Possible/worth it? 3.8L supercharger on 305 chevy - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-20-2004, 06:49 AM
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Possible/worth it? 3.8L supercharger on 305 chevy

I used to own a cougar and so I was part of some message boards and learned about all the different types of cougars. Well I know there was a version that came with a 3.8L supercharger and also other cars were put out with this 3.8L supercharger. Online and at junk yards ive priced the pieces and it seems about $300 wil lget the supercharger and so forth. I was wondering if its possible to make this supercharger work on my 305 chevy. I dont want a big supercharger with a lot of boost since it's mainly a stock engine. If this isnt really possible is there one thats affordable/that was put on a vehicle from the factory thats easier to adapt for my 305? Its an 87 TBI.

Thanks guys

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Old 12-20-2004, 07:23 AM
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The smaller supercharger will not be suitable because it will not have sufficient capacity to fill your 305, simply put the little blowers only deliver about 80 cubic inches of air spinning at factory speed, per rotation and your 305 needs 152, You also would have to reprogramme your computer if supercharging, the factory model V6 with the blower used to bypass the blower using a litttle gate setup until a certain RPM was reached this would acomodate the lack of low speed efficiency ... now, if you used 2 of them !

Ooroo

Rob
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Old 12-20-2004, 07:37 AM
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why 152? I dont want a lot of power and honestly mainly want it because of the sound it will generate and the apparence. I do not want it for horse power.
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Old 12-20-2004, 07:40 AM
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At factory speeds they flow about 351 ci of air. They can be boosted/overdriven beyond that. I have owned 3 of these and the drive snout is too short to work on a sbc in standard configuration.
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Old 12-20-2004, 07:45 AM
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so is there a supercharger that will work that doesnt cost $1000?

What about a 3.8L Supercharged swap in my truck?

It needs a good engine anyways... but thats a ford engine isnt it? lol.. is there an affordable supercharged or turbocharged chevy engine that i could get at a junkyard to swap in my truck? I just need a better engine and would enjoy it to be turbo charged or supercharged and at the same time be affordable. I dont have the environment/home to build a v8 engine or afford a crate engine at $2000 right now..
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Old 12-20-2004, 08:03 AM
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Sorry guys I was relating to the ones on the 3.8 litre GM Holden engines over here, tiny things they are; made by eaton. Fair dinkum I could f**t harder! Why not go second hand ? A swap meet 4 71 and manifold maybe. You guys must be Knee deep in HI Po parts for SBCs over there, over here they are as rare as rocking horse s**t !! If you want noise put in a straight cut cam gear drive. All in good humour guys,

Ooroo

Rob
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Old 12-20-2004, 08:17 AM
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Actually the 3.8 GM Eaton blowers are very similar internally and you 80ci per revolution may be correct. When I said 351 ci I do not mean per revolution. I used my own measurement>

3.8 @ 10psi

10+14.7/14.7=1.68027
&
1.68027x 231 ci=388ci of air at factory boost levels.

I suppose this method already calculates blower efficiency but if not and to err on the safe side as to not end up with a bunch of work and no gain>

388ci 90%= 350ci
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Old 12-20-2004, 08:56 AM
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Project87c10, You said you wanted it mainly for the sound and look. The main whisling sound on a roots blower comes from the air coming out the pulley cogs as the belt cog goes into the pulley groves. You probably wont get much more sound with regular belts.
Kevin
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Old 12-20-2004, 07:37 PM
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To 87 C10
Here is what I based my estimation on:
The 152 number comes from half the engine capacity of 305, as that is how much air can be used by the four intake strokes on each revolution.

At a given RPM an engine will need a set amount of airflow so lets use 3000 rpm to work it out

152.5 X 3000/1728(CI in cubic feet)

so the 305 at 100percent efficiency needs 265 CFM of air @ 3000 RPM

This then means the blower needs to deliver 265X1728 CI
at 3000 RPM = 457,920 CI
Divide by 80 CI ( blower capacity) means the blower has to turn at 5724RPM
Then divide again by 3000 engine RPM will give a drive ratio of 1.9 to 1 to attain efficient cylinder filling, using two of them you double the airflow and can halve the rotational speed. All this is assuming perfect world scenario. Then you can play around with drive ratios to increase boost.
BTW instead of embarking on a big thing like this and to save dollars have you thought about getting another SBC -350 or 400 and reading up as you go doing it up in phases; thats what most of us started like as a friend said to me once its like eating an elephant you just take it one bite at a time and you get there in the end.

Oroo

Rob
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Old 12-20-2004, 07:44 PM
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Have you thought about getting a gear drive? Those are supposed to make noise.
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