Need a wrenchin advice

I am about to swap out my exhaust manifolds, The question I have is this, They set that are currently on the Motor are the orginals and after 40 plus years attached to the heads I am sure the bolts will be pretty tuff to remove and I was wondering if anyone had any advice on the best way to remove them...i.e is there any prep I should do before trying to just back them out?
Also I just need to replace the Passenger side and was wondering if I should replace them both or will I be okay just doing the one side? The Set I bought are from a 425 and I have the 401. Also I would like to do this while the motor sits in the car or do I need to remove the motor? Would it be better to just put on headers, I thought that I saw somewhere on the Board that someone sells a set for Nailheads I think it was T/A performance???
I Guess by now everyone can tell this is the first time I have done this :laugh: :laugh: Any advise would be helpful and Thanks in advance,
Don

 

Other guys on the board have had luck pulling manifolds off while still in the car. I didn't bother on my Lesabre. I pulled the engine and set it on a stand so I could completely work on it. I hit the bolts with PB blaster as best I could and let it sit for a day. Then I hit ( not smash) the bolt heads with a ballpeen hammer to hopefully shock them loose. Finally I used and impact to blast 'em off. The bolt heads were rather deteriorated and I think I ended up using a 14 or 15mm instead of the 9/16 socket that was supposed to fit. ALL of my bolts came out like they were installed yesterday. I was told I was one of the lucky ones. The mileage on the car at that time was between 30-31,000.

On my old Goat I had busted off a bolt head. I removed the rest of the bolts, then the manifold, then was able to grab it with a vise grip and put a little heat to it with the fire wrench, then the rest turned out.

Make sure to use NEW bolts on reassembly, and use antiseize! Hope some of this helps. Good luck.

 

This may sound odd but try to tighten them a little first. Sometimes this helps break them loose.

 

Thanks

Matt and Eric,
I am already soaking them wit PB Blaster and I have done the tighten first thing before so I understand what you mean when you say that ,It is a good idea alot of people don't think of that but it does work sometimes.
Thanks Guys :TU: , I was just wondering if there was anything I needed to look out for when I do it.
Don

 

Busted Knuckles from when the bolt breaks. :laugh: :laugh:

 

That's why I am going to get my 500lbs. Mother in law to do it! :laugh: :laugh: :laugh: , She has so much fur and padding on her hands she will never feel it! :shock:

Don