I'm trying to learn about cam basics and considerations for selecting the proper cam for my engine. I've researched 3 different cam manufacturers websites for possible choices and this is what I've found. Hopefully the veterans of engine building can help me understand the numbers as they pertain to my car.

Here is my setup:

70 SS 454/M20/3:31 posi

454 .30 over
291 rec port heads - stock
10.1 CR
Roller tip rockers
Edelbrock Performer RPM Rec port intake
Holley 3310 vac secondary
Edelbrock RPM 7162 camshaft (hydraulic)
Stock exhaust manifolds/ 2.5" dual exhaust

I think that my Edelbrock cam is too big for my driving habits...occasional weekend shows and cruise-ins. It doesn't seem happy until I get above 3k rpm, then pulls hard to 6k. Most of the time the engine is around 2500-5000 rpm. It has a very lopey idle, almost too much. Idles around 900 rpm. I found a couple of other cams that look interesting, what do you think about them and how would they be different than what I have? I prefer to stay with hydraulic...never owned any other type.

1. Comp XE274H
Duration: 274-286 Lift: 552-555 LSA: 110
Overlap: 60 RPM range: 1800-6000

2. Lunati 02003
Duration: 309-309 Lift: 519-519 LSA: 110
Overlap: 89 RPM range :2000-6000

3. Edelbrock Performer RPM 7162(currently in the car)
Duration: 300-306 Lift: 560-573 LSA: 112
Overlap: 79 RPM range: 1500-6500

I appreciate any and all comments...I want to get the most streetable power that I can without making the car uncomfortable to drive. If you can suggest a different cam that would work better, be sure to let me know.

Jeff

Of the three, the Comp 274 (or other of about the same size) is the best choice. The Lunati will act pretty much the same as the Eddy, they are both very big. Using 10:1 as the CR, a 274 cam (or there abouts) is the right size. It will matchup better with your gearing, too. Both of the bigger cams work best with over 11:1 CR.

Duration defines the rpm range of a cam. Lift helps with producing torque in that range. Overlap is most useful at high rpm where some scavaging can take effect but is otherwise not a particularly helpful thing (it is responsible for the lopey sound we all like so much). Overlap is a result of the LSA of a cam. The LSA defines the broadness or peakyness of the torque curve. There are a number of other factors that come into play. Whole books have been written on this.

If you are interested in learning about cams in detail, I suggest getting David Vizard's book on cams and valvetrains.

It doesn't seem happy until I get above 3k rpm, then pulls hard to 6k. can you say "oval ports" :D I know,ya gotta work with what ya got, graemlins/beers.gif

Thanks Pat. I read the info on your web page and it was very enlightening. I am definitely going to get that book.
I know that there are probably several cams that would work in my application, but I just feel that my current Edelbrock cam takes too long to get in the sweet spot for my tastes. Do you think that the Comp cam will still have some of "choppiness" or lope to it?
Anyone else care to comment??

Jeff

If you want to stay hydraulic, look into the Comp LS6 Hydraulic "Nostalgia Cam". Similiar to the XE274 but with milder ramps for durability and a little wider lobe separation for a broader torque curve. Also has additional exhaust duration. Also, the Crane Powermax series built in a lot more exhaust duration which help with stock manifolds. I don't know anyone who runs a 110LSA without headers, not that it can't be done, but I doubt you would see the positive effects of the overlap without a set of headers.

RR, I guess I'm stuck with these heads and intake for now. :D

As for headers, I am getting ready to install a set of Doug's headers next weekend. They are 1.75" primaries...hopefully they will pick things up a bit.
So, should I be looking for a LSA of more than 110?

Thanks for the replies so far.

Jeff

A 110LSA will have a liitle narrower power band than a 112 LSA. IE, for a given duration the 110LSA may be 2000 - 6000, the 112LSA may be 1800 - 6200. These are not exact but are typical of how you see things listed. I usually stay with a 112LSA for the street for the better idle quality and higher vaccuum at idle. 110LSA and tighter are definitely better for drag racing. It all about intended usage and what can you tolerate in engine idle quality. I like a little lope but not so radical that the car won't idle in gear at a red light.

Might look at something like a Lunati #302A7, installed well advanced. If they could do it on a 110 lsa, I'd opt for it. The change might help add some intake velocity to those heads and wake the motor up nicely.

Do you have the specs on that Lunati cam - 302A7?
I couldn't find it on their website.
Thanks for all the input.

Jeff

Cam specs (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=021003#000004) graemlins/waving.gif

Thanks JRS....btw, do you ever go down to Milford on Friday nights?

Jeff