i getting ready to build a 350 4 bolt main to put in my S10 and i want to put a 6-71 blower on it. what do i need to do to build for a blower i know i need around 8:1 compression and a steel crank. Do i need forged pistons?Does it matter what size cam i run? Does anyone know of any websites where i can research this?

 

There is not a lot of difference between what works for a positive displacement type blower (such as the 6-71) and the now much more common centrifugal blowers. If you look at some the threads in "Forced Induction" you can see a number of issues being discussed. Some of the people even know what they are talking about!

You can make the discussion, like any bench racing, nearly endless. But to briefly summarize - yes, you need forged pistons designed for boost. They should be a low silicon alloy with a thick top ring land. There are many "blower pistons" available from the name piston manufacturers (JE/SRP, Diamond, Ross, etc.). Cam choice depends on the same considerations as with any motor. It needs to be chosen with respect to the heads and rpm range. Blower cams typically have a wider lobe separation than a cam for an NA setup (113-116 degrees is typical) and more exhaust duration as well. Some people using a positive displacement blower avoid the wide LSA as they WANT to bleed off boost at low rpm. The torque curve with this type of blower is nearly flat, often you will see 90% of max torque as low as ~1,500-2,000rpm. Traction can become a big issue because of the low rpm boost characteristic of these blowers. Depends on the combo if this will be a problem. Exhaust duration of 10-15 degreees more than intake are commonly used. There are lots of off the shelf grinds designed for the small block Chevy.

Rich

 

Thanks for the info that was very helpful.