I plan on putting a blower on my '71 Chevelle. I was wondering what the difference is b/w a 6-71 and an 8-71 blower. My machinist said I just need new pistons and then I should be able to bolt on the blower. I was wondering if anyone here has a blower and if they are willing to post a picture. Any kind of information would be helpful. Right now I have a 406 SBC which has quite a bit of work done to it. Just thought you might need to know that.

142 CI of displacement is the difference. The designation comes from the diesel engine application: The first digit is the number of cylinders (6) and the last two digits constitute the volume displacement of each cylinder in cubic inches (71). Therefore a 6-71 displaces 426CI and an 8-71 displaces 568CI. You should go with the 6-71 as a 8-71 is rather large and you really don't need an 8-71 until you get to 500CI or more and over 5psi of boost. You could run the 6-71 S/C at 1:1 and get about 12psi of boost for this you should stay at 7.0:1 compression. If you loose some boost you can bump-up the static compression level.

yes but wouldnt the 8-71 be able push the same or more amount of boost with way less heat?

yes but wouldnt the 8-71 be able push the same or more amount of boost with way less heat?

Did you forget where you posted the question?
http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=2;t=020473#000000

Despite what your machinest says there is a good bit more to making a blower motor perform than merely changing the pistons.

First off a 6-71 blower is for a 6 cylinder motor with 71 cubic inches per cylinder (426 cubic inches). An 8-71 is for an 8 cylinder motor with 71 cubic inches per cylinder (568 cubic inches)....the same applies for the 10-71 etc...

Blower motors like a camshaft with around 112-114 LSA. Any less than that and you'll just be spitting it out the exhaust. Blower motors also like large port heads. Unlike with a naturally aspirated motor port velocity is not a concern...the blower creates the port velocity. I would also shoot for a set of dished pistons, a compression ratio of around 8:1 is advisable, much more than 8-8.5:1 and you'll have to limit the boost which totally negates the idea of a blower.

That's just the performance aspect. You may want to have your block o-ringed if you are planning on running a decent amount of boost. Definitely run forged pistons. I would also consider good rods, crank and 4 bolt main caps (I am a big fan of "over building" bottom ends).

If you went with an 8-71 it would build up less heat. Plus there's nothing that says you can't overdrive the 8-71 ;) .

Whenever I was plannning an 8-71 big block motor (I have since decided to stay naturally aspirated) I was planning on running 8:1 compression with 12psi of boost.

im tellin you man go with a a 14-71 with a 1:1 rear end ratio as first gear and i bet you could still pop a wheelie if you knew how to launch

im tellin you man go with a a 14-71 with a 1:1 rear end ratio as first gear and i bet you could still pop a wheelie if you knew how to launchDo you know how much horsepower it takes just to run a 14-71 blower? I believe I remember hearing it's in the area of 400-500 horsepower...probably not the best idea for a street driven 400 small block.

no but it would be soooo coool. just to say yea my blower is bigger than yours. and the wow factor once you mash it. sides its not hard to pump out 400-500 hp i have 415 or so. and its a 2 bolt.
you could get a lil m block build it on up and your set

o yea i forgot blowers dont normally go on every day cars. my neighbor has a sbc 8 71 65 chevelle. and its street driven meaning it has a license plate as is drivin maybe 3 times a month and im sure that is what he is going to do strictly weekend driver

Properly done, a blower is VERY reliable and streetable. LOTS of new cars use them and have 0 problems. Just use common sense when setting up the combo. I know "Common Sense" goes out the window when WE start dinking with our cars. :D

Originally posted by d1_bradley:
Properly done, a blower is VERY reliable and streetable. LOTS of new cars use them and have 0 problems. Just use common sense when setting up the combo. I know "Common Sense" goes out the window when WE start dinking with our cars. :D And let's also remember not to "Dink and Drive" and "friends don't let friends drive Dunk" graemlins/clonk.gif (sorry bout that.... :D )

By the way, I guess I'll take that 14-71 blower for my 454. That with some nitrous and I can terrorize my neighborhood with about 900 HP :eek: (just kiddin' :D )

Thanks for all your replies. My motor right now was dynoed at a little more than 550 HP. This car is strictly a weekend car and does not see bad weather. I'm not unsure about what blower to get, but with your advice my decision will be easier now. Thanks