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Up Topic Welding Industry / General Welding Discussion / cast iron (again)
- - By Motohead1 (*) Date 08-26-2003 21:50
I did a search and found many post on the subject but i think my answer got lost in all the posts. :) What i would like to know is... I have a cast iron manifold from a 1g turbo Talon and it was taped for an EGT gauge at some point well i need to fill the hole in it now witch is about 5/16 of an inch the wall of the cast iron is a little bigger than 1/16 of an inch its such a small hole do i have to fill it with nickle? or what can i use to plug the hole and weld it in place? I know nothing about materials but i had the crazy idea of using a cast plumbers plug to go in the hole and then weld in place? But I am not sure of the plumbers plug is real cast iron? and if it would take the 1500 degrees that the maniflod sees on a daily bases. any sugestions? thanks. :)

Jay
87 MC SS 6 speed with a cup holder!
90 AWD Talon 5 spd
Parent - - By dee (***) Date 08-26-2003 22:33
Moto,
The hole was originally plugged with the thermocouple, which probably was set into some kind of stainless steel threaded fitting. Datcon makes a decent quality gauge at a good value, and also supplies sending units for them seperately, which may make some sense to you- they're an excellent value, although perhaps more industrial than AutoMeter... but the plumbing fitting would be the other acceptable extreme (perhaps dope the threads with anti-sieze first) Note that plumbing threads are tapered, unlike machine threads on a common bolt which has the same diameter from the tip to the head, so don't overtighten and crack anything. To play it safe dont install a cold part into a hot manifold (in case your hands are made of asbestos and the thought ever crossed your mind) as sizes will change as the temperature normalizes, and something could break.

I don't understand the need for welding at all unless you are substituting a machine thread or otherwise mismatch or damage the bung fixture threads

I'd opt to use a new gauge or at least the sender alone, but your post didn't solicit my opinion on automotive equipment... hope I helped.

regards
d
Parent - - By Motohead1 (*) Date 08-26-2003 22:42
I have an autometer EGT with is 2 times longer than the greddy EGT that was in there. it cannot go in the same hole unfortunetly so i need to plug the old one. I have temporaoly pluged it with a pipe fitting but it last about 1 week of heat cycling before it starts to blow out. as for now i keep spares with me in the glove box. :)

Jay
87 MC SS 6 speed with a cup holder!
90 AWD Talon 5spd
Parent - - By dee (***) Date 08-26-2003 23:08
Moto,
No kiddin!?!

Im afraid I dont really know the answer for you.

These meters are thermocouples I presume? Is the greddy couple not the same electrically as AutoMeter? I'm using thermocouples at work and substitute them all the time, on the other hand, the manufacturers do try to accomondate that convenience.

The answer you need should be there, but the link will be a handy asset even if it isn't... http://www.adtdl.army.mil/cgi-bin/atdl.dll/tc/9-237/toc.htm

Jeeez, I wouldnt really look forward to that job if the manifold has to come outta there to get to. There may be someone at an automotive site who could make a suggestion, and the folks at autometer should be willing to give the technical advice as to substitution and interchange so you might be able to use the old style sensor... if you want to. (why I suggested Datcon- the factory's in Lancaster PA and they give good product support)

A thermocouple crates a small current flow in proportion to the difference of temp between the coupled and open ends of two dissimilar wires; it's a function of the couple itself... the "sensor" is often merely a brazed joint... at work we use a chrome-aluminum thermocouple wire of off-the-shelf industry standard. A millivolt meter would work to read the temperature, but the proper gauge employs a compensator to allow for variation in ambient temp. There's a fair margin of error inherent in most designs- regardless of how proud the manufacturer is of their instrument, it's too complex for "real" precision. Because I customize these thermocouples all the time for special applications I'm inclined to suggest a "madman's approach" to solving this problem, and I'm having a hard time resisting the urge.

Too bad we can't get exhaust studs to back out that easily when we want 'em to.

good luck

d
Parent - - By Motohead1 (*) Date 08-26-2003 23:39
See the stainless fitting that was in there is gone its now just a bare hole in the manifold. and no the thermocouples are probly eclectricly the same but theends are phisicly difrent. But no matter since i dont have the old stainless bung for the old hole. If i did i would just blob the hole up with some stainless. hmm your onto somthing there. maby i can just find me anouther stainless fitting and screw it in. I doubt i will find one tho. :( I would like to fix this tomorrow cause if i dont i will be riding around for a week 100 miles from home with a pocket full of spare pipe plugs and wrench. :) not fun chaging one in the dark on the side of the road. At least i keep kevlar gloves with me. :)
Parent - By dee (***) Date 08-27-2003 00:23
Kevlar, huh? In my day real men used asbestos, smoked PallMall, and Stewart-Warner made the gauges.

I'm thinking thermal cycling is indeed causing the plugs to loosten as you described. You might drill the head of the next plug and insert a length of wire clear through. Tie the wire around the manifold to secure the plug from turning out until you line up the stuff you need; it should serve as an effective locking device.

"in hoc signo vinces"

cough-cough
d
Up Topic Welding Industry / General Welding Discussion / cast iron (again)

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