Technical SBC Rust Pit in Cylinder Wall, run it? fill with epoxy?

Hello All,

I have built a lot or motors, from junkyard dogs to higher end stuff with tons of machining. I picked up an old race motor, high compression pistons, solid lifter cam etc. I disassembled, cleaned, honed and plan to just do rings and bearings.

I am throwing together a 283 Small Block Chevy which is 30 over.

Most of it honed out well but one cylinder has a couple rust pits an inch or two from the top.

I do have other motors but am curious to try this and it will be in an open chassis, easy access to remove it should there be a major issue - will put my 27 T Coupe on a Double A frame.

I have read a lot of posts of people who have run motors like this with almost no issues, have good compression, no oil consumption to speak of.

I have also seen articles and posts where people have used epoxy to fill and smooth it out - seems nuts to me.

Anyone here have experience with this?

Running a motor which has some cylinder wall
pitting.

Using an epoxy to smooth out a rust pit in the cyljnder wall.

I appreciate everyone's insight.

Regards, Tim

 

Run it with the pitting, not the epoxy. IMO.

Pat

 

Won’t work. Get a Lisle power hone and hone it out .010” and find a .040” piston and ring or forget it since it’s just a pit. A scratch line or groove would be different.

 

A few pictures of the pitting would help us help you decide. We can't see how many pits there are, or how big they are, or where in the bore they are.

This one, I put a lot of miles on, no problem.

 

Pics were tough in the barn, I am not where it is today, you can feel it with your finger, would say roughly size of a quarter. It is in one area of cylinder, not a ring or all the way around the cylinder.

 

Being that big, you're probably going to want to sleeve it if you want it to run it's best and not burn oil and last a long time.

 

Are you sure it is rust pitting and not porosity from when the block was originally cast and then uncovered when block was bored .030 over. Either way with it being the size of a quarter I also think it should be sleeved. However if it is porosity, when boring to sleeve you might uncover some bigger problems.

 

Check out Cold War Motors on YouTube. They are working on a mint '37 Chev with a pitted cylinder that they fixed with JB Weld. Still waiting to see the result.

 

Sleeve one hole!

 

Giving out opinions, I'm going to say run it as it. I'd even go so far as to say if you want to dab some JB Weld in the hole, the good high temp stuff, no harm no foul. I'll tell you why, because at the end of the day, it comes down to efficency of the engine. Little will be lost if you leave it or if you fill it. But that's my opinion.

 

I've seen people do the JB weld fix too. Technically it should work, since the ring can't dig into it because it's supported by the rest of the radius of the cylinder wall, so if you can get the epoxy in there tight so it won't chip or fall out and then hone it, all you're doing is filling the void where oil would come up, it's totally non-structural.

Is it the best idea? No, but it would be a fun experiment, and what's the worst that could happen? You might have to pull it apart again if it fails, but I don't think you could do any real damage that hasn't already been done.

I want you to go for it, but only because I'd really like to know how well it works out, not because I know it'll work.

 

An area the size of a quarter is a bit big, but I think the important question is how deep? Cast is porous and I would think you would be hard pressed to get all of the oil out of the pores for the epoxy to stick well. And in many cases you need to rough up the area more than it probably is now. So I would either fix it correctly or run as is. I don't see the epoxy as a good solution.

 

It is not deep, I have other motors and blocks, but want to throw this together to see what happens, in hopes it will run decent. Not looking to spend a lot of go with machine work.

I am going to take another look at this today, will try to get good pics.

 

Many different JB Weld choices...for sure some don’t hold up to high temps?

 

I would hate to think what would happen if the epoxy gets disloged and gets caught on a valve seat.

 

Does not look good

 

I've had JB Weld fail trying to seal up a crack in an aluminum radiator (I know other's have said they've done it successfully). From that experience I wouldn't expect it to hold up in a cylinder, that close to the combustion chamber.

 

I like that Loach in your avatar. I was always scared to get in one.

 

Looks like a sleeve would be a good idea.

 

Swapping to the other 30 over block I have

 

That was my dad

 

Those little birds are bad dudes,,,,,,,some bad dudes usually ride into battle on them also !
Great pic !

Do you have a little better pic,,,,,looks a lot like a stain,,,,,,and some minor pitting ?
Looks like the worst spot is beside the shadow .

Tommy

 

I think most would say that isn't casting porosity. Looks like left overs from a head gasket leak and sitting. I'd revise my opinion against the JB Weld for that and just run it knowing it'll foul the plug a bit more and it may blow slightly blue. I doubt however it would be clouds of the stuff.

 

I would get a cheap set of rings and run the wheels off thing till it blows!

 

No to JB Weld. You’re never going to get it clean enough to bond. Then there’s the issue of honing the bore to make it straight and round again. You’re going to end up with the JB flaking off and either dropping into the pan or going out the exhaust.

JB is a mechanical bond, not a chemical one.

Pony up for a sleeve, or run it as is until you can’t live with the oil consumption or plugs start fouling.

 

I would measure the current piston to wall clearance, taper, and out-of-round in that cylinder. If not out to maximum wall clearance, you might be able to improve it some by opening it up with a fixed hone. It's not going to go away, but you might improve the surface some.

 

Sleeve or hone out .010” and get a replacement.040 piston. The just need to weigh within 4-5 grams. Compression wouldn’t make a big difference. I’m sure you could find a single piston or 2 on e-bay.
Since your going to “throw” it together and not take time with proper assembly it won’t matter.

 

Much worse has been built and ran fine

 

Fix it right and sleeve it

 

Epoxy is a great product for many situations.
One of them, that it's NOT good for is being torched, or burned..!

Mike