67 Mustang - Valve cover seal leaking - what to do - Vintage Mustang Forums
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post #1 of 14 (permalink) Old 06-30-2019, 03:13 PM Thread Starter
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67 Mustang - Valve cover seal leaking - what to do

I am working on my first Mustang rehab projects. I have a 67 with an inline 6 cylinder engine, original. The car runs great, except for this oil leak that seems to be getting worse.

Over the winter I replace the valve cover gasket with a new one. I also use a sealer when putting the new gasket in place. Unfortunately, I snapped the back middle bolt when I was putting the cover back on. I seem to have a leak from the back area. See the pictures below.

Is there anyway to seal the valve cover with out drilling out the rear bolt ? The blots are pretty small, so I am not sure how to get that bolt out ? Does the head need to be remove and drilled out ? I have tried a tap screw, but have not had any luck.

Any insight here would be helpful

thanks
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post #2 of 14 (permalink) Old 06-30-2019, 03:28 PM
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Remove valve cover, it will never seal without the clamping from the bolt.

If broken bolt is above flush celebrate and try to grab it with vise grips and unscrew it.
No go? Cut a slot in the top of the bolt with a Dremel tool with abrasive wheel or a hack saw.
Unscrew with blade screw driver.

If the bolt is flush or below you got a couple choices.
Center a nut over the bolt and tig weld the nut to the bolt down the hole. Unscrew with wrench.

No tig welder? Got a friend with one? No?

As accurately as possible center punch the exact center of the bolt. Use a LEFT hand twist drill of a size smaller than the root of the threads. drill down through the bolt. If you are lucky the ccw drilling will spin the bolt out.
If not, gradually increase the size of the drill you are using until there is just a shell of the bolt left. With a pointy chisel, collapse the sides of the bolt and pick the bits out of the hole. Run a tap down the hole to clean up the threads.

If you succeed in buggering the threads go down to the auto parts store and buy a Helicoil kit in the appropriate size and drill, tap and install the helicoil.

What ever you do , DO NOT use one of the easy outs. They will snap off in the hole you have drilled and then you are done because nothing you have will cut the hardened steel of the easy out.

Fill the area around the valves with rags so the machining chips don't get into the engine.
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post #3 of 14 (permalink) Old 06-30-2019, 03:44 PM
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ASM109 is dead on. If your try vice grips or anything else to unscrew it, maybe hit it with penetrating oil to help, some heat first. Either way you have to have that bolt to seal the valve cover.


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post #4 of 14 (permalink) Old 06-30-2019, 03:54 PM
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Edit to say I am not referring to Asm109's post as half-assed! I hit post before I saw his spot on reply...




Half-assed solutions won't work here.

Pull the valve cover.

Get some cheap paper towels and cover the valve train, and push them down into the valleys against the head. Pay special attention around the broken bolt corner.

Spray the broken bolt with your choice of WD-40, PB Blaster, JB Penetrating Fluid, Kroil, etc. Use it liberally as you drill.

Get the smallest drill bit your comfortable with - I would start with a 3/32" and then use a 7/32" carefully, as it's getting close to the 1/4" diameter of the threaded hole.

Measure the depth of another bolt hole, and put a piece of electrical tape around the drill bit shank so you know when to stop.

Make sure you line yourself up perpendicular (90 degree) angle to the bolt/hole. Give the broken bolt a good dimple with a center punch to help the bit get a good start and not walk.

Drill carefully, not putting to much weight on the drill bit - let the bit do the work.

Repeat with the next size up.



If you get too close to the threads, a tap or even a thread chaser should be enough to clean them up.


It took more to type this than it takes to do it. Just take your time... then carefully pull the paper towels up with the shavings, vacuum the area if you need to get any of the shavings or dirt out of the head, and put it all back together.

1969 Mach-1 Mustang
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Back in Dixie DSO 22 (Charlotte)

Last edited by bbmach; 06-30-2019 at 03:57 PM. Reason: NOT SAYING Asm109's approach was half-assed!
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post #5 of 14 (permalink) Old 06-30-2019, 03:57 PM Thread Starter
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Thanks guys.
The bolt is sheered off flush, so I can't grab it to back it out.
I figured those were my options. I was concerned because the bolt is pretty small. To center drill seems really difficult.
I have a MIG welder, can I use that ? Should I weld on a flat washer first and then the nut on top. Someone recommended that.

I will start with trying to left hand drill this out and go from there.

thanks
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post #6 of 14 (permalink) Old 06-30-2019, 03:58 PM
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Drill and re-tap the bolt hole... If you don't get the old broken bolt out...It will always leak. If your can't grab hold of the broken bolt, You'll have to drill and re-tap...

Get a Fel-Pro Black Rubber I6 Valve Cover gasket... Use some Permatex Blue or None at all on the Gasket....I don;t like Original cork gaskets because they fail over time and wind up at the bottom of your oil pan eventually. Also, Buy all new AMK I6 Valvecover bolts from NPD or other vendors...Don't re-use the Original Valvecover bolts because they will just fail and break/sheer off the same..

It will never leak again...

This is simple stuff...

)

Tony K.



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Last edited by NEFaurora; 06-30-2019 at 04:03 PM.
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post #7 of 14 (permalink) Old 06-30-2019, 04:01 PM
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Mig will work. Washer too make sure the hole is smaller than the bolt so the weld bead only hits the bolt not the head.

Everybody has to start some place
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post #8 of 14 (permalink) Old 06-30-2019, 10:01 PM Thread Starter
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Thanks, I am going to try to drill and tap the bolts. They are cut pretty pretty flat and I can not grab onto the bolt that is left over. Do you have any recommendations on a drill and tap set. There are a bunch of brands out there. I bought one a while back from Harbor Freight and the bit's broke right away.

See the attached pic for the sheered off bolt that I am trying to get out.
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post #9 of 14 (permalink) Old 06-30-2019, 11:14 PM
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Center-punch that bolt first so your bit won't walk. Get some decent titanium or nitrided bits and work your way up to a #7 (13/64") bit. If you got the hole centered, you might be able to use a 1/4-20 thread chaser to knock the remainder of shards out and grab them with a magnet, working your way down or, if not, a 1/4-20 tap and cut them out. If worse comes to worst you can get a 1/4-20 helicoil or other thread insert kit which comes with the drill bit, inserts and tool, and fix it that way.

Bart

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post #10 of 14 (permalink) Old 07-01-2019, 12:49 AM
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Did you break the bolt?!??, Or did someone else break it?? If you broke it, You have a good shot at getting it out without drilling and tapping... My buddy showed me a good trick years ago... Get a dremel and dremel cutting wheel or dremel stone wheel...and cut a straight cut in the middle of the broken bolt...The same width as a Flat head screw head.. Make it deep enough so it won't strip.....then just take a screwdriver and reverse screw it out.... Great trick... If someone else broke the bolt off, Chances are that it's rusted in there by now and you'll have to drill and Re-Tap it anyway.. It's worth a shot.. I've used the method with great success and saved hours of time on various projects over the years.. Heating it up with a hand propane blow torch may help also...

)

Tony K.



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post #11 of 14 (permalink) Old 07-01-2019, 06:59 AM
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All great suggestions on getting the broken bolt out.
After you get it out I would suggest looking at the valve cover carefully, I bet the gasket surface is not flat. That would explain why it leaked after you put a new gasket on, someone kept tightening it down to stop the leak and bent the area around the bolt hole. Then eventually cranked on it so much that it broke.
These bolts should never even come close to breaking, torque specs are in the manual.

Lay a metal rule on the gasket surfaces and see what you have. If it is bent you may be able to straighten it out with a block of wood and small hammer. Or, might be worth getting a new one.

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post #12 of 14 (permalink) Old 07-01-2019, 08:32 AM
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If you broke the bolt while tightening the valve cover down, then you were tightening the bolt(s) way too much. When you tighten the bolts down too much, you will distort the valve cover flange which will lead to leaks. Once you get the bolt out, check to see if the cover flange is distorted. If so, massage it so that the flange is flat with no waves in it. With a good gasket and using sealer properly, you don't need to tighten the bolts that much. Not sure what the torque specs are. I do it by "feel" Maybe someone can chime in with the proper torque spec.

Dave
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post #13 of 14 (permalink) Old 07-01-2019, 09:31 AM
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All good info posted above.

When you get the bolt out you might use studs instead. If you don't mind not being original.
Personally, I have had better luck with cork than rubber gaskets. But Tony is usually right. Plus I have 4 different valve cover's I switch to from time to time.
Here is some info I posted on another site:

Here are some options:

1. Stainless studs from Ebay around $7
2. Home Improvement Store Stainless Allthread cut to length yourself. Plus washers and nuts around $12.
3. ARP 200-7601 SB Chevy (for stamp steel cover/aluminum cover needs longer studs) around $21.

I went with the black ARP studs.

Also as mentioned earlier make sure you valve cover hole's and sealing area is flat and not warped. Over the years it gets warped from over tightening.

Let us know how it goes.

...Marco

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Schneider 264/274 cam, Headers, Recurved DSII, MSD 6A, and a whole lotta other stuff!

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post #14 of 14 (permalink) Old 07-01-2019, 10:15 AM
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Those VC bolts are probably 1/4-20 and the torque on them should be no more than 8 ft/lbs according to my charts. Use a little blue locktite to insure you don't loose any of them.

John

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