Moving up from 10mm head bolts/studs?

Q&A regarding engines, turbos, and intercoolers and power upgrades

Moving up from 10mm head bolts/studs?

Postby MWP » Sat May 23, 2020 5:26 pm

Hi guys,

I'm not keen to spend $600 on L19/625+ ARP head studs.
Drilling and re-tapping for 11mm or 12mm head studs is more attractive.

Has anyone done this? What ARP studs did you use?
Any problems with squishing the bosses around the studs in the alloy head?

Thanks :)
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Re: Moving up from 10mm head bolts/studs?

Postby Magroo » Sat May 23, 2020 11:43 pm

The only thing I can offer is when I installed regular arp studs I couldn't use a 1/2 inch drive 12 point socket because there just isnt enough room. I think it was 14mm and had to use a 3/8 drive.
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Re: Moving up from 10mm head bolts/studs?

Postby RedCelicaTRD » Fri Sep 18, 2020 11:42 pm

You can use 11mm out of an Evo 8 I believe. Same pitch and all you need to do is tap the treads, no drilling involved. The head can get squished and stick onto the stud preventing removal. Hux Racing will make you a head support washer if you email them and ask.
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Re: Moving up from 10mm head bolts/studs?

Postby MWP » Thu Nov 19, 2020 2:15 am

RedCelicaTRD wrote:You can use 11mm out of an Evo 8 I believe. Same pitch and all you need to do is tap the treads, no drilling involved. The head can get squished and stick onto the stud preventing removal. Hux Racing will make you a head support washer if you email them and ask.


That's the kind of info i was hoping to hear, thankyou!

Opening up the head bolt holes very slightly would hopefully help with that getting stuck problem.
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