6-71 Blown 408/416

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GTXperience

GTXperience

Orig Stealth Mod
Joined
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Anyone out there running a roots-type (6-71) blower on a stroked (408 or 416) motor? I may be taking a drastic change in the current build and am looking for some real world experiences. I would love to throw out some specs here but now that the 6-71 is coming into play, most of the numbers would change.

Does anyone know if any of the mnfrs make a stroker/blower kit (something with a 7.8-8.0 comp ratio)?
 
I dont know of anyone. But, a Budy of mine ran one on a 302 in a Fox body Mustang that ran low 11s with a stick. Cool little things... Or did you read Popular Hot Rodding? They have an article on them...
 
GTXperience said:
Anyone out there running a roots-type (6-71) blower on a stroked (408 or 416) motor? I may be taking a drastic change in the current build and am looking for some real world experiences. I would love to throw out some specs here but now that the 6-71 is coming into play, most of the numbers would change.

Does anyone know if any of the mnfrs make a stroker/blower kit (something with a 7.8-8.0 comp ratio)?
Click to expand...

While I can't offer any experience of a roots blower on a stroker, we ran an 8-71 on a 350 chevy in a 2700lb street car. Awesome torque right across the rpm range virtually off idle (it didn't really idle below 950rpm).

What I have seen frequently in gasoline motors is that the static compression ratio really doesn't need to be lower than 8.5 in most cases. People plan for running big boost with overdriven pulleys but then find that there's a threshold where the heat produced really limits the gains seen. I'd take an underdriven 8-71 over a 1:1 6-71 as it will produce less heat creating the same amount of boost.

Edit:- Must have tripped over this by mistake, apologies for raking up an old thread. :eek:ops:
 
Good to see you on here again Ben. With a 408 or 416 I think I would be looking at an 8-71 as well. A 6-71 was designed for no more than 426 cubic inches so you are getting near it's top limit so heat would become an issue once you start pushing the drive ratio up. As far as a stroker kit, I have not seen one, but you may be able to use a chevy piston to get what you need.

Jack
 
Hey tech is tech! Im running a 8-71 on a stroked 360, 3.79 crank with -30cc dished pistons for 387ci and 8.5 cr. The 4" cranks require a REAL deep dished piston to keep a low cr. And an 8-71 on a sb requires a 'retrofit' blower to clear the distributor. This is a blower assembled backwards with the case extension facing fowards. As being the 8-71 is 1" longer than a 6-71, the snout length is shorter on a 8-71 too.
 
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