descartesfool

I need exhaust manifold to head bolt torque specs. I have the Acura factory manual for the 1998 Integra. On my ITR B18C5 there are bolts and studs for the manifolds. The manual on page 6-60 shows exhaust to head manifold bolts and studs with nuts (7 bolts and 2 studs), but lists only torque specs for the nuts at 23 ft-lbs. There is no number shown for the bolts. A similar figure on page 6-79 also does not give any bolt torque specs. 23 ft-lbs seems quite high to use for an 8 mm dia. bolt, as most are rated at about 16-17 ft-lbs for other uses in the manual.The intake manifold figure shows nuts at 18 ft-lbs and bolts at 18 ft-lbs (25 N-m). Figure on page 9-4 shows intake manifold studs and nuts at 17 ft-lbs (23 N-m), and figures on pages 9-5 and 9-6 also do not show exhaust manifold bolt torque, only nuts on studs at 23 ft-lbs.

What torque should to exhaust manifold bolts be tightened to? Does the manual show the value anywhere I missed? I am thinking that 23 ft-lbs is almost 50% higher than 16-17 ft-lbs typically given for 8 mm bolts, so it might be too high to use for the exhaust manifold bolts.

I road race my car so reliability under high stress and load is a concern, and I don't want to damage head threads over time with all the heat and vibration. I have a lot of fasteners come loose, and I am trying to move all to V-band where possible, but head bolts remain.

vtec.dc2

if you don't want to damage headthreads,don't use bolts to begin with, get arp studs.. i always went with 23.

2BFI

I use 23 too.

descartesfool

23 ft-lbs for bolts into aluminum seems high to me when almost all the 8 mm bolts in the factory manual have a torque of 16-17 ft-lbs. Only the exhaust nuts on studs are rated at 23 ft-lbs , and other 8 mm nuts on studs are 16-18 ft-lbs, similar to the bolt ratings. I would use ARP studs, but I don't have any and I have to build the engine now.

2BFI

On the other side of the coin, can you fasten a flat surface sealing item (IM, header, TB, cyl head) with different torques? It might warp or be prone to leaks.

That was my logic when I used 23 for the bolts.

descartesfool

Steel nut on stationary steel stud can surely take more torque than steel bolt going into tapped hole in aluminum. 23 ft-lbs seems like a lot for a regular Honda 8 mm bolt.