Vintage Mustang Forums banner
Cancel
Create thread New Garage Forums

Exhaust leak at header flange - I think...

Jump to Latest
2.5K views 10 replies 9 participants last post by  MSMach1  
J
#1 ·
I have been trying to troubleshoot a ticking sound that first seemed like valvetrain noise, but I am thinking it is more likely an exhaust leak at the header flange. It appears to be coming from the right bank, toward the back, so probably #4. It is a fresh engine, so of course I am concerned about a possible cam lobe, and I will be checking preload as well, but I am going to re-install the header first with a fresh gasket and better bolts.

The question here is whether or not you think I should cut the header flange. I put a straight edge on it, and I can see that the #4 primary is about .030" out of line with the other 3. The bolts will probably pull it tight, but what would you do? Cut or not cut? These are cheap painted Hedmans, so I have no issues with slicing off #4 from the rest of the flange...

I attached pics, and I do not see any evidence of a leak. I hear the noise only when fully warmed up and running on the hot side (220* or so). Engine is a 347 with Ford aluminum heads and a hydraulic roller.

Also, when installing the engine, I added new mounts (the cheap kind) and had a hard time getting the engine to sit in the frame mounts. I had to enlarge the block to mount holes and drop the engine in with loose bolts to get it to sit. Also, the header collectors did not line up with my welded-up exhaust system, so I had to start the collector bolts, header flange bolts and engine mount bolts loose, then tighten everything up. That may have caused a bit of a bind on the headers and may have contributed to an exhaust leak.

So now the header is out, and I have new gaskets, new steel header bolts (the stainless ones were rounding off too easily) and I also got the Ron Morris adjustable mounts. Before I do a deep dive into checking my lifter preload, I want to make damn sure my headers are tight! Oh, and I also have the band type butt connectors, so if the header flanges do not line up, they are getting cut off! I will use the band clamps and get it welded up later!

Thanks!
 

Attachments

J
#4 ·
Yeah, the Remflex gaskets do sound pretty good. I already have the Fel-Pro 1415's which I have used many times without any leaks. I might add the copper spray too. Never used that before.

I guess the question here is would you cut the header flange? I am not seeing a downside; I just don't know if it is needed. The bolts will probably pull that flange into shape.

Installing headers is about my least favorite thing to. :confused:
 
#6 ·
Remflex 3003 are the gaskets you want. Nice and thick and don't blow out. Just be careful handling them as they can bend/break on the middle. I've managed to reuse mine 2 or 3 times before I have to replace them.
 
#7 ·
The problem with cutting the flange is the tube could move up or down a bit and it's a PITA to get the bolt holes to line up.
I had a set of headers for a 5.0 that didn't have the flange to connect them all and one tube was just a bit out of alignment and they were a bitch to get on.

Maybe smear a bit of high-temp copper RTV on the gasket just on that port to help just a bit and see how it goes.

Also check your cylinder heads to make sure there isn't anything below the port preventing you from getting the port flag. Unlikely since all the others seemed good, but worth checking since you have them off. Some cylinder heads require a slight grinding on the header flange.
 
#8 ·
Fix your exhaust pipes. You do not want to be pulling things into place with header bolts into aluminum heads. Use some anti seize on the bolts into the heads. The gasket for the cylinder shown did not appear to be leaking. Agree with others as to gaskets and sealing.
 
J
#9 ·
Well, I appreciate the feedback! I did not think about the one primary not lining up with the port once the flange is cut, so thanks for mentioning that. Good reason to leave the flange intact!

Oh, and yes, pulling things into place with header bolts seemed like a good idea (sort of) at the time. Funny how these shortcuts tend to do little more than create more problems and more work. I am old enough to know this, but I do it anyway...
 
#10 · (Edited)
Use Remflex or Percys.

That could have put some binding and added tension on the headers.

If the flanges don't line up at the colletors, I'm not sure the pipes will either when the flanges are cut. I'd probably just drive it open headers to a muffler shop and have collectors repositioned.

The RMP mounts are nice and make things easier.
 
#11 ·
I didn't see this mentioned, but you want to progressively tighten the header bolts over several heat cycles. You will see after a run that the bolts won't feel as tight. Several heat cycles should do it. Also, I recommend using studs in aluminum heads.
 
Vintage Mustang Forums
posts
4.2M
members
101K
Since
2001
A forum community dedicated to vintage Ford Mustang owners and enthusiasts. Come join the discussion about restoration, modifications, NOS parts, troubleshooting, VIN codes, and more!
Full Forum Listing
Explore Our Forums
General Vintage Mustang Forum Mod and Custom Forum Want Ads Concours Forum Build Forum