Header to Block bolt size?
 

Just installed Tomei UELs. We had it on a lift and torqued all the nuts fairly tight. Drove it for a week and heard one of the gaskets flapping. Got back under and noticed one of the nuts from the header to the block was missing. I knew we tightened all of them (especially that one since it was an easy one) but apparently it fell off. I was able to get a few turns on the other bolts and got rid of the noise for the most part, but if anyone knows the sizing or where to get another nut for the headers.

They're M8 threads and 14mm nuts.

They're 14 mm bolts with M8 threads, be sure to torque them down to 22 ft-lbs. For my install I used grimmspeed gaskets and high temp rtv silicone for extra insurance and haven't had a leak, it seems some headers have poorly decked mating surfaces and this prevents them from leaking.

Also your going to want to retorque these bolts down after a few heat cycles maybe after the first week of driving after they've going through heat cycles.

I've been looking around for the 14mm M8 threaded nuts, but I can't find them at lowes or anywhere. There's also a 1.25 and a 1.5. If someone could just send me a link to the specific nut I need I would greatly appreciate it.

https://parts.subaru.com/p/Subaru__/...902370009.html


Thats for the head to engine block, simple google search for part numbers....

I bought these and they work perfectly:

https://www.86speed.com/products/jdl...k-nut-kit.html

I also have the Tomei UEL header

Just realized these won’t help with your situation but they will help stop what happened the first time.

I thought JDL, said they were m10. X 1.25 steel lock tabs
Not nylocks. They will melt.

I believ3 they are m10 x 1.25