Aside from the issue of more power, are there any advantages to putting a big block motor in a 715 as opposed to a small block? Not brand specific.
I'm just curious of your reasons.
-B.
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Aside from the issue of more power, are there any advantages to putting a big block motor in a 715 as opposed to a small block? Not brand specific.
I'm just curious of your reasons.
-B.
well. I think you pretty much answered that one right there. One weird side effect I noticed on my work trucks (one BBC, one 350) is that the bigger motor got way better mileage. I'll guess that it's because of the increased torque of the big block making it easier for the motor to do the work required of it. Torque more than anything else is KING.
The other obvious advantage is bragging rights, but that goes w/out saying, so sorry I said it.
the bigger diameter pistons apply more downward force across the piston surface than a small block thus building more torque at the same rpm's. a small block has to rev higher and be built up more to achieve to same HP and tq. the 366 is a smaller bored big block that has about the same rotating mass as the bigger big blocks, thus more tq than 350 sb just not as much as say a 396.
fuel mileage may surely increase and you use less throttle to go the same speed with a bb. On low geared trucks like 715 the small block is better designed for the higher revs (rotating Mass) but when needed the big block will come to life from idle thru peak rpms like no other. its really the question of if you want massive tq and hp and if you was using it to pull or bogg or tree climbin.
So, more power is the only advantage I'm seeing unless you REALLY care about mpg? It seems to me that with the tall gears you'd need a motor that can spin pretty high since road speeds are not really designed around our trucks and also I've found that spinning the wheels in mud clears my tread quicker and helps.
So, if the 350 was too little motor torque wise, or if I wanted to go from 8mpg to 12 mpg then this would be the way to go. But if I enjoyed knowing that 3000 rpm's on my drive to town isn't really THAT hard on my 350 as opposed to 3K prms on a 366 being tough on it, then I'd want the 350?
Hmmm...
Yeah...but, if you would happen to run across a set of...Oh say 4.56 gears THEN the added torque of the big block, even a nice mellow low cube big block, will help move the heavy truck along with the taller gearing. Since you don't have overdrive, gears and a nice rat motor would be so sweet. That'll cure your boredom.
How about a 6.2L or 6.5L GM Diesel? Lots of torque and power, yet will cruse at 3000 rpm all day long....And how can you not like the manly noise that they make...:)
lots of torque and power? hahahahahahahahahahahahahahah
Ok, they at least SOUND like diesels. 140hp or whatever they made, 190? isn't really LOTS of power.
3000rpm all day long? Really? How many days?
How many you want...:) Ok maybe not 3000 closer to 2500. I have one in my M1028 and I can pull my MKT with it all day long with out any problems. (Mobile Kitchen Trailer, built on a 1.5 ton trailer frame and are very heavy. Like moving a cement block on wheels.) (Good fuel milage too.) So the engine IMHO has good torque and I'm impressed with its get up and go....so yeah I think it has LOTS of power... More than my '93 F250 with a 5.8L (read 351 EFI) had.
I don't really see the practicallity in that for my use. Were to swap in a diesel then I'd HAVE to get an overdrive tranny or get new gears. Were I to do all that or either of those then I'd much rather get a ratt motor.
No offense to the diesel guys, I can see the lure of them and the advantages- they just aren't for me.
What I was mainly asking (read that "To keep this from becoming a debate about gas vs. diesel motors") is what is the advantage of a BB over a SB. As I understand it you will still be turning the same RPM at the same speed, just using less fuel. Though if you got different gears you could go the same speed at a lower rpm and a BB could do it without stressing the motor. By that logic then a BB would last longer. Hmmmm....
But, using a SB you have a motor more designed to spin at 3K rpms than a BB and with the stock gears you have the pulling power.
Sounds to me like the way to go would be to just get an OD tranny and use a SB.
or
Get a diesel, an OD tranny, and new gears. That would be the best of all since you'd have durability, power, and cheaper fuel w/ better economy. (were you willing to spend the $)
If that's all true then why does Barry run a big block as opposed to a diesel?
I know there are flaws in the above logic, please point them out.
-B.
Barry runs a fuel injected BBC in a street legal mud truck. Stop overthinking the event. BBC has more torque. More Torque = better mileage, more trail grunt, and it's not a 350.
Once I put that stuff on a pallet...no backing out!
Tom,
I have alerted the wife to my plans and started amassing things for the ebay. I hope to have your money in 2 weeks as opposed to the month I requested. Jean Ellen is currently e-mailing you about how to suprise me with the purchase of the front locker.
I am not worried about the BB, but the gears do worry me. I may just hold those until I get more guts.
-B.
Big block = more rotating mass (more kenetic energy).
Small block = less rotating mass (more efficient).
Cause I can find a 352, or a 383 big block, and a 400 small block.
Diesel, especially with a turbo Cummins, figure that the torque is roughly twice that of the HP. Much more efficient use of the fuel, and the fuel itself contains more energy (BTU's per lb of fuel).
Now, the big advantage of the big block over the other two is that our truck isn't really that light weight. So you have to have the better gears to have enough mechanical advantage to use the small block. The diesel can use lower gears and bigger tires, get great mileage, and has tons of torque in the lower power band.
Big block, you can still rev them up to a decent RPM if need by. You can't do this in a diesel. And if you are in the wrong gear, you have enough power to power through it, where most small blocks can't do this.
Of course, add a supercharger or turbo, and you change the entire equation.
Sorry, Dave, but torque is more a function of stroke. Envision the crankshaft with the piston an the center of travel - the crank throw is horizontal. The longer the stroke, the farther away from crank centerline (fulcrum) the force is applied. Jsut like slipping a "cheater bar" pipe over a braker bar to gain leverage, the longer stroke provides more leverage against the crankshaft. Piston diamerter DOES play a role, of course but that of displacement along with stroke length.
The old conventinal wisdom stated that a "square" engine (one inwhich the stroke = bore) was a good all-around engine. An under square engine (bore < stroke) made a good torquer, and an oversquare engine (bore > stroke) made a good hi-revver (like the venerable Dodge 340). For an application with 5.87's, torque is not a big concern (breaking parts with too much is, however), but an angine capable of fast spin-up and sustained hi-rpm would be MY preference.
A 283 chebbie (3.875" bore/3" stroke) or 340 Mopar (4.04" bore/ 3.31" stroke) (note capitalizations? heh heh heh!) would SCREAM!
Go here to see other combinations:
http://www.zccw.org/Tech/Engine/06-97LongShort.html
To the torque crowd, I'dlike to see a 'binder engine swapped in!
But that's just me...
Bob
Brian, here's my opinion...
With stock gears I'd stick with a small block. First off for it's shorter stroke and lighter everything it's more suited to higher rpms. Plus with the gearing stock to our trucks, you'll have more than enough power to do most anything except full on boggin' but that's a moot point as 5.87's are a bit deep in my opinion for mud, same with sand.
As far as gaining mileage, that's a moot point too unless you spend most of your driving time at low speeds. Ideally you want to gear the axles to meet the torque curve for most conditions. With our deepass gears you jump way over that curve in all but the very specialized engines. So at freeway rpms you're too high in the revs to notice much difference either way.
Chris
5.87's are a bit deep for just about anything-- lots of rock crawlers here running 4.89's or so, w/low t-cases or something. Why? Because too low a gear in the axle doesn't let them roll fast enough to get out of their own way going down steep rock faces, and that's not good. Anyway.
Brian: Torque is king. Big blocks have more. That's it!
Following up on Bump's oversquare scenario....400 BB Dodge, 4.342 bore by 3.38 stroke....oversquare to beat the band, with some 2.08 intake valves that can go up to 2.14 right now.
Being this is big block, but the stroke is so short, it isnt a torque motor in fact is has less stroke than a 350 chevy but wil rap up faster and make more horsepower without question...comparably built of course. With 5.87 gears and especially with double tcases or other underdrive units, this motor seems to be perfect for the M715 on road and off...plenty of power for 60-70 mph cruising and not to much torque to split axle shafts like twigs off road.
My opinion, but makes sense to me!
brute4c
Thanks you guys for enlightening me.
Basically what I learned is that with the stock gears a 350 would be perfect sicne I'd want the higher rever and not need a torque monster due to the gears and torque multiplications.
With a bb, I'd need the higher gears to keep from overrevving and also to keep from twisting shafts due to more torque output.
So, right now my setup is good, and in a year when I swap in the 366 and the 4.56's my setup will be just as good.
Bump- thanks for giving me the reason why all this happens. Before it was just talk, but you backed it up with math.
Brute- Glad you're back around. We missed you.
-B.
Thanks Bump for puting up the link to that article- makes for interesting reading. I've read similar articles on the Speed-o-motive website, that was awhile back and I don't have their address handy or I'd reference it. Maybe later I'll dig it up again. All these opinions are some good food for thought.
WHAT THE F*$K?!! That table is cracked out! I can appreciate the math done, but ...it's speculation on stuff nobody does!! NOBODY built 283's with 6.5" rods.
Since I'm not up on ford or Mopar lengths, let me just give a quick real world Spiceresque nutshell on chevy.
5.7" rod length from 262 to 350 V8's. 6.0" is the next best length step for the buck and 6.100", 6.125" and 6.200" are high buck Nascar lenghts for wicked high revs and great rod ratios.
400's use 5.565" stock rod. A switch to 5.7" rods is nice and frees up some revs and is quite common. 6.0" rod gets you into wicked expensive pistons, along with possible cam clearance issues and the need to possible switch to a small base circle cam or clearanced rods.
There IS NO 400 factory Big block. 396 or 402 not 400. 400 is sbc.
Big blocks from 366 and 427TD and 396-502 all run 6.135" rods stock.
6.385", 6.535", 6.600" (a sweet Bill Miller length) and 6.800" are the most popular flat out high rev rat rods.
I get 16 miles to the gallon with my TBI350 rolling on 12.50 20 michelins with stock gears :DQuote:
Originally Posted by tacoma
If you want a big motor look at the new 4 wheeler.A big diesel I left the mag at work but I think it had 5.4 million ft lbs of torque.
There is no substitute for cubic inches........except more cubic inches