What are the odds of successfully getting the manifold screws out of a 1992 with 260k miles?

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351FUN

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I'm kicking around the idea of swapping the stock manifolds to headers, probably shorties but maybe LT on my 1992 Blazer, and my biggest concern is getting the fasteners off the factory manifolds. I don't live in the rust belt thankfully, but that only helps so much. Are there any tips or tricks I should be aware of, or is it more likely I'd end up having to pop the head off and drill **** out?
 

RichLo

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Well, there are things that I would personally do that I wouldn't recommend... but if you may do this, carry a fire extinguisher and I am not responsible for any damages.

1-6 months in advance... most spray penetrating oils are safe(ish), but keep in mind they may ignite.

2-6 weeks in advance... Keep up with the penetrating oil but add a cleaner. Oven degreaser is best but some people have good luck with things like ATF. Again, BEWARE ignitable!

0-4 weeks in advance... Keep up with everything above and immediately after running the engine spray the exhaust manifold bolts with liquid nitrogen (basically a canned keyboard cleaner but turned upside down). This is to add a cold shock to the bolts/studs so the threads both absorb the above fluids and break the rust weld all-in-one step.

And again, this is only for somebody who is willing to assume all responsibility for having a car catch on fire. If you are not prepared for that then 0-4 week should be enough for your needs. (Liquid Nitrogen is not flammable however other super cold materials may be ignitable or may be oxidizers)... BE VERY CAREFUL and do your research into what chemical you will be using!

EDIT: the 0-4 Week advice can be extremely dangerous if you have something that is on the verge of ignition and you add an oxidizer like Nitrous-Oxide or Oxygen. Both of those could fit my description for what to do. DO NOT USE OXIDIZERS!!! Stick with an nitrogen based coolant
 
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351FUN

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Yeah I definitely want to start soaking them in kroil for a while. The cold shock is a good idea.
 

evilunclegrimace

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If you are referring to the exhaust manifold bolts there is a tool that is placed between the front exhaust port and the middle exhaust port on the manifold that spreads the manifold open slightly to take the side load off from the bolts to ease their removal. GM put out a service bulletin on this years ago when these trucks first came out.
Snapon used to offer the tool.
 

someotherguy

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If you are referring to the exhaust manifold bolts there is a tool that is placed between the front exhaust port and the middle exhaust port on the manifold that spreads the manifold open slightly to take the side load off from the bolts to ease their removal. GM put out a service bulletin on this years ago when these trucks first came out.
Snapon used to offer the tool.
Lisle has it, manifold spreader tool. Inexpensive and works well. Part # 13000 - about $10-$15 depending on where you get it.

I haven't had any real trouble pulling exhaust manifolds on these trucks; warm (not hot) engine may help. Your choice of penetrating oil may help, too. I've always just done them with a 3/8" drive ratchet, by hand to break them loose, then air to run them all out.

The spreader tool could come in handy for removal, but where it really shines is on re-install. It can't cure seriously warped manifolds, and many of them are cracked already - particularly between #2 and #4 cylinders on the small blocks, hidden by the heat shield that forms the duct for the warm air tube to the air cleaner (TBI.)

Richard
 

Vanishing Point

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Here is another choice for you at your local NAPA (Crapa)!
In case you have trouble locating the Lisle tool though a little more expensive.
item is not vehicle specific.
Exhaust Manifold Spreaders
Part #: SER 774030
Line: NAPA Service Tools
$17.99
Qty: 1










/
 

someotherguy

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Here is another choice for you at your local NAPA (Crapa)!
In case you have trouble locating the Lisle tool though a little more expensive.
item is not vehicle specific.
Exhaust Manifold Spreaders
Part #: SER 774030
Line: NAPA Service Tools
$17.99
Qty: 1










/
That looks like the exact same Lisle tool, repackaged and marked up a little bit.

Richard
 

Drunkcanuk

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When I did my headers at approx 200 000km, I sprayed a little PB Blaster the night before on the engine when it was warm, NOT hot.
The next morning, sprayed a little more then started it, ran for 10min or so. Sprayed more immediately after, let cool down.
Then finally sprayed more when it was cold, broke out the 3/8 ratchet, and very carefully backed out a hair, back in, repeating anytime I felt resistance. Didn't break any, and they were fairly rusty.
But definitely spray the oil outside, stinks a lot.
Good luck.
 

Schurkey

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There are some engine families where the exhaust manifold bolt holes in the cylinder head are open-ended, you can spray penetrating oil on the back side, directly onto the threaded part of the bolt. You stand a chance of having the oil actually wick into the threads and do some good.

On a SBC, none of the holes are open on the back side. The penetrating oil would have to get between the underside of the bolt head and the iron manifold. This is practically impossible. Then the oil has to travel down the un-threaded shank of the bolt to even reach the threads.

Penetrating oil will make a lovely but useless puddle on the ground.

OTOH, it's potentially useful on the manifold outlets, where the exhaust pipes attach using studs and nuts. At least those threads are exposed.

If this were me, I'd be sure to use a flex-socket on the manifold-to-cylinder head bolts so that no side-force was applied to the head/shank of the bolt. Torque, but no side-force. Either they come out, or they twist off. If they twist off, you can remove the manifold and then soak the studs with your favorite penetrant. However, with the manifold out of the way, I would use a torch to heat the bolts until they glow orange, let them cool, and then unscrew 'em.

Liquid nitrogen? I woudn't know where to buy that around here. I did buy a can of "Freeze-Off"; penetrating oil and A/C refrigerant in a single can. The refrigerant is both the propellant for the aerosol oil, and also supposedly "freezes" the parts to break the rust-bond. Didn't do anything useful on the project I used it for. Very disappointed.
www.amazon.com/CRC-05002-Freeze-Off-Super-Penetrant/dp/B000TFTH00/ref=sr_1_3?crid=YW1FOBJJ93KU

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