Intake port filler (cast iron)

[hydrolastic]

Hello guy's, Looking at a cast iron head that i want to port. I can remove a fair amount of material from the roof of the port after that it looks like i could make it more of a down draft port if i could add some fill (1/16 to 1/8) on the floor of the port. I am thinking of everdure brazing rod. I have not done very much brazing and that was years ago. so i will probably get someone to do it for me but i just want to make sure that i am on the right track like i said this is just filler not for strenght so the easiest way to get the filler in there is what i am interested in. please no add epoxy responses cause i just am not going to go that way. Hydro

[zapster]

OK...there is some questions here that need answers but lets just cut to the chase..

Epoxy is the obvious answer.

What are you going to gain by doing what you want to do?
How do you know this will work?
Do you have access to a flow bench to see before and after results?

You may be doing more hurt than good by touching anything anyway..

But here is what you CAN do in the mean time if a flow bench is available..

Use some Play Dough in the port so you can add..subtract..shape at will before doing the final porting..

Either and or the epoxy is the way to go..
You don't need to be subjecting the ports to heat that will be needed to weld/braze your design into them without consequenses..

Warping comes to mind..

Epoxy done right will last forever and is cheap and easy...
Been there done that many times with great results...


...zap!

[Showdog75]

I'll second epoxy,it's been used by professionals for years.

[Oatsy]

What these guys said, epoxy is what you want here.

[hydrolastic]

Where the heck is Castweld when you need him???

[Showdog75]

It's not that it can't be welded but that's a stupid amount of work for the end result compared to epoxy. You will most likely have to remachine after welding as well as deal with potential cracking issues. Go for it,sounds like you have your mind made.

[castweld]

Originally Posted by hydrolastic

Where the heck is Castweld when you need him???

Im here.
One damm good reason I can think of not to use epoxy is NITRO, it will disolve the epoxy. And I suspect nitrous sprayed directly at epoxy may be a problem although I haven't tried it.

No mention yet- what kind of port? More to the point, how far down the port, and how big is the port?
The short turn in a sbc will be nearly impossible to reach, but I have torch brazed the first inch and a half of the floor on a sbc though. I haven't tried to tig braze a floor yet but it should work if you can reach it. I would try heating to a minimum of 650 degrees and give it a try. Out of the oven you will loose heat fast so weld no longer than 5 mins before reheating. A thirty min postheat at same temp and slow cooling should prevent cracks.
One caution when using silicone bronze tig on cast iron- do not puddle the iron and then add filler. The result is not machinable (hard as supermans lick). Light up on filler and hold arc untill it flows on to the iron.
Peter

[Boostinjdm]

Sorry to hijack, but I've got a similar question. What can be done with an exhaust port in an old kohler? Will brazing handle the heat? I've got an otherwise decent kohler with a corroded port. The pipe threads are gone and the two bolt holes are damaged as well. I believe it's a K321 with cast iron block.

[castweld]

Originally Posted by Boostinjdm

Sorry to hijack, but I've got a similar question. What can be done with an exhaust port in an old kohler? Will brazing handle the heat? I've got an otherwise decent kohler with a corroded port. The pipe threads are gone and the two bolt holes are damaged as well. I believe it's a K321 with cast iron block.

Hey Boost
Getting anything to stick in that kohlers port will not be easy. When the ex port erodes, the iron goes but not the carbon, nothing sticks to carbon well. The exhaust of a gasoline engine will erode bronze. Nickel will work if it sticks. Another solution is to bore port round and press in a sleeve then pin it- to accept a new pipe nipple. Or something along that idea.
Peter

[hydrolastic]

Great, So yes I plan on building a firebox to get it up to 600+ degrees then do the welding the floor of the port from the short turn to the face of the intake. I also plan on doing a setup to keep the head at temp while out of the box. I am also thinking that a kiln set for a slow cool down afterwards would be a way to go afterwards. I need to get a little more info on fluxes to use and the best way to clean the port.

[hydrolastic]

Hello again guy's, Ok did a some research yesterday and i have a bit of a plan. I want to open up this port and insert a piece of tube into the first 2" of the port to get by the pushrod tubes. This will get the port area i need. I plan to use the bridgeport to mill into the head at an 8 degree angle once the part is fit to the head i will then mill a step (lap joint /rabit) into the head where the tube meets the casting. one article said a 3 to one lap is best but i estimate a 2 to one is the best i can do i expect i can stay between the .002 - .005 clearance called for. i can easily make the part out of mild steel but if it has to cast iron could be used. Once the part is in i will need to add to the port floor to level it out at the higher angle. I appreciate what was said so far about ruining the port for flow. But this is not my first rodeo with this engine and i have gone as far as possible with working with the stock casting. This car has had several heads from the best guys in britain and optimized by the best british engine flow bench guy on the west coast. It will eventually be put onto a race engine run flat out in a 20 or 30 min race so for me epoxy just is not going to cut it. This week i am going to look into making a "hot box" with refractory bricks with an open side this will preheat the head to the reguired temp. I plan on making a jig where the head can be rotated while hot so i can get to the port from both the port face and the valve side. Then next item for you guy's is the choice of rod and flux and the size of the torch nozzle. For the nozzle i am thinking of either bending the tip or cutting it and putting a 90 degree fitting on it. preliminary choice for rod is the Aufhauser low fuming bronze rod and the brazing flux recomended. Does this sound like the proper rod to you guys? Thanks in advance. Hydro

[burnit2]

What about Spray Powder? Should be very easy. I would worry about the Brazing Rod due to expanding and contracting at different temps than the cast. Spray Poweder will never let go and is easy to machine. I have done a ton of buid up and repair on engine blocks, Manifolds etc. ( never done the application discussed here though )

[4sfed]

Originally Posted by hydrolastic

9This car has had several heads from the best guys in britain and optimized by the best british engine flow bench guy on the west coast. It will eventually be put onto a race engine run flat out in a 20 or 30 min race so for me epoxy just is not going to cut it. Thanks in advance. Hydro

So what engine are you working on?

[makoman1860]

Hey guys,
Bronze on a water cooled head will typically hold up just fine doing what you are asking of it. Cleaning and proper tinning of the cast are very important as well as pre and post heat. I also spray weld mine up using one of the softer eutectic powders with good results. Distortion is really a non issue if the process is done correctly. Epoxy is a poor choice, very poor. Good enough for a dyno run or two, but it wont last any real endurance.

[Zmechanic]

Originally Posted by makoman1860

Epoxy is a poor choice, very poor. Good enough for a dyno run or two, but it wont last any real endurance.

Z-spar epoxy will work fine for race applications or possibly even street applications with regular fuels. It will not work with anything alcohol based, and it will corrode away.

Once you put that stuff in a head, you're either going to have to corrode it away or grind it out. It's not coming out, otherwise.

[farmall]

What eutectic powders? I have a Eutectic Castolin OA powder spray outfit but not much idea what it's good for.

[con_fuse9]

I'd recommend you do the work at first in clay and test it on a dry flow bench.
Find flow bench that can measure flow, velocity of flow and swirl.

Flow by itself means little. A cylinder head that cannot develop velocity but can gulp big amounts of air is not good. At best you achieve 100% volumetric efficiency and quite frankly that will not cut it. With headers and proper intake tuning (think scavaging) you should be able to easily achieve 104% (especially at peak torque). Not sure what the Pro-Stock motors are doing but I've heard numbers like 112% batted about. Of course they only run at a more or less constant rpm.

What I'm saying is this, to achieve maximum flow, you simply open everything up: big big big. That doesn't translate necessarily into maximum filling of the cylinders. Air moving at speed has momentum. That momentum can cram extra air into a cylinder, extract all the exhaust, and exhaust momentum can actually start the intake flowing (during overlap) before the piston even moves down.

There is a limit on how fast air will flow - basically the mach number. For the sake of argument, a nice intake or exhaust port will flow about .85 mach - at that point turbulence will set in and your flow will flatten out (no use opening valves bigger). Turbulence is tough to measure. Your best tool is probably your ears. If you can hear the air flow, you are creating turbulence.

Oh, and mach number's biggest influence is temperature. So with exhaust you can actually move more air through smaller places. Higher temp = higher mach number == higher velocities in the gases.

Finally, I would suggest you read as many articles by Smokey Yunick as possible. Not because he is the best engine builder ever (debatable), but he, in his published articles, has some of the best common sense (or not so common). Keep you from wasting time and money and focusing on the problem at hand.

Me personally, I would run flat top pistons, mildly ported heads, custom headers (matched to the ports) and custom intake (matched to the ports) and pick a cam that best complements that. Heads would be opened up under the valves, smoothed out (maybe even polished), but that is it. Aluminium heads if the rules allowed, aftermarket heads again if the rules allowed. I wouldn't touch a flowbench until I knew where my power plant was deficient.