Header gasket leak

rdc767 · #1 (**permalink**) 01-27-2009, 05:13 PM

I have a 351w that has a header leak all the way across. As you can tell by the gasket it is leaking out the bottom on every cylinder. Is this the header bolts backing out or are the side pipes twisting the headers with the engine torque?
I bought some spilt locking washes to see it I can stop the bolts backing out. If that fail I will drill the head of the bolts for saftey wiring. I had to retorque them a few times over a few short hours of running.

marcalan · #2 (**permalink**) 01-27-2009, 05:19 PM

You might want to try using some RTV silicone, I used RTV (high temp) on both sides of the header gasket. I have retightened once after the initial startup.

trctrdrvr · #3 (**permalink**) 01-27-2009, 05:46 PM

I had the same problem, bought some copper gaskets and it fixed it

vector1 · #4 (**permalink**) 01-27-2009, 06:20 PM

split your headers and use rtv.

MaSnaka · #5 (**permalink**) 01-27-2009, 07:34 PM

rdc,
I found that not all exhaust manifold gaskets are the same. They would barely cover the header ports and leak. Then I discovered a gasket actually made for headers and it covered much better and no leaks. I have a 390fe, but thought my experience might help you out.

John

bobcowan · #6 (**permalink**) 01-27-2009, 07:53 PM

Place the gasket across the header flange. On some of theses cars (like mine) the header ports are considerably larger than the head ports. The gasket fits the heads, but not the headers.

Ronbo · #7 (**permalink**) 01-27-2009, 09:02 PM

It's not so much the gaskets as it is the bolts constantly loosening.

Get a set of Stage8 or Percy's locking bolts. Lock washers loose their grip from the constant heat/cool cycles.

Snakebit · #8 (**permalink**) 01-28-2009, 08:16 AM

Percy aluminum gaskets and ARP headder bolts pre drilled for safty wire, no problems. Just as a precaution, check the header flanges with a straight edge.

vector1 · #9 (**permalink**) 01-28-2009, 10:14 AM

as i said above, cut the flange between the middle two pipes at the least, i cut between all flanges and use rtv. never had a problem with things loosening if rtv the bolt threads before insertion.

don't have to worry about the flange being straight. also, if aluminum head, the expansion is considerably more than a strap of metal across the side, leads to blown gaskets and loose bolts.

hth

scottj · #10 (**permalink**) 01-28-2009, 01:31 PM

I've always used silicone only, no gasket. I too, use silicone on the threads and I've never had to re-tighten the bolts.

My LS7 came with MLS gaskets so I'm curious to see if the work as well on my self-fabbed headers as they do on the Z06... if not, I know the silicone will.

Scott

PANAVIA · #11 (**permalink**) 02-05-2009, 03:18 AM

Graphite gaskets-- may be an option as well, also make sure you are hooking the headers up with nothing else "downstream" so you are assured of a seal and the headers are not "Cocked" at an angle.

decapello · #12 (**permalink**) 02-05-2009, 08:13 AM

Is the pattern of the exhaust leak the same on both headers? If it is just one side it may be the engine torque causing the headers to lift. If it is the engine torque would it be leaking from the bottom on one and the top of the other.

PANAVIA · #13 (**permalink**) 02-05-2009, 10:52 AM

Decapellos post made me thing of this, -- are you sure your header bolts are not bottoming out in the holes, prior to the flanges being tight>? (bolts too long) if they are "close" then the tourque twist argument makes sense.

priobe · #14 (**permalink**) 02-05-2009, 11:46 AM

Here is an idea.

Take the header and lay a straight edge across the header in 3 places (straight across, bottom to top angle, top to bottom angle)

If possible do the same for the head exhaust to make sure both surfaces are flat.

Use a belt sander on the header to get it flat.

You can cut the header per port but if the worpase is on the port of the head you are out of luck.

I resurfaced my headers and head when it was off and I have no issues with leaks

Dwight · #15 (**permalink**) 02-19-2009, 05:11 PM

I have a pair of copper gasket that look just like your, leaking everwhere they could. I hung them on the wall and bought the laminated aluminum gaskets. 15,000 miles later, no leaks.
I think the headers that most of us use are not straight and most header gaskets will not seal. The aluminum laminated gasket works best. You may have to use more than one. Mike and I peeled them apart and used one and half per side because of the warp in our flanges.
I like the Stage 8 header bolts, Mike hates them.

Dwight

CHANMADD · #16 (**permalink**) 02-19-2009, 05:20 PM

The problem seems to be that the Bolts are coming loose. It is completely normal to have to retighten the header bolts a few times after initial startup.
I used to use just Silicone ,and then gasket and silicone ,but now I use stock OEM gaskets dry and nice and tight with the metal side to the headers.
I still check for tightness often.
The huge headers and sidepipes that "hang" on those bolts are quite heavy and have good leverage on the bolts!
John