Crossover Pipe - Flange mounting screws/bolts

[Jochen Woern]

Getting ready to install my 2-1/2" inch Crossover Pipe, mandrel bent, 14 gauge aluminized tubing on my '96 Burb.

Does anyone know what size the three (3) mounting screws/bolts are which connect the Crossover Pipe Flanges? Are these metric or standard?

I was under the truck this evening in order to spray the mounting screws/bolts with WD-40, thought it would help if it could soak the screws/bolts for easier removel this weekend.
By looking at the screws/bolts, I decided it would be best to change them with some new stainless steel ones, once I know the EXACT size and length.

Thanks in advance.

[Robyn]

All bolts on a 6.5 are metric
ACCEPT the 6 that hold the engine and tranny together. These are 3/8 NC thread and use a 9/16 socket/wrench

The bolts that go into the exhaust manifolds can be a bit nasty to get out.
You may want to use a long punch and a hammer and place the punch right in the middle of the bolt head and smack them a few times to "Shock" the threads and help loosen them up.
I have also had to use a torch and heat the little ears where the bolt threads are to get these out.

If the rig is a high miler dont be supprised if the bolts break off.
I have also had this happen and then had to remove the manifolds and surgically remove the little monsters.

If you are lucky enough to get them out be sure and use some never seaze compound on the threads when replacing.

The threads on the bolts are a rolled thread and have a triangle swedged shape to the bolt. This acts as a locking device to keep the bolts from working loose, unfortunately it also makes them tougher to remove later in the service cycle.

Good luck

Robyn

[tommac95]

From recollection only:
M10X1.5 about 2"(?)

My manifolds spent a while in a vise while remnant fastenings were being heated , drilled , and easy-outed ...

[Kenneth]

If you have problems with the bolts not coming out try using a candle to loosen the bolts. I read about that here on TDP. Heat the area up with a torch and then set a candle on top of the bolt to let the candle wax melt into the threads. Allow the area to cool down and then work the bolt back and forth as you back it out to allow the candle wax to work its way into the threads better. Supposedly it works pretty well. I have never tried it yet, but if you have a problem I would certainly try it.

[waynep]

I removed mine using the wax method and it worked really well. They were really stuck at 125 K and this was the only way they they would come out.

I replaced them with stainless steel and no seize compound.

Regards

[Jochen Woern]

Thanks for everyones input, very much appreciated.

NEVER heard of the candle scenario, VERY interesting for sure. I was just wondering how one could get candle wax up in this tight spot in order for the wax to flow over the thread of the bolt???????

I soaked my bolts three (3)/four (4) times with WD-40 over the last week. I tried one bolt this afternoon, it came loose VERY easy, ................... hopefully the rest of them will as well.

FYI -- The Bolt size is metric, M10x1.5 - 37.5 mm long. I will use 45 mm long bolts (Stainless with Anti/Never Seize). The 37.5 mm ones are pretty much flush with the manifolds and I rather have some extra thread for additional insurance anyhow.

ONE LAST QUESTION: Is there a seal between the crossover pipe and the manifolds or can I just unbolt the stock crossover pipe and install the new one with the flange directly (without any seal in between) to the manifold?

[Robyn]

There is a "Donut" that has a steel flange that slips inside the manifold and also has a tapered face the the Xpipe flange fits over.
These should probably be replaced. If they do end up intact and serviceable you can reuse them.

Good luck

Robyn

[Jochen Woern]

Thanks Robyn.

- What is the probability of them being in good enough shape to be re-used?

- Any idea what the cost of these "donuts" is? I assume I need two, one on each end of the pipe?

- Are these readily available at a GM Dealership or do these need to be ordered.

Thansk again and HAPPY THANKSGIVING.

[ToddMeister]

PB Blaster also works well instead of WD-40

[Hubert]

The donuts aren't much under $25ea; 2 required can't remember cost. I bought some at Advanced Auto so most any parts house can get them easily.

They are a bit misleading if you have never worked with them before. They deform/crush and seal to pipe (new pipe I'd install new doughnuts and save the worry- its more hassle for me to go back to parts store if they are bad). They also conform to the manifold and soot builds up on them so they look like part of the manifold the first time you look at them. You end up destroying them to get them out. The new ones will have a metal ring/tabs to hold it to the manifold. Once you see new ones they make more sense than viewing the old ones from under the truck.

[Jochen Woern]

Thanks a lot everyone. Just purchased the new donuts and they were 12.94/Each at the GM Dealership. Will install new crossover pipe hopefully this afternoon.

[Jochen Woern]

Cross over pipe was installed this afternoon with no issues at all.

Old bolts came loose with no problems after I soaked them in WD-40 a few times. Installed the new crossover pipe with the new Donuts as well as new Stainless Steel Bolts using Anti/Never Seize.

All went well and was pretty easy.

Thanks for everyones input.

[rustyk]

PB Blaster also works well instead of WD-40

I'm with Todd - PB Blaster is far more effective than WD-40.

[JohnC]

If you put a steel bolt into a steel manifold, both will corrode equally. If you put a stainless bolt into a steel manifold, the bolt won't corrode at all, but the manifold will. when you take the bolt out you may find there are no threads left in the manifold...

[Jochen Woern]

So what are you saying? Exchange the stainless steel bolts with regular steel bolts?