IMG_1840B.jpg.pagespeed.ic.k6aqEryIsA.jpg' alt='How Does A Cylinder Head Crack Exhaust' title='How Does A Cylinder Head Crack Exhaust' />Cylinder Heads Part I Tech Articles. If factory big block Mopar heads cause confusion, its no wonder. Other than tidbits of information released more than 2. Chryslers Direct Connection factory tech bulletins, there has been almost no comprehensive information published on the selection and modification of these commonly used heads. Although several professional porting establishments will gladly provide modified factory heads, the techniques used and the resultant flow and performance gains are, as expected, closely guarded. As a result, the enthusiast must resort to dropping the dough and choosing level X, Y, or Z in a Pro ported head. Alternatively, those who seek to improve their big blocks performance can order a beginners porting kit, haul their factory castings to the basement, and make cast iron dust. Unfortunately for our would be home porter, without access to a flow bench to evaluate progress, or spe cific information on what works, the effort is a hit or miss proposition at best. At worst, the heads can show little or no gain, or flow less. Factory Castings. Since the 1. 96. 7 7. The year 1. 96. 7 was significant for Mopar big block heads with the introduction of the 9. The 9. 15 was a performance minded redesign of the big block head, featuring revised ports while retaining the closed chamber configuration typical factory chamber volume of 7. The 9. 15 casting was found only on the 4. In standard form, the 9. Read the tech article named, Cylinder Heads Part I, brought to you by the experts at Mopar Muscle Magazine. Unless the engine is supercharged, there is only 15 psi to push air into the engines cylinders, on the intake stroke. On the exhaust stroke, there is still was more. Mike Busch, founder and CEO of Savvy Aircraft Maintenance Management, Inc. National Aviation Maintenance Technician of the Year, discusses his thoughts and. The Complete Cylinder Head Guide for Chevy Small Block Engines How to Build Max Performance Chevy Small Blocks on a Budget. How Does A Cylinder Head Crack Exhaust Port' title='How Does A Cylinder Head Crack Exhaust Port' />The year 1. Magnum engine was introduced. In step with the performance requirements of the Magnum, the engines exhaust valve size was increased to 1. Over the years, confusion and mythology arose around the 9. Magnum head. This same head was also found on all 4. New Yorker to the bosss 4. Imperial. The only difference was the smaller exhaust valve in the non Magnum engines. A throat cut and the bigger exhaust valve evened the score. For 1. 96. 8, the big block cylinder head was modified again. The new 9. 06 head was identical in port configuration to the previous years 9. However, the 9. 06 was cast with open combustion chambers typical factory volume 8. Also, the smaller 1. The 1. 7. 4 inch exhaust valve now was used in all BRB heads. Despite the popular misconception that the 9. Magnum and the new for 1. Magnum, it was actually used across the board, with the same valve sizes in all big block engines for 1. From the 3. 83 two barrel to the 4. Magnum, the heads were unchanged. Some of this confusion can be attributed to Chryslers advertising of the day, in which the 3. Magnum was heralded as coming with the 4. Magnums free breathing cylinder heads. What the mavens on Madison Avenue werent telling was that the standard 4. V, and all passenger car big blocks had the same 9. Hi Po Magnums came with stiffer valve springs fitted. With the exception of some industrial, heavy truck, and motorhome application castings, this one head fits all philosophy was carried through the end of big block production in 1. While the 9. 06 and its open chamber configuration presented a small flow improvement over the previous years 9. Racers in the know have long coveted the 9. The racers value the heads because of the superior combustion characteristics associated with the closed chambers. The 9. 06, and all later heads that shared the same open chamber configuration, did have an advantage in one arealower emissions. The less intense burn and less effective scavenging resulted in reduced levels of nitrogen oxides NOx. Our 1992 Bluebird bus with its 6 cylinder diesel developed a head gasket leak. After installing Bar s Leaks Head Seal Blown Head Gasket Repair, the leak stopped. The 9. 06 casting was retained as the BRB head for 1. In 1. 97. 1, a new casting was introducedthe 3. B, and RB although some early 1. Although the 9. 15 of 1. Exhaust ports were essentially unchanged. Factory information on the 3. Direct Connection racing manuals, and carried over into todays Mopar Performance engine book, was limited to one line In 1. B engines, and has a casting number of 3. Other than printing the wrong year and casting number, it was clear that this was a smog head to be avoided. No supporting information was provided, but in the minds of Mopar enthu siasts, the written words have long been accepted as gospel. Interestingly, these same smog heads were the recommended heads for Grand National racing when the Wedge returned to NASCAR, and in modified form were used quite a bit by Richard Petty in his domination of the circuit in the early 1. The 3. 46 head was retained as the standard big block head through 1. From 1. 97. 4 to the end of big block production in 1. All these heads were minor variations on the 3. The intake port remained unchanged from the 1. The exhaust port was never significantly changed and remained true to the form introduced back in 1. To sum up, two intake port configurations were used beginning in 1. Windows Sybase Open Client Automatic Install. The first was the 9. The second intake port type was introduced in 1. This port had a substantially lowered roof and greatly reduced short side, with a Humber Hump configuration on the cylinder wall side floor. This port was carried through on the 9. On the exhaust side, the 9. As a result of the need to run unleaded fuel, retrofitting to the late 4. Interestingly, the 4. Mopar enthusiasts discovered the performance was on par to that of the esteemed 9. This regard did not return to the earlier 3. Stock Intake Port Flow. In an effort to provide useful information about the selection of production cylinder heads, we compiled examples of popular production cylinder castings that cover the period from the major redesign in 1. For our evaluation, we brought our heads to the flow lab of the renowned cylinder head flow researcher David Vizard. David, an aftermarket performance consultant, univer sity lecturer on performance engine theory, and the author of scores of comprehensive books on performance engine modifications, allowed us access to his flow lab during the seven months we compiled the information in this series of articles. His book, How to Build Modify Chev rolet Small Block V 8 Cylinder Heads, should be required reading for anyone who contemplates modifying cylinder heads for improved performance. Although, as the title suggests, the focus is on the enemys small block, Vizards theory of cylinder head modification and port flow dynamics is among the most comprehensive and universally appli cable work available. As advised by ancient philosophers, Know thy enemy, in battle, and in racing. The intake ports of the 9. OE valves, were flowed on Vizards Quadrant Scientific flowbench. The results are shown in Chart 1. The 9. 02 and 9. 75 were omitted because the intake port configurations were essentially the same as that of the 4. Although the 3. 46 and 4. As expected, the 3. Similarly, the 9. The 9. 06 showed a flow advantage between 0. By 0. 6. 00 inch lift, the 9. The bottom linefrom 0 to 0. From 0. 4. 00 to 0. Again, at higher lifts there was no considerable difference. If analyzed in terms of area below the flow curve, the difference between the castings narrows to 2. Making comparisons in terms of the absolute flow number on our stock Mopar big block heads versus other common domestic V 8 engines is found in Chart 2. It becomes clear that the larger displacement Chrysler engines are somewhat starved for intake airflow. Chrysler never envisioned the production big block head as the last word in performance.