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Head Stud nut/washer size?

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Old Mar 16, 2017 | 09:54 AM
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sean byrd's Avatar
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Default Head Stud nut/washer size?

Well I thought I ordered the right ones from Arp but they were too big (Arp 300-8323, 7/16" -20 nut, Arp 200-8512 washer).
I looked in my Ebay history and the seller says Speedmaster doesn't sell them individually. I've tried summit and Jegs but they all say the same and won't bother telling me the Arp equivalent.
Does anyone know which nut(1) and washers (2) I need? This is for a '99-04 5.3 head stud kit.
Hoping I can order these from Arp instead of paying another $100 for some Chinese studs...

Last edited by sean byrd; Mar 16, 2017 at 10:01 AM.
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Old Mar 16, 2017 | 06:20 PM
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They are metric, the 7/16 -20 are for Small block Chevy not LS based motors. Call Summit-Jegs-Speedway Etc.
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Old Mar 21, 2017 | 11:57 AM
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The big ones are M11 and the small ones are M8. Metric sizes.
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Old Mar 21, 2017 | 03:59 PM
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The threads going into the block are metric but with the ARP's, the threads the nuts engage are often a standard thread.

You should easily be able to take a stud to a local hardware store, or even a Lowes/Home Depot and match the threads to something on their shelves.
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Old Mar 21, 2017 | 05:50 PM
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Fastenal to get the right grade...
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Old Mar 21, 2017 | 07:24 PM
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I finally got the originally seller from ebay(firstracing) to send me the replacements but only after I ordered them from jegs as well. The larger ones are 7/16 and 5/16 for the smaller.
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Old May 6, 2017 | 12:30 PM
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Originally Posted by sean byrd
I finally got the originally seller from ebay(firstracing) to send me the replacements but only after I ordered them from jegs as well. The larger ones are 7/16 and 5/16 for the smaller.
Did you happen to strip the threads out of your nuts? I also bought a set from firstracing and the first delivery was missing half the components. The rest of the set finally showed up 2 weeks later, and last night I tried to install them and stripped out several of the nuts at <60 ft lbs. They look super cheesy and I'm not sure I want to trust the replacements (if they honor their warranty) either
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