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View Full Version : New exhaust manifold bolts every time?


catamount
03-26-2012, 01:52 PM
Hey guys, from my very limited mechanical experience I know that most exhaust manifold bolts are one-time use stretch bolts.

Does anyone happen to know if our (351) manifold bolts are one-time use as well?

I don't read about many people replacing them on these forums, so maybe they're reusable?

CantRepeat
03-26-2012, 02:26 PM
I'd reused them all day long so long as they are not so rusted and corroded they are missing a lot of threads.

Lumbergh
03-26-2012, 03:18 PM
http://www.skidim.com/prodinfo.asp?number=49-2004

$16 bucks for piece of mind? Without a doubt.

If I were pressed for time to get back on water maybe, but I probably wouldn't even remove manifold with having the kit in hand to reinstall.

YMMV.

Buy once, cry once.

catamount
03-26-2012, 03:19 PM
Shoot, I never saw that kit when I placed a large skidim order last week (kicks self, orders now).

mayo93prostar
03-26-2012, 03:28 PM
I have been told that they are one time use and I change for peace of mind also. got kit from skidim.

mart_it
03-26-2012, 05:18 PM
If they look good, why change them?
I'd change them if they were head bolts, but I wouldn't touch these if they look good.

CantRepeat
03-26-2012, 06:16 PM
I have been told that they are one time use and I change for peace of mind also. got kit from skidim.

Exhaust bolts are not stretch to torque bolts.

catamount
03-26-2012, 06:18 PM
I've read reports of both. I measured my existing bolts and they're 4 1/8".

That's a suspicious size, indicating that they have indeed been stretched.

I'm sure I'd probably be fine reusing them but the boat is 24 years old and it's inexpensive peace of mind to know that I won't be snapping any of them when I torque them down later this week.

mart_it
03-26-2012, 08:29 PM
If it will make you sleep better, then ya, change them.

markismm
03-26-2012, 08:54 PM
I would suggest going with a high quality stainless bolt as the replacement. Cost a little extra, but you never have anything to worry about after replacing the bolts.

CantRepeat
03-26-2012, 09:39 PM
I would suggest going with a high quality stainless bolt as the replacement. Cost a little extra, but you never have anything to worry about after replacing the bolts.

Any two dissimilar metals will have some degree of galvanic corrosion - that includes carbon steel and cast iron (like traditional exhaust bolts in heads). The greater the difference in values of electrochemical potential between the materials, the more (faster) corrosion you'll get. Carbon steel and cast iron have very similar electrochemical potential (iron has the higher value). Cast iron and 304 stainless are just about as similar but in the opposite sense (same-ish difference in value, but stainless has the higher value).

I realize you're putting a lot into this, but this is one of those things that I wouldn't worry about too much.


If you ever have to remove them you are more then likely going to snap them off because they are seized.

Cloaked
03-26-2012, 10:01 PM
I seriously doubt these bolts have been stretched in any noticable way. I do work on nuclear power reactor vessels and when they reset the vessel head after a refuel, those 2.5" diameter bolts are torqued and measured for elongation. Small bolts like these typically would not be considered streched.

I usually order new ones for the sake of ease in reinstallation or to just have on hand. I always use anti-sieze compound and they will last through several cycles of removal / replacement.

catamount
03-26-2012, 10:49 PM
Thanks Cloaked. The boat is 24 years old so spending a few bucks on some new manifold bolts for peace of mind doesn't bother me too much. I've had some bolts sheer off before and it's not pleasant. Probably would've never happened here, but... it's a new-to-me boat and bolts are cheap.

I would suggest going with a high quality stainless bolt as the replacement. Cost a little extra, but you never have anything to worry about after replacing the bolts.

I've had lots of people tell me *not* to use SS bolts in the cast block. Haha, everyone has a different opinion. Anyway, I ordered the bolts from skidim which also come with the gasket.

Which brings us to another source of debate around here... to use the manifold gasket or not? Indmar doesn't / didn't. Hmmm.

CantRepeat
03-27-2012, 08:33 AM
You could probably run a bottom tap down bolt holes to clean them out too.

markismm
03-28-2012, 02:09 PM
Just goes to show, different strokes for different folks. Been working on boats and performance engines for 20 years and have never had a problem with quality stainless hardware in conjunction with a cast iron block, personally. I typically put some anti-seize on them as well which helps with any potential galling issues. You can do a web search and find differing opinions on this everywhere you look. In either event, stainless is the way to go for me and always has been.

CantRepeat
03-28-2012, 02:47 PM
Just goes to show, different strokes for different folks. Been working on boats and performance engines for 20 years and have never had a problem with quality stainless hardware in conjunction with a cast iron block, personally. I typically put some anti-seize on them as well which helps with any potential galling issues. You can do a web search and find differing opinions on this everywhere you look. In either event, stainless is the way to go for me and always has been.

Mark,

I'm gonna need to see this in person. What part of Martin should I meet you on. I'll bring beer for a pull too!!

Oh yeah, is your son skiing yet?

markismm
03-29-2012, 09:02 AM
We are on the south end of the lake in bama park. We usually ride over to the old ski club course past Kowaliga and run the course. Would love to give you a pull anytime. I would like a pull behind your boat as well for comparison sake. Did you enter into the Lake Martin slalom tourney last year. If not, you should have. It was a blast. Absolutely loved it. This year it should be even better. If you want to get together this season let me know. I'll pm my number to you and we can meet up. Hope you are an early riser when it comes to skiing. We are usually the first ones on the course.