Onroad/Offroad Gas Engines

[azzachaz]

Why do manufactures specify that a motor is suited for onroad or offroad?

Are they actually different designs?

[BALISTC]

The only difference is really in the porting.

Off-road engines have porting which is designed for lots of low and mid range torque, whilst on road engines have a lot of top end power.

This also affects the RPM, with on-road engines revving higher.

On small block engines, the carburettor configuration is different between on-road and off-road engines. A lot of off-road engines have rotary carbs, and on-road engines have slide carbs. Big blocks have slide carbs on their on and off road engines, so this only applies to small blocks.

[Matt]

man you know your shit. thats unreal.

[BALISTC]

Thanks dood :)

I suppose its cos I've owned heaps, and u get to learn a lot of shit through trial and error...its the expensive way, but its the only way :D

[avablast]

ok this thread is almost a yr old but just to clear up a thing small block off road engines r starting to come out with slide carbs for increased response ie: short distance from corner to jump. not all but mine does and its great.

[avablast]

slide carbs r also superior compared to there poor relations the rotary.