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Old 12-03-2002, 01:31 AM   #1
mikep
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Question about Blowers on our trucks

The 8-71 Blower sitting on top of the 454 in my dads 69 camaro has got me to thinking . Can I fit a 6-71 blower under the cowl hood of my 68 on top of a small block. I'd have to change pistons to flattop forged but other than that my bottom end is rock solid and could easily handle the extra 200 or so ft lbs of torque. If not how well do those little blowers work? Are they worth the effort? Income tax time is coming up and the joy of home ownership and its subsequent outrageous interest burden means I'll get a nice tax refund and if I play my cards right I can squirrel a little away before my wife confiscates it all.
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Old 12-03-2002, 01:45 AM   #2
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flat tops will give you close to 10-1 C/R..you'll probably need around 8-8.5 to 1..detonation is the killer of blown engines..you might try a cam with a little more duration,since you'll have a ton of torque with the squeezer..Im sure the 671 will fit under a cowl hood, hell I think you dont need the cowl. I fyour going with new forged slugs,I would look into 12cc dished pistons..
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Old 12-03-2002, 01:52 AM   #3
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Ive got "76 cc" chamber WP S/R torquer heads which actually cc to about 78 cc. Currently I am running "11:1" .125" domed pistons which actually give me 9.6:1 compression. Switching to flat tops will drop me down to the low 8's I figure which is right in line with a 6-71 figuring 10 lbs or so of boost I should be able to get by with pump gas.

Ive got a different cam with a good bit more duration I havent used in a while . Might be just right for that.
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Last edited by mikep; 12-03-2002 at 01:54 AM.
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Old 12-03-2002, 02:01 AM   #4
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ok..that makes sence..i calculate with a .020deck height and .039 head gasket and 5cc valve relief flat tops and 78cc heads the C/R will be 8.6-1..right on the edge of the happy no detonation zone
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Old 12-03-2002, 04:11 AM   #5
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Good to hear it may be possible to squeeze a 6-71 under a stock hood. That's what I was hoping for! Anyone have picture proof of it being done?
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Old 12-03-2002, 09:06 AM   #6
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If you'd like, I'll measure my blower from the block to the top of the carb when I get home today. This may give you some idea of weather or not it will fit. Another thing to remember is that you might (not always though) have to move your engine back and inch or two to accomodate the 3 inch belt drive. Also, you have to run dished blower pistons. If you run flat tops they will crack. A forged crankshaft and fluiddamper are also required. Trust me on this, there is no way around it. If there is a part to be broken, I have broke it. A blower cam (or overlap cam) should also be used.
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Old 12-03-2002, 02:35 PM   #7
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you could always go with a 142 (or is it 144) weiand/holley small blower, they will definately fit under cowl hood
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Old 12-03-2002, 03:06 PM   #8
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Like this one. I LOVE IT. tons of fun and it all fit under hood even before I got the cowl hood
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Old 12-03-2002, 03:23 PM   #9
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I have the same one as NSANE68 and it will fit with a 4 inch air cleaner and a chrome drop base. Mike you don't live to far from me (about 20 min). You are more than welcome to come over and see my set up.

I have the truck torn down right now, but the engine is still in the truck.
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Old 12-03-2002, 06:12 PM   #10
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My 6:71 measures 16.5 inches from the lowest part of the intake manifold to the top of the carb. My carb adapter plate is 1.5 inches thick. You'll have to add the air filter or scoop. My scoop is about 6 inches tall.
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Old 12-03-2002, 06:14 PM   #11
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Here's a pic:
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Old 12-03-2002, 06:28 PM   #12
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Woo hoo! thats sweet.......Im guessin the hood dont shut on that A bone
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Old 12-03-2002, 06:58 PM   #13
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Actually, a 6-71 and an 8-71 are the same heighth. The only difference between the two are 1" in length. Go with the 8-71! More boost, less heat.
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Old 12-03-2002, 07:13 PM   #14
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This is true, I wasn't sure about the intake though (small block and big block). You can underdrive an 8:71 for the same amount of boost and less friction, but they cost a little more. Also, don't forget that you can't run that stock HEI anymore. It won't fit behind the blower. I'm using a marine HEI, it's about the size of a Mallory Unilite.

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Old 12-03-2002, 08:10 PM   #15
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6-71 on a small block fitting on the stock hood. Talk about sleeper
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Old 12-03-2002, 08:32 PM   #16
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I never thought about the 8-71 heat issue.

Do the mini blowers still produce a decent amount of boost? Is there blower whine. Thats one thing I'd rather not have. They sound like they might be more practical for a daily driver. How does it affect mileage?
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Old 12-03-2002, 08:45 PM   #17
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The 144's don't whine. Contrary to popular belief, the whine doesn't come from the gears, it comes from the teeth of the drive belt running across the idler pulley. The 144's don't have teeth. Also, they put out plenty of boost, and since the belt is smooth, it allows the supercharger to kick back during backfiring, saving you from bent rotor blades and other broken parts. Most street 6:71's and higher have pop-off valves for this reason. I get 10 miles per gallon running a single 750 cfm Holley Dominator.

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Old 12-04-2002, 01:36 AM   #18
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Randy70C-10 is on the money with that last post. I haven't ever had any heat problems with my 142. I have the different pulleys to make over 8 psi of boost. If I would have went with a 177 mini I would put out more than 8, but it still is a lot of extra power.
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