torque for generic rod with ARP 3/8 bolt

General engine tech -- Drag Racing to Circle Track

Moderator: Team

rfoll
Guru
Guru
Posts: 2278
Joined: Mon Jan 11, 2010 12:44 pm
Location: St. Helens, OR

torque for generic rod with ARP 3/8 bolt

Post by rfoll » Sat May 12, 2018 5:29 pm

I have no info on the rod manufacturer, and the bolt only says ARP. This is a street motor, will likely never see more than 5500 rpm. What should I use for torque?
You do not have the required permissions to view the files attached to this post.
So much to do, so little time...

Jeff Lee
Pro
Pro
Posts: 301
Joined: Sun Jun 26, 2011 1:20 am
Location: Anthem / Phoenix Arizona

Re: torque for generic rod with ARP 3/8 bolt

Post by Jeff Lee » Sat May 12, 2018 7:30 pm

I suggest calling ARP but generically speaking I would GUESS to .0045 - .0055” stretch ASSUMING these are not old / fatiqued rod bolts to start with. The safe bet is new rod bolts.
NHRA SS/H
1970 AMX
390 4-speed
Advanced Clutches
Red Line Racing Cams

B Original
Member
Member
Posts: 131
Joined: Tue Apr 17, 2018 6:51 pm

Re: torque for generic rod with ARP 3/8 bolt

Post by B Original » Sat May 12, 2018 9:01 pm

I agree with Jeff exactly as he said

SupStk
Guru
Guru
Posts: 1493
Joined: Wed Jun 22, 2005 6:25 pm
Location: Box Elder, SD

Re: torque for generic rod with ARP 3/8 bolt

Post by SupStk » Sat May 12, 2018 10:22 pm

ARP usually has the alloy stamped into the bolt head. ie: 8740, 2000, H-11.
Monty Frerichs
B&M Machine

steve cowan
Expert
Expert
Posts: 646
Joined: Wed Jul 27, 2011 5:22 am
Location: brisbane AUSTRALIA

Re: torque for generic rod with ARP 3/8 bolt

Post by steve cowan » Sun May 13, 2018 1:47 am

SCAT RODS ARP BOLT SPECS 001.JPG
LIKE MONTY SAID,
normally stamped on head of the bolt not just ARP
hopefully not chinese junk bolt,but like the saying goes
IF IN DOUBT THROW THE CRAP OUT,
i just done a set of scat H-beams with a 2000 ARP bolt upgrade
cracktested rod ,new bolts and resize conrod
PS disregard black arrows that's for me,
You do not have the required permissions to view the files attached to this post.
steve c

Geoff2
Expert
Expert
Posts: 996
Joined: Mon Nov 09, 2015 4:36 pm
Location: Australia

Re: torque for generic rod with ARP 3/8 bolt

Post by Geoff2 » Sun May 13, 2018 5:50 am

Is the thread 3/8 or 7/16"?

rfoll
Guru
Guru
Posts: 2278
Joined: Mon Jan 11, 2010 12:44 pm
Location: St. Helens, OR

Re: torque for generic rod with ARP 3/8 bolt

Post by rfoll » Sun May 13, 2018 10:15 am

Geoff2 wrote:
Sun May 13, 2018 5:50 am
Is the thread 3/8 or 7/16"?
Serious brain fart here. They are 7/16 bolts. This is build 20 or 30 years old according to the date code. The block had no wear, has no numbers on the front pad indicating a vehicle ID. It has never been decked. It appears to have been bought new over the counter. If we assume they are real ARP bolts, would they still be 8740?
So much to do, so little time...

B Original
Member
Member
Posts: 131
Joined: Tue Apr 17, 2018 6:51 pm

Re: torque for generic rod with ARP 3/8 bolt

Post by B Original » Sun May 13, 2018 10:20 am

steve cowan wrote:
Sun May 13, 2018 1:47 am
SCAT RODS ARP BOLT SPECS 001.JPG

LIKE MONTY SAID,
normally stamped on head of the bolt not just ARP
hopefully not chinese junk bolt,but like the saying goes
IF IN DOUBT THROW THE CRAP OUT,
i just done a set of scat H-beams with a 2000 ARP bolt upgrade
cracktested rod ,new bolts and resize conrod
PS disregard black arrows that's for me,
It's not just did the bolt specification it has do with the rod manufacturer also the alloy and heat treatment process may be different manufacturers are not all uniform in there tightening specifications one manufacturer May specify torque only because the stretch method distorts their rod while another manufacturer May rely only on the bolt stretch method

B Original
Member
Member
Posts: 131
Joined: Tue Apr 17, 2018 6:51 pm

Re: torque for generic rod with ARP 3/8 bolt

Post by B Original » Sun May 13, 2018 10:23 am

But considering you're not going to turn it over 5500 I just torque it to 60 foot pounds and let it ride better to under torque it then to over torque it

1972ho
Expert
Expert
Posts: 651
Joined: Thu Nov 21, 2013 12:52 am

Re: torque for generic rod with ARP 3/8 bolt

Post by 1972ho » Sun May 13, 2018 10:49 am

I have a arp rod bolt like that with only arp/arp I was told that is a 8740 bolt with a torque of 64 ft#, this is in a eagle rod 7/16 / 7/16 .I was told all of those bolts come from arp no matter who’s name is stamped on the top (eagle,Dyer,scat)some just use a different lube for righting there bolt.

rfoll
Guru
Guru
Posts: 2278
Joined: Mon Jan 11, 2010 12:44 pm
Location: St. Helens, OR

Re: torque for generic rod with ARP 3/8 bolt

Post by rfoll » Sun May 13, 2018 11:00 am

Thanks for the replies. With no numbers on the bolt head, I was hesitant to just guess and pull a torque number out of thin air.
So much to do, so little time...

1972ho
Expert
Expert
Posts: 651
Joined: Thu Nov 21, 2013 12:52 am

Re: torque for generic rod with ARP 3/8 bolt

Post by 1972ho » Sun May 13, 2018 11:22 am

1972ho wrote:
Sun May 13, 2018 10:49 am
I have a arp rod bolt like that with only arp/arp I was told that is a 8740 bolt with a torque of 64 ft#, this is in a eagle rod 7/16 / 7/16 .I was told all of those bolts come from arp no matter who’s name is stamped on the top (eagle,Dyer,scat)some just use a different lube for tighting there bolt.

rfoll
Guru
Guru
Posts: 2278
Joined: Mon Jan 11, 2010 12:44 pm
Location: St. Helens, OR

Re: torque for generic rod with ARP 3/8 bolt

Post by rfoll » Sun May 13, 2018 2:40 pm

Does this rod resemble your Eagle rods? I have another set of them with the 8740 markings, and they are 5.7" instead of 6"
So much to do, so little time...

steve cowan
Expert
Expert
Posts: 646
Joined: Wed Jul 27, 2011 5:22 am
Location: brisbane AUSTRALIA

Re: torque for generic rod with ARP 3/8 bolt

Post by steve cowan » Sun May 13, 2018 2:41 pm

Rfoll
I put up the arp spec sheet that I have as a guide,
Scat torque there bolts to spec not by stretch
If you have a stretch gauge you can go to the trouble of doing a torque ,tension ,stretch cycle in the rod and remeasure to see if they come back to free length,
Rfoll,
I know you have been around the block a few times so you will feel the rod bolt if it is going away when you torque the bolt,
I personally stretch all my arp bolts to spec and measure the rod first without a bearing and then with bearings and check out of round with dial bore gauge.
The only problem is you do not know if they are 8740 ( probably ) or 2000 series and more than likely don't need a H-beam in that application anyhow but that's what it is,anyway just sharing my opinion,
Thanks,
steve c

rfoll
Guru
Guru
Posts: 2278
Joined: Mon Jan 11, 2010 12:44 pm
Location: St. Helens, OR

Re: torque for generic rod with ARP 3/8 bolt

Post by rfoll » Sun May 13, 2018 2:53 pm

The only thing the H beams did for this engine was to allow an internal balance on the crank. The owner of the parts traded a good running stone stock 350 smog motor for this and it only needed the crank turned and a freshen. It never ceases to amaze me that people will buy high dollar parts and then drive the car around town like an old station wagon. I have one of the ARP charts mentioned, but I remember reading here about counterfeit parts, making me leery of just cranking on the bolts without some research.
So much to do, so little time...

Post Reply