Colvin, published by Bentley Publishers. Valves Understanding that the seats in the head are important is only half the battle. This contributes greatly to delayed separation of the exhaust flow from the port floor under real-world running conditions. Polishing the chamber to a relatively fine finish is a good idea. If you follow the porting rules given in this chapter, you can expect results as per Fig 6-13. Another factor to consider is that the guide and valve stem take up room in the port and effectively cut the flow area.
This machined flat area has serial numbers stamped into it. Services are subject to user terms and limitations. L31 Vortec, truck, 64cc chambers, 1. Services are subject to User Terms and limitations. With a flat top in a 350 this would give about 12. Ported they will go about 25 more horses than this. As for output, a set of heads like this can deliver the airflow required for 540 hp for a flat-tappet 12:1 engine and as much as 585 hp for a roller-cam-equipped engine.
Angle milling raises the question as to whether we can do this operation without re-drilling or re-spot facing the bolt holes to bring them back true to the head face. Bowtie, siamesed, straight nodular iron main caps, 2-piece seal, 4. In some cases where a bigger cam is used, the spring bases may need to be machined deeper one more money absorbing op. Surfaces were finished with 100-grit rolls. The finished result was 315 cfm for the intake and 223 cfm for the exhaust at 0. Don't forget to bookmark this page or add it to favorites.
This interference must be remedied or correct torqueing of the head bolts will not be achieved. In this instance, any differences in output would be due solely to the hopefully better wet flow characteristics of the Platinum heads over the originals. Spend a weekend porting them, and you will like the results. The last three numbers of the block casting number may also be repeated in this location. Just pay attention to the short-side turn and cut the rest of the port as per Fig 6-7 and all should work as intended. Also mask the areas that need to stay as bare metal. Installation or use of this part on a vehicle operated on public streets or highways is likely to violate U.
Because of the effort to save weight, these heads are not as tough as their Bowtie brethren or any of the aftermarket heads. If you are using factory production-line heads and you do not, or cannot, spend a lot of time porting them, the good news is that there is an option. Small block casting date is located on driver side rear of block on flange forward of bellhousing. Just apply what was discussed earlier in this chapter. Look at all of the features on the heads to help determine which casting you have and when it was made.
The way to do both pocket and the more advanced porting is detailed later. Keeping the flow more active on this side of the guide is instrumental toward good swirl. The exhaust is a different matter. Going the big valve route though is not without its problems as doing so increases the valve shrouding. Aluminum, 58cc, angle plug 14102187.
This comprises a head plate and a tall graduated beaker. Next, blow off the water with an air line. . Look for the identification number on the engine block. Also noteworthy is that I have seen very good results on a 350 equipped with an Edelbrock Air Gap Performer intake.
Once these heads have been overhauled porting is relatively straightforward in the initial stages and produces good results. Each spring station will require shimming to give the correct installed height. Crate motor for years indicated. In this instance, the test engine was a 383 with a hydraulic roller valve train. The final valve seat width needs to be just a little more than that used in the head. The shops that are surviving this contraction are those willing to do work at a reasonable cost for folks like us who want to go as fast as our slim budgets will allow. After all the porting and machining has been done the heads can be readied for assembly.
Worn guided can be fixed with oversize stem valves or the installation of new press-in guides. The longest job is carving out the excess material that resides in the bowls and around the base of the intake valve guide bosses. Both sets were used on relatively low compression 9:1 truck motors with short cams around 260 degrees advertised , and both sets made better than 430 ft-lbs on a 350. On the flat part of the Distributor Deck you will find a stamped Serial Number. Note the intake curves of each of these heads, in stock form, are very similar. The trailing letters denote what the engine was installed in. The exhaust valve seat, for these early cast-iron factory heads, should be cut according to Fig 6-7.