Technical Manifold Gaskets on FE keep blowing

For headers, 3/8th flanges we’re the minimum. My old shop would use 1/2 inch flanges for custom headers.
High temp sealant was all we ever used. No leaks.

 

I worked in NASCAR in the 80's for about 6 years, when I put a set of headers on I just wiped off the cylinder head and header then put some red RTV hight temp and went racing. We ran 180 200 miles a hour for 500 miles and monday when I took the headers off the engine the RTV looked as good as when I put it on ,that's good enough for me, never used a gasket again jut RTV

 

I just used them on my recent build, hoping they're as good as everyone says they are. Strict instruction on them not to use any kind of sealer like Ultra copper or spray copper. Put them on dry and torque to 20 ft/lbs.

I also heard about great header bolts from totallystainless.com that use a really unique serrated wave washer that is supposed to lock pretty hard and not loosen. I used them as well and am hoping for the best.

 

I just surfaced that manifold as you can see in the pic I posted. I can fit a .003" feeler gauge in the worst gap. So apparently the head is not true any longer. The dry design of the top exhaust is what it seems to make the FE design leak prone.

I'm ordering yhe Remflex Gaskets, as they are easily found on the interweb.

I don't trust RTV alone to be honest. I've had it blow out when there is a slight gap.

I'm just changing the RH one now, the FelPro on the LH....we shall see how long it lasts. It was changed 500 miles ago.

Here in Maine we have E10 as well.

 

High temperature silicone is all I use for exhaust manifolds , never had a leak , my 390 in my truck with hooker competition plus headers have been sealed this way for years .

 

Those FE engines are notorious for exhaust manifold leaks, and snapping bolts. My 390 Ford truck snapped a number of bolts, and was a PITA.

 

I am putting on flex connectors on the dual exhaust. I'm thinking that will help with all the torque put on the manifolds.