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riser replacement question

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slauder

Regular Contributor
1991 std 454 log style manifolds... should i heat the engine some before trying to break lose the riser bolts?
 
slauder said:
1991 std 454 log style manifolds... should i heat the engine some before trying to break lose the riser bolts?
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I sure would.
You have nothing to loose, and everything to gain.

Penetrating oils can take days or even weeks to get into the threads where corrosion is occupying the space.
Heat will generally help.


.
 
You may want to search the archive...Knuckle47 earned his "tee shirt" doing the same job on his engines.

I'm sure you will find a wealth of information related to the servicing of the exhaust system in those threads..
 
Here's my advice (learned the HARD way): Put a socket on each bolt and, if it won't turn, STOP. Trying to force the issue will merely snap the bolt off in the head--not good! Instead, drill the heads off the stubborn bolts, then wedge the manifolds off the motor with wooden blocks. The remains of the bolts can then be unscrewed with Vise Grips (aided by penetrating oil and heat if necessary).

Jeff

PS: If this is the way the bolts want to come out, arm yourself with lots of nice, sharp bits and a centerpunch. Drill an 1/8 " hole first, followed by a 1/4 " bit, then a 3/8 " bit. And use an AC drill--not the place for whimpy battery drills.
 
Where can I get the snapping torque of bolts? I was considering ensuring I don't over exceed the force. Actually I don't think my torque wrench has settings that high. Is there a tool for such?
 
I've never seen anybody publish that data...if you are talking about the old bolts, a lot will depend upon they age and the environment they spent that time in...if you want to snap them, there's nothing like a 1/2" snapon breaker bar...if that needs help, a couple feet of 1" black pipe over the end should do it.

Personally, I'd heat them up and use some Kroil to free them up...a couple cycles should encourage even the stubborn ones to come out...an impact hammer with a flat anvil bit will also help to free up the cast iron that has "corroded" together.
 
For some reason I was thinking I would only change the exhaust manifolds if they looked bad inside... I'm planning to do the heads next year so I was going to do the manifold then.

Am I pushing it to let a 91 go another season with exhaust manifolds even though I'm changing risers\elbows this weekend?
 
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I've run those manifolds older than that, as long as they had coolant in them, should be ok. The sealing surfaces tend to be the first to get bad on FWC exh manifolds.
 
Yes FWC old log style exhaust manifolds. Good news is the riser bolts came off way easy. I had blasted them with gibs penetrating oil a week ago. Actually they were so easy that the under torque might have been reason (as DD mentioned on another thread) for the raw water in #8. I just updated my profile for the boat to include FWC
 
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I was told by a marine mechanic just a few weeks ago that manifolds (even on FWC engines) should be replaced about every 5-7 years, just like the risers and elbows. I don't agree but didn't bother to argue the point. I think that as long as the anti-freeze is changed periodically to ensure that its corrosion inhibitors are good, and the seal between the riser and manifold is good, the cast iron manifolds should be last for a long time...many, many years.

When you say the riser bolts, are you talking about the long threaded studs that go into the manifold or the bolts that attach the elbow to the riser?

Good luck with this project. It ain't fun.

Erich
 
I'm in the middle of this job myself. 1986 log style. I had one riser freeze to the studs. Long story short, I ended up replacing one manifold. They were original. I don't think there is any need to change manifolds on FWC system unless there is a lot of internal corrosion for some odd reason. Feel free to ping me if you need help. Getting the elbows back on and lined up is a bit of a pain on my boat. I piece of 2x4 to help lever the exhaust hose helps.
 
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