6-71 or 8-71
 

I just got ahold of a newly machined 400 small block. I plan on building it for my pro street trans am project. I want a roots style blower, and I also want to make somewhere around 800 horse power. i will be using stoke stroke with a 30 over bore. I already have dart pro 1 heads and I was thinking somewhere around 9-9.5-1 compression, too high? I don't care to use race fuel, not gonna drive it a whole lot anyway. Or maybe is that horsepower figure too high? i want to run a mechanical roller cam, not sure of the size yet. If that horsepower number is too high, what do I need to reach it. Not a big fan of turbo's but worth a thought Thanks

Re: 6-71 or 8-71
 

Hows your current engine in sig working out? Just curious what timeslips you're getting?

I'd shoot for lower compression, boost is more fun than compression. Try for 8:1 or so, then use the 8-71 and you should hit your goal.

I'd look at a short fill on that block, and DEFINATELY use deck plugs. Probably sonic check the block.
I'd recommend o-ringing it too, especially if you want to re-use the nitrous setup.
Going for a new cam or re-using the voodoo?

Re: 6-71 or 8-71
 

Well as far as the engine in my sig, I haven't got to run it yet. In fact I've only had my car for a few months. I got the body and title for pulling the 305 tpi and tranny. I haven't even fired the new one up yet. The 400 is my long term project for after I tub it, if I even do. I only get to work on it like an hour a week, but I'm hoping it runs good. If I like it I am going to reuse the voodoo, but if not then I will probably go solid roller with roller cam bearings and I like the idea of a clean pro street car that will run like stink to.

Re: 6-71 or 8-71
 

Here is a B&M 420 in the Z/28, Dyers 6-71 in the truck and a Wieand 8-71 on the stand.

The 8-71 moves 430 CI of air per revolution vs the 6-71 moving 413 CI of air per revolution so as you can see you can spin the 8-71 slower and still get the same boost but with less heat.
The 8-71 on the stand is a +.030 350 has World Sportsman II heads and 8.5:1 comp. we are spinning it at about 9lbs boost and figure the H.P. est. is in the high 600's. It is running 93 octane fuel but is close to the edge in needing higher, if we were to spin it any faster for more H.P. like you are looking for it would definatly need higher octane fuel.

http://i16.photobucket.com/albums/b5...r/DSC01584.jpg

http://i16.photobucket.com/albums/b5...r/DSC01576.jpg

Re: 6-71 or 8-71
 

Well the 6-71 is cheaper. I was kinda hopin to make it with it. But the 8-71 isn't that much more. Like I said race fuel isn't that big of a deal. I have also been toying around with the idea of stroking to a 427, or would that make it more unreliable and prone to blowing

Re: 6-71 or 8-71
 

My theory is the KISS method, if you are not trying to get every ounce of power out of it for racing, keep it simple, you will have more power than you can use on the street just going with a basic setup and none of the extra cost/headaches :imo::nod:

Re: 6-71 or 8-71
 

Can I come live at your house,WOW,I want all those motors,Very nice!!!!!

Re: 6-71 or 8-71
 

Lol, the Z/28 is mine the truck and one on the stand are engines I built for a couple of friends :D

Re: 6-71 or 8-71
 

Yeah no joke, it has took me like 3 years and 3 different cars to get my engine where it is now. i hope to start on the other one next spring. That is one sharp setup you got there, any of them.

Re: 6-71 or 8-71
 

What is a manageable boost level for with ore, I was thinkin like 10 lbs or so, maybe less. I found link for a 400 small block with a 6-71 build up. http://www.popularhotrodding.com/tec...wer/index.html

Re: 6-71 or 8-71
 

Any level of boost is manageable (to a point) with what level of octane you are willing to constantly run......it all begins with your static compression the closer to 7.0:1 to 7.5:1 you can get the easier it is to deal with detonation at higher levels of boost, going with aluminum heads will help also. The down side is the lower compression pistons are sometimes hard to find and usually get pretty pricey

Re: 6-71 or 8-71
 

I'll probably be running 110 octane fuel, I was wanting around 10 lbs of boost, and probably like 8.5-9-1 compression. I already have aluminum heads. I would be happy, I mean estatic with like 700-750. That shouldn't be too hard to do. I actually wanted a procharger, but the more I look the more I like a big 8-71 blower sticken up, and I don't care which one is more efficient it still makes power

Re: 6-71 or 8-71
 

:D While the roots have a lower efficiency than the centrifical as far as making power it's like apples and oranges....if you get a chance to ride in a roots car then a centrifical car the difference in the torque graph will be crystal clear :burnout: of course the downside is the acreage that is sticking out of the hood ;)

Re: 6-71 or 8-71
 

that is my favorite part. Yeah I have rode in a 6-71 car, my buddy had a 69 camaro with a real strong 454 in it. He took it out of the 69 and put it in a 57 that was tubbed and still couldn't hook. IT was scary. I have another friend with a built 400 small block in a 79. He pulled the wheels and grenaded the 4 speed about a week ago. I kinda like his set up to, a big solid roller with ported dart pro 1'a 13-1 tunnel ram and a 3.73 but I love a blower