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welding exhaust manifolds to cyl head by fiero-iwan
Started on: 07-17-2004 06:26 PM
Replies: 18
Last post by: Captain Midnight on 07-21-2004 01:39 AM
fiero-iwan
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Report this Post07-17-2004 06:26 PM Click Here to See the Profile for fiero-iwanSend a Private Message to fiero-iwanDirect Link to This Post
This might sound like a crazy thing to do but I am Seriously thinking about doing it. As some of you may know I am working on getting my old (1980) 2.8v6 running, I converted it from carb to the fiero mpfi. My goal with this engine is to have it "power" (90hp) my GT as I am saving up to do an engine swap. It could take a while before I can start my swap. But I don't ever plan on taking the heads off this engine and will probably toss it afterwards anyway, so rebuilability is not an issue. All this was some background info...

The studs of the manifold are wel and trully rusted, even some half corroded away. So to replace my leaking gasket I will VERRY LIKELY snap most if not all of them off... Then ofcourse I would try drilling the pieces out. From what I have read here it is a real PITA to do and could easily result in having to buy knew heads. Is it really that risky???

Then I thought, what if I drop the cradle and ask a friend with an electric (simple) welder to run a bead all the way around the exhaust manifolds. That would be a good fix for my situation, not ?

What do you guys think? Am I crazy, or would this work. Is it possible to do (will it actually weld together)? If so will it last, or most likely crack within a couple of miles? Will the heat of the welding fry the valves ? Or anybody out there who has actually done this please tell me the does and donts. Any input is welcome.

Thanks
Iwan

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mattm
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Report this Post07-17-2004 06:31 PM Click Here to See the Profile for mattmSend a Private Message to mattmDirect Link to This Post
I believe the manifolds are stainless, and the heads are cast. I doubt they could be welded together in any manner that would last.
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Electrathon
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Report this Post07-17-2004 06:39 PM Click Here to See the Profile for ElectrathonClick Here to visit Electrathon's HomePageSend a Private Message to ElectrathonDirect Link to This Post
Yup, it is hard enough to weld cast, let alone bonding it to a dissimilar metal. You would have better luck leaving most of the bolts out (which won't last either).
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86GT3.4DOHC
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Report this Post07-17-2004 07:02 PM Click Here to See the Profile for 86GT3.4DOHCSend a Private Message to 86GT3.4DOHCDirect Link to This Post
most macine shops will remove bolts for like 5$ each
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boristheblade
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Report this Post07-17-2004 10:38 PM Click Here to See the Profile for boristhebladeClick Here to visit boristheblade's HomePageSend a Private Message to boristhebladeDirect Link to This Post
Youre welding two totally different things.
Sorry bud, it won't work.
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IcantDo55
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Report this Post07-18-2004 02:59 AM Click Here to See the Profile for IcantDo55Click Here to visit IcantDo55's HomePageSend a Private Message to IcantDo55Direct Link to This Post
JB Weld!

------------------
Mike

85GT 4-Spd 3.4 Stroker, cam, ported intake exhaust and TB. Natural weight reduction in progress(rust).
My other toy:
WWW.IcantDo55.com

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JazzMan
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Report this Post07-18-2004 04:18 AM Click Here to See the Profile for JazzManSend a Private Message to JazzManDirect Link to This Post
Actually, with a special purpose high-nickel rod and proper pre and post heating you could actually accomplish this with a low risk of cracking the cylinder head. However, the specialized welding skills for doing this will likely cost more than the car is worth, and it still won't deal with the manifold cracking issue. When the manifold cracks again you'll end up replacing the head.

JazzMan

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fiero-iwan
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Report this Post07-18-2004 04:39 AM Click Here to See the Profile for fiero-iwanSend a Private Message to fiero-iwanDirect Link to This Post
Ok, so maybe it wasn't such a "hot" idea after all.... I am just so glad this forum is here! Saved me once again from having to find out the hard way. Only one reaction to this welding idea wasn't negative about it... But this one word reply, Icando55 has me wondering: what is JBweld?

Iwan

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TaurusThug
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Report this Post07-18-2004 10:54 AM Click Here to See the Profile for TaurusThugSend a Private Message to TaurusThugDirect Link to This Post
plus wouldnt it just crack back off after a few cycles? al that expansion and contraction would brake the welds after on a few times would it not???

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'86 Fiero GT

www.KylesFiero.tk www.XoticRydz.tk

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maryjane
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Report this Post07-18-2004 12:47 PM Click Here to See the Profile for maryjaneSend a Private Message to maryjaneDirect Link to This Post
JB Weld is a 2 part epoxy type 'fix all' product sold just about everywhere, including Auto Zone and WalMart. It requires very clean surfaces to work well. I don't think it is rated for the temp ranges encountered at the exh manifold-or the expansion/contraction you will have. It may even burn off.
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TaurusThug
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Report this Post07-18-2004 04:11 PM Click Here to See the Profile for TaurusThugSend a Private Message to TaurusThugDirect Link to This Post
jb weld is only rated for 500 F IIRC and people have tried using it to patch up the EGR tube without success so i doubt it would hold a header on.
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86fieroEarl
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Report this Post07-18-2004 05:59 PM Click Here to See the Profile for 86fieroEarlSend a Private Message to 86fieroEarlDirect Link to This Post
I would not reccomend welding heads onto ehaust manifolds..... But awhile back I welded a steal 3bolt flang to cast iron manifolds to convert to 3bolt reducer..... I welded it onto it pretty good and really don't see why welding castiron and steel is a no no, Does the heat make the two serperate or something ? I did it with flux core wire.
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JazzMan
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Report this Post07-18-2004 07:11 PM Click Here to See the Profile for JazzManSend a Private Message to JazzManDirect Link to This Post
With intricate castings like heads welding creates strong stresses in the casting which lead to cracks eventually. Cast iron is actually fairly weak, it is used for blocks and heads because those parts are relatively low stress and because compared to steel and other alloys cast iron is fairly easy to cast and machine. To reduce the stresses you have to preheat the iron, do the weld, then reheat and then slowly cool the casting. Because it is labor and energy intensive and requires a good heating oven it is generally considered impractical for welding low-cost consumer parts like engine block and head castings.

JazzMan

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DanielKJenkins
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Report this Post07-18-2004 07:36 PM Click Here to See the Profile for DanielKJenkinsSend a Private Message to DanielKJenkinsDirect Link to This Post
 
quote
Originally posted by maryjane:

JB Weld is a 2 part epoxy type 'fix all' product sold just about everywhere, including Auto Zone and WalMart. It requires very clean surfaces to work well. I don't think it is rated for the temp ranges encountered at the exh manifold-or the expansion/contraction you will have. It may even burn off.

It will burn off in less than a minute. Way back we attempted to repair a cracked manifold on a 250 I6 chevy, got to watch JB weld melt.

JB weld is amazing stuff... but not on the exhaust side.

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fieroturbo
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Report this Post07-18-2004 07:50 PM Click Here to See the Profile for fieroturboSend a Private Message to fieroturboDirect Link to This Post
 
quote
Originally posted by mattm:

I believe the manifolds are stainless, and the heads are cast. I doubt they could be welded together in any manner that would last.

LOL, you're a poet, and you didn't know it

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Francis T
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Report this Post07-18-2004 08:54 PM Click Here to See the Profile for Francis TClick Here to visit Francis T's HomePageSend a Private Message to Francis TDirect Link to This Post
Do the machine shop thing, if you haven't broken an easy-out off in it yet. If you did, it might be cheeper to just locate a useable old head and switch the bad one out.
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fiero-iwan
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Report this Post07-18-2004 09:04 PM Click Here to See the Profile for fiero-iwanSend a Private Message to fiero-iwanDirect Link to This Post
Thanks for all the advice guys and gals!

I am gonna take Francis T 's route and investigate both options.
Wonder if a machine shop would be willing to work on a complete engine, or if I'll need to take in only the heads with manifolds. If the latter is the case the second option would seem more apealing...

iwan

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Francis T
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Report this Post07-20-2004 09:57 PM Click Here to See the Profile for Francis TClick Here to visit Francis T's HomePageSend a Private Message to Francis TDirect Link to This Post
You will have to bring them the head so they can set it up on a milling machine.
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Captain Midnight
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Report this Post07-21-2004 01:39 AM Click Here to See the Profile for Captain MidnightSend a Private Message to Captain MidnightDirect Link to This Post
I would recomend to fix the original bolts, but I'll also tell you how to weld it. Conventional welding will not work because of micro-cracking. Micro-cracking is caused by a phenomenon of cast iron, that it expands as it is it heated untill it reaches a certain temperature, then it will stop expanding and actually shrink. As the temperature continuse to rise, it will start expanding again. You can see that if the whole part is not heated obove that transition temperature, micro-cracks will from at that juncture. So, succesfull welding ether has to keep the whole part above the transition temperature, or the whole part below the transition temperature during the complete welding prosess. A silicon brazing rod can be used, as it will also join to the stainless steel. Carefull to stay under the transition temperatre, by not letting too much heat get into the part.

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[This message has been edited by Captain Midnight (edited 07-21-2004).]

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