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Old 05-21-2013, 01:24 PM
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Low RPM High Torque sbc

Thinking about building a budget sbc, 6-71 Weiand blower with 2 Edelbrock 750's. Looking for a high torque monster at a reasonable RPM, less than 6500. Plan on using cast crank and forged pistons with good heads, cam, lifters (suggestions). Will probably have water/meth injection if it would be of an advantage in this type of motor. Trying to keep RPM's down and use mostly factory parts thus the 6500 RPM limit.
The vehicle it's going in:
41 Willys
355 CI
700R4/3500 stall
3.90:1 ford 9"
Race weight 3257
20%Street/ 80% strip car

Yeah, I know will need a different stall converter. Is it possible or a pipe dream?
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Old 05-21-2013, 01:54 PM
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what size of engine?over 800 hp?
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Old 05-21-2013, 02:22 PM
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Originally Posted by vinniekq2 View Post
what size of engine?over 800 hp?
355 SBC. That would be nice but don't think I'd get there in this budget engine. Pretty limited to 700HP and 600 Tq by the tranny specs.
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Old 05-21-2013, 02:30 PM
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If you want low RPM torque then you need a lot of displacement. A blower definitely helps but Going with an aftermarket block and 3.75" stroke (or more) would really get you there.

Price out what it would cost to use stock components and compare to a complete SHP short block, it'll only be a little over a grand more for more displacement and much improved durability.

BTW, are you attached to the sbc platform? There a LOT better options for low RPM torque.
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Old 05-21-2013, 02:48 PM
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Originally Posted by ap72 View Post
If you want low RPM torque then you need a lot of displacement. A blower definitely helps but Going with an aftermarket block and 3.75" stroke (or more) would really get you there.

Price out what it would cost to use stock components and compare to a complete SHP short block, it'll only be a little over a grand more for more displacement and much improved durability.

BTW, are you attached to the sbc platform? There a LOT better options for low RPM torque.
Oh yeah, pretty attached. Already has a 355 in it and never was big on big blocks. Do know where I can get a complete stock 454 though at a good price. (free)
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Old 05-21-2013, 03:17 PM
How fast is fast enough?
 
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Then I would put Vortec dished pistons in a 4 bolt Lt1 block, LT4 heads or ported lt1 heads, and perhaps a zz4 take out cam. All factory parts, all cheap, and about the best you can do in the sbc platform at 355ci.

With a blower you can maybe hit 600ftlbs if everything is set up right.
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Old 05-21-2013, 03:32 PM
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6500rpm's and 700 HP with a factory cast crank? I think I would start saving up a little and get all forged internals.
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Old 05-21-2013, 03:33 PM
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Then I would put Vortec dished pistons in a 4 bolt Lt1 block, LT4 heads or ported lt1 heads, and perhaps a zz4 take out cam. All factory parts, all cheap, and about the best you can do in the sbc platform at 355ci.

With a blower you can maybe hit 600ftlbs if everything is set up right.
Thanks for the info. I'll look into that.
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Old 05-21-2013, 03:43 PM
How fast is fast enough?
 
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6500rpm's and 700 HP with a factory cast crank? I think I would start saving up a little and get all forged internals.
A factory block will fail before a cast crank will as long as its properly machined, assembled, and tuned. RPM and tune kills cranks. Being an auto with a loose stall helps too.
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Old 05-21-2013, 03:45 PM
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A simple engine such as the GM 350HO (330HP) vortec motor would fit the bill.

Or a 350 built similar to this...

A smaller blower is more efficient at low rpm. Like a 142 blower or the 177 blower. or the Edelbrock-Eaton MP122 blower.
Keep the cam small like the 330HP crate motor cam is.

A blower just magnifies what you bolt it too.

a 6-71 roots would be a lot more efficient with a blower drive system that had a built in variable speed transmission. so the blower speed would be independant of crank shaft rpm.

Even still you can build a good street "cruiser" blower motor. The key is keep it mild.
Let the blower make the power. A dedicated water methanol injection system allows more engine compression ratio.
Don't need to get real stupid with boost. its a cruiser.. 475- 500hp is a lot.
easy on parts and fuel consumption. mild hyd cam hyd roller cam...torquey heads etc.

Whats going on with your present blower motor?
Are you looking to tame this one down? (street cruiser practicality)?

Edelbrock has a new different roots street blower in the works made for (dual throttle body direct port) EFI and intercooling and or dual carbs.
They have not released all the details. it is based on the Eaton-- Magnuson design.
The belt drive system looks a lot more street friendly than a 6-71.
Something to look at. It is on their site but little detail.
www.edelbrock.com

A 9:1 375hp mild near stock 350 engine can be easily supercharged to 475-500hp and be bullet proof. Its all about correct design and tune up. A good electronic water-meth system with a fail safe would be real cool.

cruise at low rpm in OD with a stock converter etc. Just forget about 700hp.

For mild to moderate but very street blower motor friendly hyd camshafts
look at the Crane HMV -Powermax camshafts EG: HMV260-2 HMV 266-2 HMV 272-2 and HMV 278-2
lots to choose from. Including many of the milder Crane "Z" cams.
www.cranecams.com

Last edited by F-BIRD'88; 05-21-2013 at 04:15 PM.
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Old 05-21-2013, 03:53 PM
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Originally Posted by F-BIRD'88 View Post
A simple engine such as the GM 350HO (330HP) vortec motor would fit the bill.
A smaller blower is more efficient at low rpm. Like a 142 blower or the 177 blower.
Keep the cam small like the 330HP crate motor cam is.

A blower just magnifies what you bolt it too.

a 6-71 roots would be a lot more efficient with a blower drive system that had a built in variable speed transmission. so the blower speed would be independant of crank shaft rpm.

Even still you can build a good street "cruiser" blower motor. The key is keep it mild.
Let the blower make the power. A dedicated water methanol injection system allows more engine compression ratio.
Don't need to get real stupid with boost. its a cruiser.. 475- 500hp is a lot.
easy on parts and fuel consumption.

Whats going on with your present blower motor?
Are you looking to tame this one down? (street cruiser practicality)?
Just wanted to see if there was a good way to build a torque monster on a budget without all the cost of high RPM parts. They say, "torque wins races". lol
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Old 05-21-2013, 03:58 PM
How fast is fast enough?
 
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Just wanted to see if there was a good way to build a torque monster on a budget without all the cost of high RPM parts. They say, "torque wins races". lol
Only slow idiots say that.
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Old 05-21-2013, 03:58 PM
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[QUOTE=F-BIRD'88;1677558] snip snip
A blower just magnifies what you bolt it too.

a 6-71 roots would be a lot more efficient with a blower drive system that had a built in variable speed transmission. so the blower speed would be independant of crank shaft rpm.
end snip snip

A thought, or brain fart. Maybe a fluid drive that would keep a constant RPM at the blower, kind of like a wast-gate so u'd have 8-10 lbs boost constantly.
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Old 05-21-2013, 04:25 PM
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well a Constant drive ratio is not needed. But a variable drive ratio could be a 2 speed or a 3 speed or a CVR transmission is possible.

What realistic supercharged engine power out put are you after?

Gas mileage? is that a factor?
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Old 05-21-2013, 04:30 PM
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Remeber there are already many much more efficient supercharger designs other than a Roots blower.
But all--- cost more.

Also remember.... detonation will cut up cheap parts and expensive parts too.
Lower charge air temperature is your friend. High octane gasoline is your friend too.

If you want to keep it on a budget you got to keep it simple and realistic.

Define what you want the car to do.
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