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High CR 351 or blown?

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Nuggets View Drop Down
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    Posted: 14-November-2014 at 6:14AM
Times coming to decide if I fit a blower or build a real high CR big cammed 351 that can rev it's nuts off.....personally I'm thinking blower!

What's everyone's opinion on a blown motor in a 73 Torino ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 14-November-2014 at 12:21PM
blower! (go big or go home!) Thumbs Up
JOHN
74 GRAN TORINO S&H CLONE
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90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote antlerfiend Quote  Post ReplyReply Direct Link To This Post Posted: 14-November-2014 at 1:56PM
Are you driving it or racing it?
Alex
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 14-November-2014 at 9:39PM
Driving it

Been offered a 1471 blower at a good price....bit on the big side but would look stupidly cool

This is more for visual impact than it is for performance as it'll only be running 6-8psi!

Wish I hadn't sold my 671 :(
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72 RS 351 Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 4:54AM
I'd go with either a stroker kit with a good 10:1 compression, 4V heads and big single plane intake, or a solid Cleveland build(2V or 4V) with under 9.5:1 compression, and a positive displacement blower.

That bigass blower you have would be more a looker than a runner. I'd rather have the runner/stomper real deal engine. The money/budget will be your biggest factor, any combo will be expensive, but how much is the big deal. Have fun with it no matter what.
Don

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67gt5003119 Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 5:18AM
Agreed, build a thumper. The masses encouraged me to build a cleveland instead of a 429. So I am building a 408 4v cleve with 1!:1 CR, BIG roller cam, high rise open plenum intake and full roller valve train. On paper I am looking at apprx 550-575 hp. Should pull the GTS around ok. Blowers look cool, however, they are a pain. Chicks dig em tho...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 7:25AM
Well the blower is an option, I reckon with a 1471 the Torino would look badass!

A stroker would be nice too but for the money involved id rather have the charger on top. It'll still perform and make some serious power. Just won't have a chance to be used to its full potential
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 8:01AM
Ok so bit more research. Full kit to bolt straight on with a 6v71 is £2300 plus whatever a scrap block and crank costs me so the guy can make it on an engine and machine it perfectly

If not 1471 is cheaper but would require a manifold making and might hit my fire wall.....looking like a 671 setup is the way to go!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 1:52PM
the 14-71 ~might~ fit?  but then again it might not either 
and that's a Lot of Wind if you're only looking for 6psi
here's a link to Keith_84's project thread, check the other pages for more pics but here's a good one of the back side / firewall on p5
 
 
------------------------
 
 
The data for GM based Roots blowers are:-

6:71 small diameter
Rotor dia=5.505", length=14.975", displacement per full turn of rotor=339CI.

6:71 big diameter
Rotor dia=5.778", length=14.975", displacement per full turn of rotor=411CI.

8:71
Rotor dia=5.778", length=15.905", displacement per full turn of rotor=436CI.

10:71
Rotor dia=5.778", length=17.000", displacement per full turn of rotor=466CI.

14:71
Rotor dia=5.778", length=19.000", displacement per full turn of rotor=521CI

This is theoretical displacement.


Edited by Rockatansky - 15-November-2014 at 1:55PM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 7:15PM
i'll throw in my 2 cents, there's more to it for a gas engine than just getting a blower off of a truck, the rotors need to be machined for teflon seals, and a belt driven conversion. you need about 7:1 CR. you'd want a 671 not a 6V71 they mount different. basically a 671 is a inline 6 cylinder 71 series motor, the 6V71 is a v-6 71 series engine and in the Detroit 2 stroke diesels there were 53 series 71 series V71 series and V92 series
JOHN
74 GRAN TORINO S&H CLONE
74 CORVETTE COUPE CUSTOM
90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
75 V8 MONZA SUPERCHARGED
79 COURIER VERT. SLAMMED
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 8:25PM
I know about blowers this isn't my first look ;) ie had 6v and 8v before. They were all machined etc and 8.5:1 is the target CR according to the blower expert in the UK who sets them up
The 6v is the easiest to get hold of here too, fully machined with an inlet, snout, pulleys etc it's £2300

Throw in forged pistons, a cam and another carb then I'm away!

Whereas to build a stroker with the same potential I'm looking at a lot more and no where near as cool looking

Oh and $300 plus shipping for a glass hood
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 8:38PM
no offense, just that many people think they can just get an old blower and put it on their car, and their done! not quite that simple. you know
JOHN
74 GRAN TORINO S&H CLONE
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90 S10 BLAZER 4X4 LIFTED
77 CELICA CUSTOM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 15-November-2014 at 10:10PM
Yeah I get what you mean, it's not so simple as just dropping one but I've got it covered :) just trying to decide which is better
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72 RS 351 Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 2:52AM
Originally posted by Rockatansky Rockatansky wrote:

the 14-71 ~might~ fit?  but then again it might not either 
and that's a Lot of Wind if you're only looking for 6psi
here's a link to Keith_84's project thread, check the other pages for more pics but here's a good one of the back side / firewall on p5
 
 
------------------------
 
 
The data for GM based Roots blowers are:-

6:71 small diameter
Rotor dia=5.505", length=14.975", displacement per full turn of rotor=339CI.

6:71 big diameter
Rotor dia=5.778", length=14.975", displacement per full turn of rotor=411CI.

8:71
Rotor dia=5.778", length=15.905", displacement per full turn of rotor=436CI.

10:71
Rotor dia=5.778", length=17.000", displacement per full turn of rotor=466CI.

14:71
Rotor dia=5.778", length=19.000", displacement per full turn of rotor=521CI

This is theoretical displacement.


Good data there, thanks.

How do those displacement figures get used to match to an engine, versus the modern positive displacement blowers like Autorotor, Whipple, TVS etc, which are rated in liters like 2.0(medium) to 4.0(large)?
Don

73 Ranchero with a 72 Sport front end, parked since 1990
91 Lincoln Mark VII SE, OBDII 347/4R70W
98 Mercury Mountaineer
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Big Bird Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 3:51AM
If you use the 14:71 it's kinda big and moves a lot of air, which can overwhelm your engine.
You can try to slow it down with the pulley combination, but then it pulses a lot.
The above post should be read in a "Grumpy Old Man" voice.
Almost forgot: "Get off my lawn!!!"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 4:50AM
Originally posted by 72 RS 351 72 RS 351 wrote:


 How do those displacement figures get used to match to an engine, versus the modern positive displacement blowers like Autorotor, Whipple, TVS etc, which are rated in liters like 2.0(medium) to 4.0(large)?
 
I'm not really 'up' on the formula to size a huffer to an engine, but it seems easier to me to just use cubic inches > cubic feet per minute of volume w/o having to change one or the other to metric?
 
4 stroke engines require 2 full rotations of the crank to complete each cycle, so the blower volume would need to be X2 rotations to the engine displacement
 
Weiand used the V type cases for their Megablower series, I never got excited about the mount style
 
-------------------------------
 
I don't see any need to go to a stroker kit with a blower on top, the PSI has the same effect. IMO it's either/or, no need for both unless you're looking for 1000 or more HP... and if you don't see that kind of power from such an animal it's not earning it's keep
 
I'd $ettle for a good set of Flat Top piston & Open Chamber heads rather than expensive dish pistons & spin the blower to make up the difference
 
I'm using SRP 206044 & Eagle 5780 rods in my 671 build 


Edited by Rockatansky - 16-November-2014 at 4:57AM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 72 RS 351 Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 6:29AM
I asked because that type of blower is different in how the size relates to matching to an engine, rpm range etc, versus the later PD units. As an example, the 2.2 liter KB blower I have is good for a 302 and the 15psi range, though the latest cars seem to be running 3-4 liter PD blowers on 4.6-5.4 Fords. Those just run lower blower rpm's and don't have to work as hard. I just wondered how those classic Weiand blower types are matched to an engine. I'm sure that the volumetric efficiency is a big part of it, and how they measure its displacement versus other types of blowers. Regards,
Don

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91 Lincoln Mark VII SE, OBDII 347/4R70W
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 8:02AM
yes the efficiency varies wildly in the older stuff, some of the oldies are even 2 lobe rotors
 
mines an older 3 lobe 671 w/o seals, not sure yet if it's small or large bore but it has 'one side flat' end plates
 
then I have an Eaton 62 on a 1.9L 4 banger too
 
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 9:02AM
Well I've picked up my heads tonight :) they're the smaller 58cc ones so my CR is going to climb!

Will definitely need a custom set of pistons to get CR down but that's not an issue :)

Definitely going blown, can't beat the look of one and I love the whine so it's getting built!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ilyes Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 9:12AM
58cc, that's going to raise your CR through the roof. You are looking at around 10.5 to 1 if you are running stock piston/bore with piston seating 0.025 down the hole.
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