Introducing a 1970 300 TNT convertible

[saforwardlook]

Quick update on the TNT.

As a first fix to get the cooling going, I had bought (and @david hill had installed) a Spectra Premium CU332 radiator in the spring. The idea was to have a brand new radiator in the car so it could be driven, while we looked for a good shop to recore her original 2998970 radiator. David found the right person and dropped off the rad two weeks back. Good news, he got the 2998 970 radiator back yesterday. After painting, it will be reinstalled this coming week. The (now almost) new CU332 will replace, to improve cooling at rapid highway speeds, a similar unit in Buttercup, my 1972 NYB, whose radiator is not original anyways (it likely is an old CU332 -- looks like it).

David also will be installing new manifold cover gasket. I bought the last 1968-71 Big Block C-Body Exhaust Manifold
Fastener Kit (for HP BB 383 440 engines) from 521 Restorations on eBay to that effect:

View attachment 493484

I also got from Summit three Mahle F5561K exhaust pipe flange gaskets, and a Fel-Pro MS90029 exhaust manifold gasket for U-code engines

I find 521 Restoration's choice of grades for the studs and nuts to be curious. Most of my experience with problems with exhaust manifold mounting hardware is that the nuts usually rust solidly to the studs over many decades of use. That usually results in one or more studs that shear off when trying to turn the nuts off the studs - which could necessitate taking off the heads to be able to replace the studs. I would have thought the studs would be grade 8 (harder to shear off) and the nuts grade 5 (softer to allow them to turn off easier). Is there an issue with the grade 8 steel (maybe because of higher carbon content) to cause more rust and the nuts would turn off more easily being grade 8 and the studs to be grade 5 or what do you think?

Maybe with a good coating of anti-seize compound on those pieces though, this might not be a big problem. After many hours and time in such a hot environment, though, I also wonder just how long/effective the anti-seize compound would remain in place and continue to be effective??

 

[Big_John]

I find 521 Restoration's choice of grades for the studs and nuts to be curious. Most of my experience with problems with exhaust manifold mounting hardware is that the nuts usually rust solidly to the studs over many decades of use. That usually results in one or more studs that shear off when trying to turn the nuts off the studs - which could necessitate taking off the heads to be able to replace the studs. I would have thought the studs would be grade 8 (harder to shear off) and the nuts grade 5 (softer to allow them to turn off easier). Is there an issue with the grade 8 steel (maybe because of higher carbon content) to cause more rust and the nuts would turn off more easily being grade 8 and the studs to be grade 5 or what do you think?

A couple of thoughts... First is I'll bet the "grade 8" nuts choice is more about the look rather than the spec. They are more squared off and look more "factory OEM" than most other nuts. When you think about it, the other special nuts are probably just some low carbon steel that some guy with a screw machine in the back of his shop knocks off a few hundred at a time. Again, appearance is the requirement.

With that said, the studs that break are usually the ones with the special nuts.

The studs are an off the shelf item. I've bought these same ones at my local hardware store (although it's been a few years) and IIRC, decent ones are all spec'd Grade 5. I really don't know if a Grade 8 spec'd stud would be readily available. When you think about it, Grade 8 fasteners aren't needed in this low stressed application. In fact, the Grade 5 may be the better choice for something that's heated and cooled on a regular basis.

Of course, I'm not well versed on fastener specs, so I'm not going to say what is right either.

Maybe with a good coating of anti-seize compound on those pieces though, this might not be a big problem. After many hours and time in such a hot environment, though, I also wonder just how long/effective the anti-seize compound would remain in place and continue to be effective??

I've wondered about this myself... and really came to the conclusion that the anti seize would either bake out and do nothing... Or would bake out some of the anti seize, leaving some of the product to lock the threads and actually make it harder to remove in a few years... Or would not let the nuts stay tight in use. So... rather than think about it until my brain hurts, I just put them on and hope for the best.

Last time the manifolds were off my 300, I farmed the job out. The PO had installed gaskets and of course, they blew out as they always do. Time constraints and some issues with me (I had just had surgery) and my favorite mechanic did the work. One stud broke and the head had to come off.

 

[Big_John]

a Fel-Pro MS90029 exhaust manifold gasket for U-code enginess

The factory never used that gasket. It's been my experience that a gasket used between the manifold and the head will always fail at some point, even the special RV gaskets.

 

[saforwardlook]

I personally use grade 8 studs to help prevent the not unusual tragedy of a stud breaking and the cylinder head having to come off in order to get a good aim at the problem. I use grade 5 nuts usually but was considering using non graded ones but haven't had the courage to try them out yet.

 

[ayilar]

The factory never used that gasket. It's been my experience that a gasket used between the manifold and the head will always fail at some point, even the special RV gaskets.

Correct, but I've read from both sides about whether exhaust manifold gaskets are a good idea or not.

I thought hard about this when @71Polara383 went over the engine for Medina, my 1971 Monaco -- see the discussion starting here. After reading that @saforwardlook uses gaskets on his cars, I decided to get one for Medina, and I've been happy. The one I selected for Medina, at the suggestion of @cbarge and @Dana (see the same thread), was a Fel-Pro MS90425 gasket with heat shield. Several thousand miles and 1.5 cars later is too early to tell, but so far I've had no issues.

That positive experience with Medina is why, when @david hill asked that I get the Fel-Pro MS90029 kit, I went ahead. That kit does not have the heat shield but is listed as appropriate for a 1970 U-code engine.

 

[Big_John]

I personally use grade 8 studs to help prevent the not unusual tragedy of a stud breaking and the cylinder head having to come off in order to get a good aim at the problem. I use grade 5 nuts usually but was even considering using non-graded nuts but haven't had the courage yet to try them out. Thanks for the input!

Of course, I have to question if the grade 8 stud is less apt to snap or not.

As I understand it, the grade 8 has more tensile strength, but grade 5 may be better in shear. The thought being that the grade 8 is stronger but not as forgiving. I've seen it with hot rod builders that spec grade 5 for suspension.

You know, I was always going to buy the Carroll Smith book on fasteners.... I've heard that it explains all this... I understand a lot of the thread specs and nomenclature, and spent the past almost 6 years trying to forget about things like British pipe threads, but never got into the "nuts and bolts" of nuts and bolts except for the occasional magazine article. $30 on Amazon...

 

[Big_John]

You know, I was always going to buy the Carroll Smith book on fasteners.... I've heard that it explains all this... I understand a lot of the thread specs and nomenclature, and spent the past almost 6 years trying to forget about things like British pipe threads, but never got into the "nuts and bolts" of nuts and bolts except for the occasional magazine article. $30 on Amazon...

Ahh.. Found one on eBay for $15. I'll get it in a week or so!

 

[saforwardlook]

Ahh.. Found one on eBay for $15. I'll get it in a week or so!

Please inform us on your findings from the book you ordered. I considered that snapping/shearing of the grade 8 studs might be a consequence but I reasoned that given how cheap Chrysler was when buying parts and how they would sell their souls to save a couple pennies on a part, they would have used the cheaper grade 5 or less studs since they do routinely break.

However, here is a good article to consider in the absence of better information:

Grade 8 vs. Grade 5 Bolts

The conclusion of the above article is that grade 8 bolts are better in both tensile and shear applications. Apparently when grade 8 bolts snap, they do so before stretching a bit like grade 5 bolts do which give some warning before letting go whereas grade 8 bolts just snap with a loud noise that makes folks assume they are giving way much faster. Not true according to the referenced article.

I am also considering besides using the grade 8 studs to also use stainless steel nuts since they will not corrode and bind to the studs potentially and the threads will strip before causing the grade 8 studs to shear. But I am not so certain whether the greater expansion and contraction under heat cycles will have other effects or that the stainless steel nuts would not loosen under repeated heating and cooling cycling cycles.

Hopefully John can provide us some further insight on this issue. I never want to take off a head to deal properly with a broken stud ever again.

Also, I should clarify that I do use the Fel-Pro gaskets on my exhaust manifold installations too but I do not expect them to last a lifetime and because I do not drive my cars very much because there are too many of them, I use the gaskets referenced above. The point is though, that not using gaskets will still lead to exhaust leaks due to warped manifolds after thousands and thousands of heating/cooling cycles. So there really is no timeless solution that I am aware of.

 

[Fratzog]

Due to spending much less time on this board I miss a great threads like this one. Congratulations on the purchase and thanks for the updates.

 

[1970cat]

what happened to brass exhaust nuts? do they still exist?

 

[Ripinator]

what happened to brass exhaust nuts? do they still exist?

Only on yer Jaguar. . .

 

[Big_John]

am also considering besides using the grade 8 studs to also use stainless steel nuts since they will not corrode and bind to the studs potentially and the threads will strip before causing the grade 8 studs to shear. But I am not so certain whether the greater expansion and contraction under heat cycles will have other effects or that the stainless steel nuts would not loosen under repeated heating and cooling cycling cycles.

I've always been cautioned to not mix SS steel nuts/bolts with steel nuts/bolts and never with galvanized hardware. Galvanic reaction between the materials being the issue. Years ago, I read on another forum about someone using SS bolts in an underbody repair for their daily driver and it was a disaster. That was using stainless fasteners in the existing tapped holes and the car was driven year round. Every bolt was seized and it didn't come apart without tearing up the existing tapped holes in the body.

So... I'd be cautious about doing that.

But you still have the special sleeve nuts to deal with... and in my experience, those are the ones that break. Refresh my memory... and I don't feel like walking out the the garage right now... Don't some (or all) of those nuts have a blind hole? I've looked at replacements on the web and see them both ways.



I found this on the intrawebs, and the accompanying text saying not to mix yellow and red shaded materials. Note cast iron!

 

[73Coupe]

Quick update on the TNT.

As a first fix to get the cooling going, I had bought (and @david hill had installed) a Spectra Premium CU332 radiator in the spring. The idea was to have a brand new radiator in the car so it could be driven, while we looked for a good shop to recore her original 2998970 radiator. David found the right person and dropped off the rad two weeks back. Good news, he got the 2998 970 radiator back yesterday. After painting, it will be reinstalled this coming week. The (now almost) new CU332 will replace, to improve cooling at rapid highway speeds, a similar unit in Buttercup, my 1972 NYB, whose radiator is not original anyways (it likely is an old CU332 -- looks like it).

David also will be installing new manifold cover gasket. I bought the last 1968-71 Big Block C-Body Exhaust Manifold
Fastener Kit (for HP BB 383 440 engines) from 521 Restorations on eBay to that effect:

View attachment 493484

I also got from Summit three Mahle F5561K exhaust pipe flange gaskets, and a Fel-Pro MS90029 exhaust manifold gasket for U-code enginess

Where do the sleeve nuts go? Have not seen those before and my car does not have them.
RE: manifold gaskets - I use the Fel-pros and the LH side lasted about 40k miles, just changed it. All OEM hardware, no rust issues, using anti-seize. Years ago, when taking the manifold off for the first time, the stud snapped at #7 port, but we drilled it out and installed a new stud in the car, just had to remove the inner fender and drop the column....fun.

 

[Big_John]

Where do the sleeve nuts go? Have not seen those before and my car does not have them.
RE: manifold gaskets - I use the Fel-pros and the LH side lasted about 40k miles, just changed it. All OEM hardware, no rust issues, using anti-seize. Years ago, when taking the manifold off for the first time, the stud snapped at #7 port, but we drilled it out and installed a new stud in the car, just had to remove the inner fender and drop the column....fun.

Big block in your car?

 

[saforwardlook]

Big block in your car?

@73Coupe has a standard 440 in a 1973 New Yorker Brougham, so he wouldn't have the sleeve nuts.

So what is the "takeaway" from the chart you provided @Big_John?

It looks like neither brass or stainless steel is a good choice for nuts relative to the cast iron manifolds. We know, however, that in humid environment oxidation, steel studs and nuts do corrode together, which is what leads to the studs breaking off when trying to remove the nuts.

I am still unsure, therefore, what to do to minimize having the studs break off trying to remove the corroded together steel nuts and studs due to humid environments over time (i.e. not a galvanic corrosion pathway/process I assume based on the above chart). Would using a high strength steel stud (grade 8 for example) combined with a mild steel nut be the best solution for preventing a stud from breaking off during removal given all the factors involved or is there a better solution that I am not seeing at this point (and assuming a grade 8 stud is better at both tensile and shear strength than a grade 5 or lower nut)?

Thanks!

 

[Big_John]

@73Coupe has a standard 440 in a 1973 New Yorker Brougham, so he wouldn't have the sleeve nuts.

So what is the "takeaway" from the chart you provided @Big_John?

It looks like neither brass or stainless steel is a good choice for nuts relative to the cast iron manifolds. We know, however, that in humid environment oxidation, steel studs and nuts do corrode together, which is what leads to the studs breaking off when trying to remove the nuts.

I am still unsure, therefore, what to do to minimize having the studs break off trying to remove the corroded together steel nuts and studs due to humid environments over time (i.e. not a galvanic corrosion pathway/process I assume based on the above chart). Would using a high strength steel stud (grade 8 for example) combined with a mild steel nut be the best solution for preventing a stud from breaking off during removal given all the factors involved or is there a better solution that I am not seeing at this point (and assuming a grade 8 stud is better at both tensile and shear strength than a grade 5 or lower nut)?

Thanks!

You know... I've probably owned a couple big block cars with the standard manifolds, but I can't ever remember having one off, so I never even thought about it. Everything else has had the HP manifolds, especially those Roadrunners that I owned over the years. My car had the HP manifolds installed by the PO.

My takeaway from the chart is just to not mix materials and based on it, I'd say the cast iron manifolds and SS nuts might not play well together either.

I'm really thinking that no matter what you do, there's going to be rusting in the threaded fasteners. Maybe the grade 8 studs will do the job and be less resistant to breaking... It makes sense that they will be. It also makes sense to me to use the same materials. I really don't think the grade of the nuts is going to mean much in this case.

Of course, I never figure on having to pull the manifolds again once I take the gaskets out that some PO has put it (and I've blown out). If I do, it's for some reason like a head coming off and then it's an inconvenience to repair a broken stud over a calamity when you aren't planning on pulling the head. But opinions vary on this...

 

['66 Fury I]

I like NeverSeize. What do you think? LC

 

[david hill]

I have always used anti-seize. Never had a problem w/ dis-assembly later. As for the debate on grade 8 vs grade 5 studs which would you rather drill out. Grade 5 are easier to remove. If used w/ anti seize and not over tighten I have had no problems. The chart does bring up some interesting thoughts.

 

[david hill]

Back to business, what started as broken right manifold stud turned into a heli-coil repair as damage present on the treads made a heli-coil mandatory. Pulling the inner splash panel and raising the engine slightly made the job a snap to do. Engine fire up confirms all is well again. The road test revealed that we have no dash lights. Fuses are good, pulled the upper reveal panel showed w/ light sockets removed 1 bad bulb and 1 smoke glazed glass bulb. The lenses assemb. were a clouded over blue.

 

[david hill]

I ground off the rivets, made lens material out of your kids or grandkids clear package material saved from last Christmas gifts. Now it's time to reinstall w/ led bulbs from @Bright Lights.