Exhaust Manifold Removal for Headers Install Questions

[Old60Driver]

Hey folks!! It's been a while since I've been on the forums. I've been busier than you know what, and haven't had a damned minute to tinker with my 83 K20 at all these last months.

BUT, I've got a few days, so I thought I'd drop the headers in. Might even tackle the intake while I'm at it. While I'm fairly comfortable wrenching on whatever needs it, I've actually never installed a set of headers. Lots of manifold gaskets, broken bolts, etc, but never headers.

Here are my questions:

I've never removed manifold to pipe flanges on a truck that's never been tore into. Given that it's almost 40 years old, I'm thinking that I'm just going to have to cut the bolts out. I've tried some heat, but really, there aren't any threads left. Thoughts?

Once I get the old logs out, I'm guessing I'll need to drop the exhaust system in order to install the headers. To do THAT, it looks like I'll have to drop the tranny crossmember. Unless there's any easier way?

I'm planning on having the local exhaust shop install the flanges to my existing exhaust. I'm thinking that I might need to take a look at my A/F mixture before I make the 25 minute trip over, as more flow might lean her out a bit. Sound about right?

Thanks in advance y'all!

Stay Safe!!

 

[Old60Driver]

On second thought, I'm thinking about breaking the old sawz-all out and just cutting the flanges off. Given that the headers will be considerably longer, and the exhaust will have to be modified to accept them anyway...

Thoughts?

 

[Catbox]

I didn't really have any exhaust left over from the original stuff that was under the truck when we did ours.
You can most definitely chop out the old stuff as it will just be in the way of the headers when you put them in.

For a temporary solution, we ran the existing exhaust to the new headers with some simple flex pipe.
Cheap and sufficient for a temporary solution until you can get to a place to weld it up.

 

[Grit dog]

On second thought, I'm thinking about breaking the old sawz-all out and just cutting the flanges off. Given that the headers will be considerably longer, and the exhaust will have to be modified to accept them anyway...

Thoughts?

This is exactly what I’d do. The studs in the manifold collector are toast anyway and the new pipes you’re having fitted to the headers and existing exhaust can be fitted up longer or shorter.
Just make sure you cut the exhaust pipes in a good place to weld them up to the new pipes.

 

[Bextreme04]

Yep, definitely just cut the pipe off. My headers on my 350 have the collector ending right next to the front spring rear shackle bolt if that helps visualize how far back they will likely come. I'd cut the exhaust back to at least there and then drop the manifolds out. Get yourself some Permatex Copper RTV and run a bead around the header ports before you bolt them on. I used just a gasket at first and had big leaks. Pulled the headers back off a bit and ran a bead around the ports, snugged up the bolts just enough to start pushing a little bit of RTV out, and let it set for an hour before tightening everything down to spec. Zero leaks after that.

 

[Old60Driver]

Thanks y'all!

I ended up cutting them just after the flange. I'll end up cutting them some more to get the headers in, but at least I got the damn logs out! And get this. ALL of the manifolds were easy to come out. I mean like I didn't even have to break them loose. Weird.

I had to shut it down to fire the grill up and get some dinner ready for the wife and daughter, but I should be able to get the headers in and over to the exhaust shop today!

 

[Old60Driver]

Update:

Got the passenger side installed (not torqued yet), but the driver's side is being a pain. Basically, I have an aftermarket temp sensor installed, and it's too big. I'm thinking of just grinding a bit out of the header flange (which I REALLY don't want to do), or finding a new sensor that fits.

What say y'all?? Any tips here?

 

[Bextreme04]

Update:

Got the passenger side installed (not torqued yet), but the driver's side is being a pain. Basically, I have an aftermarket temp sensor installed, and it's too big. I'm thinking of just grinding a bit out of the header flange (which I REALLY don't want to do), or finding a new sensor that fits.

What say y'all?? Any tips here?

I would grind the header, especially in that spot it wont have any effect on sealing. The only time I would think about changing the sensor instead is if they are super nice ceramic coated headers. Of course, in that spot you wouldn't see it even on nice headers.

 

[Old60Driver]

Yep, that's what I'm gonna do. Heading out to find my grinder. Wish me luck! lol

 

[Old60Driver]

Okay, got 'em in. Turns out I was impatient. It was only out by a wee bit, so I was able to fix the issue by simply turning the sensor a bit. Found out when I put my old trust headlamp on and got my peepers way down in there. Still, the sensor fitting is only 1/8" or so away from the header flange, but I'm thinking it should be okay.

Then I had to cut the a/c bracket, and figure out a bolting situation for that.

NOW, I'm on my way to the LPS to grab a shorter alt belt since I removed the air pump. lol

Cheers!

 

[shiftpro]

How does you starter wiring look? You may want to reroute it somewhat. I also like to use the heat reflective on my starter where it's gets warmed from the header. You can find this product at a decent motorcycle shop.

 

[Old60Driver]

Shiftpro - Looks good and out of the way. More clearance than I was thinking I was going to have. Still, I'll probably shield the start just in case!

 

[78C10BigTen]

Why all this talk of progress with no pics? Lol

 

[Old60Driver]

Why all this talk of progress with no pics? Lol

Haha! Good point. I'll see if I can remember how to post pics!

 

[Old60Driver]

Also, has anyone seen the episode of Engine Masters where they discuss the length of the header collector extensions? They tinkered with varying lengths of the extensions and dyno'd after each shortening of the extensions. What they found is that, while the changes in extension length didn't matter much at all for max torque, the lower RPM torque came up quite a damn bit. Thinking about seeing if the exhaust shop can add 6-8 inches beyond the collector.

Y'all ever heard of this before? Or have past experience with attempting this?