Re: [Chevelle-List] Cam

[Keith Cooper]

If this is a daily driver and will not be used for racing, I think that you have over camed the car. This does not mean that it will not run, but you might not like it. I believe you could step down 2 cam sizes myself. This looks like it might be a Comp. Cam is it?  Let's assume that this is a daily driver or show car only, you need to get a cam that is designed for 2000-5500 RPM range. This would mean that you need to look at something around 220 duration at .050 with about 515 lift. Let me give you an example. I had a cam that was 210/216 @.050 with .499/515 lift (1.5 Rocker) on 108 c/l for a small block 350.  I now have a cam that is 204/204 @.050 with 484/484 lift on 110 C/l. The car has the stock rear end which when I checked it is 2.50. I do not think that they had a 2.5 rear end on a 1971 Chevelle/Malibu so it is most likely a 2.73 rear end (Highway gear) The first cam run good but was very slow on take off and lost power between 35-45 MPH. It sounded really good on the 108 C/L and still had good vacuum. The second cam had good power at takeoff and all the way through the RPMs. It just burns the tire ups when you nail it. The first cam would not spin the tire too much. The reason the second cam worked better is the car has the small rear end ratio. I also had an Edelbrock performance intake which is designed for the lower RPM range. The first cam was in a .040 over motor and the second cam is in a stock motor. If it is too late to change camshafts, you can try this. When they do the head work, ask them to make sure the you will have clearance if you decide to change to 1.6 rockers later. By putting in 1.6 rocker, you will drop both your duration and lift down. This will move your power range down lower. If it was me I would look at a cam that was around 216-228 range with about 510-530 lift with 110-114 C/l Something else I do not understand, what do you mean waiting to hear from them before ordering the correct lifters. If this is a roller cam then their is only one type of lifter you want, Hyd. roller lifters. If this is a Hyd Flat tappet cam then you want standard Hyd lifter. I would not get into using anti-pump, or any of the other weird hyd. lifters on the market. Stick to the basic.  If you are now confused or you are worried about my advise, call Crane or Comp Cams and talk to someone on the tech line. You will know after 5 minutes on the phone, what your cam selection should be. I live in Daytona where Crane is, I will call them if you want me to.  Another thing that I am concerned about is that the head work must be compatible with the camshaft. The springs must work correctly with the lift of the cam. Most head shop want to know what cam is being installed. You must check for coil bind on the springs. You must check Rocker to Spring binding for the camshaft you are using. The spring pressure for the cam lift must be know or you will be putting too much pressure on the nose of the camshaft. You also need to check for pushrod binding. All these are related to the camshaft being used. Some facts about camshafts. Duration at .050 will tell you where the power range will be. Lower duration will usually have lower pulling ranges. Lift tells you how much air and gas you will have, which gives you more power. C/L will tell idle features. Also c/l will effect the power range. Tighter centerlines will pull more at lower RPM and idle rougher. Tighter C/L (106 versus 110) will also run hotter. C/L will also effect valve overlap(the amount of time when both valves are open). If you know the duration at special which is usually around .004-.010 subtract that value from .050. This is call the Hyd intensity. The lower the number the better performance. For mild street performance, lower duration values at .050 are better. Crane cam usually have a lower Hyd. intensity value over Comp. Cams. The cam spec. are directly related to the rear end ratio and must work together. Keith C. Cooper   Sent: Thursday, May 02, 2002 9:39 AM Subject: Re: [Chevelle-List] Cam Thanks Keith     The engine is a 396 bored .40, it has a steel crank from a 427, and forged pistons.  He is ordering Roller Rockers, they said something like 1.7. The heads are still being worked at the machine shop.  He is waitng to hear from them before ordering the correct lifters etc.  I'm told that my rear is a posi 4:10,  If so I want to replace it with a 3.55 so that I can take it out of town. The car is a 4 speed.  Right now the car came with P295 50 R15's on the rear.  There to big so I'd like to sell them ( hate to because they're new) and so with something not as wide, maybe a P235 60 R15 on rear with a 70 series on front. This is all that I'm sure of.  I have headers and flowmasters installed.    Craig ----- Original Message ----- From: Keith Cooper To: [EMAIL PROTECTED] Sent: Thursday, May 02, 2002 9:04 AM Subject: Re: [Chevelle-List] Cam What is important when ordering a camshaft is the other components in the engine. What other changes have you made to the engine and the block and heads.  This is not a small camshaft. It is made for 9.5-11.00 compression ratio. RPM range will be about over 3000 to around 5500. This is a good mid range cam. If the other engine component and the rear ratio is not right, the cam will be slow on take off. When ordering a camshaft, BIGGER is not better. This is what some people call a Bracket Racing cam. You may need a stall converter. Before it is too late, Let me know your RPM at 60 (if you know). If the block has been bored  and to want. Your rear end ratio, Your rear tire size. If your running a stall converter. Your rocker arm ratio. Crank information. head information etc. What do you want to do with this car, city driving, racing etc. If you have a basically stock motor, this cam will be toooooo big. You will not like it. Keith C. Cooper ----- Original Message ----- From: Craig & Cerena Robertson To: [EMAIL PROTECTED] Sent: Thursday, May 02, 2002 8:21 AM Subject: [Chevelle-List] Cam      Just had the guy rebuilding my engine to order the cam for it.  I'm glad he always ask me if the part his is going to order is ok, but hell I know nothing about engines.  It's like asking me to read Chinese.  The one I picked for my Big Block is as follows:   Duration 050 IN        224 Duration 050 EX.      232 Lift IN                      527 Lift EX                     553 Lobe Center             114   Says:  Lopey idle, Wild Street/Strip     I'm looking for something that sounds good, but I don't want something that I can hear myself think when riding in the car.  Can anyone tell me what I just ordered.  Thanks   Craig