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A few days ago I was driving my '77 with about 150 miles on the rebuilt engine, I gave it WOT to test the 2 -> 1 kickdown on the new Bowtie Overdrive 700R4 and immediatey heard a new noise. When I got it home and in the garage there was a ticking sound from the right side that matched engine rpm. Today I took off the right side header (Hedman 68301) and this is what the gasket looked like. The bolts were tight. So I am going to replace both sides with Mr. Gasket 7402G, high performance 1/8" thick multilayered aluminum gaskets, anyone have any experience with them?
on circle track race cars w/ sbc & headers ... we had little success keeping gaskets together ... we heard of a trick ... NO gaskets ... just a thick bead of whatever RTV was on hand no matter color.
Thick bead, let it skin over, bolt up headers but don't squeeze it all out, let it cure overnight, next day tighten bolts, then push it outside & fire it up, it smokes & stinks like crazy for a while but soon settles down & stays sealed up ... thru many races of many laps of WFO ... turns out, lotsa others were doing likewise ... YMMV
You have to re-torque them constantly for the first few hundred miles. I made it a habit of tightening mine after EVERY ride for the first few weeks after a rebuild. Yeah, it sucks but they will eventually crush properly and seal.
Now, if you are 100% sure, beyond a shadow of a doubt sure, like bet your car title sure...that those bolts were still tight....you may want to consider 'splitting' your header flange. I have a set of ceramic coated Heddman headers on my big block that just kept blowing gaskets. Same spot, every time. I took a dremel and made a vertical cut in the flange between the pipes. This essentially lets you correct any factory out of true issues your headers may have and tighten your troubled section independently. I know it sounds drastic, but it solved my problem 100%.
My engine builder told me about the gasket sealer only option, he recommended Permatex Copper. I am going to hold that on in my back pocket and use it if the aluminum gasket fails,
The bolts on the side that blew out were still tight. Interestingly the ones on the other side which are much harder to access were not tight but no blow out. There was some carbon buildup around the runners though. I am aware of the splitting-the -flange option but putting a stratigedge across the ports shows they look pretty flat. Since the aluminun gasket is designed to crush .060" it sure seems that should be enough to compensated for any slightly uneven surfaces.
Hoping that someone has used the aluminum gaskets...with either good or bad results
Put a straight edge on it and measure underneath with a feeler gauge. Probably .005" is too much.
You could take a file and try to make it flat.
It looks like when these are fabricated the tubes are welded to the flange and then the weld bead milled off. On my headers there is some remaining bead standing proud of the flange, about .030 - .040" and I assume that is per design. Five thou would be tough to hold on a mill over that length, easier on a surface grinder but I would think that if they did that then these things would cost more than they do. If I can get the header out of the engine bay I'll measure it, there is a lot more stuff in the way than there was when I bolted them on.
I tried Percy's aluminum gaskets on my '82 Z28 after arguing with the regular gaskets for awhile.
They sealed up perfect.
I would expect any brand name aluminum gaskets would work fine.
i didn't use the aluminum gaskets on my '74 coupe, but if they hadn't sealed up, I would have replaced them with some Percy's.
I did have to check the header bolts everytime I drove it for about 2 weeks. Then they stayed tight.
Good luck.
Jeff
I have learned there are $12 header gaskets. Then there are $36 gaskets. What's the difference? A good seal.
I ordered a set of Percys aluminum from Summit. When I opened the package, it appeared they accidently sent two sets. Further inspection showed layers upon layers of aluminum connected pieces for each gasket. What that does is, squeezes down and fills in imperfections of the flange.
Scottd post # 4 has the right idea. But you don't have to cut all the way through the flange. If you are familiar with woodworking, you cut a kerf. A kerf only puts the blade of a saw half way or less through the material. This allows the header to flex. If you cut your kerf on the backside of the flange, no one will see it, against the head. A kerf works well between cyl 1 & 3 and between 5 & 7. Same way other side. Several strokes with a sharp hacksaw makes quick work of that.
Good ARP header bolts (small head w/ built in washer) are a must. Like others said retorque often for the first few weeks, then a couple times a yr.
Last edited by HeadsU.P.; Feb 19, 2020 at 09:05 AM.
I tried all the gimmick bolts with locking clips...… And the best, smartest, and only way to go is with ARP studs in the heads and Felpro blue steel impregnated header gaskets. We never blew gaskets even on 800+ HP sprint car motors or my Vette.. I use the ARP 5/16th nuts to clear my 1 3/4 headers and a dab of high temp red silicone.
I even reuse the header gaskets. Installing headers is so easy with studs. You hang the gasket and then the headers. No dorking around trying to hold crap and line up bolts. Never a problem starting to catch the threads.
I have used the aluminum and copper gaskets and they have worked fine. But I have never had a good quality regular gasket fail any where if I color it with high temp RTV. I like the black. So put some rubber glove on get out the RTV put it all over the gasket sides and all. Not thick almost like your painting it. Let it skin for a few minutes. Put together let it sit over night. After you drive check the bolts for tightness a few time after every drive . I have had bolts fall out and still not have a leak.I have also used RTV only on my boat headers with no leaks
Make sure that the port opening on the head is not larger than the gasket opening. Exhaust gaskets come in different sizes. You could be forcing exhaust gasses against the gasket.
Thanks for the advice guys, all of it good. Finding fasteners that work on my headers has been a real pain. I have tried the special ones but because some of the runner tubes are so close to the bolt holes I can't get a socket over them. What works best are 3/8 stainless socket head cap screws that I can drive with an allen driver. Even on some of those I had to grind down the OD a bit to clear. I do use studs on the outsides to get everything in place but then I have to pull them out and replace with the SHCS because nuts interfere with the runners.
Good idea to check the openings in the head and gaskets to see if they match, I haven't done that.
What does the backside of your header flange look like......those round port gaskets seal round port headers.....if you have standard 1 5/8" headers, then the 1404 Fel Pro is what you want.....
From your first pic it doesn't look like you are sealing all of the flange.........
What does the backside of your header flange look like......those round port gaskets seal round port headers.....if you have standard 1 5/8" headers, then the 1404 Fel Pro is what you want.....
From your first pic it doesn't look like you are sealing all of the flange.........
Jebby
A quick look shows that everything matches up (all circular holes) but right now the headers are hanging loose in the engine compartment, I haven't pulled them out yet. Looks like I need to do that because taking a closer look I think I see why I had problems getting all the bolts in. I think they weld the runners to the flanges and then ground away whatever weld went into the bolt clearance holes. They may not have cleaned all of that out, looks like I can take a die grinder and open that up a bit. I don't think I looked at that closely when I did the installation, maybe there was some binding going on so the bolts felt tight but they weren't pulling the flange down on to the head.
Thanks for the advice guys, all of it good. Finding fasteners that work on my headers has been a real pain. I have tried the special ones but because some of the runner tubes are so close to the bolt holes I can't get a socket over them. What works best are 3/8 stainless socket head cap screws that I can drive with an allen driver. Even on some of those I had to grind down the OD a bit to clear. I do use studs on the outsides to get everything in place but then I have to pull them out and replace with the SHCS because nuts interfere with the runners.
Good idea to check the openings in the head and gaskets to see if they match, I haven't done that.
That is why I have studs that use 5/16th tiny nuts. I can run for years and never retighten anything!
That is why I have studs that use 5/16th tiny nuts. I can run for years and never retighten anything!
Ok, I did not catch that in your reply above, So I see on the ARP site that they have studs with two diameters, 3/8" to screw in the head and 5/16" coming out of the header flange. Yeah that would help with the interference. Good to know if I can't get the SHCS to work.
Blown header gasket
I have also used RTV only on my boat headers with no leaks
