How tight should exhaust manifold bolts be?

rowan194 · 27-08-2011, 11:12 AM

I removed my exhaust manifold recently to replace a welch plug. I put the bolts back on pretty much as tight as I could (lots of leverage, lots of grunting) but it occurred to me later that maybe they were a bit hard to get off because they were rusted a bit and also had threadlock applied.

I'm going to take it off again to apply exhaust gasket cement and use threadlock on the bolts (do it properly), so should I be doing these bolts extra tight again, or is that going overboard with a gasket+cement?

mik · 27-08-2011, 09:38 PM

i `d say if your grunting they may be a tad tight, if you look in au technical resources you`ll find plenty of good info(thanks Russ), including tensions.

http://www.fordforums.com.au/vbporta...article&id=234

rowan194 · 28-08-2011, 10:13 AM

Hmm, so different bolts need to be set at different tensions. Time to buy me a torque wrench. Thanks.

smoo · 28-08-2011, 12:42 PM

Wouldn't worry with threadlock clean up the threads and use a copper coat anti sieze cos the next poor bastard to pull it off might end up stripping the thread or snapping a bolt. As a guide I did an exhaust manifold on a 13 litre DAF truck last week with 10mm bolts into a cast iron head, 60nm, you probably did yours up tighter.

rowan194 · 02-09-2011, 05:10 PM

I'm having trouble finding a suitable anti seize product, when I type that into super cheap it gives me results for anti freeze

Is it basically a light lubricant, could I use some oil instead, or is there something more to it?

While I have the manifold off, is it worth giving the manifold piping and the exhaust ports a good clean? I remember last time there was what looked to be a hardened layer of black gunk that was at least a few mm thick, should I leave this as it is or try to soften it up and get it out?

Here, I found a pic:

Is that black ring meant to be there (ie a tube, protective covering) or is it the result of years of buildup?

Day-mow · 03-09-2011, 12:54 AM

that black ring is probably carbon build up. its pretty common i think. probably means your cars running to rich.

re. exhaust bolts.
i suggest buying some female hex head hightensile bolts. i dont know how many times i've had my extractors on and off and haeing the hex head allows me to get an allan key in there very easily and on any angle to undo all the bolts. i remember when i did work experience the guy said you always always snap exhaust bolts and getting them out isn't very fun. hence why the high tensile replacement (thanks dad being an engineer and getting bolts that could with stand sitting on the sun for a few minutes)

i use a product called never seize on my spark plugs and exhaust bolts and anything else really where it could rust up. after going to bunnings and super cheap we found it at a bearing shop. you dont need to paint it on. just a light coating over most of the parts that will be in the thread should suffice you well.

rowan194 · 03-09-2011, 10:55 AM

Quote:

Originally Posted by Day-mow

that black ring is probably carbon build up. its pretty common i think. probably means your cars running to rich.

Hmm, I had a look in my Gregory's manual and with the manifold off the engine has the same thick black rings... granted, it's an EL, but it would have only been a year or two old when the manual was released. They look too smooth and perfect, are you sure it's not like a coating to protect the piping from heat?

If it is gunk, would throttle body cleaner soften it up? Or some kind of liquid I can use to soak the manifold piping?

Quote:

Originally Posted by Day-mow

re. exhaust bolts.
i suggest buying some female hex head hightensile bolts. i dont know how many times i've had my extractors on and off and haeing the hex head allows me to get an allan key in there very easily and on any angle to undo all the bolts.

Cheers, looks like there's a bolt place not far from me. After this I have no plans to remove my manifold again, but at least it will make it easier if it ever does have to come off in the future. (Knowing my luck I'll probably snap a bolt when I redo it this weekend...)

Something like this? (can't remember the head size) http://www2.blackwoods.com.au/infoBA...3481&P=7064479

Might remove one bolt and take it in, to be sure.

rowan194 · 03-09-2011, 02:56 PM

^^ Thinking further about the above (sorry, it won't let me edit), you mentioned allen keys, I guess that's what a FEMALE hex head is... rounded bolt with the hex as a cutout in the head? What advantage does this have over a standard bolt head?

Day-mow · 04-09-2011, 01:07 AM

Quote:

Originally Posted by rowan194

^^ Thinking further about the above (sorry, it won't let me edit), you mentioned allen keys, I guess that's what a FEMALE hex head is... rounded bolt with the hex as a cutout in the head? What advantage does this have over a standard bolt head?

correct.

i found the advantage of the female hex head with allen Keys was i could use an allen key on an angle to tighten/loosen bolts. with extractors its not always easy to get access at a perfect 90 degree's out so getting a socket on there is quite tricky and there isn't enough space for a uni joint. useing the rounded end of an allen key (not all have these but mine do made sure of it) you can get in on the required angles to do what you need to do.

up to you but thats what i have done.

hope this helps

Day-mow · 09-09-2011, 01:12 PM

some pictures. just to explain a bit further

the Style of allan Key's i was talking about

the the hex head bolt im talking about.

these are high tensile and i put never seize on them. and have never had any issues with them feeling like they're going to snap.

my extractors/these bolts have been in 3 cars over about 4 years and regularly come on and off.

rowan194 · 09-09-2011, 04:53 PM

Have redone the manifold and flange with gasket cement now. Changed the O2 sensor at the same time.

Now I have a torque wrench it's obvious I did the bolts up WAY too tight last time. No grunting needed, in fact hardly any further exertion required once the bolt "grabbed" and I moved to tightening with a levering bar. I did them all to 27Nm.

Also made sure I didn't do up the exhaust flange bolts too hard this time (see http://www.fordforums.com.au/showthread.php?t=11342451 ). Tightened them enough that wiggling and shoving the flange didn't move it relative to the nut, then tightened a little more.

I kept the same manifold bolts (the couple of bolt specialists I asked at don't do auto bolts, and I don't plan to remove the manifold again anytime soon), but I also used anti-seize spray.

I'm glad now that I decided to redo my bolts, they were definitely too tight... could that have eventually caused the gasket to fail?

Day-mow · 09-09-2011, 06:23 PM

i donno about gasket failing but bolts snapping is possible/probable