reducting port sizes

[Sam_Q]

I know this has been covered a bit in a thread a while back but I want to specificly know if its possible to use JB weld in an inlet port and be reliable for 100,000km without the heat cyles making it fall out?

I have too sharp a bend from the port to the low flow side of my valve opening and I would like to have a more ideal radius in there.

What are peoples experiences? or is there another viable product?

[jeffro ra28]

z-spar, or epirez, Both epoxy. epirez sold by blackwoods, z spar sold by Performance Wholesale.

Had experience with epirez, and have had it fall out also.

Not a reliable thing for an endurance motor at all. Not recomended.

Good luck.......

[abently]

I'll give someone a call tomorrow for you Sam. He's used Z-spar on manifolds and that's held up fine to methanol, but I'll find out what he does with Cylinder Heads.

Most seem to acknowledge that a particular 2-pak coating needs to be applied over all epoxy's for them to resist breakdown.

Anyhow, will bump this thread tomorrow with an answer.

[jeffro ra28]

If the location of a stud ei. a manifold was allowed, then the epoxy putty can be formed around this and its usually ok. But, on the short turn of an inlet port i wouldnt recomend.

[Sam_Q]

I'll give someone a call tomorrow for you Sam. He's used Z-spar on manifolds and that's held up fine to methanol, but I'll find out what he does with Cylinder Heads.

Most seem to acknowledge that a particular 2-pak coating needs to be applied over all epoxy's for them to resist breakdown.

Anyhow, will bump this thread tomorrow with an answer.

that would be great


jeffro: theres only one place that I could really use it and its in the worst spot structualy.

[abently]

Ok, you can use Z-spar (local boat shops should have it - wet your finger with water to mould it in the port)

Now you really need to do something to the area your going to apply it. Either with a centre punch to really dimple the area, trying to force the dimple in at 45 degrees to the surface or with a blunt chisel form a few small walls. This will hold it forever. Just make sure the surface is cleaned of any oil.

If you have the valves and guides out, sandblast the port area your going to apply the Z-spar to, then dimple the area with a punch or chisel. Then clean it with wax/grease remover & kerosene or thinners.

Once finished and then the port modified, get a long shank small ball nose bit and make a trough around the Z-spar where it thins out. You want about 1.5mm thickness where it starts. This will prevent it from flaking up.

This method has held up fine for 5 years on a few sprint cars now.

Anyhow that is it. Was recommended if you could get a screw in the area to do so or even tig a small wall etc but its not essential and is only as extra insurance + less time consuming in preparing the port.

[jeffro ra28]

no offence, but how many hours of work does a sprint car do?

How many hours clocks up when you've done 100 000km's.....???

[The Real Roadrunner]

sandblast the port area your going to apply the Z-spar to, then dimple the area with a punch or chisel. Then clean it with wax/grease remover & kerosene or thinners.

so you clean it first with wax&grease remover then add oil to the surface using kerosene, sounds like a good idea.


if the head has bad short turns in it from factory then i can't see it being a great performance head from the outset but have you got a cross sectional shot to see what sort of port design it has?

could it be built up with weld? as that would be a more permanent solution to said problem.

the only problem with epoxy based fillers is that they WILL fall out, its just how long b4 it does thats the difference between brands.

cheers
linden

[oldeskewltoy]

There is a product that is a metal alloy that you might be able to use to fill a port with. The product is called "Alumaloy" The unique thing is these products have melting temps within lpg gas tempertures, making them easily workable....

They have 3 slightly different products.....
http://www.alumaloy.net/alumaloy1.htm
http://www.alumaloy.net/frames/castaloy1.htm
http://www.alumaloy.net/steelaloy1.htm

http://www.alumaloy.net/frames/videob.htm

[abently]

Sigh...............

The only way the epoxy will "fall out" is if its expansion co-efficient is too different to that of the material its bonded to. Generally speaking if an epoxy is specifically designed to be used on aluminium to a certain temperature, then you are generally assured that it will not dis-lodge itself below its max rated temperature. Only problem here is that the packaging is generally blazae about the products capabilities...

Sprint car engines see very high cylinder pressures and vibrations.

Make of it what you will.

Fact remains you either do it and stay in front of your compititors or don't and keep looking at their brake lights....

[jeffro ra28]

Sprint cars also use methanol which is a refrigirant and keeps intake ports cool.

[ed]

Sigh...............

Fact remains you either do it and stay in front of your compititors or don't and keep looking at their brake lights

*sigh*

if you cant see the difference between that and a desired 100,000km service interval, youre stupider than you generally appear

my 2c - loctite 3805

id still be generally weary of doing much inside my ports, particularly down around the SSR. for the amount of prep required to make it key in reliably at that point, id just consider lobbing in a bunch of weld

further up the intake tract, go for gold, the 3805 is awesome stuff

[oldcorollas]

Sigh...............

The only way the epoxy will "fall out" is if its expansion co-efficient is too different to that of the material its bonded to. Generally speaking if an epoxy is specifically designed to be used on aluminium to a certain temperature, then you are generally assured that it will not dis-lodge itself below its max rated temperature. Only problem here is that the packaging is generally blazae about the products capabilities...

Fact remains you either do it and stay in front of your compititors or don't and keep looking at their brake lights....

err, since we are talking about temperatures of what? 0-150deg, would you care to calculate the amount of expansion? and the resulting interfacial stresses? i can assure you it is quite small in terms of the overall material. (expansion is an issue for a few hundred or thousand degrees, but we are not talking exhaust ports here)
you can "generally" say that, but bonds are never perfect, unless of course you prepare surfaces like i do... grind, detergent clean in ultrasonic, acetone in ultrasonic, then ultrasonic and vacuum the bubbles out of the mixture, then pour onto metal, vacuum again to remove any bubbles at the surface and cure at 60-80deg...
and ya know what? we still get imperfect surfaces, with epoxy designed to adhere to those surfaces and designed to have similar expansion to the metals of coursewe are only talking microns of debonding, but combined with vibration, is a recipe for failure.

most people put too much faith in "glue"

as Jeffro said, if you have a mechanical stud to retain the "blob" it will last longer, bu how long until it cracks and falls out? just dimpling the surface might work in the short term, but i would not bet engines on it..

and competitors tail lights? when was the last time you saw "competitors tail lights" on the road? how often do you think the engines of front runners in any category "are not" pulled down

[jeffro ra28]

What sort of descent sprint car engine which has probably got 20-30 grand worth of cylinder heads on it has epoxy ports anyway? If it were designed properly in the first place it shouldnt need epoxy filled ports. And if it does then it says alot to the dodginess of the design in the first place, let alone the dodginess of epoxy encrusted ports.

[abently]

What sort of descent sprint car engine which has probably got 20-30 grand worth of cylinder heads on it has epoxy ports anyway? If it were designed properly in the first place it shouldnt need epoxy filled ports. And if it does then it says alot to the dodginess of the design in the first place, let alone the dodginess of epoxy encrusted ports.

You do understand that some rules stipulate using only certain cylinder heads cough *holden 308 red/black/ blue etc* cough........

I've used loctite 3805 personally. The only thing I noted different with it from other epoxies was that the loctite was definitely more tackier. The shelf life of it was only a month max once opened so be prepared to use most of it that day if you can.

Anyhow I think we've gone through all the for and against arguments so I'll just leave it here. The poster can make their own mind up on what to do.