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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
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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?
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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.
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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
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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
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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

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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.
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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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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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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 9:26AM
They're 302c heads so very small chamber! I'm running stock everything on an 8:1 engine so this should get me to 9.5:1 with the standard pistons

This will do for a quick power fix until the blowers paid for and installed
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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 11:46AM
std 4" bore, 58cc chambers & 8cc factory dish 1973 pistons makes 9.9:1
 
4.030" 3cc FT's kicks it up to 10.65:1
 
I just realized you're 'over there' so the 2V blower inlet manifold is a possibility, no such thing here
 
are you sure you don't want to go with the 4V inlet & heads?
 
here's a pic i gleeked from Antlerfiend, shows the 4V outline on 2V Aussie heads
 
 
and I happen to have pics of a 2V blower manifold
 
 
... and a 4V
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote californiajohnny Quote  Post ReplyReply Direct Link To This Post Posted: 16-November-2014 at 6:54PM
wow, that's a tall blower manifold! is that because of the front mounted dizzy?
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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 7:01PM
Can't get 4v over here that easily so they're out. Plus I have these now as well as 2v headers. Aussies with a bit of port work are good for 500 so that's plenty really

Plus they'll have excellent quench
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 18-November-2014 at 10:27AM
Well the CR is sorted, 13cc hypereutectic pistons plus 104 thou cometic headgaskets brings me down to 7.97:1 :) going with the 6v71 blower too

Soooooooo if anyone has a dual carb, offy 360 or similar open chamber 2v manifold I'm on the lookout for one!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 18-November-2014 at 1:22PM
I'm getting 8.3:1 ?
 
FWIW I  wouldn't do .104" gaskets... the quench you wanted is hurt pretty bad & the cost alone could be added to a more proper set of pistons
 
MLS gaskets require specific surface prep, the decks need to be much smoother than for old school gaskets. unfortunately not too many guys are aware of this before slapping them on & TQ'ing them down, then they only last a matter of minutes run time. add surface prep machining to the cost of this route http://www.crankshaftcoalition.com/wiki/Head_gasket
 
another FWIW, the cylinder pressures you'll be seeing pretty much negate the need for quench
 
there was a mob that did some really nice work opening up the closed chamber heads to leave only 1 quench pad, Kostecki Engine Centre but they've packed it all up, they had some real nice articles w/pics on their page but it's all gone off the web now
--------------------------------
Tim Meyer specializes in 'off the shelf custom' pistons that have taller CH than ordinary aftermarket pistons. he's worked with KB pistons to produce a line of specialty pistons for Clevelands with specs that you can't find anywhere else, he may be able to supply the dish you need, together with opening up the chambers some to leave the 1 quench pad you could be in clover
 
 
Tim recently posted this;
 
"Visiting with Keith Black piston one time, we talked about the importance of quench.

They said they saw a big improvement with 1 quench pad,

but when they added a 2nd or 3rd quench, there was no gain from there."

 
looking for the old thread on the Kostecki modified chambers I found this
 
found the thread w/dead links


Edited by Rockatansky - 18-November-2014 at 1:32PM
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 18-November-2014 at 1:34PM
Hypereutectic Shocked
 
gotta be Forged on this one
 
no if's & or but's
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 18-November-2014 at 7:48PM
I'm getting 8.3:1 ?

I stuck the numbers into Wallace Racing's CR calculator, 3.778 or whatever stock rods are, 3.5 stroke, .015 deck height after machining, 4.1 HG bore size, 4.020 over, .104 thou HG, 58cc heads and got that?

FWIW I  wouldn't do .104" gaskets... the quench you wanted is hurt pretty bad & the cost alone could be added to a more proper set of pistons
 
A proper set of pistons isn't available, no one seems to sell anything with a dish and I'm not paying £1500 for a set of custom ones in the UK. I can get the CR to 9.5 or 9.66 then run 4psi instead of 6psi though which would still get me up to 12.5:1 ish CR under boost. This is fine as all UK gas is 95 RON, American (crap gas) is 91 for the most part when looking at the CR specs on BDS's site they state 12.4 as the max street CR so with our higher octane gas it'll be ok. We even have 99 RON at most stations too. The only set of pistons I found which would work (or I thought they would) unfortunately turned out to need a rod with 3.750 stroke but were a 24cc slug.

MLS gaskets require specific surface prep, the decks need to be much smoother than for old school gaskets. unfortunately not too many guys are aware of this before slapping them on & TQ'ing them down, then they only last a matter of minutes run time. add surface prep machining to the cost of this route http://www.crankshaftcoalition.com/wiki/Head_gasket
 
The blocks being milled so that wouldn't be an issue, a milling machine should give that surface finish with a slow pass and couple of thou cut. If not they have surface grinders etc etc.
It was one of the performance shops in the UK who suggested them £240 inc VAT so about $375


another FWIW, the cylinder pressures you'll be seeing pretty much negate the need for quench
 
If that's true I could just rebuild my 2V heads with OC and ramp the boost up as they're 76cc heads! I never gave them a thought as OC heads are a piece of sh*t usually

Tim Meyer specializes in 'off the shelf custom' pistons that have taller CH than ordinary aftermarket pistons. he's worked with KB pistons to produce a line of specialty pistons for Clevelands with specs that you can't find anywhere else, he may be able to supply the dish you need, together with opening up the chambers some to leave the 1 quench pad you could be in clover
 

I looked at his site but couldn't see anything in the cc range I needed and no doubt a set of hist custom ones will be a couple of grand!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nuggets Quote  Post ReplyReply Direct Link To This Post Posted: 18-November-2014 at 7:49PM
Originally posted by Rockatansky Rockatansky wrote:

Hypereutectic Shocked
 
gotta be Forged on this one
 
no if's & or but's


No need, the supercharger guru in the UK who I spoke to stated that as long as I don't plan on ramping up the boost past the 6psi target they should be fine.
The hypers can take it in his professional opinion
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rockatansky Quote  Post ReplyReply Direct Link To This Post Posted: 19-November-2014 at 7:47AM
Hypereutectic pistons fail in mild street Naturally Aspirated builds every day. the reason they exist is because they run much tighter tolerance than even standard cast pistons, they don't expand with temp as any other type of piston does. the problem is they're brittle, they crack split, shatter & splinter very easily... they were designed for stock daily driver extended warranty applications. whoever first suggested that they could be used in performance builds should be hauled off Wacko
 
here's a thread with a pic of a piston that's about to blow apart, http://351c.net/board/index.php/topic/3116-diagnoses-of-piston/
 
yes the build was flawed & the piston was subjected to extreme abuse, but that's the kind of thing that's normal in getting a blower build dialed in, the bottom end has to be able to deal with things being a tad off & a lot of abuse. hypers do not fall into that category. ever. even at 6 psi your Dynamic Compression will be more than what the piston in that pic saw. Forged pistons are just part of the deal, stock cast pistons would be (slightly) better than Hypereutectic  
 
this article points out that hyper alloy is a product of the quest for low emissions, and also addresses alloys for Forced Induction Wink
 
-----------------------------------
 
yup the open chamber head has been knocked for so long nobody thinks they're worth their weight in dirt
 
 
with much support from other members, check it out 
 
Originally posted by Rockatansky Rockatansky wrote:

the Open chambers aren't all that bad. consider that the use of the anti-knock agent Tetra Ethyl Lead was discontinued in 1974 and it's early substitutes (if any?) didn't quite do the trick. an Open chambered Cleveland will behave exactly the same as a Closed chamber Cleveland if the Dynamic Compression Ratios are the same... DCR being the balance of camshaft timing & static Compression Ratio
"Both varieties of the 351C cylinder head, quench combustion chamber and open combustion chamber, are poly-angle cylinder heads. The quench combustion chamber head is simply a poly-angle head with some small quench areas added on either side of the valves ... it is not a wedge style combustion chamber. Eventually you'll learn to think of the two styles of 351C heads in the same terms, instead of thinking of one as different or superior to the other." ~ G Pence
 
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