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Old 09-18-2022, 08:40 PM
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Default Water neck sealing -- what's the best way?

Hey tribe. Thanks again for the excellent help I got on my last issue, the alternator / wiring PITA. Very helpful. (All of you were right, it's not the alternator.)

I'm getting some leakage from the water neck base of my '71 Formula 400, so I'm replacing it. It's a paper gasket, not the o-ring kind. I know leaks on these necks can be both common and persistent... what's you guys' take on the best way to seal these? Should there be gasket sealant between the gasket and manifold, water neck and gasket, or both? Should I put silicone on the bolt threads? Finally -- is there a certain torque value for these bolts, or just get it good and tight? Again, my thanks for all the expertise on here.

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Old 09-18-2022, 08:59 PM
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Your best bet is to go to the parts store and get a can of a sealer called "The Right Stuff". It's the best there is, hands down. It is leaps and bounds better than any other RTV out there. I use it without a gasket, but you can use one if you like. If your water neck is pitted, I also recommend grabbing a new one. They've gotten cheap for new ones, I think RockAuto has them for $10-15 or so. Hope this helps!

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Old 09-18-2022, 09:07 PM
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I had to have the mating surface milled a little on the intake itself. Just wouldn't seal even with new water neck. Right stuff is good product so try that 1st.

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Old 09-18-2022, 09:21 PM
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if you ever have to change a thermostat DONT use the right stuff!There is better sealants.I use Hylomar on both sides of the gasket.Take the fixture and put a piece of sandpaper on a really flat surface and run it on the paper until flat.Try to clean the intake side real good.Should NOT take much.Good luck with your project.Tom

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Old 09-19-2022, 10:05 AM
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i have used permatex ultra black or grey on most gaskets for these engine, never had a
stock water neck leak or other areas leak. i usually use the supplied gaskets too with just a thin coat of the permatex to help seal any pitting or imperfections.

but i also use the chrome O-ring type water necks on 2 of my cars, they work great & have never leaked, beauty of that style neck is you can remove it multiple times without hassle of cleaning old gaskets or sealers & when the O ring gets too old & flat you just buy a new one for a dollar & its like new.

torque rating for most 3/8 bolts like this is about 25-30ft/lbs. i snug them up after a few heat cycles & check every year or 2 for tightness. same with most other bolts, especially header bolts, cant just tighten them once & forget it then blame the headers or water neck etc for leaks.

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Old 09-19-2022, 05:52 PM
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Okay, thanks. Yeah, I'm replacing the neck, should have specified that at the gitgo. Of course the rear bolt broke off at the head. Once I get it drilled out, what are good replacement bolts? Stainless steel?

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Old 09-19-2022, 05:56 PM
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Quote:
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i have used permatex ultra black
^^^This. Good stuff!

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Old 09-19-2022, 05:58 PM
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I would not use stainless. They can gall quite easily.

If you don't have the factory bolts available, just use good zinc plated bolts from your local hardware store. You can also go all the way to cadmium plated grade 8 bolts, but they are not necessary for such a low torque situation.

Hope that helps.

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Old 09-19-2022, 08:56 PM
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Not saying it’s the best way but my water neck always seemed to seep eventually no matter what I did. Sometimes after a few years and sometimes not so long. Years ago my dad bought me a water neck like this….

https://www.jegs.com/i/JEGS/555/511301/10002/-1

…..thinking it would solve my issue. I left it in a box for years thinking I would have better luck with my original water neck. A couple years ago I think I decided to try it while replacing my thermostat and I’ve not had a single drop escape since. For what it’s worth.

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Old 09-19-2022, 10:06 PM
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Yes. If the mating surface on your manifold isn't all pitted up, it's hard to be an O-ring for sealing, IMO.

John

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Old 09-19-2022, 10:30 PM
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Flatten the sealing surface of the neck with a file. I've even rubbed them around in circles on concrete to do this. Then DO NOT over-tighten it when reinstalling. That's how they get warped in the first place.

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Old 09-20-2022, 09:10 AM
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I have pretty good luck lapping the bottom of the neck on a surface plate and using a file on the intake.

I did contemplate trying to figure out a way to mount the neck in the lathe and cut an o-ring groove but never came up with anything. If anyone has any ideas on fixturing a neck in a lathe or on a rotary table on a mill .. I'd like to hear it.

I'd go the o-ring route in a heartbeat if they made one non-chrome and identical to the OEM piece.

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Old 09-20-2022, 09:39 AM
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Quote:
Originally Posted by Baba O'Riley View Post
Okay, thanks. Yeah, I'm replacing the neck, should have specified that at the gitgo. Of course the rear bolt broke off at the head. Once I get it drilled out, what are good replacement bolts? Stainless steel?
standard grade 3 bolts are fine, best way to prevent corrosion/rust is to use anti-seize, just be sure to adjust the torque about 10%.

if originality is not a concern, the O-ring necks are great & for $10-15 are well worth it, with all the aluminum & chrome parts people use on non original look engines, these look & work great.

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Old 09-20-2022, 11:46 AM
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I'd use grade 5 because they would be less likely to twist off if they get any corrosion. Plus, I'm not aware of the factory ever using grade 3 bolts anywhere on automobiles.

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Old 09-20-2022, 12:11 PM
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I'd use grade 5 because they would be less likely to twist off if they get any corrosion. Plus, I'm not aware of the factory ever using grade 3 bolts anywhere on automobiles.
sorry, meant grade 5. the bolts with 3 dashes on them... was early in the morning so confused the 3 dashes with grade 3.

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Old 09-20-2022, 01:21 PM
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Okay thanks, one other thing please -- what's your preferred spray-on for loosening broken bolts? A couple car guys I know say WD-40 isn't that effective, one recommended PB Blaster aka B'laster. I'm going to use a bolt extractor on it but want to give it an overnight soak in something that will hopefully loosen it a little. It's the original manifold so of course it's pretty frozen in there.

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Old 09-20-2022, 03:08 PM
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As others have mentioned lapping the housing is important. The aluminum deforms over the years.
I have used an old truck mirror and a piece of 400 grit wet dry sandpaper for years. Get the sandpaper wet and make circles on the sandpaper. Be careful to always keep the gasket surface flat to the sandpaper.

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Old 09-20-2022, 04:19 PM
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Quote:
Originally Posted by Baba O'Riley View Post
Okay thanks, one other thing please -- what's your preferred spray-on for loosening broken bolts? A couple car guys I know say WD-40 isn't that effective, one recommended PB Blaster aka B'laster. I'm going to use a bolt extractor on it but want to give it an overnight soak in something that will hopefully loosen it a little. It's the original manifold so of course it's pretty frozen in there.
PB blaster or liquid wrench are both good penetrating oils, another brand thats very good but hard to find is kroil.

for heavily corroded/rusted/seized bolts, none of those will do much good... heat is the best option & will get out almost any stuck bolt/nut if used right. the idea is to heat/expand the outer area the bolt goes in to, then loosen the bolt while that area is still hot. if that doesnt work or you cant get to the outer area to apply enough heat, the bolt itself can be heated, to red hot if possible, then let cool before removing, the bolt expands when hot breaking free the rust bond, then when everything has cooled it should come out easier. sometimes a few times are needed.

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Old 09-20-2022, 06:29 PM
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Originally Posted by 78w72 View Post
PB blaster or liquid wrench are both good penetrating oils, another brand thats very good but hard to find is kroil.

for heavily corroded/rusted/seized bolts, none of those will do much good... heat is the best option & will get out almost any stuck bolt/nut if used right. the idea is to heat/expand the outer area the bolt goes in to, then loosen the bolt while that area is still hot. if that doesnt work or you cant get to the outer area to apply enough heat, the bolt itself can be heated, to red hot if possible, then let cool before removing, the bolt expands when hot breaking free the rust bond, then when everything has cooled it should come out easier. sometimes a few times are needed.
Excellent, thank you. I'm a little nervous using flame right next to the carb, but there's those $10 mini-torches that throw a pencil-sized flame. If the penetrating oil doesn't work I'll try that.

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Old 09-21-2022, 09:55 AM
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if theres no leaks & the air cleaner is on, using a propane torch should not be an issue, just use common sense & direct the flame away from the carb & be sure theres adequate ventilation... always a good idea to have a fire extinguisher near by in the garage too regardless of using a torch.

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