Exhaust Manifold Replacement

[Marko56]

I'm replacing the exhaust manifold on a 1992 Indmar Ford 351.  Seems like a fairly straightforward job, provided the bolts come out cleanly.  Talked with Indmar, they gave me part numbers and torque specs.  Will use all new bolts and gaskets, obviously.  Any pointers on doing the job?

Thanks

[backfoot100]

Patience is a virtue. If they're rusted and/or corroded in there chances are pretty good that you'll end up snapping a couple off. Soak them for several days with something like PB Blaster, Liquid Wrench or Kroil before you even try to remove them. Actually I've heard that a 50/50 mix of acetone and ATF is better than anything that you can buy (like those listed above) but I've never used it myself. There is documented data that the acetone/ATF mix needed considerabley less force to loosen torqued bolts than any of the others commonly found on store shelves.
If you still end up snapping one, get an EZ out from your local Lowes, Home Depot or hardware store. Drill out the center of the bolt so you put the EZ out in it and then torch it to try and get it to loosen up.

Good luck.

[backfoot100]

Just realized that I gave you information for removing the risers. Are you talking about the manifolds or the risers or both? If it's the manifolds, they should be quite a bit easier than the risers.

[Mike Harry]

"Actually I've heard that a 50/50 mix of acetone and ATF is better than anything that you can buy (like those listed above) but I've never used it myself. There is documented data that the acetone/ATF mix needed considerabley less force to loosen torqued bolts than any of the others commonly found on store shelves"


Not only is this true, its VERY true. In no way have I ever used anything better.

[Marko56]

I'm just replacing the manifold, but to do that I need to remove the riser, as I plan on re-using it.  The riser appears to be in fine shape.

If the riser bolts are stuck, I can take both manifold and riser off as a unit and work on it on the shop bench.

Why would the riser bolts be more of a problem then the manifold bolts? 

[backfoot100]

Why would the riser bolts be more of a problem then the manifold bolts?

Marko,
I'm assuming that you have the cast iron manifold/riser which is by far the most common. The gasket between the manifold and the riser is thin and the manifold is subject to heating/cooling cycles over the life of them. Traditionally, the gasket is the first thing to start a slow seeping kind of leak and will start leaving a tell tale trail of corrosion on the outside of the manifold. Most owners disregard it because it isn't affecting the engine performance and the seeping leak will now corroded the hell out of the bolts (which are also situated straight down into the manifold so the water will find it's way around the threads compounding the problem even more).
The manifolds themselves are not subject to the leaks like above because any leaks here are generally letting water into the cylinders which are a much more catastrophic failure potential. As such, they get fixed immediately if not sooner. So the manifold bolts generally will come out much easier than the risers. The manifold bolts are also much larger than the long skinny riser bolts which helps (and they're threaded into the head sideways instead of straight up and down so any water has a tendancy to drip off). I also think that if the manifold bolts are rusted tight, it's generally just the head rusted to the manifold and not so much the body of the bolt rusted to the head. In that case, wizzing off the head of the bolt and removing the manifold gives you a nice long heavy stud to wrap a vise grips around to help "persuade" it.

[Marko56]

Thanks to all for the info.  You are correct, the riser is cast iron.  There is no surface rust at the seam of the riser and manifold, so I'm hopeful.  I plan on "testing" all of the bolts tomorrow night.  I'll mix up some acetone/atf beforehand.  If it all comes apart easily, I'll verify my parst list before I order them.  If I have problems, it'll have to wait until Saturday.  Wish me luck! 

[Joel]

Eddie,   Now that you mention it...  I do have some light signs of seeping at the manifold/riser connection and yes I didnt think anything of it...   One more thing to add to the "To Do" list   

Thanks for the info!

[backfoot100]

  If I have problems, it'll have to wait until Saturday.  Wish me luck!

Marko,
Another thing you'll want to do is try and make sure that the manifold and the riser have a nice flat surface before you bolrt them bak together again. The heating cooling cycles will warp them slightly which is how they start to leak in the first place.
Get some fine emery cloth and with flat block of aluminum stock with the emery wrapped around it. Some guys I know have used a flat piece of glass with the emery taped to it. Whatever you use it needs to be perfectly flat. Use a figure 8 motion of the emery over the riser and manifold gasket flanges. You'll see pretty quick if it's warped or a little uneven. Cut it just enough so that the whole flange surface is nice and even. Then you can bolt it all back together.

Eddie,   Now that you mention it...  I do have some light signs of seeping at the manifold/riser connection and yes I didnt think anything of it...   One more thing to add to the "To Do" list   

Thanks for the info!

That's exactly what I'm talking about Joel. It's never an issue or a priority until you start having more significant problems.
Think about it for a minute.....If it's leaking on the outside, it's probably doing the same on the inside. It's just a small seeping thing that isn't very significant. The problems come when it starts to leak bad on the inside. Which it will eventually do if left unattended. Then you start getting water in the cylinders and you can have serious problems then.
Granted, it may be several years before it turns into a leak significant enough to cause engine damage but the moral of the story is to fix it and not ignore it.

[Joel]

Got It Dude!!!   Thanks   

[Marko56]

I used the 50/50 mix of acetone and ATF and it worked great.  All bolts loosened easily.  Can't tell you how relieved I was.  Parts have been ordered. 

[backfoot100]

That's great. Glad to hear it.