Welding manifold

Post by **Stig** » Wed Apr 16, 2008 10:52 am

Anyone know if it's possible to weld a cast exhaust manifold? A guy down the road has a kit car based on an Austin 1300 and says the manifold's cracked. I was wondering if it's worth offering to weld it for him and if my little 90A gasless MIG would be up to it.

Post by **alex_holden** » Wed Apr 16, 2008 11:30 am

There's an article here about welding cast iron with a MIG set: http://www.mig-welding.co.uk/cast-iron.htm

Post by **bmcecosse** » Wed Apr 16, 2008 1:44 pm

If it's the cast one - then don't waste time - they are ' 10 a penny' and the welding won't last 5 minutes with MIG. Only hope is heating it red hot - and then stick welding with special 'cast' rods - really not worth it for such a common part. So saying - i've never heard of them cracking anyway - what's happened to it ?

Post by **minor_hickup** » Wed Apr 16, 2008 3:09 pm

I've heard of them being migged up by leaving a reasonable gap and heating them in the oven to about 220oC before, welding in short runs. Apparently mig brazing is a good way of doing this! If it is the cast manifold then as BMCEcosse says they're easy enough to find. But sometimes it's nice to give these things a go. I spent yesterday welding the top plate on an old lawn mower!

Post by **Stig** » Wed Apr 16, 2008 4:10 pm

I don't really know what happened to it, the guy just popped round Monday night to ask my advice (I'd offered to help him do a service as he's not that mechanically minded) so I've not actually seen it. I suggested he should try Ebay for a replacement but then wondered if it might be weldable, sounds like Ebay would be the easiest option now then.

Thanks guys.

Post by **Packedup** » Wed Apr 16, 2008 4:52 pm

A Mini LCB should fit, and can be had for 30 - 40 quid for a cheapo. I'd imagine a Mini cast manifold would fit (and is probably the same thing!) and can be had for free on a good day.

It might be worth having a play with the old one to weld it up for fun, but for speed and effectiveness slapping a replacement on would seem the best idea.

Post by **Spag** » Wed Apr 16, 2008 8:12 pm

I have MIGged a few cast zorst manifolds with no ill effects.

Toast it first with a blowlamp if your worried, or just crank up the power and let rip to ensure good penetration and heat soak!!!

Welded some steel tube to a the cast Toyota manifold for the 4AGE in one of the Minis to make a Y piece. Don't tell, but I did this straight from cold and has lasted for 18 months which is a bit of a surprise for a bodged butt weld to cast !

Post by **rayofleamington** » Wed Apr 16, 2008 9:39 pm

brazing can work ok on cast manifolds... (it worked ok in Africa)

Post by **minor_hickup** » Thu Apr 17, 2008 2:06 pm

I believe on the PPC rolls royce they had to chop the exhaust manifold into three to weld in a bit of bentlly turbo manifold. They couldn't get the mig to take so brazed it. I'm sure a turbo manifold will see more heat than a moggy ever will unless its driven into the sun!