Hey all, Ive been having issues with a fresh built 390 based 445 motor Boeing headgaskets. It had happened twice,both times on drivers bank. First time on old headbolts on standard felpro gaskets. It sucked the metal ring in on 7 and 8 but no obvious blow between cylinders. So i ordered up a set of Felpro 1020 gaskets and new Arp bolts, and installed by the book with no gasket sealer. It looks like it burned a hole between 6 and 7 but gasket looks good otherwise even though i had a minor oil leak right around cylinder 8 which was almost certainly coming from between head and block.

I want to note both head and block were decked flat for the build. I believe the block was .012 and heads .006

Only thing i found out of normal was that the timing was a bit advanced the second time as it would begin to ping under load. Runs on 91 no ethanol.

Whats next?
I'm going to double check for flatness but maybe studs? As far as i know, 1020 gaskets are some of the best out there for the FE.

I'm hoping someone older and wiser than me is seeing something im obviously doing wrong...i just don't know what it could be at this point and i don't like throwing parts at things.

Compression ratio is right around 10 to 1, iron heads.

Thanks

 

Chase the threads in the block with a tap and make sure they are nice and clean? The one time I had head gaskets go on a motor I built, the threads in the block were all screwy and the tap cleaned them up nice and never a problem afterwards. I learned from that mistake. I was young

Other than that, if you run the head bolts into the block without the head on, are they all bottoming out about the same depth, AND check the exposed length of the bolt and make sure they are going in far enough that the head and gasket would be held strong enough?

 

I will also ask if you are lubing the bolts with motor oil?

 

Bolts were lubed with supplied arp slippery stuff in the box

 

Never thought to chase the threads, i will check them out!

 

When's the last time your torque wrench was calibrated?

 

Bought a brand new kobalt unit for the job, but never had it calibrated...didnt know that was possible to be honest.

I also have an old trusty beam style wrench i use.