Thank you Many944s for the head polishing inspiration

[speedracing944]

Nick,
Thanks for showing me your polish job on that turbo head during the wrenching party. You inspired me to do the same on my N/A head. My 8 year old son also joined in a helped polish for a good 45 minutes. The intake ports are now as smooth as a babies bottom.

Speedy

[many944s]

D@mn...
I inspired someone... Scary!

Thanks though! Do me a favor, since your valves are still in the head, attach your cam tower (with the lifters in place) to the head. Once it is attached, rotate the camshaft so that each intake valve opens. When the first intake valve opens shoot a good deal of brake cleaner through the port, followed by alot of compressed air! Then do this for each of the other three intake valves. You will want to make sure there aren't any bits of aluminum left in there to cause problems!

-Nick

[thoen]

Nick,
Question about your procedure... When the tower goes on are the belts are they connected and at TDC? Or is it done before the belt part? What does this do to the valves.
BTW I am saving up to get one of your heads!!!

[many944s]

Actually, the head is off the engine. I wouldn't recommend ANY port work be done while the head is on the engine, as there is no way to prevent filings from falling in the cylinders!! The procedure doesn't do anything to the valves themselves, rather it cleans up the rough casting surface inside the intake ports to allow for better air flow.

P.S. I'll keep a head to the side for ya

-Nick

[speedracing944]

Here is a pic of one of the ports.

Notice all the aluminum dust covering the valve. This is the bad stuff you are talking about Nick!







Speedy

[speedracing944]

Speedy

[speedracing944]

I measured the width of the port on my old head and it was 1.595"

With the polish it opened it up to 1.605" so a 0.010 increase.

I am going for the maximum placebo effect and this mod will yield me an extra 30 HP as felt by my back-side-dyno !!!! JK

Speedy

[many944s]

Nicely done! Heck of a forearm work-out isn't it

[speedracing944]

I am what I am!

Speedy

[m73m95]

I did about the same on mine, but I went a bit farther. I kept grinding untill the whole taper was gone. Its pretty much a straight shot to the valve now. Its "port matched" to the gasket I guess.

I never drove my car before I did this, so I don't know about any gains, but it sure makes me feel like it did something for my engine lol....so +1 on the placebo effect!

[HondaDustR]

I really want to do this for my car! Great work! I've done it and learned alot on several single cylinder lawnmower engines and a 4 stroke dirt bike motor with noticable results, but never did it to a car head. I want to grab a cheap 944 head off of ebay and rebuild it, port and polish it, and shave it down a little, swap it in and see what a difference it makes.

Just be sure that whatever you change, to do it as close to the same as possible for the others so the engine flow balance doesn't get too screwed up( it might actually improve from stock if you're good!) Just be sure all the ports are the same width, and if you changed the shape at all, that it's changed on the others as well. Some always have worse imperfections than others and consequently, take more material removal to get it looking good.

Just that! Imagine a stage II (my own grading system) port and polish, piston crown polish, shave the head, port match the head and intake manifold, retard the cam timing a tooth, floor the throttle, and never look back! (okay...back to reality...)

[HondaDustR]

Originally Posted by m73m95

I did about the same on mine, but I went a bit farther. I kept grinding untill the whole taper was gone. Its pretty much a straight shot to the valve now. Its "port matched" to the gasket I guess.

I never drove my car before I did this, so I don't know about any gains, but it sure makes me feel like it did something for my engine lol....so +1 on the placebo effect!

From my sketchy understanding, you probably don't want to completely remove that taper. It creates a slight choke point that accelerates the fuel charge, the same as what happens in a carburator, so it atomizes and swirls the fuel to fill the combustion chamber more evenly. It's what keeps port velocity high enough at lower speeds.
Your port velocities will go down at low rpms with a resulting loss of efficiency, but it should improve top end flow and performance. It would probably be a lot more of an advantage with a cam profile more optimised for high end power, as the stock cam is definitely more of a low end/midrange profile (and a bottom end to be able to handle higher revs so as to get even more benefit, and new fuel maps (and injectors) to compensate for higher volumetric efficiency, and a bigger exhaust system for top end power, and lighter solid lifters and different rate valve springs to control those big valves at 7000+ rpms) but would only be suitable for performance or track driving, as all that low end torque will disappear. But it sure would be awesome!

[m73m95]

I would agree with that, but I didn't go as radical as I think you're picturing in your mind. I ground the taper out, but not all the way down the port. I guess its more of a funnel shape than the abrupt taper in the stock head. The air would have more of a venturi effect (like a carb) and not a tumbling effect (from the height of the stock taper)

I bought the car with a blown head gasket, so as I said, I didn't drive it before my mototool molestation, but I certianly can't imagine it having any less low end torque. For an NA car, it pulls like a bastard.

[Ritzblitz]

I wouldn't recommend doing any radical porting. From what I understand, the way the air flows is very deceiving and it's hard to know what happens without an airflow bench.

Don't want to rain on any parades, and I'm also not sure if this is even true, but I heard that polishing a port doesn't really have any advantages. Reason being- air flows better over a slightly dimpled surface than a smooth surface. Kind of like how a golfball with dimples flies better than a plain old sphere. Any input?

[speedracing944]

Originally Posted by Ritzblitz

I wouldn't recommend doing any radical porting. From what I understand, the way the air flows is very deceiving and it's hard to know what happens without an airflow bench.

Don't want to rain on any parades, and I'm also not sure if this is even true, but I heard that polishing a port doesn't really have any advantages. Reason being- air flows better over a slightly dimpled surface than a smooth surface. Kind of like how a golfball with dimples flies better than a plain old sphere. Any input?

I will let you know after I have fluid dynamics this fall

I don't expect many gains but I am going for the placebo effect kind of like putting on NOS stickers and thinking it adds HP.

Wow my car is fast! It must be from the port polishing I did.

Speedy

[m73m95]

The dimples on a golf ball are uniform in shape and size.... the rough casting stuff is not.

Anything major in porting I agree is useless on these cars. Especially if the rest is stock. But, polishing is worth the 1/2 hour of time. Its not 87hp, but it does help the air move faster.

With a carburated engine, where the fuel mixes with the air long before the combustion chamber, you need the air to swirl/tumble around to keep the fuel mixed with the air. In a fuel injected engine, the fuel mixes with the air inches away from the combustion chamber, and its atomized better when its shot out of the injector than fuel that is sucked out of a carb, so more focus should be made to get the air into the cylinder faster, and cleaner to get the best performance.

The factory wouldn't waste time on polishing the ports. Like I said, its not a significant advantage, so it saves the factory money without losing anything.

[TSNAPCRACKLEPOP]

fluid dynamics as i applied it to ventilation systems in hospital life support....the tubing thru which air flow in a ventilator circuit is corrugated its entire length

[speedracing944]

Originally Posted by TSNAPCRACKLEPOP

fluid dynamics as i applied it to ventilation systems in hospital life support....the tubing thru which air flow in a ventilator circuit is corrugated its entire length

But is that to improve air flow of to allow easier bending of the tube? Corrugated is much much easier to bend and you can also achieve smaller radiuses before pinching occurs.

Speedy

[TSNAPCRACKLEPOP]

as i recall, the turbulence aids the center column of air in faster travel/delivery thru the tube in the center, while the outer air swirls down the tube. in intakes, the turbulence would seem to help mixing the charge in carburated engines. i dont know about port FI tho... i gues thats where BOOST helps

[looneybin]

I did read that you don't want to polish the ports on a fuel injected motor if the injector cycle does not match the valve opening of the cylinder.
The fuel charge just sits in the port until the valve opens to let it in.
The polishing benefit is if your motor has a carburetor(s)
In that time (millisecond) the atomized fuel will - because of surface tension - stick to the smooth port & loose some of it's atomization.
If the port is left rough, the fuel will stay turbulent & not stick to the rough port wall.
I'm not sure all of this is fact, or if this has any effect on a street car, just something i read once apon a time