Cams

[tsr1933]

I am new to this site and have a question I'm sure y'all can answer!!! I'm having a cam put in my 318 and I was wordering if I'm gonna feel a big differance when I get it back? I told them I wanted the best cam they could get because it does not seem to have the power I think it should have

[451Mopar]

Camshafts are one of the more difficult subjects because it is part engine building and part tuning.

The Tuning part is selecting the correct cam for your application and that works with the rest of the engine and chassis combination.

Selecting the wrong cam could make the vehicle run bad, or even dammage the engine.

Assuming you carefully choose the correct cam, then you have to install it, and make sure all the valve train parts work with it. This is the Engine building part, of degreeing in the cam, checking valve spring pressures, valve spring coil bind, piston to valve clearance, pushrod length, lifter pre-load, and other measurements that should be cheched when the cam is installed.

Will you feel the results? It all depends on the difference in the cam size and if it was installed correctly, but even though it may be the correct cam and installed correctly, it will not correct other problems if they already existed in the ignition, fuel systen, exhaust, etc.. It is probbable you will have to re-tune the engine to get the full benifit of the new cam.

[dirty dan]

Sounds like good advice to me.

[tsr1933]

Well, let me give you a little more to go on!!! I'm having the dealership put it in! A friend of mine works as the service shop manager and put one in his dakota and he says it runs like a bat out of hell!!! I'm just not sure because its only a 318 and I didn't want to spend the money if I'm not going to see a big differance!!!! I'm sure they will hook it up right !!!!! Tanks for the input !!!! I have a 2nd gen k&n system and flowmaster exhaust. He said I will need to get a new computer and headers soon!!! Any ideas on some headers (not to expensive tho!!!!) and a new computer?

Thanks

[rumblefish360]

I don't know what you think a big diff is in power. The 318 doe's fairly well in the trucks. The big problem is weight. The truck is very heavy. A cam should be part of the intire build up. No just a part to be bolted in and expected to whoop up a seat of the pants feel.
Alot depends on the cam installed. Also, the new computer is a good thing to take advantage of the new cam. Headers help alot to. Save your money for a Supercharger. There are kits for the truck. It can add 40% more power to your ride. And yes, You will feel that!

[451Mopar]

You sort of confused my by calling the 5.2L a 318. I know it's the same, but most people who refer to the 318 have the older carburated engines, while most of the people with the fuel injected Magnim engines usually refer to them using the Metric size of 5.2L.

As I mentioned before, if the engine was running correctly (no problems) the effect of the cam depends on the difference between the sizes. A larger cam (dratation and lift) makes power in two ways. The higher valve lift allows the heads to flow more air/fuel into the chamber so the higher lift should help power at all RPMs. It is possable to have too much lift, but with the possable selection of cams that would work in your application it should not be a problem. Duration greatly affects where the power band IS. A larger duration will tend to move the torque curve up to a higher RPM, and this will make more power, but you may reduce the low RPM torque the engine originally had.
Theres more to it than that, but that is the basic idea.
Your friend may have a cam that has quicker ramp rates that may be only slightly larger in duration, but because it opens quickly (and likely has more valve lift also) you get alot more airflow "area" under the new cams lobe profile, but only moves the torque curve up the power band a small amount so you end up maintaining the low end torque.

Anyhow, Headers and a free flowing exhaust will really help. Increasing the exhaust efficency is usually one of the first modifications to get more power and gas mialage. I don't know too much about headers for these trucks, but usually the more expensive ones are worth the money. I would ask the guys in the truck section here on Mopar Chat for their recommendation, same for the computer stuff.