924Board.org

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

Anyone welded the cyl head for any reason?
I'm interested in what material did you use when welding the head aluminium.
There are some air bubbles trapped during casting in some areas that i want to fill (weld)
and i'm interested in what material should i use when welding so i dont get problems like they wont mix or the expand differently and create tensions.
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Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

The machinist welded the head that is now on Shaggy. . .similar situation, the sealing surface was slightly pocked from corrosion.

Can't tell you the material, though.
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WeiBe (1987 924S 2.5t) - 931 S3

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

Could you please give him a call and ask or smth?

AFAIK the old heads contain Mn for stiffness and the new ones Si..for...whatever.
I have to match the materials otherwise problems might appear.
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Kenodog · Joined: 25 Jun 2003 Posts: 2669 Location: Vancouver,B.C.

We use this in aerospace to do exactly what you need to do in both aluminum and that most porous and hard to weld of all materials,magnesium. It works VERY well and since its FAA/JAA approved for use on gas turbines and reciprocating engines im sure it will be good for your 931. Easy to use and very durable.

http://www.tedpella.com/technote_html/891-60%20TN.pdf
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1979 Euro 931, Olive
1981 931, Sabine
1991 Ford Ranger XLT 4x4, Ricky
1996 Ford E-350 ex-FedEx Van
2014 Mazda CX-5 (Kinderwagon)
2019 KTM 790 Adventure
2024 KLX300
2024 KLX140

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

This glue is fantastic...but i want to do repairs in the combustion chamber.
In this pdf i can see shear tests at different temperatures and the higher the temp the lower the shearing force....and it stops at 150°C

Are you sure it can handle that pressure,fatigue and heat ?
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Kenodog · Joined: 25 Jun 2003 Posts: 2669 Location: Vancouver,B.C.

If you are using it on the splitline between the head abd block then it will work fantasticaly,but do NOT use it inside the combustion chamber thats not what its meant for. Basically everything JB Weld says it does ,this stuff actually does.Its a bit expensive but it works amazingly.
_________________
1979 Euro 931, Olive
1981 931, Sabine
1991 Ford Ranger XLT 4x4, Ricky
1996 Ford E-350 ex-FedEx Van
2014 Mazda CX-5 (Kinderwagon)
2019 KTM 790 Adventure
2024 KLX300
2024 KLX140

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

how bad is the damage in the combustion chamber if you intend to use it in the combustion chamber? I've got some little spots there, but nothing that should be welded or something.
The mating surface is the important bit here I think...
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

i've looked at the head...and saw nothing..but the shop handling the reconditioning says that there are some cast air bubbles around the valve seat of cyl1 intake...and that half of the seat is somehow suspended.
they want to take the seat out, machine a +1.5mm bigger hole, weld with new material, machine it back to specs....and then insert a new valve seat.

i've asked for detailed pictures...i havent seen any damage or casting bubbles when i took it off.

i forgot to mention...this is a performance cars shop in Budapest.
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Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

I'd like to see it, because we replace valve seats aaaaallllll day and I've never seen such things. Enlarging the hole 1.5mm is quite a lot too... I think it would do less harm to keep those casting bubbles with a new seat (it won't fall out

) than introducing all the heat from welding. but I can't judge that over the internet

The seat is suspended? That means it has gone deeper in the head, right?

Sometimes valveseats are welded as a way to get them out, if you aren't careful with that, the aluminium gets damaged by the splatters.

I'd like to see pics

I have seen a weird casting fault on a bmw cilinder head which caused clearance between the seat and the aluminium of the head... the seat 'popped out' a small bit. Didn't have a good explanation for that... but it was not just a bubble, it was a real dent.
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

i have asked the shop for pictures....i did not see anything with my naked eye(i'll post some pics of the head fresly taken off the engine when i get home)...but they say that there are gaps around the valve seat and that they want to machine a 1.5mm(per radius..so 3mm in diameter) larger hole then fill it with welded aluminium....but i'm thinking more and more to leave it as it is...it has lived 30 years like this..it can live more.

the guy there says that if the seat comes out and breaks...all hell is loose...true...but i dont think that the seat will ever come out. there is no sign of it even moving...so..maybe it is held quite well...or maybe it was welded in from the factory.

pictures later this week..they are busy now.

EDIT: here are some pics of the thing when i took it off....you cant see shit in these pics...the guy says the damage is around the intake valve of cyl 1...near to the firering.

Uploaded with ImageShack.us

Uploaded with ImageShack.us
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Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

Can't see anything wrong on those pics.

Seats cannot be welded to the head, they rely totally on the tension provided by the head.
Not sure what the correct english word is (anyone can tell me?) but the seat is about 0.10 mm larger in diameter than the aluminium. Crimping tension or something like that?

I have never seen a seat coming loose, but I have one XR600 head where one seat has some dents around it and I've heard stories that sometimes the seats fall down in those heads.
In car heads I've never seen it though.

Why wouldn't they just put in a larger valve seat? that's the easiest option and since you're welding contaminated material, chances are that you'd get air bubbles in the welds themselves and create the same problem. I'm no aluminium welder so I can't say if that happens, but from the aluminium I've seen welded, I know that when I machined it, it was still crap.
_________________
"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW

"Interference fit" or "press fit"
_________________
Toofah King Bad

WeiBe (1987 924S 2.5t) - 931 S3

Martijnus · Joined: 29 Dec 2006 Posts: 2019 Location: Netherlands

morghen · Joined: 21 Jan 2005 Posts: 9102 Location: Romania

So the shop insists that i do not use this head as it is on an engine and it needs to be sorted out.
They've shown me similar or worse damage repaired by them for rally cars and big HP car...600+
They said that they found a Magnesium alloyed Aluminium welding wire and they are going to weld it in the weekend.

I bought another head...just in case...and if all goes well..this new head goes on my other engine...into the 932

(now just needs a set of pistons and an alternator and its complete)
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