[TurboRay]

For those who don't already know, Tim Ottinger is a professional cylinder-head porter with many years of experience modifying/porting a wide variety of different cyl heads. Fortunately for us, Tim has kindly offered to donate his time and expertise in order to help us correctly modify "our" heads for improved performance. Kudos to Tim for taking time from his busy schedule to do this!!        :thumbup:       

I have volunteered to be Tim's "posting liaison".....meaning that he will be sending me step-by-step pictures and captions to guide us in understanding and implementing the techniques necessary for proper modification - and I will post 'em in this thread. My only function will be to resize Tim's pics (if necessary) and to add HIS caption/narrative to each. I may do some very minor editing - but only for spelling, grammar or clarity.....I will NOT change the meaning in any way.

The completed thread will eventually be placed in the FAQ section by Paul......so, it is NOT intended to be the usual question-and-answer type of thread. Otherwise, it would become too cluttered and lose focus. Therefore, please DO NOT post any questions or comments (a reminder will be posted in red at the end of each segment). Paul &/or the mods will be monitoring and WILL edit/delete any frivolous or distracting posts/comments.

If you DO feel the urge or necessity to add a helpful comment or ask a pertinent question that will benefit the discussion, there will be a companion thread in which to do that. As the thread evolves, it may be periodically edited with additional/helpful comments from Tim or possibly even from y'all. Either or both of these threads MAY be stickied at the top of General Tech, depending on Paul's preference to do so.

Let's get started!

     

BASIC TOOLS (from top to bottom)

1. An old valve with the head cut off. This is placed in the guide to measure from and needs a stop to keep it from falling thru. An o-ring works, but we just weld a spot on it. If you can make 4, it keeps you from having to move 1 from port to port.
   
2. Carbide burrs. If I had to limit myself to the absolute minimum, I'd have these two: A 3/8" oval and 1/2" oval. They usually come in shank lengths of 2" or 6". We get the 6" and cut them down to 4" on the 1/2' oval.....and 4-1/2" to 5" on the smaller 3/8 oval. The reason for dong this is because the longer the shank, the greater the deflection - which makes the bit harder to control. Cutting it down helps a ton.
   
3. Calipers - dial or digital doesn't matter.
   
4. (Inside) dividers. As an alternative, you can also make metal or plastic templates (look like upside down "T") for each measurement - which are very handy, especially if you're doing different types of heads, or different valve sizes in the same type of head.
   
5. Safety glasses (not shown) are a MUST!
   
6. A brush (not shown) to clean out the guides (gun cleaning brush).
   

■ Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

(2nd Installment)

1st Cut - Set divider to .450" and, using 3/8 oval, grind till divider just fits. Without the divider, your intake port should look like the "alternate view". Notice that we don't grind the area just under the valve seat. That's a different dimension and we will get to that later. Duplicate this cut in all 4 intake ports.
     

Alternate view:
     


2nd Cut - Set your divider to .500" and - still using the 3/8" burr - grind till the divider just fits. Without the divider or v/stem, your port should look like the "alternate view". Again, do NOT cut up just under the valve seat. Duplicate this on all 4 intake ports.
     

Alternate View:
     


3rd Cut - Divider still at .500", continue grinding the other side of the bowl till the divider fits. Without divider or v/stem, your port should look like the alternate view. Duplicate in the intake ports. 

Alternate View:
     


Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

(3rd installment)

4th Cut - Now that we're warmed up, switch to the 1/2" oval, and let's get some meat out! Work the right side of the guide boss down. Leave a little material (as in the pic), as we will clean it up later. Do this on all 4 intake ports before proceeding to the next step.
   



<font color=navy>5th Cut</font> - Work down the left side of the guide boss, still using 1/2" oval. You ARE doing each step on all 4 ports, aren't you??
   



6th cut -  Switch back to 3/8" oval  and trim the right/back side of the guide boss. DO NOT grind up into area previously ground in step 3! This is important if you don't want to hit water.
   



7th cut - Trim the left side of the guide boss. Be cautious here, and don't try to cut it as deep as the right side. There is DEFINITELY water here.
   



8th cut - Switch back to the 1/2" oval and grind the left side (from here on referred to as "inside") bowl to .600". Again, don't grind back in the area done in previous step and don't cut upward into the area under the valve seat.
   



9th cut - Work the right side of the bowl (from here on referred to as "outside") to .680". AGAIN - don't grind into areas previously done. It will be looking pretty haggard right now, but that's OK! We're setting dimensions right now, then we'll doll it up shortly. There's a method to the madness.....
   

 

Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

(4th installment)

10th cut - Still using the 1/2" oval, and VERY CAREFULLY, grind the area just under the seat to .600". This is referred to as the "throat" and is the minimum area under the seat that forms the venturi. This dimension is critical, so again, be careful!
     


Detail - The black lines show what was ground in the last step (above). Notice as we go counter clockwise around the throat, the cut fades as we approach the short turn. We'll get there when we flip the head to work the short turn. Continue around clockwise till the entire throat is at .600 (with exception of the short turn, of course)
     


Steps 12 & 13 - Now to clean this mess up! Still with the 1/2" oval burr, BLEND everything out, leaving a .080" or so flat spot at the throat. There will be a step/ledge at the top and bottom of the throat, but that will be taken care of during the sanding. Should be looking pretty sporty now...
     

     



Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

(5th installment)

Step 14 - While we still have 1/2" oval, cut the leading edge of guide boss as shown.
   



Step 15 - Switch to 3/8 oval to do the finish trimming.
   



Step 16; The dreaded short turn - For the first cut, set dividers to .600 (remember the throat dimension?). You CAN do this cut with 3/8" oval, but the smaller bit can cut "ditches" if you're not used to it. The 1/2" oval will cut smoother, but removes more material, so go SLOW and cut a flat just under seat area. Do NOT try to blend it into short turn! That comes later.
   

Your port should look like this. Do ALL 4 ports before going on to the next step.
   



Step 17; Short-turn gauge/template - Before going any further, we have to make a gage or "template" for the short turn. We'll need a protractor and a piece of plastic or thin sheet metal. Set the protractor at 22° from vertical (68° on the protractor), as shown below.
   

Now, make a template as shown at the top (short-turn gauge). Alternately, you can use an adjustable "angle finder" as shown below the gauge.    



Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

(6th installment)


Step 18; Short-turn bowl - Notice there's a "peak" that the gauge is resting on.
     

Step 19; Short-turn bowl (cont'd) - Grind the peak FLAT till the gauge fits as shown below - BUT, see step 20 first.
     

Step 20; Short-turn bowl (cont'd) - Leave .060"-.080" of "throat" dimension as shown by the black "Sharpie" line below. Take your time, and get this as flat as possible on all 4 ports.
     


Reminder: Please do NOT post comments or questions in this thread! 

[TurboRay]

(7th installment)


Step 21A; Shaping the "Turn" - Now we're going to start shaping the short turn, beginning with widening. Start with the right corner and widen all 4, as shown below.
   



Step 21B; Port #1 - On this port, we add a little more depth on the right - as shown below - to "tilt" the floor and "bias" flow because of the turn in that port.
   



Step 22A - Now move to the left corner of the ports and widen 'em all (as depicted below) the same as we did in the 1st step - BUT, cut the tilt/bias to #4, instead of #1.
   



Step 22B; Port #4 - As stated above, the tilt/bias needs to be cut in the opposite direction as #1.....i.e., on the left corner instead of the right (cuz it turns in the opposite direction!). [• Ray's note: At this point, Tim apologizes for neglecting to take a pic of this "opposite" tilt/bias for #4 (which would've been depicted below) - but, I think we can easily "visualize" what he neglected to photograph by looking at the pic of port #1 (step 21B, above) and imagine the "bias" on the opposite/left side  <thumbup>  ].



Step 23; Detail - At this point ports 2&3 should look as depicted below. 1&4 will be similar, but - when you stand back and look at them - the tilt/bias of #1 will be lower on right, whereas the tilt/bias of #4 port will be lower on left.
   



Steps 24A - Now we're going to radius the "peak" of all the short turns as depicted below, leaving 22° flat (black lines). Again, ports 2&3 are the same.
   



Step 24B; "End Ports" - Note that the short turn of #1 (as depicted below) is tilted/biased to the right, whereas #4 (no pic    ) should be tilted/biased the same amount.....but to the left.
   



■ At this point, we've completed what is known as an intake-"bowl port", which - after sanding - should flow in the 180-190cfm range.



Reminder: Please do NOT post comments or questions in this thread!  

[TurboRay]

BUMP!