Another driver side header question

[oc192]

I didnt want to hijack the other user's thread so I started a new one. I am taking my car in Friday to have the driver side header removed, welded and reinstalled. The guy doing the work made the suggestion that I cut a piece of the crosspipe out and weld in a flexible braided hose type material to give the header some play when the engine torques. He suspects that could be what causes these headers to crack. He made this suggestion after I told him the headers are known for cracking in the same spot. Does this sound reasonable or should I just leave the crosspipe alone.

Thanks,
Don

 

[bogies87]

I am no expert on this but one would think the flexpipe would not withstand the pressure that builds in the pre-turbo exhaust. In other words the turbo relies on exhaust flow/pressure to spool the turbo. If a flex pipe was installed it would be the weak link causing a leak or blow out.

 

[3.8L V-8 eater]

Of all the x-over pipes I have ever seen or owned, not counting all the ones I've seen for sale including aftermarket... Never have I seen that done to a x-over pipe..Not only does it sound hoaky, but it will look cheap...I would think of having someone else do this work for you...If he would have suggested having a gusset welded between the two primary tubes then I would say you might be in good hands......

 

[turbojd]

X2, never heard of someone doing that to the crossover pipe.

 

[Chuck Leeper]

It's NOT uncommon to use the flex joint....The flex joint relieves the twisting stresses, allows the cheapo connector flanges to seat better.
The entire header system moves when the engine moves. The failure of the header is due to 20+ yrs of heat cycling, poor design, poor quality materials.

 

[TurboBuRick]

When the motor torques the point of stress is on the turbo housing. There may be a little on the header turbo flange but providing the turbo bracket is in place there's not much.

A slip joint on the other hand may relieve some some stress but not due to motor torque. Due to heat. You would be surprised how much heat expands metal. A slip joint will help with that.

Check this out. Put the tips of your fingers together. This simulates v8 turbo exhaust system in a Turbo Buick configuration. Your thumbs are the crossover. The rest of your finger are right and left banks. As the banks heat up they expand pulling out ward on the crossover. With your hands you can see it does not take much movement to drastically pull in and on the crossover. Now magnify that to the actual size of the headers.

I have a Poston's crossover with a slip joint. (knock on wood) Haven't cracked a header in a long time.

RL

 

[GNVenom]

I welded in braided expansion flex joints directly into both sides when I fabricated the headers on my project. Plenty of expansion with two turbos, but no cracks, loose bolts, etc - yet.

 

[TURBOPOWERED68]

i was just reading a thread on one of the boards if not this one, where the guy was/is fabing his own headers and he used a flex connector on the driver side of the cross-over pipe just as you described.
thread title i think goes-"bored, broke something "??? look for it. also the from the pictures the guy is a professional at what he was doing not a back yard put together job.
good luck.

 

[TurboBuRick]

I welded in braided expansion flex joints directly into both sides when I fabricated the headers on my project. Plenty of expansion with two turbos, but no cracks, loose bolts, etc - yet.

That's a nice set up but hard to compare to a twin turbo hybrid. If the header turbo flanges were cracking a piece of flex pre turbo would definitely help but we're talking driver side header here. No turbo or down pipe on ours. Apples and oranges.

RL

 

[GNVenom]

Yeah, that's true. I think the place for the flex joint would be where the OP was thinking, at the crossover. I think some people believe that the torque of the engine somehow twists the crossover pipe and cracks the header on the drivers side....not a chance of engine torque even budging the crossover though.

I think if you could fit a flex joint between no. 3 and no. 5 on the ds header, it would prevent that crack at the weld joint.

 

[oc192]

Yeah, that's true. I think the place for the flex joint would be where the OP was thinking, at the crossover. I think some people believe that the torque of the engine somehow twists the crossover pipe and cracks the header on the drivers side....not a chance of engine torque even budging the crossover though.

I think if you could fit a flex joint between no. 3 and no. 5 on the ds header, it would prevent that crack at the weld joint.

I think that is where Casey (guy doing the work) was going with the suggestion. If the crosspipe wont budge then the energy will be transferred to the ends and break at the weakest point. I checked out a picture of a flex joint on summit, I can't see this leaking or blowing out.

http://www.summitracing.com/parts/PSM-82-4218/?rtype=10

 

[JimP]

I'm surprised no one mentioned Kirban's driver's side replacement header , it's a direct bolt-on I have been using this without any issues, my cross over pipe was looking a little weak so I also bought the cross over they were selling too. Everything bolted right up, still no leaks and no cracks after about 7 years.

 

[TurboBuRick]

I think that is where Casey (guy doing the work) was going with the suggestion. If the crosspipe wont budge then the energy will be transferred to the ends and break at the weakest point. I checked out a picture of a flex joint on summit, I can't see this leaking or blowing out.

http://www.summitracing.com/parts/PSM-82-4218/?rtype=10

Might put a piece of flex in the crossover close to the flange. That would help but a slip joint at 6 oclock will do a better job IMHO.

Let us know what route you take.

RL

 

[turbofabricator]

Check this out. Put the tips of your fingers together. This simulates v8 turbo exhaust system in a Turbo Buick configuration. Your thumbs are the crossover. The rest of your finger are right and left banks. As the banks heat up they expand pulling out ward on the crossover. With your hands you can see it does not take much movement to drastically pull in and on the crossover. Now magnify that to the actual size of the headers.



RL

OH...GREAT!!!! Now I've got carpel tunnel....THANKS!
The design of the drivers header is the culprit. The #3/#5 joint has one long pipe and one shorter pipe that are butt welded. Expanding in different planes due to significant heat. Run you engine in park at 2,000 RPM for about ten minutes. They will glow so bright they'll look almost transparent. Add to that the expansion of the cross over tube and it puts alot of stress on the joint. Cracks will appear. On a turbocharged engine, any material used WILL crack, the better the material and design, only delays the onset of cracking. (unless you fab them out of unobtainium........THAT stuff NEVER cracks!!)

 

[TurboBuRick]

OH...GREAT!!!! Now I've got carpel tunnel....THANKS!
The design of the drivers header is the culprit. The #3/#5 joint has one long pipe and one shorter pipe that are butt welded. Expanding in different planes due to significant heat. Run you engine in park at 2,000 RPM for about ten minutes. They will glow so bright they'll look almost transparent. Add to that the expansion of the cross over tube and it puts alot of stress on the joint. Cracks will appear. On a turbocharged engine, any material used WILL crack, the better the material and design, only delays the onset of cracking. (unless you fab them out of unobtainium........THAT stuff NEVER cracks!!)

You have to admit that's a good simulation. Glad someone got it.

I know designs the problem and I agree there is no permanent fix.

RL

 

[slimtastic]

ive put flex's in crossovers befor and with no problems at all...if it was a super high boost application i would also put two adjustable link bars across the flex section just to limit expansion from backpressure but gennerally it isnt a problem

 

[charlief1]

It's actually funny to me that you bring up the flex pipe section. The HA cars, except for a few of them, got a flex pipe in the up pipe to the turbo. It makes perfect sense to use one and if you look at the stock IC headers you'll notice a weird looking section on the passenger side. It's supposed to be a flex joint with out the covering. Putting one in the cross over will make it easier to fit and keep the stress off of the headers