cam selection

Richgrsc

Richgrsc

Member #049
GCC Member
Location (City)
O'Fallon
First Name
Rich
Last Name
Schipper
I’m building a new engine, a 331. Eagle forged lower, JE SRP pistons, AFR 185 heads and a Ford GT 40 intake for now, stack injection in the future.
Here is what I can’t decide on, a cam. I’ve read just about all the horror stories there are about Comp cams and destroyed gears on either the distributor or the cam. I don’t want to deal with that BS. I’m using a stock Ford distributor. It will be about 90% street driven. I’m leaning to staying with a Ford letter cam. I have an E-303 in in my currant engine, like it’s low and mid range torque, but looking for a little more on the top side. An X-303? Anyone use Lunati cams? Looking at their #20350603, improved HP & torque over the B & E ford cams. How about the Trick Flow stage 1 or stage 2? I'm sending a question to Flow Tech Induction (Ed Curtis) for a custom grind, will see what they say.
 
Rich,

I've had several discussions with Mark D about the cam in the 331 that I have. You might try him.

Bob
 
Rich
This article on camshaft selection was published in Engine Builder Mag. just this week. May answer some questions and generate even more.

Paul
 
Rich,

The article from Engine Builder Magazine is a very basic starting point and worth the read....but cam selection and cam tuning is a subject that would take a very large book to cover adequately.

Just keep in mind that it is very easy to over cam an engine for the street. As a result most engine builders will tell you it is FAR better to under cam than over cam if you are building an engine that will see ANY street use.

There is nothing wrong with an E-303 cam. Probably one of the best cams Ford has produced for a small block. However every cam is a trade off. There is no free lunch. You can gain increased HP at higher RPM...but it will be at the expense of low and mid range torque...driveability and fuel economy.

I would suggest keeping your current cam and invest in some retard bushings or keys for your cam gear. A great deal of performance can be gained by simply retarding your cam for improved HP.
We learned that lesson years ago in stock class racing where degreeing stock cams made a very measurable improvement in top end performance. In some cases as much as 3 - 5 mph in trap speed. The nice thing about it too is that if you ever want to go back to increasing lower and mid range torque...it is accomplished with a simple change of bushings or crank keys.

The other issue is that you need to measure your actual cam position (opening and closing points) before making any changes. Don't assume that the stock crank key and cam chain will give you the camshaft timing Ford intended. I has to be measured and confirmed. Then you can make changes from that baseline.

Too often people pick a cam based on Peak HP numbers not realizing that they give up too much usable street performance "under the curve" at lower RPM's.

Here is a short article that touches on the subject....

http://www.deltacam.com/tech.php?p=3

Another issue with higher horsepower cams is that they are hard on the valve train. To increase lift and duration the cam grinders utilize faster acceleration ramps on larger cam lobes. This in turn requires heavier valve spring rates to avoid valve float which adds more wear and tear to the valve train. The higher lift may also require modification or replacement of your valve guides, seals, and valve spring retainers.

Look for any articles by David Vizard or Joe Sherman on the subject. They have written a number of easily understood articles on the subject pertaining to small block Chevy's...but the concept is the same for any engine.

I also think you will realize a lot more top end performance from your AFR heads...while keeping the good driveability of your E-303 cam.

You don't specify...but which valves are you planning to run with those heads?
 
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