I have the worst luck with header gaskets. I just got a new 351 based combo together and the first time i smash the throttle i pop a brand new set of percy aluminum gaskets on my #8 cylinder. The header flanges were sanded flat before i installed them and all the arp bolts were snugged up tight.

Do i have a back pressure issue causing my gaskets to push out?

Should i only run silicone?

Ive also tried remflex and had the same issue

 

Did your bolts back off from vibrations? I know you tightened them before hand. Always the same exhaust port? Did you check both sides with a straight edge afterwards? Ultra copper rtv could be your solution. You could try splitting the flanges between each exhaust port if all else fails.

 

The rtv really only works well when everything is flat. It's suspicious that it's more than one brand of gasket and the same cyl. I would recheck flat, and port mismatch. Also, what headers? Do they have a thin head flange? And just to have all the info, what's the combo?

 

I like to use the Cometic MLS type gaskets, may want to give those a try if you haven't yet. You may also want to try a set of locking header bolts to make sure they aren't backing out after start up.

 

If the flange is true the head likely is not. The graphite style gaskets are the best as far as filling in imperfections that I've seen. Usually sold as "REMFLEX" I'd check that the manifold surface with a machinists edge.

Might also cut the aft manifold runner from the flange base to allow max flex. Similar to how these are cut in the middle.

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What kind of header/flange? How thick is it? Has alignment been checked?

 

I noticed when I replaced the gasket on Sunday that some of the bolts had loosened up a bit.

I'm running a pony down stage 3 hotside and I had to have the 1/2 flanges sanded as they were quite uneven when I received them.

I didn't think to check the mating surface of my afr205 heads but I couldn't imagine them being warped

Im going to try a set of Percy's locking header bolts

 

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here's the blown Percy's gasket

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I've run Percy's gaskets with no problems. Can you tell if the gasket was compressed around the port or not? Thinking it must not be.

 

Check out nxcoupes coyote build thread. He used stage eight headerbolts, they cost a bit more but once they are set they never back out. It is cheaper to try this first, but like force fed says splitting they manifold flange also helps.

 

Listen no joke I used every type of header gasket and it’s a turbo car with lots of backpressure and the flanges were not true so the back side by #5 and especially #7 it’s warped and well I even used all the aluminum ones .120” thick and the one one to now hold for 7 months leak free is

“remflex graphite”

get the thick ones!!! Like .120”
I bet you will thank me just remember they are graphite and soft you have to be alittle more gentle and torque evenly and heat cycle the bolts retighten and forget about it I do once in awhile check the bolts that’s it

 

Am I the only one that doesn't run a gasket? Belt sand the flange flat, loop of grease around each port. Install and forget about them.

 

Dude I have and one side would be ok for alittle while that side was most true as in surface but the other side wouldn’t ever hold with my backpressure in my setup!
I still use copper rtv on my turbo to t6 flange never blew out

 

I don't run header gaskets either . Just some ultra copper rtv.its a wonderful thing to have flat surfaces actually I suggested splitting the flanges but no harm no foul. So how did the repair go?

 

Also running copper RTV on header and T4 flange here. Gasket schmasket.

 

Red high temp RTV works great for me.

 

I use stock manifold gaskets doubled. Paper to paper and the metal sides out. I have zero gasket problems since I started doing that.

 

If your blowing out Percy and especially Remflex gaskets you must have an issue somewhere. Id check the head to be sure. Ive use Remflex in some janky situations and still never had issues. I use them pretty much religiously for the reason they have never failed on me.

Do your ports properly line up?

Maybe look into the stage 8 bolts or using some NordLocks if your having back out issues. I will say stage8s are a royal PITA if access is tight...but they do work

 

I totally will agree remflex gaskets at least the .125” thick ones I will boost to hell and not have an issue where all other aluminum same thickness will blow out under boost have picture if needed lol

 

I use blue loctite on the bolts .

Im using the new high temp grey silicone now , but have also used remflex .

keeping bolts tight is key .

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