I run a 670 avenger on top of my l69 which I know is over kill. That being said, since I know for a fact that my car doesn't make full use of that carb...If I were to add a cam would I actually gain fuel mileage due to the increased Hp/Tq and the less throttle under the same carb settings required to move the car. I figure where it runs so rich now I probably won't even have to adjust the carb after the install.

 

Well yes and no. Fuel consumption is a function of RPM and throttle position all things being equal. So putting in a different cam could in theory improve gas mileage by requiring less throttle for a given RPM. That being said the cam should be chosen to match everything else to promote efficency over some range of RPMs other wise parts will fight each other so to speak. So say you had high flowing heads and intake with a huge carb and decided to put a peanut cam in it to improve gas mileage not only will your performance be bad but the gas mileage will also be worse due to the mix match of part making the efficiency of your motor be poor at all RPMs. Its like if you put a large CFM carb on that would operate at peek efficency at 5k RPMs and the cams peek efficiency is at 3K the combination just wont allow it to do anything well. A motor makes power by all parts working together in harmony to maximize efficiency to generate more power and gas mileage. That being said there are probably cams out there that would improve gas mileage but again if other parts were used that better match that cam may have a much better gas mileage than that and better performance. The two kinda go hand and hand as really the 2 ways of making more power are greater volume or efficiency. However even match parts may yield less gas mileage as lets say you selected a cam to match everything else which is designed to operate efficiently in the high RPMs this hurts your low end which would hurt your MPGs if you normally ran in thoes lower RPMs which you usually do on the street. If its really running that rich though you need to adjust it a cam wont fix that as carbs always need to be tuned to whatever the set up is (though some carbs are set up with the idea of being used on racey motors its not to say that to make the AF right you need to change the cam or the changing the cam will eliminate the need to tune the carb).

 

Wow, Thank you for taking the time to write that up for me. I plan to use a pretty good step up from stock cam to take advantage of my long tubes, performer rpm, and 3.73's. The plan is to make the cars peak horsepower around 5K. Pretty sure the torque will be around 3K. I don't figure it will act to much different than it does now minus the loping of the cam. It's always been weak down low due to the huge carb ,but I like it that way due to my T-5 being such a weak tranny. Thank you again for the info tho.

 

Well so far it sounds good. I think your carbs a bit big but you already know that. I love the edelbrock performer RPM intake had a lot of good luck with them. Also having the long tubes and a steep rear match it well. The heads and cam could really use a change though. Depending on what you toss into it for a cam and stuff i suspect your peek torque will be closer to 4k but again depends on a lot of things. I think you would deffinetly do yourself a lot of good changing the cam though because as bad as factory heads tend to be their cams tend to be even worse even though the l69 got the more "radical" cam than the base lg4. Stick with something tame like the comp cams XE256H and it will probably give you some good gains across the board from idle on up. Could do a lot better with some heads like even cheap vortecs though as you dont really have a lot of compression at 9:1 (radical cams kill compression) and the flow rates arnt the best but that cam is tame enough to work with it just fine and not be a bad miss match while trying to give you good top end performance. I think youde really like it but im sure someone else will pipe in with there recommendation or even give comp cams a call or fill out there cam help form (its free).

 

Well I was thinking about running the xe262 but when I put all of my info in the Comp6 dyno program it says that my peak hp will be at 6K rpms with my current exhaust, head flow numbers, (I have the 416 heads which are supposed to be excellent factory 305 heads) and intake discription. The program also lists the xe268 http://www.summitracing.com/parts/CCA-CL12-242-2/ as a good fit for my use. It's peak hp was around 5K according to the program with my setup. I talked to another guy about this cam and he says it's pretty street able and will give me that nice lope sound.

 

Either one would be ok. Personally if it were down to one of thoes two ide side with the 262 if for no other reason that the 268 will build power outside of your rev range.