You guys ever wonder why some people want a big cam like the "GM 847" and others run the numbers with a small cam like the Crane 227? I'd personally like to know how those "small cam" guys do it

 

Good combination of other parts and weight reduction.

 

In my case its a good combination and very minor weight reduction..I'm 3600ish race weight..I have always been a big fan of high lift, low duration...John Lingenfelter was on to something years ago....

--Alan

 

It aint the small cam guys doing anything special, it is just that most folks fall into the age old hotrodding pitfall of bigger is better and go too big.

 

The difference is where the cams are making torque. Since HP is just s function of TQ and RPM, the larger cams make more TQ up top so more HP and that's what gets guys to buy them. The problem is that the useable RPM range for the larger cams is so high a clutch dump at the rev limiter or a huge converter and a high RPM shift point is the only way to get those cams down the track quickly. A small cam is much more effective a lower RPM and doesn't need as much stall and as high of a shift point to work effectively.

That also goes with weight... if you have a 3600+lbs car then the car needs TQ at launch or stall RPM, if you don't have it there then you can never get the car to accelerate down the track because you give up so much 60ft time getting the upper RPM HP when you need more TQ at stall/launch RPM.

Bret

 

My understanding is this:
More duration = more tq/hp at a higher rpm.

So, what do we do to get more torque lower in the rpm range? More lift?

 

Well the one thing that interest me in street cams that race cams don't worry about is that they require more attention to more details.... Your question is pretty general.... "So, what do we do to get more torque lower in the rpm range? "

Now don't take that as bad, I'm highlighting that for the case that what you are looking for is a wider RPM range. Not just the high RPM side but of the lower RPM range. Which leads into why I find street cams interesting. A typical good race motor for drag racing will limit itself to a 1500-2000rpm range that it works in. Now a street strip guy with say a medium stall of 3000rpm will shift at 6500rpm, so it's up to 3500rpm range for the motor to run. That's not the most significant part, just the added RPM to the range. If you run a 2000rpm range in a drag motor that shifts at 8000rpm then you are only using 25% of the RPM range of the motor. On the street strip example the 3500rpm is 53% of the RPM range of the motor, which is pretty wide.

Now say you need to take into account the drivability and idle, then you have more areas that you need to focus on, and it's usually in areas where the motor is moving in and out of tuning peaks for the intake and exhaust which makes everything more difficult.

Bret