E30 Zone

How good is JB weld? I read that it's used to re-shape cylinder head ports. Has anyone used it for this purpose? Wondered how permanent it is.

Great, i heard its what held Concorde together during its later years!

I've used it a few times, once to repair a Vauxhall Nova cylinder block that cracked, and on cracked sumps. It works pretty well, though preparation of the surface prior to applying it is important if you want a decent fix, and beware that it is somewhat porous and will allow some oil to seep through.

Nobby_N wrote:Great, i heard its what held Concorde together during its later years!

Didn't work very well in the end then...

I want to reshape the inlet ports on my 325i (eventually) and I was tempted to have some welding applied but am wary of the head getting distorted.

It will crack and fall out eventually, putting it inside an engine is a ticking time bomb

+1. When you consider the heat and fuel cycling that the cylinder head goes through, it's probably a no-no.

I found an American tuner website and the bloke uses it on all his race 'bike engines to modify inlet ports. He has apparently never had an issue with it and he has used it on a lot of engines, some of which have had several seasons of racing and his engines put out more power than some "works" engines. I'm wary about using it but I don't know anyone personally that has used jb weld in ports. I know epoxy has been used in 2 stroke moto-cross engines for years (although I haven't seen it personally), but like the engines mentioned above, they are race engines and get stripped regularly. Has anyone on the zone got experience of using it for port modifications?

The British alternative is Araldite, Half of a Ford Cosworth DFVs cylinder head was made from it.

AardHawk wrote:The British alternative is Araldite, a Ford Cosworth DFVs cylinder head was made from it.

I've used araldite for bonding parts and mending bike cranckcases but had mixed results.

ive used many araldites. they are nothing like JB weld in my experience.

lots of people successfully use JB weld and other similar products on ports but preparation is the key. you need a good surface to bond to so it needs to be very rough and jagged, gouged, grooved etc to increase surface area and allow it to mechanically key into. also it needs to be extremely clean so clean with IPA or similar. when you think it is clean then clean it again.

Surface prep, surface prep, surface prep.

I've used JB weld once. When a stray bolt went through an escorts bell housing, puncturing into the gearbox itself. It held up very well and never leaked but I'm f*cked if I'd put it anywhere near an inlet tract!!! As Dan says, it'll lunch the engine if a lump falls away!

Seen it used to repair the top of a bore in an old Saab 99 many years ago when I was a boy.
Used it a lot for thread repairs and cracked cases on bikes.
Bike dyno jet kits you used to glue a brass shroud in the airway of the carb it still there after 11years and seeing 14000rpm on a regular basis.

You could try a bit in your exhaust port if you don't trust it.

JB Weld's website FAQ says they do not recommend it for use in combustion chambers:

http://www.jbweld.com/faqs/

Just saying what was done.

I'd be surprised if it would be effective for repairing the top of a cylinder bore, unless it was a bit right at the top where the piston rings don't reach to.

I use it in ports all the time. People who say it will eventually fall out obviously either dont know what they are talking about or didnt clean / prep the surface properly. I have heard stories of people having it in wet ports for over 10 years and still going strong..... so it WONT fall out!!!

personally i wont use anything else in a port.

1. scuff the surface really well big cross hatching grooves and dents with the corner of a burr, reverse cone shape works well

2. clean with water based degreaser then detergent, use a tooth brush give it a good scrub

3. rinse REALLY well, use the tooth brush again and lots of fresh HOT water

4. dry it off with a hair dryer not your compressor (might have oil or dirty moisture in the line)

5. its really sticky and it slowly keeps running so think about how you need to dam it and set the level before you start.

6. mix it really well and use