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  #16 (permalink)  
Old 08-18-2010, 12:21 PM
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Sure sounds like a lot of effort for little to no return. I had a brand new bone stock '75 Nova SS with a 350 2bbl with a 3 speed standard transmission . As soon as the 12 mo 12,000 warranty was out I installed a Q-jet manifold and carb and a set of cheap headers and full dual exhaust and got 24 mpg highway . Just my $0.02

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  #17 (permalink)  
Old 08-18-2010, 03:22 PM
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I don't know where you got your automotive education, but it sounds to me like you'd be a LOT better off w/a Rambler that might get 25-30 MPG than to waste your time on a long rod/short stroke V8 SBC built for mileage.

Why would you think of the huge-A 4L80E anyway? There are smaller, lighter, more energy efficient trannys than it. It's like comparing a TH400 to a C4. And if mileage is your do-all/end-all, run a stick.

At the end of the day, it's far more HOW you drive than WHAT ENGINE is under the hood, within reason, AFA mileage goes. There are sites that cater to aggressive mileage tactics and techniques- I believe you'd do well to tune in to those to see what can reasonably be done- and there's a lot more to it than you might expect.
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Old 08-18-2010, 04:04 PM
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http://ecomodder.com/forum/ is one 'Hypermiling' forum that I've heard mentioned on this forum. They say: "...where performance is judged by fuel economy rather than power and speed. EcoModders employ a combination of vehicle mods, driving techniques, and common sense to squeeze every penny out of the pumps."

Driving tips from same site: http://ecomodder.com/forum/EM-hyperm...ecodriving.php

Good luck.
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  #19 (permalink)  
Old 08-18-2010, 04:19 PM
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Thanks cobalt, I want to convert to stick in my van eventually. You are of course right, I can get better mileage with a manual shift tranny. My van I drive now has a 454 and 5.13 gears in it, I may be trading it for a same sized but later model van with a nice lift gate, and a better liquid cooled honda generator as opposed to my onan. It also may have a different rear end ratio because it has the 6.2 liter diesel and th400. But if I were to keep this van the only hope of getting even a few mpg better would be a overdrive tranny such as a 4L80-E, the th400 it has now coupled to the 454 equals about 4100 rpm at 72 mph which just isnt cutting it. The van weighs nearly 14,000lbs. How many ft/lbs does a 454 produce anyway? 400ft/lb at 1800 rpm? Well I could get that with a 327 at 4100 rpm easy. Be right in the torque peak too. All this is a mute point as I hope to trade this van that runs great for the 6.2 diesel van that doesnt run but has the lift gate and better generator. Either way, Im still going to build my high winding motor and if it doesnt get better gas mileage then so be it, but either way, I will still get to have a motor that frightens young children and makes lesser men afraid when I rev it up. Then I will just have to slap it in an s10 no big deal. It is what I want to do, get lots of torque at a high rpm. I don't care if it makes sense, i don't care if it doesn't make sense. If you havn't built a motor just like this, then how would you know really for sure that I won't get better gas mileage even? Here goes: Ok so smaller journal, less drag. Less piston side loading, less drag. No overdrive, less drag. More piston dwell+less needed timing=less force trying to drive the piston backwards, less drag. I say I should try it and see what happens! I will not be drag racing anyways so what does it matter. If my 454 motor gets its torque peak at 1800 rpm in stock form, then smaller motor spinning twice as fast making the same torque should be fine with the right gearing, only better mpg is my theory. I swear some of you guys seem like my dad and want me to know that "if there was a better way everybody would be doing it". Maybe there is a better way but nobody tried it!! If you guys havn't tried it maybe it's because your dad said the same thing only you just believed him. Im a dirty rotten stinking biker with long hair and billy goat beard and a dog that rides on the back of my two stroke motorcycle everywhere I go, I live in my van most of the time and I have lots of babies with lots of women. I didnt get this way because I follow whatever everybody else is thinking tho ok? Its my reponsibility to myself to prove my dad wrong see? He is getting old tho so I gotta hurry.. 6.2 with a turbo prolly get better gas mileage anyway than any of this stuff, but Im going to build me a super obscure long rod sbc just because. I will prolly put it in the s10.. That's just me tho. It is so much fun to talk and debate about this stuff with smart people, I love this website, I wish Ide gotten on here years ago.
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  #20 (permalink)  
Old 08-18-2010, 04:27 PM
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I will be the first to admit that I have not tried to build a high winding anything for mileage. If nothing else, I admire your tenacity. But I do disagree w/your take on OD. Given the correct rear ratio and a OD tranny, mileage WILL go up, all else being equal. And don't forget- a lower first and closer splits of a 4-speed AT w/OD will aid mileage as well.

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I swear some of you guys seem like my dad and want me to know that "if there was a better way everybody would be doing it".
I have to smile when I read your take on your ol' Dad's advice. I was amazed as I got older how much smarter MY Old Man got!!
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  #21 (permalink)  
Old 08-18-2010, 05:25 PM
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Yeah I didnt mean to suggest that an overdrive tranny wouldn't get better overall gas mileage on most common setups really, especially on a long stroke tractor like low rpm engine like a 383 400 454 etc but rather trying to say that the parasitic drag of an extra set of gears turning the drive shaft at a faster rate than the actual crankshaft is turning could hurt gas mileage compared to simply having a taller rear end gearing
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  #22 (permalink)  
Old 08-18-2010, 05:27 PM
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What surprises me here is that it got to be the fifteenth post in this thread before 'camshaft' was mentioned...

That would have to be a critical part of any project where you want power and economy.

I am also bewildered at the suggestion that it takes over 350 cubes to make a car move. I've seen a lot of very fast cars with engines two thirds that size. But at the same time, some of them can be thirsty little devils too.

As has been well recorded here, how you drive is going to have a big part in producing good mileage figures. But there is nothing to stop you developing an engine with thrifty and docile low rpm performance, but which lifts its skirt and runs if you push harder on the loud pedal.

As mentioned again, if there's a lot of experimentation involved, you'll spend many times more on achieving this than you'll ever save at the bowser.

But I don't blame you for trying, and for making it a dream or goal not to be sacrificed to the altar of doing it like everyone else does.
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  #23 (permalink)  
Old 08-18-2010, 05:40 PM
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Quote:
Originally Posted by Dirty Biker
...but rather trying to say that the parasitic drag of an extra set of gears turning the drive shaft at a faster rate than the actual crankshaft is turning could hurt gas mileage compared to simply having a taller rear end gearing
The flip side to this, is taking off from a dead stop.

Just running a high rear gear is not the "answer", if you're dropping out of the bottom of the torque band every shift.

To get a short enough gear to easily get moving- PLUS having a tall enough rear ratio for good mileage in high gear- requires more gears to keep the drop between gears to a minimum. Or an OD.
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Old 08-18-2010, 05:47 PM
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A Borg-Warner R10 or R11 should cope with the torque generated here...

It was something I was going to mention. That Rambler would have had a 0.7:1 R10 fitted, very popular in fifties USA motoring.

Anyone serious about fuel consumption would have to consider a manual transmission. A direct top gear 5-speed would be nice, used in conjunction with a reasonably low rear end ratio, but there's not so many of those about.

For ease of installation, the overdrive version of the New Process A833 would be the simplest answer here.
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  #25 (permalink)  
Old 08-18-2010, 07:09 PM
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FYI decreasing the strole will raise the amount of parasitic loss for a given hp level... if you really want some good sbc milage I would consider a 400 with TPI. Basic 9:1 compression and an almost stock cam (maybe something like an XE256). Smaller engines do not directly correlate to better mileage.
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  #26 (permalink)  
Old 08-18-2010, 08:23 PM
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@turbolover well according to this guy I duuno if he is right or not but he seems very smart too, Dr. F. W. Lanchester, one of the earliest true geniuses of the internal combustion engine, analyzed this problem over 90 years ago, and correctly decided that comparing motors on the basis of size only gave an unfair advantage to motors with more cylinders, and favored those with larger bores and shorter strokes. So I would have to disagree. Also, wiki says on bore stroke ratios, "At a given engine speed, a longer stroke increases engine friction (since the piston travels a greater distance per stroke) and increases stress on the crankshaft (due to the higher peak piston speed). The smaller bore also reduces the area available for valves in the cylinder head, requiring them to be smaller or fewer in number. Because these factors favor lower engine speeds, undersquare engines are most often tuned to develop peak torque at relatively low speeds." Can you quote a source of those things or at least tell why you think them and said them? Thanks man.

@raybell I do not have money for a new really fancy and expensive overdrive tranny but might be cooler if I did.. I am trying to create an engine that gets just enough torque for what weight I carry at the rpm that I spin at 75 mph without overdrive. I believe that non overdrive trannies are better because its coupled directly to the driveshaft in high gear, reducing heat and friction. I like low geared rear ends so I have good take off, I just want a motor that is purposfully designed to turn the rpm needed for 75 mph sustained. But thanks man for the encouragement on the earlier post

@cobalt327 I do not need a high rear end gear if my motor is made for the thing I use it for do I? Now a high rear gear might be good for the guys that have all that crankshaft leverage and like to keep the rpms low. It costs alot to change the rear axle ratio in a big truck, prolly 600 dollars or more, I just thought it would be more fun and cost the same to build a motor with a higher torque peak. You know, a purpose designed engine. Anyways they practically give these things away here where I live, I got all four my motors for less than 220 dollars.
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  #27 (permalink)  
Old 08-18-2010, 08:44 PM
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I would never recommend anything fancy or expensive...

You will find pickups around that have the Borg-Warner overdrive units bolted onto the back of their transmissions, I believe that Chevrolet pickups had the R11 on the back of 3-speed transmissions through the early to mid-sixties. So they'll bolt straight up to your engine, right?

I had an Austin with this kind of overdrive, it was stupendous on fuel. I used to sit on 100mph all the time in it... and got 24mpg while doing so! This in a car that weighed a ton and a half empty and was never empty.

Of course it did have that other fuel saver fitted, the ubiquitous SU carburettor... they are great for both performance and fuel economy... look at the way they are mounted on the Rover 3500 V8 some time for ideas on saving fuel with a V8.

Getting back to the B-W overdrives, they come as a unit with the trans, so it's a complete installation, the mainshaft of the 3-speed is set up to fit into the overdrive and there's a link between the overdrive and the shifter mechanism to prevent you engaging reverse gear while it's in overdrive.

They come set up with relays and so on, but I prefer to operate them manually so you have a clutchless 6-speed transmission. No oil pumps in them to sap power (like the Gear Vendors unit...) and if you find one it won't cost you much.

Of course, if you find three I want you to send me two!
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  #28 (permalink)  
Old 08-18-2010, 08:58 PM
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What you quoted is for themost part true, and is only a very small part of what you need to consider. You need to think about a lot more aspects. I appreciate your fervor but it is slighty misguided.
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  #29 (permalink)  
Old 08-18-2010, 09:05 PM
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Hey dirty biker, I have an idea for you.
Build 302 with bout 6:1 comp ratio,hang a couple of turbos,one on each bank.
Airesearch 510s should do it, run about 40psig boost max,dont do blow throghs,just suck gas or maybe better yet,run alky,in that case you can up comp ratio some,little anilyne n nitro wouldnt hurt any either,that ought to lite up that van and scare people real good.
And hey talkin bout bikes look up what roadog did you can actually tow the van with motorcycle if one of your turbos overspeed and throw off compressor wheel
Use a good pair of holley dominators for carbs n remember when u run alky go to 7:1 F/A ratio
Good luck to you and please send pictures!!!!

Last edited by topwrench; 08-18-2010 at 09:17 PM.
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  #30 (permalink)  
Old 08-18-2010, 10:10 PM
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How about this, I build me a 327 block with pistons meant for a 350 engine with 6 inch rods and my 283 crank using 6.250 inch connecting rods. With a motor with that rod ratio a stock 350 cam will not behave the same way, and I am curious to see how it does. Don't need turbos (but I wish), don't need overdrive dont need big heads because it will actually flow better with smaller ports according to this. A high rise dual plane manifold and an adjustable cam gear might be nice. Already have the block, crank, stock 283 heads, stock 327 manifold, and long tube headers. Fun stuff, thanks for helping me figure out what rods and pistons to use everybody. I wish I could run that setup thru desktop dyno but I dont have it... Maybe one of you guys do tho?

Here is a cool article on rod ratios, http://victorylibrary.com/mopar/rod-tech-c.htm

Here is a you tube vid of my old lady and dog and I riding my gt750 motorbike before I changed engines.

http://www.youtube.com/watch?v=2whyAQ35wkQ

If I dont like the results of my crazy motor I spose could sell the 327 block and crank to a corvette guy. Theres one on ebay right with the same casting numbers, block only, for 1000$.... woohoo... Mine is flint michigan made with the plug in front and everything.. Gotta love craigslist man...
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