Do timing events play a bigger role on MPG?

XE258.........IVO -4...IVC 32...EVO 44...EVC -8 Lift I .533 E .544

XE264-12....IVO -2...IVC 34...EVO 45...EVC -7 Lift I .544 E .544

XE264-12....IVO -4...IVC 36...EVO 47...EVC -9 Lift I .512 E .512

Given every thing equal, for arguments(sp) sake, GT-40 intake, 24lbs, shorty headers, 165 AFRs, Car weight, etc.

Just looking for something that is going to get good MPG with some extra grunt. I saw where the guy that had a 5.0 in a MGB was getting 30MPG with a XE264, so it got me thinking.

Just looking at the XE258, one would think that would be the better MPG cam with its smaller lobes, but I think the timing events plays a bigger roll, or are the cams just too close to call?

For economy you are looking at the wrong cams. The extreme energy and high energy cams are not made for economy. Look at the RV cams if you want economy.

X2......but yes the lower the cam duration the better mpg you should see. I believe a stock cam sits around the 250 duration mark.

The weight of your car and the gear ratio are the biggest factors. If you have 2000 RPM's at 60 MPH, your in a good place.

Then having a correctly tuned vacuum advance connected will gain you at least 30% more MPG. That is assumming your ingition is set up correctly to begin with.

The power the egnine makes is not as big of a factor as you may think. Having a larger then you need carb is a good way to loose fuel too.

Many folks on this service with 300 - 400 HP motors and are getting 20 - 28 MPG, in 3000 pound cars. Don't need an MG. I am getting 22, and I expect that to go up as I tune my motor better....

Earlier IVC will build cylinder pressure.

This is the cam I used on my roller 5.0 setup. I couldn't be happier driving this thing on the street, tons of torque it comes on strong right above 1000 rpm and pulls with the Edelbrock RPM heads to 6k easily. Torque? do you want to buy some? I have extra to sell you! Throttle response is nuclear, and gas mileage is awesome! I am using the cam with a 9.6 static compression ratio, Weiand stealth intake and Carter 625 AFB. 10* initial timing, vacuum advance connected. 3.55 gears, T-5 trans in a 3200 lb car. (86 GT) It idles right at 850ish, noticeable slight lope, but very responsive all over. I can drive at 1300 rpm in overdrive around town at 45mph and it will not protest.


Isky #2 street/strip grind

.480/.500 lift, 210/218* at .050", 257/265 at .006" 112lsa

IVO -4 BTDC IVC 34 ABDC <at .050"
EVO 44 BBDC EVE -6 ATDC

-10 of overlap at .050"

If you compare the specs on this cam to comp's XE258HR, they are just about the same, all except comp's .533 and .544 lift. I went with Isky due to the lower lift, and less wear on the valvetrain. I have no valvetrain noises.

lowering revs is the best way to get better milage. Very close to that is making your car lighter. To get best economy you want a cam that optimizes low rpm power, good flowing exhaust, and a well tuned fuel injection system. But you can still get good mileage withough the wussy cam and FI. I get 20 mpg in my 67 mustang with a 300 rwhp 302, 3.80 rear gears and a 650 DP holley tuned for max power. The only thing I have that says "milage" is my t5 transmision with a .68 overdrive.

If you want to spec race a cam for economy here are some of the things to look for. There's probably more, it's been a while since I kept cam catalogs next to the toilet!

Overlap. The number of degrees where the exhaust valve and intake valve are both open. You want that to be as small of a number as possible. Zero at 0.050 of lift would be good. Zero at 0.020 of lift would be better.

Lobe separation. You want it to be wider. That will also reduce overlap. 114 is good 116 may be better. Narrow cams are more peaky with higher HP numbers but normally less overal torque, especially down at low rpms.

Fast acting lobe ramps - but you will have to get better springs to control the action.

Typical RV, Towing cams are close, but they usually have slow ramp rates and low to moderate lift. Cams like the Extreme energy and other are closer, but only in the smaller versions. As duration increases, so does overlap!

You can have your cake and eat it too with the bleed down lifters that will reduce the cam specs down a size at idle. You have to plan to use these as they are normally used to civilize a thumper and can lead to problems on a short cam.

Thanks for the input guys. I am going with a Custom