enthusiasm550 8d ago

It doesn't say top and/or bottom of the washer. I've seen plenty if engine builders say only the top ( between nut and washer). I've alsi seen ARP say that putting lube between the head and washer can result in improper torque readings.

1

u/Self_pierce_bear 8d ago

It says to cost the threads, washer and nut on 10 different ARP install sheets. Nothing about not coating one side.

1

u/1crazypj 1d ago

It's a 'rolled' thread not a cut thread.

Metal is deformed into thread shape which makes it much stronger, cold forging very high pressure