Cosmo Kramer

Under the gasket sealing area. I would probably trust it under the sealing area if it was applied then machined perfectly flat with the heads. Under the gasket in the non sealing area it will seal the crater and prevent further pitting.

JB gets a bad rap as a "dar ya go I fixed it" solution but it is pretty good stuff. When I was 17 I bought a Dodge pickup real cheap, the PO left straight water in the block over the winter and it froze and split the block. I cleaned the split and patched it with JB and it never leaked a drop. Some guys that restore old tractors have used it to repair split or pitted cylinders, it actually stands up to piston rings scraping against it.

James Bailey

Yes Mark invariably it quickly becomes a monologue .......it is as if the shear number of words adds weight to the argument and the last words carry the most significance. Perhaps your assumption that I even seek a dialog or communication is flawed.

BC

I understand JB weld has its merits. It does not hold up well... Chemically, in my (somewhat limited, but still real-world) experience.

mark kibort

it does work on radiator punctures in paper-mache form.

GregBBRD

Seems like this should be true.

Sadly, it is not.

I get heads cut front to back crooked, side to side crooked, and every combination of the two.

Like anything which people do for others, if they don't give a crap, it turns out like crap.

GregBBRD

We can only hope!

AO

Way back, I had a HG failure on my GT and it was because a pit formed right at the fire ring - allowing coolant to enter the combustion chamber. Yuk!

I sent my heads to the mad scientist, Todd T in Green Bay who also happens to also be a master fabricator by day. He carefully heated my heads, welded them then peened the repair area to make sure the grain was uniform (his words), then decked the heads.

I recently had the heads off and they still look great!

I know several people who recommended going the JB Weld route. It might have worked, but I chickened out. If you need to do valve guides anyway, it "might" be cheaper to just get a set of heads that are in good shape.

If I need to fix my lawnmower, then I would have tried the JB weld in a heartbeat.

69gaugeman

I had pitting on the heads of my GT. It was not under the fire ring, so I cleaned it and left it alone. There are picture on TOS showing it. That was two years ago and some 30,000 km. I use G12 VW coolant, because I have seen a LOT of audi heads that have NEVER had any corrosion on them. And these cars get coolant changes very infrequently.

At some point I am pulling the engine and am going to do a proper rebuild fixing the cylinders. If the damage has not changed from when I did it two years ago, I'm not going to bother fixing it. More work and money for something that won't affect performance or reliability. That of course still remains to be seen.

69gaugeman

JB weld is not affected by coolant, that is for sure. Have fixed several radiators (Including 928 radiator) and NEVER had a leak from the repair. People get a little too religious about some things. Epoxy technology has come a LONG way. Hell, Audi and Ford glue their aluminum bodies together with epoxy.

karl ruiter

Before you put JB weld on your cooling system or engine please do this experiment: Mix up a batch of JB weld and pour out two test plugs. Let it cure then place one plug in hot water. Just out of the office water dispenser is fine. Let it soak in the hot water for a little while, then remove it and play with the two samples to compare the physical properties.

I have a product that uses an adhesive to bond a bulkhead to a manifold. Initially we used JB weld, but went away from it because we did not get consistent properties. When units come back from the field we update them including removing the JB weld and replacing with the new adhesive. Soaking in hot water is always enough to get the JB weld off of the parts.

But do the experiment yourself. Probably should do this for anything you were going to put on your cooling system or engine actually. Think Feinman and O rings.

Imo000

I've JB welded a leaking all aluminium 928 radiator (many others here have too) years ago and it is still holding. How do you explain that?/

wpgshark

With most adhesives surface preparation is key. This is only mechanical bonding. Very flat surfaces, contaminated surfaces, low JB weld surface area to JB material volume, any kind of messing with it before it is cured, and, using the wrong JB weld, will all most always result in failure. Proper application and it is pretty neat stuff.

Historically, many people who have tried to use it as a short cut, short cut on preparation as well. Thus the horror stories on failures. I would expect that a pit in a head would be an ideal location for a high temp, possibly aluminiumized, JB weld as long as the pit was properly prepared there should be a very good mechanical adhesion surface. I've used it on several external castings on Volvos, and for lots of things on my old bass boat motor, and when properly applied it is amazing stuff, short cuts always lead to failure. Many of my uses see all manner of fluids and I can't say I've ever seen a failure based on fluid exposure.

I would be reluctant to use it under the fire ring, but for the corrosion pits, it would seem to me that it would be at least as acceptable as a filling in a tooth, which probably sees a far more harsh environment.

Just my 2 cents

Todd T

I could do the grinding and the welding needed to fix these heads, then have them resurfaced at Baril Machine in Green Bay.

You have to be very careful when welding, too much heat can damage the heads.

While the weld is still hot, I take a flat punch and carefully peen the weld with the punch and hammer.

JB Weld could work but risky if any of the material comes apart inside the motor. Not worth the risk in my opinion. To do it right you need to grind down the area to reach virgin metal, fill with the JB Weld then still machine the head.

Do it once, do it right. Have them welded.

Ad0911

As explained before, the heads of my car are reconditioned already, (guides, valveseats cut 3 angles, surfaced) but there are pits outside the fire ring and outside the block area (so basically the hollow coolant area).Although covered by headgasket, should I do it all over again? That would mean:
- Take out the valves
- weld the pitted area's
- machine the heads again
- put in the valves again
Seems like throwing away a lot of money from the previous headjob. Mind: these heads are not on the engine yet. They are just waiting to be joined to the engine.

wpgshark

There is a range of repair options.
The most expensive and the best is new heads.
The least expensive and possibly least desirable is to do nothing.
Everything between these 2 extremes is more or less good at more or less cost with more or less risk associated with it.

This is where value comes in.

Based on your description my personal value meter would lead to the lower cost options of doing nothing, and maintaining good antifreeze, to doing the JB weld, as based on what I've read it is likely to work, and if it fails I don't see small particles of JB weld in the antifreeze having a significant chance of causing any damage, is the chance 0? no. Is it significant, I don't think so.

The pits are from poor antifreeze or poor antifreeze change out cycles, I have volvos going on 20 years with 350K km that I've had the heads off on and no issues, I do change antifreeze every 2 years using volvo coolant. Arguably if going forward your car gets a good antifreeze procedure, the existing pits are unlikely to grow and they are unlikely to be a problem. Therefore there is little, not 0, risk of not doing anything.

Time and $ are limited, things to do on the car, required and desired, seem to be unlimited, the decision you make is based on where you want to put your resources. I have a number of areas that I would rather put mine.

It is a tough decision though as everyone wants to do the best they can.