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One reason, or legend, is the precat on the downpipe, it kept heat longer in that section of the engine bay, causing un even cooling of the head (it would cool faster up by the intake cam then the rear turbo side of the head). Another legend is when they torqued the head to factory spec, it wasn't enough, someting like 50 or 70 ft/lbs, some insanely low amount, which also helped contribute to failures for legend one.
Felpro or other OEM style HGs are fine for stock engines, at least for about 80k miles, which is where most 7M's popped anyways, but for any kind of real engine work and power, a Metal head gasket should be used, and comes highly recommended by ALL SOGI members, including myself, but be careful which you get, I've seem 1.2mm TMS MHGs pop under 14 psi boost, and the head was put on with ARP bolts @ 86 ft/lbs. The GReddy line of MHGs seem to hold up best overall, and are available in multiple thicknesses to compensate for any head work, from 1.2 up to 3.0 stopper type.
As for "you can't overheat them for long" Well, in general engines can't be overheated at all, but its worse for the M series due to their iron block/al. head combos, I've seen a head warp from overheating in the time it took the gauge to register 3/4, pull over, shut down, it was gone. Yes we were watching the gauge at the time (well, I was anyways hehe) and it hit 3/4 and it started smoking, end of the head. It was so bowed that it was better to just get another head and start over, it was stressing the cams. I've also seen an N/a get so hot it melted the dist. cap off of the dist. lol. ARP hardware is almost mandatory if you plan to go over the stock torque spec, which i believe was 72 ft.lbs or something like that, with ARP hardware (bolts or studs, bolts are usually the choice) you can go up to 120 ft.lbs, there are a couple here that have gone that high I think..maybe you can go higher, but its not required, 86-90 should be plenty. Remember to heat cycle the engine 3 times to make SURE it has seated and that the bolts are holding their torque.
This is just advice that I gathered from numberous builds, and I live in the desert, where the motto seems to be "oh no, not again".
Felpro or other OEM style HGs are fine for stock engines, at least for about 80k miles, which is where most 7M's popped anyways, but for any kind of real engine work and power, a Metal head gasket should be used, and comes highly recommended by ALL SOGI members, including myself, but be careful which you get, I've seem 1.2mm TMS MHGs pop under 14 psi boost, and the head was put on with ARP bolts @ 86 ft/lbs. The GReddy line of MHGs seem to hold up best overall, and are available in multiple thicknesses to compensate for any head work, from 1.2 up to 3.0 stopper type.
As for "you can't overheat them for long" Well, in general engines can't be overheated at all, but its worse for the M series due to their iron block/al. head combos, I've seen a head warp from overheating in the time it took the gauge to register 3/4, pull over, shut down, it was gone. Yes we were watching the gauge at the time (well, I was anyways hehe) and it hit 3/4 and it started smoking, end of the head. It was so bowed that it was better to just get another head and start over, it was stressing the cams. I've also seen an N/a get so hot it melted the dist. cap off of the dist. lol. ARP hardware is almost mandatory if you plan to go over the stock torque spec, which i believe was 72 ft.lbs or something like that, with ARP hardware (bolts or studs, bolts are usually the choice) you can go up to 120 ft.lbs, there are a couple here that have gone that high I think..maybe you can go higher, but its not required, 86-90 should be plenty. Remember to heat cycle the engine 3 times to make SURE it has seated and that the bolts are holding their torque.
This is just advice that I gathered from numberous builds, and I live in the desert, where the motto seems to be "oh no, not again".
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