Ummm...Araldite in a cylinder port?

[CompoSimmonite]

A series intake and exhaust ports on same side, and inlet port runner will get a lot hotter than crossflow head. I would say if you decide to use JB weld failure is pretty likely, as it doesnt seem to have much metallic content, and not going to stand up to heat as well as Devcon. If that was my head I would either grind away the step, or repair properly with welding. Bearing in mind the bodge job thats been done on it, if you not run motor then crack testing would be well worth doing.

I agree. After all it's not as if alloy OHV heads for the sidevalve are easy or cheap to find so why not remove it and get the job done properly "once and for all" by welding in new material.

 

[cardiffrob]

http://www.ebay.co.uk/itm/DEVCON-AL...339408?hash=item1a0ce2cb10:g:JbYAAOSw5IJWgU-E

Is this the stuff??

 

[cardiffrob]

Strangely, Devcon Titanium and Ali putty both show a max temp well below that of JB Weld. (177c against 250c)

 

[cardiffrob]

Ah, I thought I'd seen that name somewhere. Found these in the garage. Not exactly what I need but I'm sure it will come in handy somewhere, someday.

 

[chevy2]

A mate of mine has often used jb weld on the intake runners of ali heads after breaking through due to some heavy porting to increase flow rates on race engines.

 

[CompoSimmonite]

If the inlet of the head think of the absolute worse that can happen - JB Weld or whatever comes loose and gets sucked into the cylinder. Do you want to risk that ?

 

[cardiffrob]

Hard for it to get loose. There will be an ali tube stuck between the JB and the air and held at the ends by butting up against the step in the head and the manifold face. The JB won't actually be exposed to air in any way. So, how hot does it get???

Mmmmmm...BACON!

 

[Chris Stevens]

If you have to use epoxy rather than proper repair, why not get the best possible material for the job? JB weld doesnt appear to have much metallic content, and as such is far less suitable for this type of job than Devcon.#

Always amazes me when people have major problems due in many cases to the want to save maybe £10-20!

 

[cardiffrob]

Devcon shows their putty as being LESS tolerant to temperature than JB, this from their own website. EGT might be perhaps 600c, intake 10c and waterjacket 120c so the material would have to lie somewhere in that lot. I tried Techsil and Vitcas just now. Vitcas suggested their silicone-based 1300c sealant to hold the ali sleeve in place. That stuff can't cause any damage if it gets through and certainly won't melt!

On reflection I've decided to say sod it and weld a stub of steel onto the inner face of the manifold, just as it has been on the engine during the last 20 seasons of racing in NZ. If it didn't cause trouble during racing then I shouldn't have trouble going to Tesco.

Many thanks to all contributors.

 

[graffian]

There's lot of different types of Araldite, all Ciba epoxies were called Araldite I used something like 5252 for making mudguards.
Devcon seemed to be the epoxy people used for manifolds, I always wondered if it use was more to do with being able to buy large packs almost anywhere than anything else?
I knew people who had manifolds sculpted with Devcon, but when they altered ports they usaly welded them, some heads used to get 40 hours welding! Round port hemi heads.

If you have to use epoxy rather than proper repair, why not get the best possible material for the job? JB weld doesnt appear to have much metallic content, and as such is far less suitable for this type of job than Devcon.#

Always amazes me when people have major problems due in many cases to the want to save maybe £10-20!

I thought Devcon was a pretty standard epoxy, It doesn't withstand powder coating. I use jb weld to fill stuff I am going to powder coat.
I think it's recomended it's not used above 600F. I am guessing the stuff I have is JB weld classic or something like that,
I bought it in JC penny's in 1989, I don't believe in plastic metals so the stuff wasn't opened till I started powder coating.

 

[Chris Stevens]

Devcon shows their putty as being LESS tolerant to temperature than JB, this from their own website. EGT might be perhaps 600c, intake 10c and waterjacket 120c so the material would have to lie somewhere in that lot. I tried Techsil and Vitcas just now. Vitcas suggested their silicone-based 1300c sealant to hold the ali sleeve in place. That stuff can't cause any damage if it gets through and certainly won't melt!

On reflection I've decided to say sod it and weld a stub of steel onto the inner face of the manifold, just as it has been on the engine during the last 20 seasons of racing in NZ. If it didn't cause trouble during racing then I shouldn't have trouble going to Tesco.

Many thanks to all contributors.

Devcon is the best epoxy to use for altering ports, due to high metallic content. Its not got much to do with max temperature. If JB weld were superior then I am sure it would be more widely used by anyone modifying ports professionally. On A series, seems a much better idea to use steel stubs as you suggest, as configuration of head may well lead to problems with using epoxy.

 

[Farside]

I went away from home for a couple of weeks, and when I came back it had all leaked out a crack in the bottom.

I had a foreign holiday like that, too.

 

[mangocrazy]

A guy called Motoman in the USA swears by JB Weld for reducing port sizes. Here's one such page:

http://mototuneusa.com/power_news_--_homework.htm

 

[optima21]

A guy called Motoman in the USA swears by JB Weld for reducing port sizes. Here's one such page:

http://mototuneusa.com/power_news_--_homework.htm

yeah thats the site that I saw years ago that made me reduce the ports on my head using jb weld

 

[Chris Stevens]

yeah thats the site that I saw years ago that made me reduce the ports on my head using jb weld

How much increase did you get on the dyno?

 

[optima21]

How much increase did you get on the dyno?

it went up from 88 bhp to 98bhp at the fly with just induction mods (the standard engine has 75bhp) , there will be more power if I ever get the engine remapped.

the standard port is on the top in the pictures and an early version of my modified ports are at the bottom .

rather than spending money on silicone rubber for taking castings, I used alginate with a bit more water. alginate is the stuff dentists use for. it does shrink and goes hard as it drys but it work well for showing the shape of the ports

 

[mangocrazy]

Nice one. I've got an old VFR750 that I have a spare engine for that I'm thinking of having a play with. I like the theory behind what Motoman says, very interested to hear the results you got from it. A boost of 10hp is certainly not to be sneezed at. From the castings it's obvious how much the flow has improved.