port polishing

[1974datsun]

what tools do you need to port polish?

[Braden]

anything that is small enough and manuverable enough to remove small amounts of metal, i have used various objects wrapped in sandpaper for finishing work, slow, but you wont get into trouble when your doing it by hand, powertools (air grinders, dremels, etc) are good for some things but in my opinion unless you are removing large casting marks get rid of them, there have been many people ruin otherwise good heads because they got carried away with power tools

[hughdogz]

Ferrous and non-ferrous cutters for pneumatic grinders to remove material

 

Sandpaper rolls that will smooth out the new surfaces. Also, buffing wheels to actually polish. Polishing doesn't help that much.

 

At least for an L-head unshrouding the values makes the most difference of all. You can also radius the runners and widen the bowls too.

[steve g]

i bought one of those port-it-yourself kits from summit years ago, it has about 10 different types of dremel bits "dremel not included" the kit was $90 or so. it has done about 2 complete heads and i think there is still enough for one more.

[datzenmike]

Ferrous and non-ferrous cutters for pneumatic grinders to remove material

 

Sandpaper rolls that will smooth out the new surfaces. Also, buffing wheels to actually polish. Polishing doesn't help that much.

 

At least for an L-head unshrouding the values makes the most difference of all. You can also radius the runners and widen the bowls too.

 

I agree. The L head is almost perfect as is. The intake runners can be left rough help hold the boundary layer. Exhaust can go mirror shiny... it doesn't really help the flow but prevents carbon from clinging to the walls and building up. Both valve guide bases can be streamlined.

[hughdogz]

I totally agree with you guys. If you don't know what you're doing, you could make the flow a LOT worse!

 

Skib is also learing from BRAAP how to do porting / head work :thumbup:

 

I'm sure he has pics...:rolleyes:

 

Here is my first attempt.

 

Thanks Datzenmike, I forgot about mentioning removing the valve guide "lumps".

[Skib]

Ill make a proper post when Im more awake :P

 

carbide bits for alum are not cheap :eek: I dropped about $60 on 3 of them last time

[HRH]

You need a long football aluminum cutter. That's about the handiest. As for porting, transfer the pattern of the large bore manifold you're going to use, onto the head. Mark that with a sharpie, and start going to town on the head, but don't cut too far as then you'll hit water.

 

For the flow, all you want to do is make the path to the valve as easy as possible. Ideally it would be a straight line. Think of a pvc 90 degree elbow like plumbing wise. If you could straighten out, or smooth the flow to make it a 45 degree elbow, it's that much easier to move volume in it.

 

Or better yet, think of yourself as a miniature mountain bike rider and picture riding down the intake into the valve bowl. To take all the fun out of it and make it as easy as possible, it would be a straight line, right? Now apply that to the runner.

 

To make sure you have them equal, find something like a ping pong ball, or socket that's the same size, and fit it inside each hole, making sure it goes in the same amount, etc.

 

Should look something like this:

 

[paradoxx]

the book says:

 

Jim Wild from Wild Enterprises has determined that while polishing does not improve the airflow, it does enhance buyer acceptance of the finished product. He says that eliminating the unnecessary polishing can cut time and cost by one third.

 

Unless you have big chunks of aluminum around, which I don't think its the case.

[HRH]

True that, the law of diminishing return. If there is large slag or casting leftovers, sure get that off. But the guys who polish their entire heads with croakus cloth are wasting their time.

 

I think I did about 220 grit to finish off the runners, and that was just fine and smooth.

[69FJWagon]

what tools do you need to port polish?

 

REBELLO RACING!!! Best in the business and worth every penny :D

 

I have thought about learning but to really do anything other than port matching without a flow bench to check and make sure you a close to equal on all the ports can do more harm than good from what i understand

[steve g]

polishing the intake ports is a good idea if you are running a huge overlap cam on a somewhat street driven car, It keeps the carbon from collecting in the intake port and restricting airflow.

[Z-train]

the book says:

 

Jim Wild from Wild Enterprises has determined that while polishing does not improve the airflow, it does enhance buyer acceptance of the finished product. He says that eliminating the unnecessary polishing can cut time and cost by one third.

 

Unless you have big chunks of aluminum around, which I don't think its the case.

 

So now we are racing books.

 

 

polishing the intake ports is a good idea if you are running a huge overlap cam on a somewhat street driven car, It keeps the carbon from collecting in the intake port and restricting airflow.

 

How the hell does carbon run BACKWARDS(against the incoming charge)up the intake runner?Polishing INTAKE ports is NEVER a good idea.

[steve g]

with huge overlap there is a moment when the intake and exhaust valves are open at the same time, at idle the the exhaust gases will travel up into the intake tracts (intake reversion). With polished intake ports it allows the carbon to break off easily early in the stages rather than piling up and clogging the ports and back of the valves

[Z-train]

Polishing intake ports is NEVER,repeat NEVER a good idea.

[datzenmike]

Yup. Stock intake opening is 16 degrees BTDC so some exhaust will still be leaving, but not much. Higher overlap with up to 35 degree intake openings can be found. Strange things happen with valve events.

[steve g]

Yup. Stock intake opening is 16 degrees BTDC so some exhaust will still be leaving, but not much. Higher overlap with up to 35 degree intake openings can be found. Strange things happen with valve events.

And if someone has the balls to drive a radical overlap cam on the street daily they rarely have the chance to drive the engine at its full potential so reversion can occur, polishing the intake ports help reduce issues down the road... its not a practice to build more power but a practice to help keep your heavy overlap cammed motor running properly. Or simply let the engine never idle under 2500rpm but then the lopey idle sound is gone

[datsunfish]

I have always heard that polishing reduces the atomization. 100-220 grit paper to smooth it out should be good enough. Port and polish kits are available on the snap on etc. tool trucks for around $50. I use a router bit to cut the aluminum. Heres my cheezy video on how I do it and I have successfully done a good handful of heads and mainfolds. Over porting will reduce intake velocity which reduces torque. You also want to make sure the flow is straight down enough at the bend for the same reason. I mainly do it to bring things to L20b stock head and intake port size. Good for L16 mani a87,w53 heads.

http://www.forum.ratsun.net/showthread.php?t=11121

[Jesse C.]

Match Porting, cleaning up the intake port, blending in the valve bowel and polishing the combustion chamber should be all you really need for a street motor without going nuts. If you really have the time and patience, clean up the exhaust port and feel free to polish it if you like.

 

Totally strip the head before you work on it to avoid damaging parts and makes it easier to work on the head. Work on a bench and barstool as this is going to get a bit tiring and tedious. If possible, jig something up to hold the head at an angle to make it easier on yourself.

 

Clean the head as good as you can. I used Dykem Blue to mark my area to grind out and used the intake/exhaust gasket as my template. Use gloves if handling the grinder as it will get really cold if you have some moisture in your air source. Take breaks and don't drink to much as this is not an operation where you want to make to many mistakes.

 

Places like Jegs, Summit or Speedway have kits available and make sure you get one intended for Aluminum as the Iron kits will clog up really easy with aluminum material.

 

So turn up the tunes, pack the cooler with some Cokes, wear your safety gear and have at it!

[Skib]

 

So turn up the tunes, pack the cooler with some Cokes, wear your safety gear and have at it!

 

thats how I do my porting :fu: