Do one head or both?  I mean, come on, you already known the answer to that.  I'm not going to pump rainbows up your you know what.  If one failed how long is it before the other one does?  Do you really want to pull the intake etc. again? 

My questions would be: What gaskets did you use?  What does AFR recommend?  Did you check to make sure all the passages were lined up correctly?  Was any sealer used? 

All you really know at this point is that its leaking.  Presumably its the gasket, but I'd pay real close attention to everything else.  A crack could have developed for example. 

Hey, I'm right there with you.  I've lived with a lot over the years on DDs because of that.

I had good luck with the top end FelPros on SBFs over the years, but I used Cometic gaskets on my 331 due to a ton of guys on various forums with racing experience with them praising them so highly.  Also, they were available in the 4.030" bore size I wanted.  AFR recommends a Fel-Pro 1011-1 for most of their SBF heads I believe.  I don't think you can go wrong with either.  I used the Cometic C5511-040.  Neither of those gaskets is cheap, but IMO with only 10 head bolts (though mine has ARP studs) SBFs need the best gaskets you can get, especially if you are running them hard.  I wanted to be able to spray my 331, so that was also part of my decision. 

If you go with a Cometic, make sure to research surface prep of heads and block. I understand Cometics require a surface prep that is not typical to what is needed if your using a Felpro gasket.

Bullet Bob wrote:

Interesting...Back in '15 I put AFR 165s on the 5.0 in the Heap and used the recommended 1011-1 FelPro gaskest.  Right from go it had a very minor, yet annoying, leak at the back of the right head.  Under normal driving if didnt' seem to leak but if it set for a couple of weeks it would leave a palm sized puddle.  The way it was running down I thought it was from one of the soft plugs so I loaded it up with a couple of tablespoons of black pepper and it stopped for about a year.  Then came back and I re-peppered it.  
When things went south earlier this year I pulled the heads and discovered that the AFR heads have an oversized coolant hole at the end that gets very close (1/16") to the edge of the gasket. 
Heads and block have been freshly surfaced so we'll see if that fixes the problem...if I ever get the engine back together, that is.

BB1

Did you torque the head bolts again after initial run in?
 

TKOPerformance wrote:

Did you torque the head bolts again after initial run in?
 

Absolutely!  Butt (TS&T), the block was not freshly surfaced.
 

TKOPerformance wrote:

Bolted to Floor wrote:

If you go with a Cometic, make sure to research surface prep of heads and block. I understand Cometics require a surface prep that is not typical to what is needed if your using a Felpro gasket.

Its actually about the same, Cometic recommends a 50RA finish, whereas Fel-Pro recommends a 50-60 for aluminum and 60-80 for cast iron.  The higher the number the rougher the finish.  You would not be able to observe a difference in a 50 RA vs. an 80 RA.  The measurement is in micro inches in terms of height peak to valley for the surface.  You'd need a microscope to even see it.  A factory MLS gasket may want a very fine finish like a 30 RA, but the Cometics are made with different sealing material to accommodate a finish rougher than what a factory MLS gasket would want.  They wisely recognized that all of their gaskets are not going to be used on clean sheet builds, and if you are replacing a gasket due to failure you are stuck with whatever finish the block and head had before you tore into it. 
 

 
I knew there was some differences but not sure how much. I wanted to throw it out there as something that should be considered.