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Old 11-11-2009, 08:18 PM
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8-71 wieland 350 sbc build questions

Ok so I have an '79 camaro that I want to build a 383 stroker with an 8-71 to top it off...besides the block work where do I start..ive rebuilt small blocks befor with success but never a stroker or supercharger so I need some help...it says the charger needs a 7.5:1 - 8:1 CR and not sure how close you have to stick to that? Any answers?

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Old 11-11-2009, 08:35 PM
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The c.r. you build to depends on how much boost you want to run. I'm running 10 - 12 pounds with an 8-71 383, street driven car, I'm using JE forged -31 dish pistons, putting me right at 8.4:1 c.r. with no issues, but I also run a BTM. I ran at the strip in July with a straight 6AL, aggressive timing and yep, detonation took it's toll, in a big way

For obvious reasons, I installed an alcohol/methanol injection system to compliment the rebuild, call it insurance on steroids.

I overbuilt my motor with splayed billet mains. If you're not a savage (yeah right, he he, with a blower motor...) you could get by on 2-bolts and cast parts I suppose. I'd never build a blower motor on the light side myself.
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Old 11-11-2009, 08:40 PM
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ok so can this build be done and still run on pump gas? and Im just not sure where to start on parts I need. I looked at the stroker kits on jegs and summit and they have some with 9.somethin CR...what would that do?
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Old 11-11-2009, 08:48 PM
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I would also like to know about what heads to run and if you have to do any milling to them?
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Old 11-11-2009, 08:55 PM
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Your first purchase should be a book called "Street Supercharging". Bone up a little on the subject before you start buying parts. It's not rocket science, but having a decent foundation will prevent problems down the road.

With that said, What is your goal? do you want the blower for the look and sound or do you want to make power? If you want to make power, keep the compression as close to 8:1 as you can. No more than 8.5:1.

You are not going to find a "kit" that will give you what you want. A rotating kit can't accurately list what the compression ratio will be, because that all depends on your heads, deck height, head gasket, etc...

Do you already have your heads? If so you have to build around them.

If you are trying to make power you want all forged parts (crank, pistons, and aftermarket rods, I prefer H-beams).

Do you have a budget in mind?
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Old 11-11-2009, 09:03 PM
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Well I have been told that going forged is better so prolly go that route. Oh and Im going for the hp and ft. lbs and the looks and sound will just come with I guess. I will look into that book you told me and read up.

Im actually in college at wyotech in laramie wy. now and as soon as I get done Im gonna start with a 4 bolt main 350 and figured that would be a good start. The money Im not to worried about because this project is going to take a while I figured so I can just save up.

The heads I was thinking about starting with some 202s cuz my buddy has a pair he will sell but what would you recomend?
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Old 11-11-2009, 09:57 PM
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If you want max reliable power on pump gas with a 8-71 blower build with a real 7.5:1 cr. The lower cr allows more boost with little or no boost spark retard resulting in more real, reliable power on pump gas, everyday.

It is easier/more cost effective to achieve that with off the shelf parts (350 D dish pistons 350 5.7" rods) by building a simple 350ci motor.

A 383 stroker motor is not nessessary as the 8-71 blower makes all the power.

With the money you save by building a simple 350 instead of a more costly and complicated 383, get some decent NEW aftermarket 200 to 220cc intake port hi flow heads. You want something with a large combustion chamber.

For max performance and power combine with a street mechanical roller cam.
Use 2 boost referenced 750 cfm holley or BG blower carbs.

You need to install a fuel system on the car that is capable of feeding this motor at max power output.
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Old 11-11-2009, 10:00 PM
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So your saying a 350 w/ an 8-71 will produce as much as a 383 w/ a 8-71?
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Old 11-11-2009, 10:07 PM
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Quote:
Originally Posted by straightracer
So your saying a 350 w/ an 8-71 will produce as much as a 383 w/ a 8-71?
A 350 done right with the right 7.5:1 cr and better heads than what your friend is offering you will run with more blower boost and less retard than a 383 with the wrong cr and so so heads that will be limited on boost, requireing power robbing spark retard to avoid detonation on pump gas.

Building a 350 costs less than a 383 allowing more $$$'s to spend on better new heads, where it counts.
You end up with a simpler, stronger, more powerfull reliable motor that goes faster, longer.
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Old 11-11-2009, 10:19 PM
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alright well im gonna look into it more and see what I can do...if I stick to 7.5:1 CR what kind of boost do you like I could run
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Old 11-11-2009, 10:29 PM
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Quote:
Originally Posted by straightracer
alright well im gonna look into it more and see what I can do...if I stick to 7.5:1 CR what kind of boost do you like I could run
10 to 12 psi on good pump gas with little or no retard.

Remember boost is actualy a backpressure reading of what is not getting into the motor and making power.

A motor with real good heads and cam and exhaust with 10psi boost on the gauge will produce more horsepower than a different motor with not so good heads, cam, exhaust and showing more than 10psi boost on the boost guage.

It's how much power the motor actually makes that matters. That is determined by how much air and fuel go into the motor, not how much is trapped between the motor and blower. "boost".

The motor that breathes better than another will show a lower boost gauge reading and make more horsepower than another motor that does not breath as good. That other motor will show more boost on the gauge because it is not taking as much air in. Therefore more boost on the gauge with less power output for the same blower pulley drive ratio.

cost-reliability-power-bang for the buck- simplicity the 350 is better. Especially when on a budget.
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Old 11-11-2009, 10:34 PM
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Ive always been told that the greater the boost the greater the PSI of air being forced into an engine? is that what your saying or is that not it? Ive never really been around turbos, chargers, boost, etc. so Im sorry if im asking alot of questions.
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Old 11-11-2009, 10:43 PM
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Quote:
Originally Posted by straightracer
Ive always been told that the greater the boost the greater the PSI of air being forced into an engine? is that what your saying or is that not it? Ive never really been around turbos, chargers, boost, etc. so Im sorry if im asking alot of questions.
No, "boost" is the back up pressure in the intake manifold.
It's a reading of what is not getting into the motor.

More blower drive ratio will raise boost and push the air harder into the motor but the higher blower drive speed heats the aircharge more, increasing the tendency for detonation, requiring more spark retard to avid knock or better high octane gas.
Heated air is expanded, air. Expanded air is less dense.

Its about getting the right balance. The right balance is critical to getting the most RELIABLE power on pump gas.

Power means nothing on the street if the motor $$$eats itself in 5 seconds$$$ And it will when the combo is wrong.
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Old 11-11-2009, 10:48 PM
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Imagine you and 14 of your buddies trying to push (boost) a piano thru a small doorway.

A lot easier with a bigger doorway. Don't need as many pushers. And the piano gets thru the door in much better shape.
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Old 11-11-2009, 10:48 PM
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ok so where do I go or who do I ask to find the "right" combos? If im gonna spend the money I want it to last!

so I got this info now:
forged parts, stay close to 7.5:1 CR, 200 to 220cc high flow heads, roller cam, two boost 750cfm holley carbs.

any other advice. whats the best thing to do about fuel and air?
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