Okay, the 2151 at the time the previous owner bought them apparently was different than it is now in one aspect: on the passenger-side header the rear primary (#8 cylinder) did not have its flange continuous to the other three. IOW, there was a gap cut out of the flange between #6 and #8. I assume that was to clear the dipstick tube and the ECT sensor in the head. Also, the rear-most bolt hole is slotted, to make installation easier. That's fine as long as the header bolts stay snug. But like a dumbass, I neglected to check those header bolts annually, and one came loose on each side of the engine. The loose one on the passenger side was the second-from-rear, and it worked its way out all the way. It was gone. Who knows how long it was like that, and still sealing well enough. But then the rear-most bolt apparently loosened a bit, too; and that's the one in the slotted hole. So that rear primary then had no bolts holding it on and no continuous flange to keep it in place. Probably due to heat cycles and/or vibration, it worked its way out from the rear-most bolt in the slot, and eventually cracked off near the collector (but the weld at the collector did not actually break).

The main lesson here is to check your header bolts for tightness periodically! The header gaskets were Felpro 1405 gaskets, which sealed great, but may have compressed slightly over time. Probably once a year you should check to make sure no bolts are loose, and certainly any time you replace plugs (since you're in there already). I've also changed to Remflex gaskets, which are supposed to never take a "set" with compression and therefore should never require retightening of the bolts. Guess what? I'll still be checking them.

Also, the replacement 2151 I bought doesn't have that gap cut into the flange anymore. So if this happened again, it would not break. The tradeoff is you have to pull the dipstick tube (reinstallation is a bit of a pain, but not too awful) and maybe the ECT sensor.

 

I wish I could remember what exactly U Tube video it was, but it was a back to back comparison of various headers. Don't recall the hp and torque numbers, but what I do remember vividly was that with uncoated headers, the temp in the dyno cell was absolutely roasting while with the coated headers it was merely warm or hot.

 

Yeah maybe, but for the cost and effort, I think I'll stick to header wrap!

 

I've used header wrap on exhaust system, went from couldn't get hand close to exhaust pipe to you could touch it (briefly, very briefly). definitely works. First thing I did was paint the exhaust pipe with high temp paint, then as I wrapped the pipe, soaked the header wrap with high temp paint; worked well and looked good.

 

I've heard of soaking in water to aid installation, but never paint? What was your technique?

 

I read the instructions and it mentioned using water, but I never was a big fan of following instructions. I forget the brand, but I got several cans of the highest temp header / exhaust manifold paint (1250 degree ?) first painted the exhaust and let it dry, then I just soaked the header wrap as I wound it around the pipe. I think I layered on three wraps, all soaked with paint. When that dried I gave it a coat or two more of paint. After everything dried and cured, it worked perfect. I used white paint; although that paint is also available in black and grey. It's a matter of taste, but white radiates heat the least. All this was on the exhaust pipe that ran very close to the front, and then very close along side the oil pan of a factory V8 chevy Monza (which I had put a 345 horse crate engine clone) and there wasn't room ...and California smog laws wouldn't allow... moving, the exhaust. It really helped and made the best of a bad situation.