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Exhaust bolts, can I loosen them up?

dutchjeep

NAXJA Forum User
I about to embark on the great exhaust-manifold-replacing trip. Any good suggestions to make sure I don't snap those manifold bolts? Can I use lubricants to loosen them up? Which one should I use for that?

Thanks!
 
I'd start spraying them with some kind of penetrant like PB Blaster. Hit emseveral times, maybe in the evening so they can soak all night a few times.
 
Also, DO NOT "snap" the wrench when you're trying to loosen them! Work smoothly and FEEL what's happening - if a bolt is starting to let go, yo'ull feel the difference and you can STOP and deal with it another way.

"Another way?" Sure - if the bolt gets terribly stuck, get a fine-flame torch (a "pencil torch" is just perfect for this - you'll want to heat the head of the bolt red, and touch a block of paraffin (or a candle) to the threaded part of the bolt. The wax will melt and wick into the threads, and will get farther in as the bolt cools and contracts. Let the bolt cool until you can touch it with a bare finger, and try again. It should come loose this time.

Don't reuse the bolts - replace them! I prefer to use bronze or brass, 3/8"-16x1.75". Studs for the ends and the centre can be made from brass allthread rod (3/8"-16 again) - cut to about two and a half inches long. Replace the nuts - the OEM studs have two thread pitches - 16TPI going into the head, and 24TPI under the nuts.

Use LocTite #272 to retain the bolts, and apply a LIGHT coat of RTV copper to BOTH sides of the new manifold gasket before it goes in - it also helps.

5-90
 
Ok, will use the PB Blaster and will be very carefull. Thanks for the torch-trick! I will certainly make sure not to re-use nuts and bolts. Thanks for the input. Much appreciated!
 
He, if I use loctite on the bolts will I be able to get the bolts loose again if needed?
 
dutchjeep said:
He, if I use loctite on the bolts will I be able to get the bolts loose again if needed?

you can use the blue loctite, not the RED. avoid the Red.
I used antiseize on my manifold bolts. I checked the torque a few times after now that its been 2K miles since the header job and they seem to be holding just fine.

I never thought of loctiting the header bolts actually. i would rather have to check em each now and then rather than have em jam and get busted off the next time i need to remove em for something.

john
 
dutchjeep said:
He, if I use loctite on the bolts will I be able to get the bolts loose again if needed?

Yes, you can.

LocTite comes in various "grades"/"strengths" - I don't recall the colours, since I key on numbers, but you select according to your application...

#222 - Low strength. Use for "maintenance" screws (adjustments and such) and most screws under 1/4" nominal diameter. Breaks free with hand tools

#242 - Medium strength. Use on 1/4" and up, may require light heating to break loose.

#272 - Medium strength. Usually breaks with hand tools. Formulated to withstand exhaust heat (don't use anything else, if you want it to work. I tried #222 and #242 once, just to see what happens. Good thing I torqued the bolts properly - I couldn't even find residue of the threadlocker!)

#545 - Hydraulic Sealer. Combines threadlocking and thread sealing in a single compound, breaks with hand tools. Works well on power steering and brake lines.

PST - Thread Sealer. Similar to "Teflon pipe dope" (which I usually use as a substitute,) this will seal threaded joins against water/air leakage. Breaks with hand tools.

#640 - Sleeve Retainer. If you use this on a bolt, make DAMN sure you don't want to get it out again! Requires heat and power tools to break - since it's designed to keep a smooth sleeve in a smooth bore...

Again, use either #272 or NOTHING on exhaust bolts, since nothing else can stand up to the heat!

Bear in mind that using LocTite doesn't change any torque specifications, but the following changes should be considered mandatory (unless otherwise defined, torque specs in manuals are for "clean, dry" threads...)

Engine Oil/Chassis Grease - Listed torque x .67
Teflon Pipe Sealant - Listed torque x .75
Anti-Sieze Compount - Listed torque x .5

Other thread compounds should let you know what changes are to be made. Note that using typical "threadlocker" compounds (LocTite #222/242/xxx) should NOT change the listed torque value for a bolt - they're formulated not to...

5-90
 
Which bolts are you talking about? The bolts in the head or the bolts that connect the manifold to the front exhaust pipe?

The bolts that connect the manifold to the pipe, just snap them off. Use new studs or bolts with the new manifold (the manifold may even come with them).

The bolts in the head usually don't snap, they generally come out pretty easy. Just go slow and take your time to make sure they all come looss nicely. You really don't need Loc-Tite on them when you re-install either. If you do use Loc-Tite, just make sure you get the right stuff. Read the package, colors and numbers vary by brand, "Loc-Tite" is actually a brand name. Some of these compounds have to be heated to pretty high temps before they'll allow the bolt to come loose. Either way, there's no threadlocker on them from the factory.
 
anony91xj said:
Which bolts are you talking about? The bolts in the head or the bolts that connect the manifold to the front exhaust pipe?

The bolts that connect the manifold to the pipe, just snap them off. Use new studs or bolts with the new manifold (the manifold may even come with them).

The bolts in the head usually don't snap, they generally come out pretty easy. Just go slow and take your time to make sure they all come looss nicely. You really don't need Loc-Tite on them when you re-install either. If you do use Loc-Tite, just make sure you get the right stuff. Read the package, colors and numbers vary by brand, "Loc-Tite" is actually a brand name. Some of these compounds have to be heated to pretty high temps before they'll allow the bolt to come loose. Either way, there's no threadlocker on them from the factory.

Essentially correct - you don't need to use anything on those bolts. I'm just paranoid. If you do use anything at all, use LocTite #272 or equivalent - the "regular" threadlockers (#222 and #242 - and equvalents) aren't going to work worth a damn with all the heat around there...

Save yourself some trouble as well - see if you can get brass nuts for the downpipe studs. Don't ask me why - ask yourself next time you have to take them off (since it's going to be VERY easy to do!) I don't use steel replacement hardware on exhaust work, haven't for the last 25 years, and for a very good reason...

I've done quite a few posts on this particular job as well - were I you, I'd probably take the half-hour to find them and see what I've missed here (since I'm not thinking in that vein - too much electrical work lately...) I've got to do a decent writeup one of these days...

Also, before you get started, I'd see about getting a 9/16" socket with an inbuilt universal joint. GREAT for getting the lower back bolts, and you don't have to do any "torque adapting" using it. Saves a lot of wear on your nerves and your knuckles...

5-90
 
5-90 said:
Save yourself some trouble as well - see if you can get brass nuts for the downpipe studs. Don't ask me why - ask yourself next time you have to take them off (since it's going to be VERY easy to do!) I don't use steel replacement hardware on exhaust work, haven't for the last 25 years, and for a very good reason...

I see you live in SoCal. Try doing that in the North where they salt the roads. All the threads below the nut will rust and rot so bad that nut isn't going anywhere after a winter or two anyway.

I usually just don't use studs for this reason, I'll just shoot a bolt through the hole. If the exhaust ever has to come apart again, I just break them off and use a new set of nuts/bolts/washers.
 
anony91xj said:
I see you live in SoCal. Try doing that in the North where they salt the roads. All the threads below the nut will rust and rot so bad that nut isn't going anywhere after a winter or two anyway.

I usually just don't use studs for this reason, I'll just shoot a bolt through the hole. If the exhaust ever has to come apart again, I just break them off and use a new set of nuts/bolts/washers.

Try again - SF Bay Area. However, I did grow up in Lafayette, IN - and I started using brass there wherever possible. Exhaust studs were made from brass threaded rod, underbody stuff was either stainless or brass - and if I HAD to use regular steel, I typically found SOMETHING to coat it with. Always do a job with the mind that you're going to be the next poor schmuck to do it, and when I do, all I have is my Gerber Multi-Plier 600DET and my SwissChamp...

There are sound engineering reasons for material selection - but they always end up using plain steel because beancounters get involved in engineering decisions (a subject about which they typically know slightly less than nothing...)

5-90
 
5-90 said:
Try again - SF Bay Area. However, I did grow up in Lafayette, IN - and I started using brass there wherever possible. Exhaust studs were made from brass threaded rod, underbody stuff was either stainless or brass - and if I HAD to use regular steel, I typically found SOMETHING to coat it with. Always do a job with the mind that you're going to be the next poor schmuck to do it, and when I do, all I have is my Gerber Multi-Plier 600DET and my SwissChamp...

There are sound engineering reasons for material selection - but they always end up using plain steel because beancounters get involved in engineering decisions (a subject about which they typically know slightly less than nothing...)

5-90

Brass studs would resist rot a lot better, yes. I thought you were referring to a brass nut on a steel stud. I prefer cheapo steel disposable bolts to expensive brass studs, but I guess either way works. Once you fix an exhaust pipe or manifold, it should be quite some time before it needs to be taken apart again anyway...unless it's a pre-2001 Honda Civic, but that's another story.

Beancounters are the whole reason cars today are made of like 99% plastic...awsome ain't it :D
 
He, thanks about that 9/16" socket with the universal joint. Will get one for sure!

Tim
 
I will be getting that APN manifold everyone is talking about to replace my cracked stock on on my 94. I just wanted to check out a few things based on my reading, hopefully a few ppl will chime in.

From my understanding the stock dish washers can be re-used, but the original bolts should not be used. My question is , can grade 8 bolts of the same spec be used ?

On the gasket i should spray a few coats of copper spray on both sides..

Does that all sound ok ?

Thanks
pete
 
jeepsrock said:
I will be getting that APN manifold everyone is talking about to replace my cracked stock on on my 94. I just wanted to check out a few things based on my reading, hopefully a few ppl will chime in.

From my understanding the stock dish washers can be re-used, but the original bolts should not be used. My question is , can grade 8 bolts of the same spec be used ?

On the gasket i should spray a few coats of copper spray on both sides..

Does that all sound ok ?

Thanks
pete

Yes, do replace the bolts. However, don't use SAE8 - use SAE5. The harder bolts are more sensitive to annealing, and will lose strength faster SAE5, CRES, bronze, and brass will all hold up better than SAE8 - with brass or bronze being best.

DO reuse the dish washers - they're needed to help spread clamp loads.

Spray copper should work - I don't keep any around, so I don't know. I do keep RTV Copper around, and I know that works. THIN layer only, please!

Once you've done the job, would you please confirm the bolt sizes for me? I'm thinking they stuck with 3/8"-16 x 1.5", but I'm not sure. All my data is on RENIX engines.

If you use ISO/Metric screws instead, I'd not go with a property class (stamped into the screw head) higher than 9.8 - same reason for not using the SAE8.

5-90
 
Try a marina supply store (boats use a LOT of brass and bronze!) or order them from an outfit like Small Parts or Fastenal.

I've been trying to talk my local hardware store into carrying hex head capscrews in brass, and some fine thread and ISO stuff in CRES, but so far unsuccessfully... WiP may end up carrying bolt kits for various jobs, I'm thinking, just so you can get everything all at once without guessing.

5-90
 
I used brass nuts on my downpipe studs two years ago and they still come off easy even though they have gone thru a couple of harsh NE winters and all the road salt we use.
 
dizzymac said:
I used brass nuts on my downpipe studs two years ago and they still come off easy even though they have gone thru a couple of harsh NE winters and all the road salt we use.

^^^^^

That, people, is precisely why I use brass undercar. I drive cross-country a couple times a year, so I see it ALL. I try to make things as easy for me to deal with as humanly possible, and it usually pays off.

5-90
 
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