Turbo cam question

Any boosted application will require wider lobe centers. Forget everything you know about naturally aspirated engines, as boosted applications require a different throught process.

The reason for wider LC's is to prevent your engine from dumping the fresh [pressurized] air-fuel charge down the exhaust pipe. In short, unless you're running a full on race car (wide open throttle only), you will LOSE power trying to cruise with a cam on tight centers - and it will be a dog on the bottom - and/or very peaky.

I've ran quite a few blower motors over the years (Roots style from BDS) and, yes, the "milder" cams don't have much thump, because there is no reversion (sucking back at the exhaust port due to over lap on the intake and exhaust valves when the piston starts traveling down, and short LC's) with wide lobe centers and a supercharger. However, you can buy blower cams that thump hard - but you'll be wading into "race" territory with your build...

Additionally, your volumetric effiiciency will go up with wider lobe centers as it's not unusual for boosted applications to run over 100% VE.

My advice is to talk to someone who specializes in your application. For roots type blower, I call Craig Railsback (BDS), Don Hampton, etc. For turbo applications - discuss your build with persons specializing in centrifigal blowers. Why gamble when there's a wealth of knowledge from people that have decades of experience ? You'll be much happier in the end. The guys at Comp also sell to the blower crowd and they are very knowledgable - provided they get full disclosure from the builder on intended use.

With blowers, 112-114 centers are the norm. A good "RV" cam works very well with blowers too, on the street. Who needs a thumping cam when you've got that 8MM drive belt screaming, or blow-off valves purging, everywhere you drive it ?

Southernman