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Tuesday question: marine exhaust manifold.

arse_sidewards

arse_sidewards

Red Skull Member
Joined
May 19, 2020
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Trying to take the manifold off this. 2/4 bolts came out. Nuts came off the studs just fine. Studs are still in there. 2/4 bolts snapped.

Yes I could just take a grinder to it but it's a nice manifold in good condition so I don't want to.

I don't care about marring the head or exhaust flange as long as it's not so terrible I can reasonably mill them back to flat.

Anyone got any tips for getting it off the head?

Yes, I tried hitting it with a hammer, sticking a crowbar between the manifold and the head and both at the same time. I'm gonna add heat tomorrow but it's a giant aluminum casting and the studs are in the middle of it so I'm not hopeful.

Engine in question, riser has obviously been removed.
attachment(2).jpeg
 
if all the bolts are broken or removed what do you have left? Is it just hung on the studs?
 
vinegar.

or any acid weak enough to eat the corrosion but not strong enough to eat the aluminum.
 
Rattle the ends of the studs with a flat punch on an air chisel. Try to get the corrosion powder to crumble up a bit in the holes. Heating helps do that too, use a rosebud on oxy/acyteline torch to hopefully dump enough heat in but not melt localized spots.

If that fails drill the studs halfway down so there's still enough stump to weld a nut on after the manifold is off.
 
upgrade to the cast iron manifold, i think that's the only one available now. It will save cylinder #4. hole saw with the pilot bit removed, make clearance.
 
You mentioned 4 bolts 2 studs. I thought there were 8 fasteners on those? Its been a very lont time since I messed with a merc inline though so Im probably wrong.
 
SLOWPOKE693 said:
Lay it over on the intake side and spray the studs down with the penetrating oil of your choice and let it soak for a few days. Go back to it everyday, tap around the studs and reapply the penetrating oil.
Click to expand...

Exactly this.

One step beyond this, instead of penetrating oil, use ATF.
 
Break the bolts, remove manifold, extract bolts from head.
 
LR Max said:
One step beyond this, instead of penetrating oil, use ATF.
Click to expand...
Add a bit of acetone to the ATF for bootleg Kroil. Or use Kroil :laughing: When I worked in a boat yard one summer, a lot of 20-year-crusty shit got the "hose-down, dick with it, and walk away" treatment.

EDIT: too slow by a minute :frown:
 
I'll jump on the ATF/Acetone bandwagon. It doesn't stay mixed for shit, so I kind of whip it up in a small cup with an acid brush or whatever and then dab it where it needs to be.

I had a mercury outboard that almost all the exhaust chest bolts broke off on upon disassembly....gave me all the ATF/Acetone treatment/smack with a hammer a few times, more ATF/Acetone for a couple rounds, and all of them came out relatively easy with vise grips...
 
Lbhsbz said:
I'll jump on the ATF/Acetone bandwagon. It doesn't stay mixed for shit, so I kind of whip it up in a small cup with an acid brush or whatever and then dab it where it needs to be.
Click to expand...
If you have a bottle or can with a spout + cap (like an old pint Kroil can), you can shake it up right before applying.
 
I laid it over on on its side with ATF and PB blaster.

That, a bunch of tapping and the mini pipe wrench got the studs out.

attachment.jpeg


The broken bolts are still stuck. I stuck the porta power in there and used a punch to hammer the studs. It sounded/felt like they were doing shit but 20min later nothing had happened. So I cranked the porta-power to 11, laid it back over and left it sitting.


attachment(1).jpeg
 
too late I guess

no oil, rattle on it with the air hammer with the bolt holes facing down so the aluminum oxide will fall out as powder
but you've oiled it so now that sand is stuck in there forever
good luck
 
Lbhsbz said:
I'll jump on the ATF/Acetone bandwagon. It doesn't stay mixed for shit, so I kind of whip it up in a small cup with an acid brush or whatever and then dab it where it needs to be.

I had a mercury outboard that almost all the exhaust chest bolts broke off on upon disassembly....gave me all the ATF/Acetone treatment/smack with a hammer a few times, more ATF/Acetone for a couple rounds, and all of them came out relatively easy with vise grips...
Click to expand...


the acetone evaporates. get use to the consistancy when you first mix it. i use and mix in a solvevent bottle, it stays pretty good.


i dont have google time tight now but i did once find a write-up/ test that basically proved that aft/acetone is around 5x more effective than Kroil, and 10x more than any other penatrant. iirc on the order of magnitude
 
Porta power didn't do jack shit. After moving it around to wiggle the manifold a bunch of times I broke off one tip of the spreader thing. From there I decided to cut it so I hit the stud on the far end with the angle grinder. That let me move the manifold enough to wiggle and pry it off.

Ports are crusty as fuck. Gotta love the crystals that coolant makes in an environment with plenty of iron and aluminum.

attachment.jpeg
 
That portapower attachment is about as useless as they get. Should have rattled around everything with an air hammer to help break up the corrosion around the studs to start with.
 
manifold flange looks very 460
did they actually choose to make something correctly (using off the shelf existing parts)?
 
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