They have 500-hp capability but work out best if cammed to give about 480 hp. With a singlepattern flat-tappet Comp Cams cam 276-3 profile on a 108-lobe centerline angle 430 hp and 440 ft-lbs is on from a street-driving 10. In a nice well geared car with at least a 2000 rpm stall converter on the automatics you can run up to a 224 duration. Even 1 or 2 thousandths. While on the subject, I will tell you what to avoid and what to use if your build involved factory heads. 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.
There turns out to be several changes to this head that deserve investigation before blindly diving into the small-block Vortec head game. There are good ones and there are bad ones, some are just better choices than others. Iron Maidens We can classify iron production heads with several different categories, but the simplest is by combustion chamber volume. If more compression, say 12. Do not grind away too much metal in this area. But it can be done. Correcting Excessive Guide Clearance If seats need reconditioning, consider the method of acquiring the desired valve-stem-to-guide clearance.
Keeping the flow more active on this side of the guide is instrumental toward good swirl. Again, the Vortec heads do require slight modifications should you choose to run a set of 1. To look at the Vortec head, it appears to be just another iron production head. Also the larger cylinder bore eliminates some the valve shrouding that is a problem for 305 engines. Air flow facts on 305 heads. Although the crankshaft looks like it is a solid, unmovable hunk of steel, if not properly stored in a upright position, it will bend. Written by Chris Petris and Posted with Permission of CarTechBooks.
These offsets are available in 0. If wear dictates going to the 2. The stock springs are somewhat weak and with the retainer-to-seal limitation, any more cam than 0. Consider that the top portion of the spring travels the most distance during valve lift. The Vortec heads also do not use a guideplate to position the stamped rockers over the valve as is done in traditional small-block heads.
The heads are a 40-lb weight saver, but these heads are completely underwhelming as a street performance candidate. Edelbrock to match the casting to the intake. Stick with conservative durations, especially if you use a automatic transmission, anything over 224 degrees duration at. In this instance, the test engine was a 383 with a hydraulic roller valve train. Certainly with a small cam, this would contribute to detonation problems even with 93-octane fuel, especially on hot days. You're better off going with aftermarket heads aluminum that will work with your existing intake base's bolt pattern.
All this results in the same top end as the smaller valve and longer cam, but with a smoother idle, more torque in the low speed range—and better mileage! Any of these plus a steady hand can be used to do 90 percent of the work on the heads. Most camshaft manufactures will have recommendations of what you can do and what you may have to do to get the proper combination. The 305 heads have a smaller combustion chamber 60. Overall, the conical springs end up being only slightly more expensive than removing the heads, having a machine shop modify them for bigger springs, and also installing new seals. Final Drive Ratio Stock ratio, 3:50 or less Stock or slightly modified up to 3:73 Gears from 3:50 to 3:73 Gears from 3:73 to 4:50 Gears from 4:50 or higher Induction stock stock needs mods to fuel pressure or injectors, slightly modified intake Needs mods to intake, throttle body, injectors and fuel pressure Major mods needed Valve Spring Pressures Seat press-90lbs, open press-250lbs Seat press-100 lbs, open press-260lbs Seat press-110lbs, open press-280 lbs Seat press-120lbs, open press-300 lbs Seat press-125 lbs, open press-325 lbs For those using a 1987 and later small block, there are choices ranging from stock to high performance. Pit Stop - April 2013 Wendell T.
With a special grinder wheel and some patience you cam eliminate this to get rid of the ridge that will improve air flow. Engine Tech also supplies valves that not only have oversized stems, but also heads typically 0. In as-cast form, they used to be the hot ticket for an easy bolt-together build that produced good results, but many later designs have overtaken them. Fig 6-16 shows the results. In addition, the chamber size comes in around 58-cc, which means a flat top 355 smallblock with a near-zero deck and a 0. This is good for reducing and again freed up horsepower. The easiest way to reference any production head is with the last three digits of its casting number.
Because it is so easy to achieve professional-looking results, you may want to re-work all the ports. . At this point, the heads and everything going into them should be thoroughly cleaned. The second tool lowers the height of the guide while also reducing the top of the guide dia-meter from 0. This makes the real estate in between the rocker arms somewhat restricted, which means that typical budget aluminum roller rockers generally will not clear a Vortec head valve cover. The combination of the larger intake valve and a good three-angle aftermarket valve job produced some decent flow numbers. By lowering the guide height, this increases the retainer-to-seal clearance, allowing more valve lift.