Head port/mod and JB Weld

I have a rusted up and tired log head, and a buddy with a machine shop, so I thought I'd mess about with it and see what I could do for my 200 while I look for a 250 that doesn't cost $500(!) bucks.

I thought that first, I'd radius the inside corners of the log by popping the freeze plugs at both ends and maybe duplicating them in the side of the log opposite 2/5, for access. I'm a little worried I may radius too much, and thought I could maybe shore up the intake walls there with JB Weld? Think that would hold up?

I also thought that, rather than mill off the current 1V riser and fill in the lows with JB Weld (and using spacers to clear the valve cover), I could just build up the area around the riser (with JB) and hog out the extra material at ~45 degree angle from the carb. Think JB could handle that, or would it be prone to fracturing and leaking? I know just because you can use JB as a filler doesn't mean you can necessarily mean you can create a full mounting mass to bolt a carb to.

Maybe machining a large aluminum carb adapter would be better...with a 6 or 7 inch flat spot hogged out on top of the log?

Don't know at what temp JB breaks down but it does. Know of one attempt to use JB to raise intake port floor came loose first run.
There are other hi-temp epoxy paste that would be better.

I have yet to see any type of epoxy that doesn't have some portion of it come out or loose when used in either an intake or exhaust area.

well, that's that. I'll work on an adapter and see what I come up with.

8) i have seen jb weld used in fairly high temp situations without issue. the key is surface preparation, it must be meticulous. here is some information on jb weld;

http://www.jbweld.net/products/jbweld.php

Check these guys out:

http://www.cotronics.com/vo/cotr/

It worked great for a few years on my exhaust port divider. However, I think the reason it failed was that it couldn't hold up well to the vibrations of the engine, since on the Oz 250 head, there was no ridges to help hold the port divider in place where the US head does have ridges. The US head held with contronics for 2 years until I removed the head and it was still in there tight. The Oz250 head failed in 1 year.

So what I'm exploring now is shaving the top of the log (3 or 4 inches on each side of the 1V) and brazing a riser to it. I mean, I am just messing around, but I don't want to make something too fragile. I just thought JB might be an easy/lazy alt to brazing with comperable longevity.

In my experience, at least on ships, JB Weld doesn't hold up well to machining. I was on a ship once where we used it to repair a start air valve so we could start up one of our main diesel engines (huge suckers). It would hold for one start. After every start, we had to re JB weld it (or DC Duct Tape as we called it).

Don't get me wrong, I love JB Weld. I recently used it along with some bread clips to reshim my volvo's AC compressor from the compressor exterior. $1 repair to fix a $350 part. Can't beat it.

I agree that JB weld can be used, but it might be best to look for other epoxy's.

Elmo, ClassicInlines head porter, mentioned the putty he uses was used in WWII on ships, it can even dry in water the stuff was so effective, that's why he uses it. I don't know what the stuff is called, but I have had my log head built up with this to be hogged out for the 2bbl.
Warning though, because it needs something to hang on to Elmo placed screws/bolts around the area the putty hangs on to for extra grip and a safety that the stuff won't come off. Elmo has never had a head come back to him because of leaks or heard of one leaking in the last +10 years he's been using this stuff.

I wish I remembered what it was called though.

I have noticed a big difference in the JB Weld I used years ago repairing damaged motorcycle side covers and what I bought recently. Old stuff I used to allow to setup overnite, and the new stuff sets up really fast. New formula? Got no idea. Even cures blackish in color rather than the gray I was accustomed to.

AND what bout the heat in that area (I know it's minor, but a factor), not sure bout JB & heat...
Any 1 know...
:

' wondering about using for log mod a special bonding adhesive from 3M , SEM .. ,. . What's stuff available rated for temp wise?. possible alternative to brazing or Epoxy ? . Used it for body panels - it's as dense as weld..

Any difference in thrmal expansion/contraction rates than the cast log will possibly seperate . Note that Offy uses rubber O-Rings for mating 3X1 Tri-Power to bored outboard ports and OEM gaskets on center.

alternative to brazing or Epox
powerband-
there's an epoxy that "takes the heat"?
TIA,

That cotronics stuff is rated to like 2500* and we used to use it on gas turbine exhausts and it worked great.

cotronics
3M's SEM.
I gotta find this stuff. Is it available to general public like me? How supplied, costs, MSDS?
All ears (eyes in this case)
:

The cotronics stuff is available to general public.

http://www.cotronics.com/vo/cotr/ea_machinable.htm

That stuff says its machinable and stable to 500*F.

Just call them up. I think they made me order 3 tubes, which sucks since it has a shelf life (or what i ordered did) of like 6 months. Think it cost me like $20.

chad":1d3g7xqm said:

cotronics
3M's SEM.
I gotta find this stuff. Is it available to general public like me? How supplied, costs, MSDS?
All ears (eyes in this case)
:

Click to expand...

I'm an amateur but the local auto body supply stores and mail order offer different brand "systems" which is just their available dual tube gun and selection of body panel, body fascia, epoxies and fiberglass type formulas. 3M and SEM are brand names offering gun and tube assortments. I went with local supply's brand for counter service.

'fer instance:

http://www.levineautoparts.com/sem1.html

HAve Fun

As a builder I have used West Systems for 30 yrs but it aint this exotic (2 me) stuff. Thanks all!! (gettin too ol' 2 keep up w/all this).
Will down load for later .
Again, Thanks All, over n out...

I know jb doesnt hold up on exaust at all. As a cheap ass I am I tryed to fix the steel exaust donut on my old international truck.and about 20 minutes of driving and it was broken down and turned to ash.

Yep. 'J-B' DOESN'T like heat :fume: . A few folk's I know have tried some of the same type of repairs on Headers,Intakes,ect to no avail. I have some 'stuff' in the Garage(can't remember the name I'll reply to this tommorow...)that's somewhat similiar to J-B,it claims to be heat reasistant. I got it from work,from the Guy's in the Steamfitters dept. ~OO6.