Valve lifters…solid/hydraulic/roller tappet/flat tappet?

[blykins]

Originally Posted by zrayr

I'm no expert, as all that know me will attest to, but the one thing I think you are overlooking is the relationship of small ports to intake charge velocity. If the intake ports are not matched to the rest of the engine, i.e. too big, the velocity will drop and the gas will fall out of suspension. The same thing happens when you try to put a "too big" carb on a relatively small engine. A mild cam will mitigate this somewhat as you suggest, but not enough, and throttle response will suffer and you will end up with a huge bog that can't be tuned away.

Z.

I would agree with that 100%. Add volume and flow, but take away velocity, and you end up with a port carrying a lot of inertia. A "slow" port is hard to get moving and is considered lazy until the higher rpms. If you don't have enough cam, it doesn't matter how well the heads flow, it won't pull the rpms that you want. It's true that you need less duration as head flow increases, but that doesn't mean that you can have a 600cfm head and a 205° duration and spin to 7000. (Just for example's sake...)

The dyno sims are a great "ballpark" tool. Unfortunately, Desktop Dyno and EA Pro show about 7-8% high compared to the actual dyno that I use. Desktop Dyno seems to be WAY off when it comes to torque numbers as well.

There's NO way that a 302 set to peak at 7000-7500 will have a flat torque curve settling around 400 lb-ft. An't no way. An't gonna happen.

You also have to look at it this way....dynos are cool for breaking in an engine and seeing what kind of power it puts down, but at the end of the day, you can't get on it and drive it. A dyno gives no indication whatsoever as to how the engine will be on the road, in a car, with a transmission and rearend behind it. It gives no indication of how much you'll have to slip the clutch taking off or how fussy it will be cruising at 1500 rpm.

What you would see in reality with this type of combination would be a torque peak at around 6000 rpm, with probably around 100-150 lb-ft available at cruising rpms. The curves would look more like a steep hill instead of having any flatness to them at all.