valve guides set in JB weld

[Txpowdercoater]

i got a bunch of flatheads given to me, one (1972 B&S 5hp) looks like a new build stalled, (new .020 piston, alum rod etc) so upon closer inspection, I find the new valve guides are set in JB Weld. I dont know how big the hole is and how much JB is there, but at top of valve guide is JB all the way around its diameter.
I know JB is awesome stuff, but is this really gonna hold up on the exhaust side or is it junk or repairable. thanks

 

[funky ole]

jb won't hold up to exhaust heat.it will soften and melt out,bringing the guide with it.

there are different sizes of guides that can be used. the briggs guide is smaller in diameter than say a ez bore guide,which can be had .312, .314 and .316 outside diameters.
it just depends what they bored the guide out with.

 

[Txpowdercoater]

jb won't hold up to exhaust heat.it will soften and melt out,bringing the guide with it.

there are different sizes of guides that can be used. the briggs guide is smaller in diameter than say a ez bore guide,which can be had .312, .314 and .316 outside diameters.
it just depends what they bored the guide out with.

I figured it would last about 5 minutes at best , ok, so I guess I get a torch and heat em up to see what jb drips out and maybe loosens the guide? I need to get the exhaust side out and install a new guide, the intake will be fine, I use JB for filling in dents etc at the shop and I bake it at 400+ and its ok there no problems, but exhaust temps are greater than that one would think
or better question, how do you remove guides?

 

[glenn baine]

the old man that used to build my race car engines used it all the time to match port my the heads never had a problem :shrug:

 

[buckeye]

Is that Glenn Baine? Where ya been man?
Now back to subject.

 

[Txpowdercoater]

the old man that used to build my race car engines used it all the time to match port my the heads never had a problem :shrug:

I can see port matching in the intake runners to heads etc, but in the exhaust side matching? I would think it would be no good at those temps but in the stock 5hp, mebbe it will work, I've decided to bolt it down on the bench and put it under a load and see how it likes it, worst case the guide shifts and valve sticks and then ya know, oh well.

 

[125ccCrazy]

to remove the guides tap a 7mm thread in the guide then use a long 7mm bolt, a 7mm nut and a big washer to cover the valve seat.....screw the bolt in the guide, tighten the nut down against the washer and it pulls the guide out.... I've replaced several guides in briggs 5hp blocks...you will need a hone so you can hone the guide to the proper clearance..

no idea why someone would jb weld the guides in?, they are a press fit...I'd be concerned its not straight thus putting the valve on a bind..

 

[Txpowdercoater]

yeah, weirdest thing I've seen inside one. they are in straight though, at least the P.O. got that correct

to remove the guides tap a 7mm thread in the guide then use a long 7mm bolt, a 7mm nut and a big washer to cover the valve seat.....screw the bolt in the guide, tighten the nut down against the washer and it pulls the guide out.... I've replaced several guides in briggs 5hp blocks...you will need a hone so you can hone the guide to the proper clearance..

no idea why someone would jb weld the guides in?, they are a press fit...I'd be concerned its not straight thus putting the valve on a bind..

 

[roccosbike]

View image in gallery​

This 8HP Tecumseh,has an intake I fabricated to accept one of those oval bore mikuni carbs.I ported it too and used JB weld to mach port the intake to the block

View image in gallery​

You can see the JB weld on the left side of the left port (intake)It runs really good.

 

[Txpowdercoater]

nice clean work, I dont doubt at all that jb is good on the intake side, I'm gonna fire this one up and guess we will have some real world data on the exhaust side application pretty sure its gonna be "no bueno"

View image in gallery​

This 8HP Tecumseh,has an intake I fabricated to accept one of those oval bore mikuni carbs.I ported it too and used JB weld to mach port the intake to the block

View image in gallery​

You can see the JB weld on the left side of the left port (intake)It runs really good.

 

[funky ole]

jb weld,the regular stuff melts at 700 degrees. says it on the package.

try this. use jb on a part, let it dry and then keep it wet with gas. find out what it does.it loosens up and may come out where you put it.

if it were me,i would ream that old guide out and try to take as much jb with it. use a ez bore kit with a .312 ream.if you take it out with that,your good to go. if you were to pull the old guide out with a 7mm tap and bolt,you may find that you'll need to ream anyway,but the guide won't be there to keep the ream aligned in the bore.now you have more issues than most can deal with.