Piston Failure

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Do both sides and deck the heads. Give it a fighting chance.

You have serious detonation issues to do that. Start working on learning to read plugs. And A/F meter is a help, but you still need to read plugs.
 
Also, take a look at the imprint patterns around the various coolant passages; Ima thinking that deck ain't quite flat and probably not quite rough enough, and/or just maybe the intake was trying to lift the heads across the valley side.
At 180psi my 100Xs are doing fine, so I know they can take a licking.
 
I had that happen twice with felpro’s. I know they call for no need to retorque, but I started to torque them and let them sit over night. Then back each one off a 1/4 turn then retorque in order. They always turn a bit more and have stopped pushing the fire ring towards the valley. Then I finally went to cometic.
 
Better you blew a head gasket than one of your pistons, for sure. I wish that was what happened to my engine instead of the opposite, I was also running Fel-Pro 1008's IIRC... no matter my current engine is better anyway, Cometic head gaskets with ARP head studs holding down ported Edelbrocks.

Definitely get a wideband O2 sensor on there and check the plugs frequently. And machining the decks is a good call.
 
as is checking your block with a machinist rule up down and sideways
4 head bolts are tough I retorque
Three are also HD Marine/ truck/ industrial gaskets available (or were) from Victor and McCord stainless cores and better materiel but may be thicker
happens again then o rings or are your fel pros the o ring ones?
 
The Felpro 1008 is a good head gasket...I've used that gasket on my current motor (13:1), previous stroker motor (10.8:1), and my previous 2 nitrous motors with no issues. Like others said, deck the heads (check the block surface while you're there), use good head bolts (like ARP) and try again.
 
I checked the heads with a machinist's straight edge not even two months ago before I put this setup together. They weren't perfect but within .003"-.004" if I remember correctly. I've already called the machine shop and talked to them, I'll pull the other head this afternoon and double-check how flat they are before any final decision. But as of now I'm looking at heads milled, gaskets, probably new head bolts/studs, check the block deck. They're magnum heads and if I remember correctly from the last time I looked, ARP doesn't offer a head stud kit but they do have bolts.
 
Charlesvolare said:
I checked the heads with a machinist's straight edge not even two months ago before I put this setup together. They weren't perfect but within .003"-.004" if I remember correctly. I've already called the machine shop and talked to them, I'll pull the other head this afternoon and double-check how flat they are before any final decision. But as of now I'm looking at heads milled, gaskets, probably new head bolts/studs, check the block deck. They're magnum heads and if I remember correctly from the last time I looked, ARP doesn't offer a head stud kit but they do have bolts.
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Mill the heads. .003 out is too much. A feeler gauge and straight edge is NOT a dial indicator.

Again, give yourself a fighting chance. Mill the heads.
 
I got my heads milled, ended up taking 0.010" to get them flat. also got my rockers shimmed perfect while I had the heads off.
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I put everything together and now there's a few things:

1) There's been a slight leak at the rear drivers side the past few times I've had the head off. I usually remedy this by a bottle of bars block sealer and the problem is solved. I switched the heads around to the other sides and even with the heads milled and switched, it still trickled. Bottle of sealer fixed that though. (I really suspect block deck issues now)

2) Fixed that small persistent issue, idled up to temp a couple of times. No leaks, no smoke- good to go. Drive around the block (~5 miles, warmed up and hammered it a little). Got back home and there's coolant residue on top of the timing cover and running down the drivers side. Wiped it clean.
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Borrowed a cooling system pressure tester and pressurized the system, it's definitely leaking. Its hard to tell where from, maybe the intake to head, maybe head to block. Made sure the intake was torqued to spec and switched from a 16lb cap to a 7 lb cap, and went for a spirited test drive in the rain....
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0.010" off the heads shouldn't affect the intake mating should it? I'll take another look at the head bolt torque as soon as it stops raining. This is with flat heads, fresh gaskets, CLEAN surfaces. Maybe RTV squeezed up into the coolant port when I was setting on the intake and affected the seal? It's difficult to tell if it's leaking at the top and running down the head/block crack or if it's pushing out from said crack.
 
My 340 just blew the head gasket on number 7, it also started to blow cylinders 3,5. I went with Felpro 1008.
 
It's pretty low quality and bad lighting, but I pointed my inspection camera at the intake/head/block area and pressurized the system. You can see it reflecting as it's leaking. Hoping its a bad seal at the intake, maybe rtv sealing the valley squeezed up into part of the coolant port and somehow is causing a leak. I've sealed intakes dozens of times without problems, but there's a first time for anything. Imy open to opinions if someone has any other explanations.

 
I always smear a thin coat of RTV around the water ports on my intake gaskets. Both sides of the gasket.

I had a bad leak there when I swapped my OE magnum intake for my edelbrock intake. I replaced the cheap gaskets with some “premium” fel-pros and still had a leak. RTV cured the leak for good on the 3rd try, so I always do it now.
 
Regasketed the intake, still leaks. I'll make a new thread with all of the details since I don't think it's really related all too much to this one.
 
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