Rusted Manifold Bolts??

[Shaun78]

I have a few that you can't even tell there's a bolt there. I uses PB Blast on them ALOT and chizzeled the crap surrounding the bolt. I spent 2 hours on this so far. What are some ideas on the best way to deal with this? I can't get a good grip even with a metric socket. 1998 7.4 L MPI. I definately am not removing the engine to do this so that out. Maybe drill the bolt heads,(if I can find them) or try the sockets made for rounded,striped bolts.

 

[muskie hunter]

Re: Rusted Manifold Bolts??

I have a few that you can't even tell there's a bolt there. I uses PB Blast on them ALOT and chizzeled the crap surrounding the bolt. I spent 2 hours on this so far. What are some ideas on the best way to deal with this? I can't get a good grip even with a metric socket. 1998 7.4 L MPI. I definately am not removing the engine to do this so that out. Maybe drill the bolt heads,(if I can find them) or try the sockets made for rounded,striped bolts.

I had the same problem on my 1996 7.4. Access isnt easy. Lay accross the engine and carb, stuff your arms and head down in there and drill the bolt heads. If its like mine, the bolts only screw into the head about 3/8 inch. Once I slid the manifolds off of the headless bolts I was able to remove the bolts with my fingers. On the 7.4 the bolts seem to be almost countersunk in the manifold. I added a flat washer to each bolt and went with a bolts just a tad longer than factory. The washers will make it much easier to get to the bolt heads next time. hope this helps.

 

[Mkos1980]

Re: Rusted Manifold Bolts??

I accually had one that was flaking away as I was trying to remove it. I ended up grinding the edges with a dremel down to a size where I was able to pound a 1/2 socket on it vs the 9/16 which it used to be.

 

[Shaun78]

Re: Rusted Manifold Bolts??

My engine is EFI so laying across it is impossible to fit. I can squeeze down there to possibly drill the heads with a rt angle drill but it will not be fun and easy. What did you use to clean the crap around the bolt head to get a socket on it?

 

[Bondo]

Re: Rusted Manifold Bolts??

Ayuh,............

It's Alot Easier to just Grind the Bolt Heads Off,......
Then side the manifolds Off the remaining bolt shafts,+ Remove them with vise-grips if still necessary.....

 

[mcleaves]

Re: Rusted Manifold Bolts??

Man I am getting the shakes just reading your title. I went through this a couple seasons ago. I was too damn stubborn to pull the engine and ended up drilling and grind them off. even tried cutting the manifolds themselves. Took me about 3 weeks working on it here and there several sets of drill bits and having to purchase a drill doctor to keep the bits that survived sharp enough to do the job.

It completely sucked.. Forget the rust eaters. They are useless to you if the bolt heads are junk. Just get to work drilling.

If I were to do it again the engine comes out and they get torched off. Then I could stop from making a mess of the bilge and clean up what needs cleaning in there instead of wrecking the place.

And there is a big I told you so coming from Don right now I suspect!

M

 

[Don S]

Re: Rusted Manifold Bolts??

And there is a big I told you so coming from Don right now I suspect!

Wasn't even going to post on this one. So many times I have said it would be easier. Just nobody believes me till after they do it the hard way, usually taking days and/or weeks of hard work.

 

[mcleaves]

Re: Rusted Manifold Bolts??

Wasn't even going to post on this one. So many times I have said it would be easier. Just nobody believes me till after they do it the hard way, usually taking days and/or weeks of hard work.

Never again.. EVER!

 

[JustJason]

Re: Rusted Manifold Bolts??

if the manifolds are junk and you don't care about them try getting in there with an air hammer

 

[Lou C]

Re: Rusted Manifold Bolts??

One thing I noticed on my old OMC is that they used studs and nuts to attach the manifolds to the head. I changed the manifolds a few years back and the studs and nuts had no corrosion at all on them, and because it's a stud and nut, when you spray penetrating oil it can actually get to where it needs to be (threads!) unlike with a bolt going thru the manifold casting into the head. So why do most engines use bolts, instead of studs and nuts? Cost? because it's sure easier with the studs and nuts, even with salt water use!

 

[sterndrive]

Re: Rusted Manifold Bolts??

This may sound a little scary, but I've done it several times.
1. Remove exhaust elbow
2. Place a large diameter pipe into exhaust opening
3. Strike pipe with sledge
The manifold is cast, it will snap at the bolts
The bolts can then be easily removed with vice grips
The worst that can happen is you'll break the spark plugs when the manifold drops Good Luck

 

[JCF350]

Re: Rusted Manifold Bolts??

The vast majority of folks out there just plain don't know how to drill.

1. Go down to a industrial supply house and get you some short "tool steel" drill bits and drilling wax. The fancy special coated, special tipped bits are junk.

2. Get yourself a QUALITY variable speed drill motor (this is going to cost in the 150 to 200 dollar range for a 3/8 drill).

3. Drill a PILOT hole then use the larger bit, use a speed of between 150 and 300 rpm with liberal use of the wax.

Takes a little more than 2 hours if you have to drill the heads off all the bolts.

If you can't get a drill on it PULL! the engine then do the above. With the engine out your drilling time will be less because you can lean on the drill a little bit (not a lot!) so you'll need less break time than just using your arms alone.

 

[Shaun78]

Re: Rusted Manifold Bolts??

would an angle air grinder work? I saw one on home depot site. it looks small enough,perfect for bolts but i'm not sure how they work as i never used one.

 

[sterndrive]

Re: Rusted Manifold Bolts??

It's not a matter of drilling or grinding technique. It's all about the access. Big block manifold bolts are tucked up under the manifold, right next to the spark plugs. There is not enough room to get in there and drill or grind. Besides, He said he didn't want to pull the engine. The method I described above will grt the job done guaranteed!
As an aside, I always remount with Stainless hardware.

 

[JustJason]

Re: Rusted Manifold Bolts??

a die grinder will work also

 

[pine island fred]

Re: Rusted Manifold Bolts??

I am assuming you are pulling the manifolds to replace them. They are cast iron and will break. Get yourself an iron mallet and start hitting the manifold in the same place. You dont have to swing like a sledge hammer just keep hitting in solid blows. Eventually the thud sound will change to a ting and you are home. You will be able to figure it out from there depending on where the cracks formed. Us a small pipe wrench to remove the bolts.
SAWZALL saws dont work on cast iron to well no matter what blade you use. regards FRED

 

[DHPMARINE]

Re: Rusted Manifold Bolts??

This won't help now,only in the future.

When buying a boat,it may look fabulous.But look at the engine compartment. See how accessible things are.Even if you don't do your own work,you'll be paying someone to do it.

Recently I've been at boat shows/dealer shows and said "there's a $1000.00 starter" Sure gets me strange looks.But when you get down to it,that starter can't be removed until the engine is out of the boat ! And that engine sure won't come out easy.Love those rear entry boats.

Your bolts should not be that rusted.But they are because we were sold quieter motors.That meant more insulation.And less ventilation.Can I say condensation?I am sure you've seen morning dew on your motor.

The added heat this causes is hard to address.Mercruiser has several Service Bulletins on it.But they have to use GM engines,make a package,and then the manufacturer stuffs it where they want

So much for my rant.


DHP

 

[Shaun78]

Re: Rusted Manifold Bolts??

What tool and attatchment can I use to grind the heads off. An air grinder with a cutoff wheel is to big to fit in that tight spot unless they make really small discs.

 

[Bondo]

Re: Rusted Manifold Bolts??

What tool and attatchment can I use to grind the heads off.

Ayuh,.........

Use whatever weapon you can muster Shaun,.....

A 4" Grinder would make Quick work of the task,.......
A Rotozip with a Carbide Burr would also do the job.........
I suppose a Dremel would too,..... If you wanted to invest the Time........

It mostly comes down to Access............... Both to the Problem,+ the Tools...........

 

[seatek]

Re: Rusted Manifold Bolts??

What tool and attatchment can I use to grind the heads off. An air grinder with a cutoff wheel is to big to fit in that tight spot unless they make really small discs.

Use a deburring bit. They're made out of carbon steel and come in a variety of sizes and shapes. Cost ranges between 25 and 40 bucks. You'll also need an air powered die grinder, the electric ones are useless. Make sure that it has interchangable collets so you can use either 1/4 or 1/8 shanked bits.