Building up intake runners - Epoxy??

[collinsda]

Hi all, just a quick question about building up areas of the intake runners etc...

I was just wondering if anyone could recommend a particular type/brand of epoxy or another suitable substance. I know a lot of engine builders use epoxy for this but I don't know which type and I'm reluctant to do it by trial and error for obvious reasons ;-)

Also, other than weld build-up and blending, is there an easier way to fix small holes in the cylinder head?? Most of the holes are in areas between the intake and exhaust valves so I don't particularly want to weld there (the engine is a small capacity race bike engine). The holes are very small, typically 0.5-0.75mm in diameter. Should I be concerned with them at all - could they be a source of pre-ignition??

Thanks,

D.

 

[collinsda]

Found the thread I was looking for on the site. Thanks.

 

[EHudson]

Devcon works as an intake filler.

Are the small holes between the valves a crack? That is the usual spot for them due to the thermal stresses that are set up between cold and hot ports. You need to be concerned about valve seats dropping out of the head if cracks propagate. If the holes are just casting imperfections I'd leave them alone.

I have seen non-welded crack repair in heads performed by drilling and tapping overlapping holes. The first crack is drilled and tapped. Then a screw is coated with commercial block sealant and screwed into the hole and cut off flush. The next hole is drilled overlapping the first screw a bit and finished the same way until the crack is filled. Machining the head for new seats is usually involved.

Most of the cylinder head welders that I know of are in the tiny town of Chapin, Illinois. There are three there, I think. Chapin Cylinder Head was one place - They usually repair cast iron heads but have done aluminum repairs.

good luck

 

[CamRon]

I've heard of using jb weld to build up ports and increase velocity in motorcycle cylinder heads. If it can hold up in the ports, it should have no issue in the runners.

...Cameron

 

[Greenlight]

Moroso sells a two part epoxy putty called "A - B". It is a "clay-like" substance that you mix the two parts together in your hand. You have about 15 minutes to form it in place. It take about 2 hours to harden and 8 hours to fully cure. It's easy to form it to the shape you want by hand. I've used it in intake manifolds and intake ports in cylinder heads with good success. If you keep your fingers/hands wet with water while forming it in place you don't need to do any grinding afterwards. Moroso sell it, but I've also seen it used in the oilfield where downhole temperatures reached 600 degrees F without failure.

J-B Weld is good too, but doesn't form as easily (more liquid than A-B).

 

[collinsda]

That's great lads, cheers.

EHudson, no, the small holes are just porosity in the head - from the manufacturing process I'd imagine. Do you not think they are worth repairing? It's a race engine and I am concerned that tiny 'pockets' like that in the cylinder head would be a source of pre-ignition. Should I be bothered at all? I'm in Ireland so Illinois is a bit of a trek ;-)))

Greenlight/Cameron, cheers - I'll have a look for that stuff.

D.