Question about Blowers on our trucks - The 1947 - Present Chevrolet & GMC Truck Message Board Network

mikep · 12-03-2002, 01:31 AM

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.

bigjimzlll · 12-03-2002, 01:45 AM

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..
Jim

mikep · 12-03-2002, 01:52 AM

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.

bigjimzlll · 12-03-2002, 02:01 AM

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

Alvin · 12-03-2002, 04:11 AM

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?

*Randy70C-10* · 12-03-2002, 09:06 AM

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.

nate68 · 12-03-2002, 02:35 PM

you could always go with a 142 (or is it 144) weiand/holley small blower, they will definately fit under cowl hood

NSANE68!!! · 12-03-2002, 03:06 PM

Like this one. I LOVE IT. tons of fun and it all fit under hood even before I got the cowl hood

chaptr2 · 12-03-2002, 03:23 PM

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.

*Randy70C-10* · 12-03-2002, 06:12 PM

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.

*Randy70C-10* · 12-03-2002, 06:14 PM

Here's a pic:

crazy longhorn · 12-03-2002, 06:28 PM

Woo hoo! thats sweet.......Im guessin the hood dont shut on that A bone

69custom4x · 12-03-2002, 06:58 PM

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.

*Randy70C-10* · 12-03-2002, 07:13 PM

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.

Crazy Longhorn- I sold the hood.

Danny69' · 12-03-2002, 08:10 PM

6-71 on a small block fitting on the stock hood. Talk about sleeper

mikep · 12-03-2002, 08:32 PM

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?

*Randy70C-10* · 12-03-2002, 08:45 PM

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.

chaptr2 · 12-04-2002, 01:36 AM

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.

12-03-2002, 01:31 AM	#1
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	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. __________________ No truck :-(

12-03-2002, 01:45 AM	#2
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	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.. Jim __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

12-03-2002, 01:52 AM	#3
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	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. __________________ No truck :-( Last edited by mikep; 12-03-2002 at 01:54 AM.

12-03-2002, 02:01 AM	#4
bigjimzlll Senior Member Join Date: Dec 2001 Location: Redding,CA...USA Posts: 4,736	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 __________________ It's called "drag racing" if they called it "tic..tic..WHAM!..BANG! F*&K!!!", they'd have to keep the magazines under the counter with the other men's publications click the clicky to join the site.... http://67-72chevytrucks.com/vboard/payments.php 67 lwb..first hotrod in 25 years..540 best ET is 9.45 @ 141.44 Anderson,CA

12-03-2002, 04:11 AM	#5
Alvin Never Done? Join Date: May 2000 Location: Ohio Posts: 1,435	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? __________________ Ethel - The Legend Continues... Ethel has been sold.

12-03-2002, 09:06 AM	#6
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	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.

12-03-2002, 02:35 PM	#7
nate68 Registered User Join Date: Jan 2000 Location: ca Posts: 1,110	you could always go with a 142 (or is it 144) weiand/holley small blower, they will definately fit under cowl hood __________________ 68 short step, 406/700r4, 9" w/discs.

12-03-2002, 03:06 PM	#8
NSANE68!!! SLICER AND DICIER Join Date: May 2001 Location: Quuen Creek Posts: 1,383	Like this one. I LOVE IT. tons of fun and it all fit under hood even before I got the cowl hood Attached Images __________________ 01 Tahoe 22's 2/4 drop and tv's 68 chevy money pit 51 chevy belair 95 Honda 900RR 05 GMC Siearra (company truck)

12-03-2002, 03:23 PM	#9
chaptr2 Registered User Join Date: Mar 2000 Location: Olalla, WA Posts: 705	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. Attached Images __________________ This is only my opinion and it is subject to change. 70 GMC Short box stepside Blown 388 Stroker 72 K/5 Blazer 350/SM465/205

12-03-2002, 06:12 PM	#10
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	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.

12-03-2002, 06:14 PM	#11
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	Here's a pic:

12-03-2002, 06:28 PM	#12
crazy longhorn Fabricate till you "puke" Join Date: Jun 2002 Location: Ill Posts: 9,403	Woo hoo! thats sweet.......Im guessin the hood dont shut on that A bone __________________ 69 longhorn,4" chop,3/5 drop, 1/2 ton suspension/disc brakes,1 1/2" body drop,steel tilt clip, 5.3/Edelbrock rpm intake/600 carb, Hooker streetrod shorties,2 1/2" exhaust/ H pipe/50's Flows , 6 spd Richmond trans,12 bolt/ 3.40 gears....

12-03-2002, 06:58 PM	#13
69custom4x Registered User Join Date: Oct 2002 Location: Albuquerque, NM Posts: 24	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.

12-03-2002, 07:13 PM	#14
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	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. Crazy Longhorn- I sold the hood.

12-03-2002, 08:10 PM	#15
Danny69' Registered User Join Date: May 2002 Location: Spokane, WA Posts: 93	6-71 on a small block fitting on the stock hood. Talk about sleeper __________________ 1969' LWB [Work in Progress]



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12-03-2002, 08:32 PM	#16
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	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? __________________ No truck :-(

12-03-2002, 08:45 PM	#17
Randy70C-10 Account Suspended Join Date: Mar 2001 Location: Virginia Beach, Va. U.S.A. Posts: 15,320	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. Last edited by Randy70C-10; 12-03-2002 at 08:47 PM.

12-04-2002, 01:36 AM	#18
chaptr2 Registered User Join Date: Mar 2000 Location: Olalla, WA Posts: 705	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. __________________ This is only my opinion and it is subject to change. 70 GMC Short box stepside Blown 388 Stroker 72 K/5 Blazer 350/SM465/205

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