blown 87

I agree.

BC

Correct kind of. Photobucket is a hosting site, so you load them there, kind of like when you load them on your website, and then you simply post the img tage here in [img] things. It allows you to put photos on the web without resizing them.

BC

This is why I suggested photobucket, as when you have a large photo or small photo - it skips this step. I upload 2MB photos all the time and some of those are the pictures at the start of the thread.

The_Remora

Greg, once you upload the the images to photobucket, that is where they will 'live' on the web. You then copy the image code (IMG) tag line from there on the photobucket site, and that serves as the photos 'address'. You paste that image code 'address' onto Rennlist and it creates a sort of window in your post that a viewer can see through to your image on photobucket.

photobucket is great, totally free and allows you to make subdirectories to organize different photo galleries for various projects. And they never spam me.

This is a great thread, and not because I'm planning on porting heads any time soon, but I just love reading about this highly technical stuff, especially a black art like porting which very few people know to do correctly.

GregBBRD

You guys are great! This is why I wanted the kinder, gentler 928 Forum. I knew that I'd get tons of crap, if I didn't know how to post a stinking picture.....probably "forum speak 101," for all you guys.

I'll go to photobucket, tonight and see if I can do it that way. I have absolutely no clue what language Fabio was using when he wrote about modifying the pictures...I was completely lost right after "resize them by opening them in MS Paint." I can't seem to even find MS Paint, in my local yellow pages. I took my camera over to the paint counter at Home Depot, at lunch, and they didn't seem to be able to help.

Heh, I'm a simple mechanic.....you know.....the guys that were so slow they couldn't pass the art class, in school. I need a map to find my way to work everyday.

Speaking of art, I have no idea what skills it takes to be able to port and polish successfully. I know that in drafting, I could draw like a mad man. Straight lines were not an issue. However, my bushes and trees looked like retarted stick people. If you can feel a small dent in your car, with just your finger, I know that is good. The whole porting thing is a combination of visual response and the ability to feel small differences. If you can take an oval hole in a piece of aluminum and make it round, with a die grinder, without using anything but your eyes, you will be good at this.

The second thing that is required is the ability to take two oval holes and make both of them the same size and shape....only by eye.....with a die grinder. I can walk up to a set of heads and tell how long the person that did them has been porting and how good he is. I have a customer with a 928 stroker engine that had his heads done...somewhere else. The ports are like fingerprints...no two are even close to the same. They've got lumps in some places and holes in another....no two of which are in the same location. It's like I gave them to a kindergarden class and turned them loose...only allowing one kid to do each port. He asked if I could fix them and make them all the same.....I said sure, but I'd need a new set of heads to start with.

I've got clues, that I use, to help with this, so that you don't create your own set of lumps and holes.

Let me work on the pictures tonight. If you wake up in the morning and the server that hosts Rennlist is gone....it's not my fault!

greg brown

BC

KNowing Fabio's Avatar, he had "HOPE" that you could "CHANGE" your pictures, but photobucket is more like the other party - efficient and effective for posting pics. (OT forum joke)

BC

I am forming a plan here.

It looks like I could do some non-invasive work on these heads and possibly get some airflow improvement without really changing the structure of anything.

Here, I can see that there are some casting flaws (I guess they could be flaws) by the exit of the intake valves into the chamber - past the valve seat. I think this should be smoothed or removed:



Also, in addition to the step just outside the intake valve seat, there is just one area on the combustion chamber surface that is different than the rest - like a casting flaw:




Going more into the actual ports, I was told by hammer (and I believe him) to not touch the short side radius. That to me is the bottom of the port. The bottom of the exhaust port seems to have a large step in it seen here just past the smoothness after the seat:





And on the intake port, I think the pictures I published above of a different 4V head show that there should be no steps in the intake path before the valve seat angles, which I do see in these (my heads):



Finally, this is what I have done to protect the sealing surface on the head:



Finally, should some of the material that is very close to the edge of the exhaust valve seat be taken away?

largecar379

I am late to this discussion, but here's what I know:

I have not seen or heard much about port/head rework regarding any of the 928 heads.

Those few that have done it, do not report any significant gains. (I have my own opinions as to why, but that is another discussion)

A few months ago, I took my heads (16V Euro) to Nicken's Bros Racing, near me, in Conroe, TX. They are long time drag racers, have a huge number of trophies in sportsman class wins, and are currently the engine builders for Erica Ender's NHRA ProStock team. David Nickens is her crew chief. These guys are working on heads that have ports big enough to put your fist in, so it was fun to see them work on my "small port" heads......They remarked that they looked very similar to a small block Chevy head.

What I had done:
(not in exactly this order)

mild port and polish (similar to what they would do to a Super/Stock class car)
unshroud the valves
clean up the combustion chambers
5 angle competition valve job
remove the steel inserts in the exhaust ports
port match the intake (Euro intakes) and exhaust ports (MSDS headers)
lightly mill the head/block mating surface
install valve springs according to spec

intake ports were 23mm, now 25mm (diameter)
exhaust ports were 21mm, now 26mm (diameter)

My headwork was priced at $1650 for the pair, finished and out the door, tax included.

As you may see in the below pics, the ports are not polished mirror smooth, but still retain a slight amount of roughness. this helps the air/fuel mix remain mixed in suspension, as opposed to separating when traveling down the port.

I also asked them to do a volume comparison with a junk 4 valve head I had, and they said the 16V Euro's would easily out flow the 32V (read: cfm's)

I did not go super big on the porting. This is important, as our 928's are mostly street cars, requiring low end torque to retain drive-ability. Those of you who have 2.20 rear gearing (not me, I have 2.75:1 gears) will need all the low end torque you can get, just to get the car moving, unless you are running a supercharger......turbo's are another issue (I'm not going there).

the biggest road block to good head work is that most (hotrod) shops haven't a clue as to what a 928 is, much less worked on one.....even less, knowing what to expect when you put a 928 head on a flowbench. And if you do find a shop that does kow what a 928 is, it's more likely Porsche (friendly) and pricing to go with the marque.......

I am continually amazed at how little the 928 has been modified, with the exception of folks like Sterling and the illusive Todd/Wisconsin bunch......

Sterling is on the right track, in my opinion, with cutting a huge amount of weight off the reciprocating assembly (enables the engine to rev quicker/higher), but there is still much to be done with cam profiles, valve train components, and headwork. His vario cam setup has some interesting possibilities, although I have not seen larger cam profiles in his build of late. Perhaps he will do something about this in the future....

My limitation will be with cams, due to the 16V cam only being able to take a .500 lift. Duration is another matter.....I am considering a "cheater cam" profile, similar to those used in the "Stock" drag racing classes, where the lift dimensions must retain their original spec, but the duration numbers can be changed--usually lengthened. You end up with a (relatively) smaller lift/long duration cam profile that makes huge amount s of torque, but doesn't really perform well above 7500...... I am also considering modifying the cam towers themselves, but I shouldn't be too speculative on that at the moment. Lifters [cam buckets] are something else that can be improved upon (I have a contact that tells me he can build a set of lifters [cam buckets] that will extend my rpm range to near 8000 without any issues).

it will be interesting to see where all of this experimentation leads, but most of this stuff has been done with domestics many, many years ago......

--Russ

largecar379

Brendan---


not to rain on your parade, but if you've never done headwork, don't start (learn) on an expensive 928 head. you may do more harm than good. materials removed are not easily replaced, if need be.

see my above post to get more of an appreciation of my advice......

this is definitely something I would leave to an experienced professional.

good luck--

--Russ

V2Rocket

the intake side should be rough like it is because it helps atomization.

largecar379

I believe I said that.........

--Russ

Vilhuer

Were these S3 or later head design?

Warren928

I have done porting and polishing on an engine, woke it up quite nicely, and looking at your last three pics, you could get in there and take out 2 mm of there all the way around, but not near the valve stem or seats, taper it down to nil near those points. You gotta change valve sizes if you are going to port all the way to the seat. Then make sure you match port the intake manifold side and gasket to match in terms of material removed.
Its not rocket science, but some people would scare you into beleiving it is.

That should give you more flow, and bernoulli's airflow concept should offset SOME of the bottleneck near the valves.

Don't use a stone wheel, it will clog up and expode from the heat, use a HSS or forged made grinding wheel, I prefer the oval shaped one, it makes nice porting cuts that are pretty smooth. I ran mine off a dremel, and yes it did die after that job, you would be better off with a motor from harbor for $40.

Get a book on it, or a video. That might help with those ******* about cutting into a head with a high speed tool. I had a friend who use to port and polish engines all the time for championship jetski racing, and he showed me the process. Alittle time on the aircraft engineering side didn't hurt, either.

6.0-928S

Brendan,
In my opinion you can smooth & cleanup the areas that you point out in the most recent pics & pick up some small gains which is the way I interprete what you mean to do. Without getting carried away I see no harm in blending those areas.

Hammer

FBIII

Leaving a port rough for atomization goes back to the carburator days. We don/t need atomization since the fuel is shot directly at the back of the intake valve from the fuel injector, which if operating correctly has atomized the fuel.