ribs

So...I read this board and several other boards often. I see some terms used that I may kind of know what they mean, but don't know the full deal. So...if you would help me out:

Port and polish - what exactly is involved in doing this? What tools are used?

Shot peen - I have no clue.

Deck - as in deck a head...do you remove a bit off the bottom to bump compression? What would you use to do this?

3 angle/5 angle grind - I believe this is part of port and polish...I don't know what a grind is, much less 3 or 5 angle.

Cross drill a crank - I imagine you drill holes into a crank to lighten and allow better oil passage, but I would like to know more about it.

Knife edge - goes along with cross drilling a crank, all though I have no clue about this.

Indexing a turbo - is this when you rotate the turbine or compressor side around the shaft to line them up with the hot or cool pipes?

I know there are a bunch more that I don't know but can't think of right now. If anybody would be so kind as to tell me what these are or give me a link to an automotive encyclopedia that would explain this stuff I would be much obliged. Also, if anybody has more terms to dump into here, go for it...maybe we can get a small advanced automotive dictionary going on here.

emilysgranny

OK Ribs ,I will give it a try.
1. shot peen. The equivalent of sand blasting,but using special grit ,which can be made of plastic ,steel,and other materials usually in ball form but not always.The concept is to achieve a uniform surface for flow , looks or to act like a forging process to strenghten the surface qualities.
2.decking. the removal of some amount of material off the flat surface of the head.It can be done several ways ,but generally on a steel head it is done in a blanchard grinder. On an alum head it is generally done on a special table like belt sander for small amounts of removal and a milling machine for greater amounts.When your head come back from a rebuilder and you see the lines going 1 way on the flat surface they have generally taken about .002-.004 off the surface.The more metal you remove the more you raise the compression .

Devildog2067

3 angle valve grind: grinding the edge of a valve at 3 different angles. It almost looks like it's faceted in an edge-on view.

emilysgranny

Ribs; some more.
1. cc ing. ; the art of metal removal from the head in the combustion area ( around the valves ).It's desired affect is to make the volume of 1 cyl equal to the volume of the other cyls.This is done to make the engine run smoother and takes some strain off the crank by virtue of eliminating the difference in power between cyls,ie the crank does'nt have to absorb the deflection difference from firing cyl to firing cyl.Kind of like when a bolt is loose then tightens then loose again , your muscles feel the diff and so does the crank.In high rpm cars its critical and can also affect the timing.

emilysgranny

Porting and polishing ; the art of removing enought metal in either the intake or exhaust manifolds or the head itself to increase the ability of the charge to flow easier or for a greater volume to flow through.It is most desirable to match the sizes at the mating surfaces. Generally it is done by hand with a small dremel hand grinder and is a tedious process.These surfaces do not have to be a high polish like chrome but enough to remove the roughtness out of them to notice a diff.The sizes you can make these ports and manifold tubes are dictated by the wall thickness.

emilysgranny

Knife edge as pertaining to the crankshaft ;Very simply means when you have a sharp edge on the oil hole it is referred to as a knife edge. This sharp edge can literally shave the bearing surface and thusly is not desirable. To remove that edge just stone it or polish it very carefully with very fine grit sand paper 600 grit until you can feel the edge is smooth.

Danno

Huh? I think that last procedure is more correctly known as de-burring. There are special tools used for that and it's a pretty typical procedure after any machining operation.

I always thought that knife-edging was cutting the counterweights into a beveled knife-like point. This reduces weight and less oil-splash when the counterweight swings into the oil in the bottom of the pan. Here's a photo of a crank that's been "knife edged":



Typically you can remove 10+ lbs from a 944 crank this way.

Turbo Indexing is the rotational relationship between the two sides of the turbo (turbine & compressor) with the center section:



In this photo, I've rotated my new Huntley Stg2 turbo to match my stock K26/6 before installation.

Cross-drilling a crank is discussed in this thread: <a href="http://forums.rennlist.com/scripts/rennforums/ultimatebb.cgi?ubb=get_topic&f=15&t=003359" target="_blank">cross drilling crank</a>

Here's a dictionary of general <a href="http://motorera.com/dictionary/car-dicb.htm" target="_blank">automotive terms</a>

951Gary

As I understand it, 3 & 5 angle grinding would be done to the valve seat (the hole in the head) rather than to the valves. The more angles/grinds there are, the closer the seat approximates a smooth radius. The smooth radius is most beneficial to flow when the valve is beginning to open and also near the end of closing. It's likely any good automotive shop would give you a 3 angle job, and a tuner shop is more likely to use a 5 angle job. A true radius seat would be nice for flow, but is likely to have too narrow a seating surface, which will erode the valve or seat. You can imagine then that there is a magic width for the center angle which makes contact with the valve. I think the width is often about 0.020" (0.5 mm)

BTW, porting and polishing is a real art. Hogging out intake ports to make them as big as possible is often the wrong thing to do. In fact, some motorcycle motors do better with material added to the intake ports... Tuners spend many hours tinkering with heads on a flow bench, checking the effect of a modification at valve openings for the cam they'll use. Given this learninc curve, you wouldn't want to take your 951 head to the world's best Chevy head porter, unless you're willing to pay him to learn a new head.

Gary

emilysgranny

Danno;I was merely trying to point out what in the machining world is known as a knife edge . Your post and picture were excellent as it pertains to a cranshaft, as was the following post on the art of porting and polishing.