Replacing 250 exhaust manifold

[wydomkr]

I'm going to be changing the exhaust manifold on the 69 I just picked up, it is broken at the flange where the pipe bolts up, I've never had a 6 cylinder anything, are there any tips, tricks or gotchas I should be aware of or is it just an unbolt the old one and bolt on the new one? Thanks.

Keith

[dougs69c10]

take it apart as one piece, intake and exhaust mani, then swap the exhaust mani, and then put it back on as one piece, its that easy

[shelby987]

When I replaced mine, I replaced most of the bolts and caps that hold the flange to the head with doubled up grade 8 washers and hardened bolts. You can do this will all but two of the caps that put pressure on the flange (I believe these are the caps at the #1 & #6 cylinders). I felt that this made installation easier (no orientation issues because the washers are round, and not ovals like the originals) and it gave a greater area of pressure to seal up the gasket.
I had to put in headers and an intake at the same time, but I would recommend a second set of hands if possible, as both need to be removed/replaced at the sametime.

[Brad]

First, I would replace the very first and the very last bolt with studs. This will make putting the manifolds back on alot easier! Be sure to use studs with a fine thread- that'll make the manifold seal better.

Second, when bolting the two manifolds together, be sure to lay them on a perfectly flat surface because if one manifold is crooked from the other one you'll get a vacuum leak or an exhaust leak after you've bolted them to the engine block. The gasket used for these manifolds isn't the best and so this is really important. You could also use copper gasket maker on the gasket, but I've never had to.

Also, if you want to be absolutely sure you have a perfectly flat surface once the manifolds are bolted up to each other, you could take it to a machine shop and they can machine the surface that bolts up to the block. I've done that before and it works great.

Third, be prepared to climb in and get cozy in your engine compartment. It's not fun putting these back on, but I could think of worse things I wouldn't want to do!

[wydomkr]

Thanks for all the informative instructions, I should have mentioned that the replacement I got is both the intake and exhaust still bolted together so I don't have to split them, should make the job easier. The thing that worries me the most is breaking off the bolts that hold it on, I absolutely hate drilling out broken bolts, never have been very good at it. The replacement exhaust manifold does have one of the studs messed up where the pipe bolts on, I'm still soaking that with penetrating oil preparing it for removal, hopefully that doesn't break either. I tried heating it alittle bit, but didn't want to get carried away since cast material is kinda brittle.

Keith

[shelby987]

are you talking about the heat pipe between the exhaust manifold and the intake manifold (where it bolts together?)

A side note about vaccum leaks on these engines, I had a bear of a time with mine, and when I put in my built 250, I will have my headers and intake machined flat prior to installation, in the meantime, I got everything as snug as I could, drove the truck for a couple hundred miles, and retorqued everything, seemed to help a bit (a good tip is to use pipe fitting wrenches with the 6 points of contact). These wrenches let me get a good hold on the bolts and get a good amount of torque on them without rounding anything off.

Brad, good idea with the studs, wish I had of thought of that! Oh well, there will always be a next time.

[wydomkr]

No, I'm talking about the exhaust pipe to the muffler. One of the two studs where the exhaust flange and donut mount up, the threads are screwed up.