TR4/4A TR4A exhaust manifold crack story

[PeterK]

Yesterday, I was moving some stuff up to my loft over my shop. At the top of the stairs off to one side, I had a 4A exhaust manifold that had "the crack" between 2&3 and that I was saving to have heliarc'ed someday.

Well the next thing I knew I see the manifold cartwheeling down the stairs, taking out the edge of one stair on the way down to continue to smash into a pretty decent driver's door (r.i.p) then bounce back to the concrete floor and break in half at the crack. Bummer. Still see it in slo-mo.

I inspected the crack to find that the seemingly small crack was 2/3 around and a repair probably wouldn't have helped anyways. Door glass and mechanism is still good though!

Somedays, everything I walk by seems to cling to my feet and fall. Just one of those days I guess.

 

[prb51]

We've all had those moments, sorry about the door.
I'm replacing my radiator (again, going alloy now) and found a 4mm hole in my iron header, just age and rust thru. I'm replacing the unit with a diff one, probably start today. Hopefully it won't grow wings.

 

[MDCanaday]

This is a tearfull story but the manifold can still be saved if its bolted to a head first and brazed with the high temp brass used for exhausts.These 4a units are rare and worth the effort to save(IMHO).
MD(mad dog)

 

[tomshobby]

This is a tearfull story but the manifold can still be saved if its bolted to a head first and brazed with the high temp brass used for exhausts.These 4a units are rare and worth the effort to save(IMHO).
MD(mad dog)

This is possibly the better way to make the repair. If you do here is something to consider.
The joint should have from 1 to 2 thousandths of an inch space between the parts to be brazed. This relatively tight fit will produce an extremely strong joint. As the joint clearance increases to about 10 thousandths of an inch the strength of the joint decreases rapidly. That difference being possibly from up to 130,000 down to less than 50,000 psi tensile strength. Beveling the joint is not good for strength when brazing.

 

[PeterK]

I was told to heat the manifold as hot as I could get it then heli-arc it because it is cast.

Is brazing a better choice?

I doubt I'll fix this one but have another one with a slight (looking) crack.

 

[tomshobby]

There will be some challenges to welding it. Aweman would probably be better qualified to correctly answer this question.

The only reason for my thinking that brazing might be better is because some of the effects that heating and cooling can have when welding. I have welded a lot of cast but it was years ago and I do not even think the same alloy rods I used are even available anymore.

I am also thinking in terms of doing it myself. You would possibly be hiring it done.

 

[AweMan]

Exaust manifolds are one of the most difficult castings to weld.
Two reasons:
1. contaminants, that bieng the rust on the outside {Yes easily removed either by grinding, media blasting, or chemicaly} and the carbon deposits on the inside {Not so easily completely removed}

2. During the course of service {Use} the Hot, Cold scenerio changes the molecular structure of the casting itself.
{usualy what causes the crack in the first place}
The weldability of any particular {Manifold} is determined by the structural integrity of the casting. {How hot this casting has ever been in its lifetime}
High heat on casting changes the molecular structure resulting in turning a ductile casting into the brittle {normally non weldable} white cast iron.

I won`t go into all of the spcifics here, the bottom line is, for the home repair brazing or even silver soldering is by far the best bet in a successful repair. The trick is to thouroughly clean the area to be repaired both inside and out. FILE a groove slightly past the crack on both ends but not completely through the crack.

The reason I don`t recomend grinding this groove is, grinding will smear the carbon content of the casting {Not the carbon caused from use of the engine} over the iron particles resulting in a lesser bond of the brass or silver. alloy.

It is IMPORTANT to preheat the casting to NO MORE than cherry red before attempting to apply the alloy. this preheat is best suited to an oven so the whole casting can be preheated for best results, However if an oven is not available preheat an area around the damage somewhat larger than the damage itself with an Oxy Accetylene torch.

After application of the alloy it is IMPORTANT to, normalise the casting {Bring it down to room temprature} SLOWLY. This is best accopmlished by either post heating the casting in an oven or covering it with casting sand so that the residual heat left from preheating and alloy application can escape as slowly as possible.

The Alloy.
Silver Nickle or Brass Nickle is best suited for exaust manifold casting repairs the advantage to silver nickle is it will take far less heat to apply than the brass alloy does.

Many exaust manifolds are found to be NON repairable for various reasons, Carbon precipitation resulting in molecular change {turning the casting from ductile cast to white cast} caused by excessive heat. And corrosion {rust} relieving the casting of its iron content and leaving behind {NON weldable} iron oxide in its place.

Things to consider.
Prep is everything in welding, clean and prepare your area to be welded.
Pre heat, and post heat are a MUST DO!
Go slow, don`t get in a hurry. Control your heat, don`t let the casing become too hot {anyting over JUST STARTING to turn cherry red is too hot.}
Use the PROPER flux and alloy.
Dress your weld with a sander while it is still hot this helps stress relieve the area. Place your casting in the post heat oven or bury it in casting sand immediately after dressing the weld. DO NOT dig it up until tomorrow *SMILE*

Don`t be dissapointed of your repair doesn`t pan out, there are many reasons casting repairs can be unsucessful.

If you are the "Faint of heart" type individual casting repair is best left to an accomplished welder that has many sucessful casting repairs under thier belt.

With casting repair even accomplished welders win a few and loose a few as well. Especialy the hot/cold scenerio castings.

I hope this answers at least some of the questions concerning cast iron.

Kerry

 

[tomshobby]

Thanks Kerry, I guess I put you on the spot but like when I learned to weld. Always go to the best you know of!

 

[AweMan]

No problem Tom:
As you all know, Or will know if you research the cast welding info on the web.
There are many many types of cast iron welding alloy products available.
Even bieng a professional welder we do not get a chance to use and try out each and every alloy or technique.
There are vast improvements in welding technology each and every day.
Most of my cast iron repair experiance has been heavy equipment castings, Transmission housings, sprague housings, differential housings, engine blocks and the like.
These heavy castings are repaired using the Arc Welding process. ALL of the principls to casting repair apply to ALL casting repair, weather it is a light casting or heavy one. That is to say weld prep, pre and post heat. Stress relieving and so on. The only difference bieng the process used. I.E. brazing or arc welding and the alloy used to accomplish the repair. Out of all the arc welding cast iron repair rods I have tried and used over the years I have to say the one I like best is Allstate 4-60 super {I HAVE NO VESTED INTERST IN THIS COMPANY OR ANY OF THIER PRODUCTS} only to say I have used this particular product and that it preforms as advertised. I like the 3/32 size for the simple fact that even on a huge casting heat is your enemy. And with the smaller size rod you can keep the heat input to a minimum much easier. There may be other products on the market that preform as well or even better, I can only attest to the fact that I have personaly used this product and can recomend it for heavy casting repair. It MAY even work to repair an exaust manifols but I can`t honestly say that I have made such a repair with it.
As I stated before, the HOT/COLD scenerio castings are difficult to sucessfully repair due to the corrosion and precipitation problems these castings encounter.

 

[tomshobby]

Kerry, the last I did a lot of welding was more than 20 years ago as a millwright in a large gray iron foundry. All size of parts, some weighing several tons and subject to much stress.
Steel alloys, aluminum, and cast alloys. A lot of cast manganese alloys. And like you, gear boxes, some big enough to crawl in. Inside, outside and all kinds of weather. 120 feet in the air or in some corner under a machine in the basement. And there is no describing the dirt. A lot of 1/4" rod but also like you liked 3/32" for cast. I liked some of the Welco alloys for cast and I do not think they are around anymore. Like I said it was a long time ago and I forgot more than I remember. Probably would come back if I started welding again though. I did teach some basic welding on the Tech College level.
The big thing I do remember is that I am glad I know how and very glad I don't have to do it anymore.

 

[AweMan]

I actually enjoy Welding, I get great satisfaction of Reparing a broken part and especialy the fabricatin process. The thought of producing a product that will be on this earth and possibly if not probably in use long after I am gone to my grave. Yes welding technology grows by leaps and bounds almost daily. Even bieng an active welder working in and around the trade it is difficuly to keep abrest of all of the advancements. One of my ambitions was to teach welding at some point during my tenure as a journeyman welder. I did get to do just that in Texas. Yearly the D.O.D. would send Army Reservist and National Gurad welders as well as some of the contractors welders to our shop for welding skills and certification. It was my job to teach these guys how to take and pass our certification process. Which consisted of six materials, aluminum, stainless steel, magneesium, inconel, titanium, and 4130 aircraft mild steel. .030 tubing in the G-4 Position. NO turning the tubing on the fixture allowed, No inclusions allowed, excessive penetration NOT allowed. NO contaminants allowed. NO discoloration allowed {very difficult to do with Titanium}.
NO High Frequency tracks allowed {Very difficult to do with Magneesium} Excessive bead width NOT allowed. All welds were xrayed as well as visualed by our lab techs. AND they weren`t in the least shy about failing you for very minor infractions either. Another thing was that if you did not work a specific alloy within a thirty day period your cert for that alloy was null and void, you had to re certify in that alloy. A very stringent cryteria on aircraft engine parts not to mention a paper trail {sarcasticaly} that would almost cover the entire earth. {Who did what to each and every part}.
/bcforum/images/%%GRAEMLIN_URL%%/lol.gif

I also held and maintained a boiler plate/pressure vessel cert. for about 20 years as a Heavy mobile track and wheel vehicle welder. Worked in a fab shop for about ten out of the 20 and on the shop floor reparing and modifying various military vehicles for the other ten. The last ten I did in South Texas as an Engine Aircraft welder. Many many times I also did the work you describe, repairing heavy castings for various vehicles, including cast iron, magneesium, and aluminum castings. T.I.G. welding is fine for Aluminum and Mag. but as for cast iron I found my sucess rate declining dramaticaly when I tried the T.I.G. process. In my opinion the concentration of heat in the T.I.G. process works against you when reparing cast iron. I don`t know, Just my opinion.
Like you I forget most of what I know until i`m faced with a delema of which, sence retirement are becoming dramaticaly less and less each passing day.

 

[PeterK]

So anybody want a broken 2-piece TR4A exhaust manifold before I toss it into my metal recycling bin?

 

[TR3driver]

Kerry, I just want to say Thanks! for all the tips. I'll never be a fast welder, but I hope someday to be a half-fast welder /bcforum/images/%%GRAEMLIN_URL%%/grin.gif

Any tips for fabricating repair sections to be welded to cast iron exhaust manifolds ? I've got a Stag exhaust that is missing one of the 'ears' for the downpipe studs.

 

[AweMan]

Randall:
I have built up many many "Ears" on castings over the years.
Here is what I do.
Thouroughly clean the area to be repaired. Media blast it if possible.
you will need some cast iron {High nickle content} arc welding rod {the smaller the diameter the better.} 3/32 or smaller if you can find it.
Pre heat the area to be repaired to 500 degreese or above but not more than barely turning red.
Using the arc rod build up the area well beyond what the actual finished ear will be. Once you begin welding DO NOT let the area cool below the initial 500 degreese {better to keep it slightly red} Don`t go too fast you will get the part wayyyyyyyy too hot. Once you have excess material to work with built up where the ear should be, sand/grind the shape you desire {with exception of the machined or engine head side} {this side will need to be machined flat as well as the hole relocated} Once you reach the desired shape by sanding/grinding you need to normalise the casting {bring it to room temprature as slowly as humanly possible}. bury it in casting sand, or you could place it in your home oven {preheated to as high as it will go} then hour by hour decrease the temp by 100 degrese. PSSSSSSSSSST don`t let the wife see you or tell her I told you to do it Hahahaha.
Once the casting is cool {room temp} take it to a machine shop for the final cut on the surface that bolts to the head and have the hole relocated {an exaust manifold gasket makes a pretty good template.
Once again exaust manifolds are subject to precipitation and corrosion as described in previous discussions. However, one can not determine if the manifold in question is repairable until one trys it. And besides even if you are not sucessful at least you tried and gained some insight.
Again, also build up ALL surfaces beyond what the final cut will be to ensure enough material can be removed to attain the final desired shape. Watch your heat, {not too hot} Take your time but don`t let the casting get too cold either. Sand/Grind the final shape, post heat, machine shop for finalisation, and you should have a useable product.
Hope this helps.

 

[AweMan]

Peter:
I would not even attempt to repair a manifold broken into two pieces, only as a last resort {not to be had anywhere at any price}.
And then It would take an extensive fixture to hold all of the pieces in the correct orientation, and great patience and preserverance. The main concern on a casting in this condition would be distortion caused by the welding process. It could however be done. The cost however would be excessive i`m sure.
One thing that broken manifold is good for at the present condition is to practice welding cast iron.
If you are not interested in that, toss it out. /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif

 

[TR3driver]

Indeed it does, thanks again !

BTW, I worked out the use of the kitchen oven long ago with my (now deceased) wife. The price of cooking car parts was dinner at her choice of restaurants (good idea anyway since they usually stink) and a visit to the beauty parlor.

 

[AweMan]

Hahahahahaha Randall:
You got off cheap at that!
ME! It cost me a new stove, my wife refused to cook in the old one after I decided it was a good idea to pre heat an aluminum casting in it.

 

[Bugeye58]

"But <u>Dear</u>, aluminum is an essential nutritional element. I was thinking of our health."
Yeah, like <u>that</u> one would fly. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
Jeff

 

[AweMan]

Jeff:
You do know my wife! OR is that just women in general.
I tried explaning that tin foil is aluminum /bcforum/images/%%GRAEMLIN_URL%%/crazy.gif
AND ... I did have the part wraped in foil. /bcforum/images/%%GRAEMLIN_URL%%/rolleyes.gif
I suppose it was the smell of the degreaser that permiated the room that gave me away.
/bcforum/images/%%GRAEMLIN_URL%%/lol.gif

 

[foxtrapper]

Personally, I find exhaust manifolds darn easy to weld up. Get a Lincoln Ferroweld rod or comperable, strike the arc, and join the pieces. Easily done, no preheating or such required. The joint is obviously welded, but causes no problem with functionality.