I am trying to learn the terminology of the cam. I don't know how to select the proper cam for my project. For example, I've heard people say a cam with more exhaust lift is for low rpm application. Can anyone help me or guide me to a book that can explain the theory of cam operation, and its affect on engine performance. Thanks.
http://www.v8buick.com/showthread.php?s=&threadid=26217&highlight=cam+explanation I would ask some of the users here instead of trying to make a decision from such an article. There is also a head to head comparison on the dyno at www.trishieldperf.com. There are a lot of other considerations like whether the cam reduces your vacuum so much that it affects vacuum dependant power options like power brakes. Also as a practical matter, stop light to stop light, a less radical cam may whip the hi po cam plus have smoother driving characteristics. There is also the consideration of how many degrees, if any, the cam is installed advanced which affects where the max. power ban is versus rpm.
thanks Thanks for responding. I see a ton of info on cams, and I don't want to select the wrong one. When I look through the catalogs, I see numbers that I just don't understand.
Right place Chris. You have come to the right place to ask questions about Buick motors. Maybe Jim Weise will see this and help answer the questions. Or perhaps Jim Burek. Both Demi-Gods in the land of Buick Motors:TU: Just keep coming back and you will get the answer that you want.
Greg is right . Their broad experience with cams over many street and strip engines gives them special insight. I know JW has addressed this issue in the past. Suggest you search old posts under Weise and cam.
If you're interested in finding a cam for a specfic engine combo and application, then you may just want to ask which cam to use. I have asked both Jims about it, and they came to the same consensus basically....Both of them Told me to use a specific TA cam, and the other mentioned another brand, which I am also considering...it's just a matter of me pushing the button.
Re: Right place I really appreciate these responses. It is easy to find literature about Chevys but not the other GM engines. I'm assuming that they are different. If I can understand why I'm doing something, it makes everything else easier. Most of my posts are why questions because I don't trust the Chevy people; they have led me wrong before. I only have this site to turn to, but I apologize if I'm wrong about my assumptions. Again, Thank you:TU: .
Chris, It would really help if you told us what you expect out of the motor, and how you intend to use the car. Do you want a street car, race car, or street/strip car? If you simply call TA performance and tell them what kind of performance you are looking for, and what engine your car has, they can recommend a cam for you. What a performance cam does is lift the valve higher off it's seat(lift), and holds it open longer(duration), so that the motor can breathe effectively at higher RPM's where it can make more power. When you increase duration, you move the power band up the RPM scale. You gain top end power, and lose some at the bottom end. Once you select a cam, you need to make sure your torque converter, and rear gearing will work with it. A supplier like TA Performance can answer all of these questions. Good Luck.
Chris, to select a cam, we would reaaly need to know the parameters of what you are trying to accomplish. What compression are you looking at, what torque converter(if automatic trans is used), what rear end gears. What are you looking to do with this car. You don't need to make cam selection difficult, but it helps if we know what you are trying to do. Are you trying to build a nice 450 or so horse 455 on pump gas or are you building a 12to 1 engine looking for 550 to 600 horse or more? I have some real favorites for different applications and I know Jim W. has some as well. You can read info from some of the sites listed in this thread to learn about cams in general just for your own information. Jim Burek P.A..E ENTERPRISES
It's not all that difficult to choose the right cam. Here is a few of things you need to know: 1- Cylinder head flow- There are two things to consider here. The peak intake flow- this will help you decide what RPM range your motor will perform best. Generally, if you don't have good heads, a bigger cam (one with a lot of duration) is only going to hurt you. It will decrease the torque on the bottom end, and you still won't get much if any more horsepower on the top end. There are exceptions to this rule that cheat the heads somewhat with a long duration and low lift (by using high velocity to charge the cylinder). Poston sells a lot of cams like this. You pay for it with a rough idle though. Ratio of exhaust flow to intake flow: 80% is where you want to select a cam with the same duration @.050" for the exhaust and intake. Any time the ratio is worse, you will need more exhaust duration. Many unported or mildly ported iron heads can benefit from a split of up to 20 degrees, which is big. Some here will tell you 10 is enough in most cases. 2- Intended RPM range. The intake duration will determine where the peak horsepower occurs, and where the torque curve starts. This has a lot to do with what your heads will support. If you don't have the cylinder head flow to support the RPM range, you need to consider your options. Give up idle quality and run a bigger "cheater" type cam, or build a torque motor (low intake duration builds a lot of torque- and a nice and flat torque curve.) Big torque can make quick ET's with the right combination. If you're building a street motor that you don't want to turn a lot of RPM with, this might be the way to go. If you don't want to run a higher stall converter, you will need to use a cam with less intake duration. This will build torque on the low end (so the car isn't a slug off the line). The trade off is in mid and upper horsepower. This is where good heads are really of benefit. With good heads, you can use a smaller cam and make huge torque, and also good horsepower. 3- Static and dynamic compression ratio. If you are running a pump gas motor, it is generally agreed upon that you can run a static compression of 10-10.25:1 max (with iron heads- aluminum will allow slightly more- up to about 10.8:1). What is less talked about is the dynamic compression ratio which is dependant on intake valve advertised duration, the static compression ratio, and the intake lobe center. If you go HERE you will find a good calculator for figuring out the dynamic compression ratio, along with a good article explaining what it is all about. Using the calculator, you will find that you need about a 7.5:1 dynamic compression ratio for pump gas. Many of the motor combinations on here that are proven to run on pump gas come out to that number when using the calculator, so it is proven to work. Put the simplest way, given a static compression ratio, you need to manipulate the cam advertised intake duration and intake lobe center to come to the correct dynamic compression ratio and RPM range. Here Is another article on valve timing events that explains some of this. Here is another one on matching the cam to the headflow.
Re: Re: how to select a cam for buick engines I'm trying to get high to low 13s. I can use a 1969 430 or a 1972 455. I don't know how many horses that will require. I have a long tail 400 transmission with a 2200 stall. My rear-end needs attention, and I don't know where the start. I would like this to be a daily car but if it is not possible, I'll have to live with a weekend warrior. I tried to use a budget, but Ive spent $1000 on this and have not wnet into the engine. Any help would be greatly appreciated.
I would think that you could be at low 13's with a stock BBB motor. At the most, add some headers, and make sure it's in a good state of tune and that everything is right. A Poston GS-118 might work well. I had one in a 400 motor, and it seemed to turn on at 2500, so you might be close with that stall. Maybe something a little smaller would be more appropriate though. I would do a gasket match on the heads and make sure they have a decent valve job, port match the intake to the heads, and run a small cam and headers. You might be surprised... I would use the 430- better compression and heads.
For comparison's sake, my buddy has a 68 GS 400 convertible with a 76 455 with 70 cast pistons. He has 68 430 heads that he cleaned up converted to Stage 1. The intake is a Edelbock performer. He has KB pulse headers and a TA 212 cam. The rear is a 3.90 posi from a 69 Stage 1 car. Tranny is a rebuilt Olds TH-400 short tail with a 3000 stall converter. His best ET was 12.70 and it consitantly ran 12.7's. He probably could have chosen a different cam and gotton better results. He also has this cam in his 69 Sportwagon 400 with 3.42 gears and a basicly stock 400 (only a performer intake). Tranny is a 67 SP-400 with a 4000 high stall- 1800 low. That car ran a 14.5. Bear in mind that this car weighs 4500 lbs with no one in it with a 1/4 tank of gas. The TA 212 is a very streetable cam and as you can see made a reletively heavy car (68 covert) go pretty quick. I got one for my 70 455 that will wind up in my 71 Skylark. We'll see how this cam responds to a similar setup to the convert but with 3.42 gears.
Eeny meeny miny mo, catch a camshaft by the lobe, if it's choppy it will run, go hit the streets and have some fun! LOL! Jim Burek P.A.E. ENTERPRISES
