torque for generic rod with ARP 3/8 bolt
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Re: torque for generic rod with ARP 3/8 bolt
RFoll,
I hear ya,
I just done a full year of buzzing a set of scat I- beam rods with 3/8 8740 bolts in my 383 sbc to 7600 rpm
Pulled the engine for some upgrades,bearings could be used again,I was kinda surprised,
327 sbc with heavy pistons and stock rods and bolts torqued to 45 ft/ lbs to 7000 rpm
Some people think I am crazy,maybe I am
I hear ya,
I just done a full year of buzzing a set of scat I- beam rods with 3/8 8740 bolts in my 383 sbc to 7600 rpm
Pulled the engine for some upgrades,bearings could be used again,I was kinda surprised,
327 sbc with heavy pistons and stock rods and bolts torqued to 45 ft/ lbs to 7000 rpm
Some people think I am crazy,maybe I am
steve c
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Re: torque for generic rod with ARP 3/8 bolt
Not sure if it's been mentioned yet but overall length plays a role in final torque specs too. Since many of these bolts are custom spec'd for various designs they are slightly different than shelf parts.
For example many are 1.4" lengths(like my scats) compared to the more common 1.5" shelf parts. Iirc, only about 5-6 ft/lbs difference but worth a phone call to be sure. Could also look at the part#'s replacement bolts specs and instructions to get a better idea as well.
For example many are 1.4" lengths(like my scats) compared to the more common 1.5" shelf parts. Iirc, only about 5-6 ft/lbs difference but worth a phone call to be sure. Could also look at the part#'s replacement bolts specs and instructions to get a better idea as well.
Re: torque for generic rod with ARP 3/8 bolt
The torque should be the same no matter the length, to create the rated tensile clamp load in the assembly.
But the stretch will be proportional to the length at the rated tensile clamp load.
But the stretch will be proportional to the length at the rated tensile clamp load.
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Re: torque for generic rod with ARP 3/8 bolt
My bad.. you are exactly right and thanks for the clarification. It's the rod mfgrs that change the torque ratings based on their rod designs(extra reinforcement "meat" in the big ends), and tailored towards the specific ARP bolt which was designed for them, despite the bolts being of similar metallurgy and diametrical sizing to a standardized shelf part#.
So maybe better to say.. IF.. the bolt being used for a specific rod part # is the true and correct replacement part #?.. then use the mfgrs rec'd torque specs. If it is a standardized shelf part#?.. then use the rec'd specs from ARP for that specific part#. Either way though.. mic'ing will be mandatory and you may end up resizing the rods big end depending on its specific big end design and past usage history. And probably moreso true if it's a lower scale/lighter weight rod design and you stray away from the specific replacement bolt # designed for it.
Hope that helps the OP any little bit at all!
Re: torque for generic rod with ARP 3/8 bolt
I'm thinking it's getting 60' lbs. with ARP lube. This application could run 305 rods and stock bolts. Thanks to all who responded, Rick.
So much to do, so little time...
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Re: torque for generic rod with ARP 3/8 bolt
Way too high for an 3/8" 8740 and might want to look over arp's genetal torque spec's before going that route.
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Re: torque for generic rod with ARP 3/8 bolt
RFOLL says they are 7/16groberts101 wrote: ↑Mon May 14, 2018 10:20 pmWay too high for an 3/8" 8740 and might want to look over arp's genetal torque spec's before going that route.
i am not sure they even do a 3/8 bolt for a H-beam Scat, Eagle rod
hopefully someone correct me if i am wrong
steve c
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Re: torque for generic rod with ARP 3/8 bolt
Ok.. apparently I'm too broke to even pay attention. lolsteve cowan wrote: ↑Mon May 14, 2018 10:37 pmRFOLL says they are 7/16groberts101 wrote: ↑Mon May 14, 2018 10:20 pmWay too high for an 3/8" 8740 and might want to look over arp's genetal torque spec's before going that route.
i am not sure they even do a 3/8 bolt for a H-beam Scat, Eagle rod
hopefully someone correct me if i am wrong
Well then.. I'll flop the other way and say 60 isn't enough.
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Re: torque for generic rod with ARP 3/8 bolt
classic GRobs thats funny,groberts101 wrote: ↑Mon May 14, 2018 10:43 pmOk.. apparently I'm too broke to even pay attention. lolsteve cowan wrote: ↑Mon May 14, 2018 10:37 pmRFOLL says they are 7/16groberts101 wrote: ↑Mon May 14, 2018 10:20 pm Way too high for an 3/8" 8740 and might want to look over arp's genetal torque spec's before going that route.
i am not sure they even do a 3/8 bolt for a H-beam Scat, Eagle rod
hopefully someone correct me if i am wrong
Well then.. I'll flop the other way and say 60 isn't enough.
looking at spec sheet 8740 bolt in 1.4'',1.5'',1.6'' between 60-65 ft/lbs
i think RFOLL good to go,
steve c
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Re: torque for generic rod with ARP 3/8 bolt
Back in the early 90's generic sm blk rod hit the world scene of hot rodding as an alternative to stock rods.
scat Eagle and others sold basicly the same looking rods. While the bolts were stamped ARP when you took them apart did they have the ARP lube on the threads??
Scat and Speedway motors offered them with arp lube where Eagle suggested same ARP does as today to use 30W motor oil when no ARP lube is on hand.
If they showed sign"s of their lube then I would bet they are Scat rods and you could use the chart for torque and stretch for the 8740 bolts. Compare to the Eagle chart for other possibilities as the lengths differ between the 2 manufactures.
Back in the 1st days they were offered with a shot peened option and the surface was really rough compared to today's method's of shot peening rods.
scat Eagle and others sold basicly the same looking rods. While the bolts were stamped ARP when you took them apart did they have the ARP lube on the threads??
Scat and Speedway motors offered them with arp lube where Eagle suggested same ARP does as today to use 30W motor oil when no ARP lube is on hand.
If they showed sign"s of their lube then I would bet they are Scat rods and you could use the chart for torque and stretch for the 8740 bolts. Compare to the Eagle chart for other possibilities as the lengths differ between the 2 manufactures.
Back in the 1st days they were offered with a shot peened option and the surface was really rough compared to today's method's of shot peening rods.
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Re: torque for generic rod with ARP 3/8 bolt
I would be conservative and go with the smaller torque value, whatever that may be for a mild stock type application.
If you are concerned about that then you need to replace the bolts!
If you are concerned about that then you need to replace the bolts!