The medium-blue curves are for ports that are to a basic full porting job. Normally, you will use three or maybe four 80-grit emery rolls per cylinder. Brad, I wish you could feel my truck to get a good comparison. Cylinder Head Detailing and Assembly What we are discussing here is relevant to any pair of heads that you may have stripped and modified, be they factory or aftermarket. The stock seat geometry is, like the rest of this heads design, very effective. Note the large short side turn on the exhaust. This works well if you are building a 350 or a 383 that really must be a nice street driver.
With a hydraulic roller cammed 383, this goes up to 470 ft-lbs and 470 hp. This also applies to our new-generation precision-cast heads. The first of these is the aluminum L98 Corvette head casting, produced between about 1986 and 1993. The light blue curves are the result of installing 2. Once all the cutting and grinding is done, the finishing touches can be applied using an emery roll.
If you must have armored seats, you should consider using an aftermarket head because these heads have them out of the box. Typical results can be seen in Fig 6-15. Apart from the basic de-shrouding of the intake and exhaust by sweeping out the chamber around the valve, the 186-style casting also benefits from some chamber reshaping. If anyone on here has a spare one they are interested in selling off for destructive testing purposes. When I first got into Ford modular porting I took a stock plastic intake and cut it up to allow a single runner to mount without the plenum or anything else. Depending on the position of the seats, the coming together of the head face and seat usually occurs, on stock heads, when 0. Angle milling is our alternative to conventional flat milling.
See Fig 6-10 for the results. After a very labor-intensive build, I produced a class-legal 368 hp. These are easy to identify due to their tall, narrow shape and somewhat radiused top profile. They have produced good results in out-of-the-box form and responded well to basic porting. This situation represents geometric shrouding and assumes that the air flows evenly around the valve. What they really want is something that produces results good enough to get excited about.
We have moved on, and I will deal only minimally with factory-produced heads. It is a combination that would suit naturally aspirated or forced-induction applications; however, the stronger alloy, thicker deck surface, and better clamping capabilities make them best suited for boost or juice. Ideally, the valve-stem-to-guide clearances need to be about 0. Since their introduction in 2006, these heads have been showing championship winning form on many circle tracks. Canfield, Edelbrock, and Dart have all, during my dyno testing, proven to be very strong performers when used with an appropriate combination of compression, cam, valve train, and induction.
Because, it was already bad an extra unwanted imperfection made little difference to overall flow. Be prepared for a lengthy haul even with a carbide. This illustration shows the key elements toward finding exhaust flow and with usually little machine shop expense. The stock head dotted curves are blue for intake and red for exhaust. Each style has its own dedicated valvecovers and coilpacks mounting apparatus. Now guys are running more cam with my same set up and less worry about kissing a valve. You can be sure that some big parts house will have one or another of these heads on sale during any 12-month period.
With the highly constrictive rules, the front-running competitors were, according to the chief Tech man, finding about 335 hp max. From my dyno testing experience with these heads in both the 180- and 200-cc versions, I have concluded they have what it takes in terms of swirl, combustion efficiency, and wet-flow characteristics. However, for novices, a point of concern is blending the ports and chambers into the valve seat areas. Volumes around the 60-cc mark are fine for a sane low-buck street 350 with flattop pistons in flush to the top of the block. The circle around the valves shows the room needed for it to be free of shrouding.
For example, the first X will be a Letter from A through L. What do you think that would do to the flow? A little engine degreaser and a wire brush often makes this job easier. This applies until the valve reaches one quarter of its diameter in lift 0. This along with milling of the deck surface will allow a slightly higher compression ratio to be achieved. The only way to see a significant increase from the intake in the 0- to 0. The point that must be kept in mind is that at mid- and high-lift the flow exiting the cylinder is from the center on out. Doing so should net about 170 cfm at 0.
Mike also owns and operates Birchwood Automotive in Creston, Ohio, where he builds custom engines, street rods and performs vehicle restorations. These push the heads farther up the block face and give better manifold alignment later during assembly. The company is known for extensive flow and dyno testing of all its heads as well as affordability. As far as aftermarket heads are concerned, there are several brands of iron heads that work well out of the box and port up very easily to deliver very professional results even when done by a novice. Keeping stock displacement and changing from 243 heads to L92 heads drops the static compression ratio from 10. Pay attention when interchanging heads and blocks to check for potential valve-to-bore interference.