IHADAV8.com - Turbo Buick Tech, and Nonsense
Tech Area => General Buick Tech => Topic started by: ~JM~ on June 26 2021, 11:51:30 AM
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Removed my headers & see the crack on the rear tube on the driver side header. Haven't really examined both very closely yet. What should I be looking for? I've heard mention of cutting the mounting flange & creating clearance for expansion & contraction. Also heard of an additional brace welded in. Are the heat shields typically cut off & then tacked back on after repairs/modifications? I have a spare set of heads to bolt up to.
O2 sensor bung repair? My O2 sensor has been cross threaded. I chased the threads, but I believe it has probably been done before. The O2 sensor will not thread in & seat flush. Any reason a new bung couldn't be positioned about 90 degrees away from the original one? I need to mock it up before selecting a final position, but I'm thinking there should be a spot available with better access for sensor replacement.
Thank you.
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my experience is that cutting the flange may make the problem worse, not better. Some put a gusset between three and five to add more strength. I'm not sure that helps either Probably does not hurt is about the best I could say LOL The tubes are old and thin and that adds to the problem.
A good welding solution that uses tig and floods the inside of the pipe with gas to make the repair as clean as possible is probably the best solution and make sure the entire area is heated up so the cooling off is over a larger area rather than stressing along the weld helps.
the most effective solution is to replace the header in question...wel l, not effective in the cost for sure. smh. The Chinese imports are cheap, fragile, thin, and may not fit. Not much of an option at all from all the reviews I have read.
My first thought on the O2 bung is to heli-coil it if the correct threaded insert is available. There is no reason you cannot add another bung, tho. Just make sure it is in a place that the wire to it will not get burned. I would keep it as close to the turbo as possible but a little lower should not hurt. It needs enuf room to allow all six cylinders to be mixed so you get an average reading.
As long as it does not leak, it should not hurt to have a 1/16" of clearance between the base and the bung, imol.
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I wont offer and advice on repairing the header tubes other then good luck. The O2 bung is easy. Its a sparkplug thread so a sparkplug thread chaser like a Lisle 20200 will do the job. If not a sparkplug repair kit with helicoil will work. I wouldn't try and drill holes and reweld a bung on 35 yr old shitty stainless steel.
(https://www.amazon.com/Lisle-20200-Thread-Chaser/dp/B0009OMYCO/ref=sr_1_4?dchild=1&keywords=spark+plug+thread+chaser&qid=1624730594&sr=8-4) (https://www.amazon.com/Lisle-20200-Thread-Chaser/dp/B0009OMYCO/ref=sr_1_4?dchild=1&keywords=spark+plug+thread+chaser&qid=1624730594&sr=8-4)
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good advice
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This is what the old O2 sensor looked like when I removed it. The threads in the O2 bung are not "square" or "plumb" for lack of the correct term. The threads are angled into the bung causing the thread tap or chase to follow at an angle. I was able to clean up the threads to accept the new sensor, but the base of the sensor does not meet the shoulder evenly. It sits at an angle.
What type of cleaning process should be performed to prepare for a successful repair?
What replacement options are available. Prefer to avoid imported parts.
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Hmmm... The picture appears short & wide.
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I would just try and use the thread chaser and screw in a new O2 sensor with some high temp RTV on the threads. Your only sealing exhaust gas and not compression. It should hold and work. Even if it goes in a little off center, it won't effect the O2 readings.
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Hmmm... The picture appears short & wide.
Some windows rescaling programs seem to not reproduce accurately here. I don't recall if Paint works okay or not, but I generally use an aftermarket routine with no problems.
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my experience is that cutting the flange may make the problem worse, not better. Some put a gusset between three and five to add more strength. I'm not sure that helps either Probably does not hurt is about the best I could say LOL The tubes are old and thin and that adds to the problem.
A good welding solution that uses tig and floods the inside of the pipe with gas to make the repair as clean as possible is probably the best solution and make sure the entire area is heated up so the cooling off is over a larger area rather than stressing along the weld helps.
the most effective solution is to replace the header in question...wel l, not effective in the cost for sure. smh. The Chinese imports are cheap, fragile, thin, and may not fit. Not much of an option at all from all the reviews I have read.
My first thought on the O2 bung is to heli-coil it if the correct threaded insert is available. There is no reason you cannot add another bung, tho. Just make sure it is in a place that the wire to it will not get burned. I would keep it as close to the turbo as possible but a little lower should not hurt. It needs enuf room to allow all six cylinders to be mixed so you get an average reading.
As long as it does not leak, it should not hurt to have a 1/16" of clearance between the base and the bung, imol.
I have another dumb question... I can't remember which tubes the dipstick passes between. Need to verify clearance before welding a brace between tubes 3 & 5. Thank you.
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comes between 3&5. Bracket on the tube goes to the top bolt of number three
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comes between 3&5. Bracket on the tube goes to the top bolt of number three
Thank you. I was thinking that was the case. Reinforcement bracket needs to be kept short. Any idea of height limit?
I'm in the midst of juggling the car details, contractors & painters. :icon_eyes:
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Neither of my cars has a factory header on the drivers side so I cannot say for sure. The crack is generally on the back side of the joint between the two pipes. I think a gusset would have to be put as low as possible...dow n around the area where the heat shield is.
gnonxy has done a lot of work on his factory headers, you might send him a pm and see if he took any pics of whatever he has done :)
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probably the best advice I can give you is to buy a stock replacement header from TA Performance as they sell their version singly if so desired
http://www.taperformance.com/proddetail.asp?prod=TA%5FV2009D
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Local fabricator was able to weld driver side header & swap O2 bung. I asked him to add an extra O2 bung in a location that I think will provide easier access.
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The new O2 sensor bungs are a slightly taller profile. I'm hoping the O2 sensor will still function correctly. Might take a bit longer to warm up fully.
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looks nice
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Now 2 of the 3 sensor openings (lengthwise) are in the direct flow path. The upper portion of the third window is right at the transition of direct flow path & the bung recess. Couple of the pics are not displaying the width correctly.
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Local fabricator was able to weld driver side header & swap O2 bung. I asked him to add an extra O2 bung in a location that I think will provide easier access.
The welded work looks great, but personally I would add a piece of steel to add more strength between both tubes to prevent future cracks. The photo is what I used and welded inside the header's shield area
Also since the headers has been welded you might need to check and see if the headers flange are warped, and if so check out some machine shop that will use a milling machine or use a belt sander.
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I provided a spare head to use as a jig. I will check with a straight edge.
That reinforcement piece you added looks like a good idea.
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...Also since the headers has been welded you might need to check and see if the headers flange are warped, and if so check out some machine shop that will use a milling machine or use a belt sander.
Driver side flange failed the straight edge check. Passenger side is OK.
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I don't care what ya do to prevent cracking. THEY WILL CRACK AGAIN. Even new headers crack when your racing a car. Nature of the beast. :chin:
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Dan, that is a good point. I don't know many materials that will last too long being heated up to 1700 degs and then allowed to be cooled back down before the cycle is repeated. None that I can afford....
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Dan, that is a good point. I don't know many materials that will last too long being heated up to 1700 degs and then allowed to be cooled back down before the cycle is repeated. None that I can afford....
UNOBTANIUM
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Large cars [diesels] don't seem to have a problem near as much. Do they stay hotter for longer or something?
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I did not know diesel cars used headers, but I don't guess I looked under that many hoods. I assumed they used cast iron manifolds for long life. For some reason, I thought exhaust temps were relatively low to our forced aspiration hot rods.
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Large car is trucker lingo for class 8 trucks,
They get the manifolds hot and cool many times a day.
Even if they are cast, I don't see the issue if they last,
Places like Bully Dog and others can port and polish them and that brings the pyro numbers way down.
Could back pressure be part of the problem?
Could a ''proper'' cool down help?
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With all the aftermarket cast manifolds - turbo and n/a coming out for the LS, it might be viable for someone to do a set of stock replacement pieces in cast iron/steel/stainless. People have made well over 2000hp with the stock LS truck manifolds so flow isn't an issue if designed correctly.
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I don't know anything about heavy trucks nor how the headers compare to the thin wall stainless headers on Buicks so some one more knowledgeable will have to answer. I have seen many a cracked cast iron manifold off cars that had failed but I doubt that has anything to do with modern set ups.
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When I was a fleet mgr for a very large fleet of mix use vehicles we kept a large inventory of heads and exhaust manifolds. They all crack after rough use comparable to racing like Grumpy said. Now talk about our thin wall garbage, 35yr old stainless headers with a million heat cycles.
No way to make them better or add any life to them. Try TA headers or maybe custom Kooks headers if you want something that may hold up a little better.