I am using a 4age from a AE86, what thread is used for the exhaust manifolds in the head?????
I have no bolts that seem to fit, 3/8 UNF is very close,

it should be metric, after you find the size go to Mcmastercarr and order them there, they have the best prices for hardware

M10 x 1.25 pitch apparently.

Cheers... jondee86

If anything on your motor is a standard thread it has been raped by a previous owner.
Everything should be JIS.
10 x 1.25

After a bit of messing around, It seems that the threads in my head for the exhaust are not 10 x 1.25, but 10 x 1.5, it did seem a bit ambitious expecting a fine pitch bolt to hold in alloy.

I was thinking about this as most engine/transmission bolts used
in the AE86 are metric fine. So out of curiosity, I went and pulled a
couple of studs from heads I have in the shed. This is what I found...



Based on this, it would seem that your head must have been reworked
at some stage to take the M10 x 1.5 studs. Standard metric bolts (as per
the one shown above)are readily available in engineering workshops,
but metric fine are a lot less common. Maybe someone just used what
they could find ?

Cheers... jondee86

In the JDM days, i would find Flywheel bolts in there to replace an overtightened bolt that stripped the head.

I've seen sets of studs for sale, I think made of stainless, but they come in sets of odd numbers (not specifically for one engine or another) and in various pitches. The ends can be tightened using a hex key (or a socket? I forget). I was thinking about getting them for the intake and exhaust.