I read the following article in one of my magazines, which was talking about an engine build they had just completed, and thought I would share it with others;
CAMQUEST 6 ASKS, “CAN WE DO BETTER?”
Our 540-cid Chevy big-block Mark V engine was a standout performer. It did everything we asked it to do. But did we optimize the performance? Did we get everything we could from the combination? Knowing that we were up for anything the learning curve might throw our way, we decided to test our camshaft knowledge against the newest programming available from COMP Cams-the CamQuest 6 Cam Selection Software.
As touted in the materials, the CamQuest 6 is a PC-based camshaft selection program that allows the user to find the right camshaft by answering a few application-specific questions from the program’s drop-down menus. Sounds simple enough, so we took the program for a testdrive.
First, we input the parameters required by the program, such as engine type, compression, carburetion, cylinder head type, etc. The program offers up an amazing number of possibilities. For our Mark V big-block engine, the program was easy to understand and required little intuitive thinking on our part to fill in the grids accordingly. Our only “gray” area occurred with regard to the flow figures of our ported RHS Pro Action 360cc cylinder heads. Having the exact measurements here would give us more accurate information in terms of the total calculation, but we were comfortable in running the simulation with the data we had in hand. The CamQuest 6 calculated the data and kicked out a number of good, better, and best camshaft choices. Interestingly enough, our model RA306-10 (0.680-inch lift and 306/319-degrees of duration, 110-degree lobe centers), the one that generated 649hp on the Westech dyno, was not the top CamQuest 6 selection. So what did CamQuest 6 recommend? Camshaft grind number RA296ER-8 with less duration and more lift on 108-degree lobe centers.
To determine how much better the smaller-duration camshaft would be, we did two virtual installs using CamQuest 6. As it was the top pick, the program used grind RA296ER-8 and displayed the results, along with all of the recommended ancillary COMP Cam parts like lifters, retainers, springs, locks, and other parts that should be used to achieve the optimum performance. Grind RA296ER-8 (the top CamQuest 6 camshaft selection) features 108-degree lobe centers, with only 296-degree intake duration (304-degree exhaust). Lift was increased to 0.714 inches. Our new estimated horsepower-nearly 689hp. Torque-655. So why the 30hp difference? We decided to investigate.
According to Westech’s Steve Brule, the camshaft chosen for the dyno test featured a large amount of duration-too much for the application due to the engine’s limited compression. With a pump gas compatible engine such as this, the increased duration actually allows cylinder pressure to be reduced, slightly lowering peak power.
“This type of engine (540-cid Mark V) can handle a lot of lift, but too much duration is a detriment,” says Brule. “The excessive duration, however slight, actually bleeds off intake charge. It negatively affects the volumetric efficiency and increases the exhaust gas temperatures. But the higher lift is not a problem; in fact, it gets the valve moving slightly quicker, helping fill the cylinder more fully, making more power. Al long as you don’t have valve to piston problems, lift is only a positive thing.”
The camshaft selection process has long been a black art by both pro and novice engine builders, leaving lots of room for interpretation. How do you know you have purchased exactly the right camshaft for your engine? In the past there has been only one way-to trust in the expertise of those who are believed to be experts. Today, real experts are easy to find, such as those answering the phone at the COMP Cams Cam Help hotline. Unfortunately, many builders don’t make the call and rely on their friends and pseudo experts to advise them. With the engine building requiring not only cubic inches, but all cubic dollars to build bug power, it’s safe to believe there are now two very reliable sources for camshaft advice-Cam Help and CamQuest 6.
By Cam Benty Custom Classic Trucks September 2006
Selecting the proper camshaft is definitely a black art for me and if this can help, great. If not, then it is interesting.
Ron
Camshaft Selection
Linear Mode
