260cam and 270cam which is best

[Anonymous]

Which cam is better for a 250 in a light vechile under 3000 pounds with a 4 speed that will be a daily driver. It will have a crossflow head, headers performance muffler, 500 cfm holley 2 barrel. Lots of highway driving and freeway highspeed 75 mph cruising and over 100 mph if I wind out 4th gear. Lots of offroad this is not a rock crawler however I may occassionally run over littler rocks under 2 feet tall but mostly dirt and climbing up mountians, I want enough torque to get up with friction but I would use my speed and momentium to fly up the mountian more.

I do not care if the idle is smooth I just want a strong runner.
This is a scout 800 33 inch tires with the stock 4.27 gears and a T18 .

 

[Anonymous]

will I have enough low end torque with a 270 cam and aussie head?

 

[Lazy JW]

For good low end torque you need something close to a stock cam. If you use the crossflow head with a mild cam and a turbo you should be able to accomplish your goals, but enough cam to pull that much speed normally aspirated in a Scout with suffucient ground clearance for rock climbing.....I dunno It is difficult to make a small engine like that be all things for all purposes.
Joe

 

[Anonymous]

This is not going to be a rock crawler I plan to be mostly in the dirt.

I see what you say that a 250 may be too small for the street and offroad.

 

[goinbroke2]

I'd say 270 with those low rear end gears. The difference of the 2 cams is around 500rpm. In other words, the 260 will pull and peak around 500 rpm lower than the 270. Cross flow head, minimal slow driving or "grunt" work, 270 all the way.

 

[Hot 6t Falcon]

Hunter,

The bigger the number on the cam, the higher your compression has to be. Unless you're going to do a turbo (not particularly suited for low speed work) or nitrous, look to achieve a compression around 9.5 to 9.8 to 1.

The added compression will give you back the the low speed torque lost to the bigger cam.

Just sticking a crossflow on a 250 won't accomplish this. If you have the head, cc the combustion chambers, figure .040 for the gasket, and go to the web site in my signature.

Click on "Compression Calculator" in the left column. It is PRE-SET for a 200 so make these changes to the pre-set numbers
Change the stroke to 3.91
Change the Combustion Chamber Vol. to 62 (my guess. if you know the cc, enter that.)
Change the gasket to .040
Change the deck clearance to .125
Leave the rest and click on "Calculate"

It should show 7.9 ompression - too low for a EITHER cam.

By using 255ci V/8 piston (They stick up .085 higher in the bore - thus reducing the deck clearance to .040 and they are flat-tops w/o a dish) your compression will jump to 9.9 to 1. Try changing the deck clearance from the .125 you entered to .040 and chane the piston to "Flat-top" and the dish to 0, then click on "Re-Calculate."

Fun toy huh?

9.9 compression is WAY TOO HIGH for a turbo or nitrous.

Good Luck,

 

[Anonymous]

doesnt the aussie head crossflow have 1.73 rockers?
and by uing bigger rockers and a bigger carb say 500 cfm would that raise my volumetric efficiency?

I use the falcon six calculator but I do not know what the volumetric efficiency is of a 250 crossflow with a 500 cfm holley 2 barrel.