Installed a new Remflex manifold gasket a month ago and it has already blown out to the left of the exhaust port on the front of the engine, pushed out to the thermostat housing. Before installing, I had the intake and exhaust face machined to a flat surface. Any reasons why this might have happened? Should I have re-torqued the manifolds down after initial install and warm up? Wondering what steps I can take to get a good seal next time.

What torque value did you use?

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

We used 10-ft pounds.

Remflex gasket spec is 5 lb·ft. I don't know for sure that 10 lb·ft would make a gasket failure more likely, but I tend to follow the Remflex people's advice on the subject.

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

I have retorqued remflex gaskets up to 15 lbs and not had a problem, it's best to follow the manufacturer's recommendations as Dan suggests...

One thing the composite gasket cant take is a bad lean out or a backfire... so if the cylinder is really really lean, or if you are "shooting ducks" on occasion... (can cause a "blow out" if the backfire occurs right out of the valve...)

Any chance the manifold studs or thermostat is leaking? That material does not like liquid.

Did the manifolds stay together after they were surfaced, or did you take them back apart?

The manifolds where together when machined. The lean burn and liquids is a good point. The spark plug on that cylinder does have the appearance that it is burning quite lean. I also changed the radiator and thermostat shortly before it blew. I might have gotten water on the gasket while doing this which might have been the cause.

My question was whether they stayed together after they were machined. The two bolts and stud holding them together aren't a precise fit so if they were loosened after they were machined they would have had to been aligned before tightening.

We never loosened the manifolds through the process. We didn't notice any leaks at the hot box, so left them connected.

What are your thoughts on water getting on the graphite gasket during the radiator flush? Do you believe that would have been enough to cause it to blow out?

House keeping detail:

Unless you installed new studs in head and new nuts, torqueing or clamping force seen by manifold stud to stud can be all over the map.

In other words actual clamping force on one cruddy stud could be half that of a new stud.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

It's not the torquing level, it's the exhaust pressure. The lean and/or back fire hypothesis sounds right to me. If anything it might not have been tight enough. If it were leaking around the gasket and it backfired or otherwise there was a pressure spike, it might have failed at the leaky area.

Also, the hypothesis about the gasket getting soaked from manifold studs might be a contribution. I had one do that, it was soaked with coolant and very soft (didn't break though, I've never had that happen). I noticed mine was wet when I saw steam rising from from between the manifolds and the head but I didn't have any exhaust leaks.

brian

_________________
https://tinyurl.com/yynpj4v2

Thanks for the replies. I'll post a follow up after we get it apart again and have a better look.