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  #76 (permalink)  
Old 10-25-2007, 08:21 PM
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That's pretty clever and impressive. Good job!!!

Now I see where the extra weight is at. By the way keep the fender skirts. (streamlining)

Now for some fun. If you drive on mostly highway or at least paved roads, you may be able to install a sheet plastic or stiff rubber belting spoiler below the front bumper. Wrap it smoothly around to the front edge of the fender by the wheel. Try to seal off the the bumper too. It needs to be vertical. You want the air to go around the car and not under it. The object is to block off air flow under the car. The lower to the ground the spoiler is the better. 2 inches from the ground is about as low as practical. Then try and block off as much of the front grill as you can. Clear plastic sheet with say a 6 inch hole in the middle. This is an attempt to streamline the front end a little. My winter fronts are worth about 1 mpg on the highway on my dually. I can run them year around if I don't tow heavy. I completely block the grill and leave only direct opening to the engine oil cooler. You might try an electric fan if you haven't already. You can adjust the opening size for cooling too. If you could make a rounded edge sort of funnel shape but round it will increase the efficiency of this opening about 15% ( from my fluid dynamics stuff).

If you could lower the car about 2 inches keeping the front slightly lower than the rear would help too. Then look at a side air dam under the rocker panels. Clear vinyl so it doesn't look too ugly and is flexible. To be really effective this needs to be as close to the ground as possible and as close and flush to the outside edge as possible. Nearly all racing groups either ban this or severely limit it as it is really effective in creating a partial vacuum under the car. It can have a little outward flare if possible right at the bottom. Even a piece of 1 x 1 inch aluminum angle facing out would be good. This makes air flow around and under it very inefficient which is what you want in this case.
If you wanted to hide this a little you could start it say flush with the inside of the front tire and taper it back to about flush with the outside of the rear tire. Make a mini pan the seal off the bottom of the car and make the air flow thru the tunnel as smooth as possible. You already have the fender skirts in the rear so leave them.

A partial vacuum or reduction in pressure under the car will cause a great flow of air in the small hole in the grill. the hot air from the radiator and motor will try to fill this but the the reduction in pressure will be more and the exit air will flow out the rear. This has a secondary effect of reducing the turbulence behind the car which is a major cause of drag. It's hard to streamline a "shoebox" (as the tri 5's are called here ) but every little bit helps. You could experiment with cooling by leaving the hole out and have an opening above the front spoiler that lets some air in.

The best example of this type of cooling and streamlining is the P-51 radiator. This is exactly what was used and while a lot more complex it was a gain of about 25 mph which is huge in aerodynamics.

A good example of this also is the 89-96 T-Birds. The grill opening is way to small to support cooling and the radiators are about 1/4 of the frontal area of yours. The cars have the air dam and opening as noted. The Super Coupes have outside rocker air dams too and the cars are very low to the ground. I had the spoiler ripped off my Super Coupe when I hit a tire tread on the highyway. The car almost immediately over heated. I thought I had broken the radiator but the spoiler was dragging on the ground. A few tie wraps and it was back in place ...problem fixed.

It is really tedious to make a belly pan but if you can get some RV belly pan material it's worth it too. This stuff is corrugated plastic similar to corrugate cardboard but much more durable. If you do this you only need to start at the fire wall.

There was a recent test of a big dually like mine in a truck magazine and they did all of this. They also taped up the holes in the front wheel simulators (hub caps) and made a plastic flat wheel cover for the rear duallys. They added an RV trailer belly pan too, altered to fit of course. They added a downloader tuner like mine and ran it on the mpg program as I do. They removed all the extra weight like the spare tools and jack and spare tire. The truck eventually got 30 mpg!! at 55 mph. Not bad for a 7500 pound truck with 6 wheels on the ground.

You really got me going on this stuff. I'm going to extend my truck front spoiler and put a slightly smaller tire (1/2 inch dia) on the inside dual. I run 80 psi all around (except in the winter) on my tires. Even though the center wears faster the cost per mile difference (shorter tire life) is less than the gain in mpg. EI.. I save more $$$ in fuel than I spend in excess tire wear.

Keep up the good work.

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Last edited by bentwings; 10-25-2007 at 08:29 PM.
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  #77 (permalink)  
Old 10-25-2007, 10:11 PM
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What magazine was this in 2 or 4 wheel drive?...I'm planning on building a 2wd diesel rig for mpg as soon as I can.
Shane
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  #78 (permalink)  
Old 10-25-2007, 10:52 PM
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It was in one of the Diesel truck magazines I think. Back about 4-5 months or so. It was 3rd gen Dodge common rail Cummins.
Here is a Cummins recommendation. Try it, it may help come decision time.
http://www.powerspec.cummins.com/sit...ng/gearing.htm

My truck is 4 wheel drive....it's just that all 4 are on the rear axel. haha

For starters my truck is 2-4 inches lower than most 4 x 4's.
4.10 gears, limited slip, 5spd, Smarty box, tonneau cover.

I'm at 19.6 mpg overall for 12k miles with 3 light tows and 1 over 13k.
Aerodynamic disaster with the front grill guard and wide towing mirrors. The grill guard is for shredding deer before they hit the radiator and I need the mirrors for towing.
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  #79 (permalink)  
Old 10-25-2007, 11:14 PM
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Quote:
Originally Posted by bentwings
It was in one of the Diesel truck magazines I think. Back about 4-5 months or so.

My truck is 4 wheel drive....it's just that all 4 are on the rear axel. haha

For starters my truck is 2-4 inches lower than most 4 x 4's.
4.10 gears, limited slip, 5spd, Smarty box, tonneau cover.

I'm at 19.6 mpg overall for 12k miles with 3 light tows and 1 over 13k.
Aerodynamic disaster with the front grill guard and wide towing mirrors. The grill guard is for shredding deer before they hit the radiator and I need the mirrors for towing.
I'd like to build a 73/74 short wheelbase stepside chevy lowered 3/5 - 4.5/6 tonneau cover, airdam, rear roll pan(possibly) nascar exhaust system.....Big daul system fo $150 ...now I'm thinking of a belly pan too I wonder how that stuff holds up to heat? T56 6 speed transmission No Air conditioner(gives me headaches ) 6.5 diesel planning on twinturboing and intercooling,probabally mildly port the intake and possibly the heads keep the boost at 15psi max .most likely build custom turbo manifolds instead of trying to adapt the factory pieces, daul electric fans. dont turn the fuel up much.I figure with at lowboost unloaded going down the highway at 55 or so 30mpg or so would be obtainable what do you think?

Those brushgaurds/wiches do really improve aerodynamics dont they lol I've got a big one on my 85 K10 ....Really should run one on the 2wd when I build it since the 73-74 grilles are so hard to find but I probabally wont, I found a deal on one recentally and have had the 6.5 for a while nowHere is the grille
Shane
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  #80 (permalink)  
Old 10-25-2007, 11:51 PM
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You need to put a 12 valve Cummins in the truck. This is a popular swap. Simple mechanical injection that responds to easy tune ups. No ignition system, no glow plugs, just grid heaters. A very easy motor to work with. A 1 ton would be the best truck. Long bed. You will need all the weight you can get on the rear end. In any event the Cummins weighs about 1100 pounds. Twice what a SBC weighs so you need some beefy front springs,a-arms, roll bar, shocks, spindles. A very complete good one runs about $3500 +/- a little depending on year. Get as late as possible 98 was the last year for the 12 valve. 300k miles is still a good motor. The NV4500 is a good manual trans. Kinda pricey but right in line with any other diesel trans. Forget any automatic that is not a diesel automatic and built at that. You are looking at $4000 or better. A diesel will hammer the living daylights out of a car automatic or manual trans.

You will need a Dana 70 or 80 rear end. Anything less will be scrap iron very quickly. There are several dually conversions for these including fenders.

Forget the 15 pounds boost. That's cruise towing light. I get 30 easy with mine. 35 is about top with the stock turbo. You really need head studs to go much more anyway. Many guys run 75 pounds on the street. no bull. You usually run about 5 pounds under very light load. Don't forget there is no throttle plate, throttle body or anything that even looks like it on these. Throttle is controlled by the fuel pump alone. More fuel=more power.

You will need one big radiator. Try to use a stock Cummins and MAKE it fit. Use the stock belt fan. 2 16 in electric fans won't even come close to the stock fan for moving air. Use the stock fan clutch. A lot of Cummins engineers spent a lot of time designing and developing this system. It's good and it works everytime. Diesels don't make any heat idling but make up for it when on the road.

Consider some massive brakes. There will be no such thing as too much. My truck weighs 7500+ and has what I thought were big brakes but the new stuff makes mine look like go kart stuff now.
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  #81 (permalink)  
Old 10-26-2007, 04:33 AM
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Thanks for the aero tips Bentwings. However, I use the Bel Air for commercial wedding drives in the summer in Berlin (my website:www.classic55.de )
As these cars have a tendency to overheat I cannot cover up any part of the grill. Stop-and-go traffic at 90+F has only been possible since I installed a big Griffon aluminum radiator and a big electric fan. I would like to lower the car but first will need a new exhaust system as the present one is really poorly installed and hangs way too low. So I'm waiting for it to rust out first. Should be pretty soon, something started to rattle in the muffler recently. As for airdams and skirts, it would alter the stock appearance too much. Except for a belly pan, and maybe a small airdam, that might be OK, again only once a higher hanging exhaust is installed.
Several aquaintances have mentioned that I should go back to cast iron ram horn manifolds. They claim that headers always get worse mileage. The theory being that the scavenging (which helps boost top end power) results in a small amount of fresh charge being drawn directly into the exhaust during the valve overlap time. This opinion is also on the flowmaster website
Quote:
By reducing the backpressure, some amounts of raw fuel (and fresh air) will be "scavenged" into the exhaust system. So by reducing the amount of air and fuel in the cylinder at the time of combustion.

A degree of cylinder pressure will be lost (a decrease in available torque)
Effective air/fuel mixtures will be leaner (possibly leading to parts damage).
Ignition spark requirements will change.
The exhaust system's temperature will rise (owing to the burning of air/fuel mixtures in the exhaust manifolding and pipes).
Exhaust gas temperatures will increase (particularly notable during engine dynamometer tests).
There will be a tendency of back-fire (or popping) during deceleration of the engine.

And while other conditions may arise (depending upon how a given engine is configured), the ones listed here are probably the most common.

In Flowmaster's experience, as an engine's backpressure is decreased, valve over-lap should be shortened. Again, for example, if an engine were running a camshaft of 106 degrees lobe separation before a backpressure reduction, selection of a cam of 112 degrees would tend to:

Retain more fresh air and fuel (thereby increasing cylinder pressure or torque)
Reduce or largely eliminate combustion in the exhaust system
Require less high rpm operation for optimum power
Require less ignition timing
Require a decrease in jet size
Decrease inlet charge contamination by a reduction of exhaust gas in the intake track
.
full article: http://www.flowmastermufflers.com/backpressure.html
The tiny cam I have installed (240H from Comp Cams) has a 108 deg lobe separation and probably a fair bit of overlap as it designed for economy with stock manifolds. In my application it probably causes 'over scavenging' and loss of torque as described in the quote above. Since max economy with reasonable power is my goal, I think I need a bit more backpressure to simulate stock manifolds. I don't want to go through the trouble or expense of changing the cam to something with less overlap. At WOT the scavenging probably significantly helps power. I have a pair of spring-loaded exhaust tip valves lying around (Turbolator). Going to install them and see what happens... Idea is that under low load they're closed, increasing back pressure. But under high load the exhaust forces the flap wide open for minimal restriction. Sounds like it might work for my purposes.
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  #82 (permalink)  
Old 10-26-2007, 07:43 AM
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be a man dodge tree bark!
 
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did simular stuff 17 years ago to mine...excuse the mess it s old and has alot of mile on it...524,660.8...
although the air damn (along with one driving light) was ripped off by a racoon last spring.yes i have had slightly higher water temps but blame that on the fact the big radiator was taken out of the truck trying the aluminuim junk thats in it now..the 4 core stock one was leaking...it also fits and seals better then that junk one. the oil temp has been the biggest issue this year running 220 at 70mph at 2900 rpm... and running 230 to 235 towing at 65mph... used to stay at 210 no matter what...

getting the air out and moving was a big milage gain to me..along with taking the clutch fan off.
thought about belly panning it but never really wanted to spend the time ,,,
overdrive would get me to the low 20s on gas.....




the small duct is for the oil cooler..stock gm lower air damn mounts behind it

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  #83 (permalink)  
Old 10-26-2007, 09:17 AM
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Serious racer thats a nice 79 can we see some more photos.

Bent Wings The Cummins engines are very good and probabally the best light truck diesel engines availabel Didnt realize that they didnt have glowplugs though,a deffinate plus

But the diesel into half ton is kind of a side effect of high gas prices and I prefer short wheelbase I really Like the 73-87 chevy pickups but there milage is poor in most cases last check on my 85 was 10mpg (the same truck when it had the 6.5 got 19-nearly 22)
The 6.5s are realitively light at 887 lbs but they have a high compression ratio 21-22:1 which demands lower boost preassures.So my thinking behind this whole scheme is to have my dream truck AND be able to use it as a daily driver while getting near econobox milage.

Shane
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  #84 (permalink)  
Old 10-26-2007, 10:03 AM
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be a man dodge tree bark!
 
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1980 if i could find the correct grille it would be cool...its not that nice ..its due for a total tear down and go over..someone hit the passenger side in the grocery story last year...i dented the tailgate hauling my dirt bike up north on the carrier..and the hood well it cracked and needs to be redone.... but after 21 years of owning it and driving it everywhere and over 400k i say it owes me nothing.. only died on me twice in 21 years both times... electric fuel switch overs...guess what two mechincals valves in the trans hump...15 years since no let downs..
i will say it is all gm sheet metal ..



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  #85 (permalink)  
Old 10-26-2007, 10:30 AM
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Berlin..Air, Well I guess that the aero stuff is out. I didn't know you your application well enough. As for the cast ram horn, I can't say as I have gone backwards as they say. I know a lot of the streetrod guys run them. They polish up nice and ceramic coat them. There is an aftermarket one from Speedway Motors that is an improved version. Never tried them however. Flow master makes some good reading. I'm thinking if you are really running at low rpm that it probably makes sense. Most of the time the street motors are cruising at 2200 of so. Much less and there just isn't the power. We really like them to roast the tires at will. hahah As they note the total combination is very important. I'd have to think about the backpressure. I've had nothing but supercharged or turbo charger cars and trucks for so long that I've lost touch with the NA operation. I've always had the biggest exhaust practical on these hot rods. My SuperCoupe had only a 3.8 v-6 but 3 inch dual exhaust all the way back. It was the only way to really make effecient power. I didn't see a loss in mpg in fact it gained. Probably because the blower was more effective...didn't have any resistance from the back flow of the exhaust.

My truck has just a straight pipe from the turbo to the bumper. No gain or loss untill towing then it is better. Some guys have 5 inch exhaust on these.

As for cooling the streetrods guys with tri 5's all have big radiators and big fans. At many of these events you can be in walking speed traffic for hours so cooling is important. Hardly ever see anyone having problems.

...4x4, A buddy of mine has the GM diesel in a suburban. 87 or so I think. 3/4 ton. Pretty heavy. He has had 3 trans ans several head gaskets replaced. I hauled him home a while back and got better mpg hauling him and the trailer than he gets cruising under his own power. I don't know much about this motor. There are a few around and I hear they do ok when running right. I don't know if there are any tune up mods available.

seriouracer. nice truck. It looks well worth updating. Maybe consider a Duramax. I can't help on them. The new ones are very good. Getting that out of a Cummins guy is saying something.
here is a truck forum for GM some good stuff here.
http://www.62-65-dieselpage.com/
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  #86 (permalink)  
Old 10-26-2007, 10:50 AM
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be a man dodge tree bark!
 
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thanks!

Not worth the little bit of milage the deisel provides at the cost of deisel. Not to mention if this combo dies i can fix it along side the road and get home..
There was a company putting cummins in c/k20 an c/k30 back in the 80's in Elkhart In. I have part of one of thier kits.
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  #87 (permalink)  
Old 10-26-2007, 11:04 AM
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Here is an interesting article on light truck aerodynamics carried to the max. I wanted to do this with my dually but I just don't have the time now. The apperance has to grow on you. haha But pretty impressive results.

http://www.evworld.com/article.cfm?storyid=870
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  #88 (permalink)  
Old 10-26-2007, 05:47 PM
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Where did you get the hood with the trans-am scoop make it? The earlier grille threw me, dad used to have an 80 shortbed.Want me to watch for a 80 grille to come up on ebay etc?
Shane
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  #89 (permalink)  
Old 10-26-2007, 05:54 PM
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www.car-part.com several 80 grilles there
Shane

Last edited by Chevrolet4x4s; 10-26-2007 at 05:54 PM. Reason: linky no worky
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Old 10-29-2007, 07:18 PM
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Here's one data point for a 6 banger in the sixties.
I had a '61 Biscayne, three speed with a 235 six and very little money.
It got to the point the gas gauge was down at empty and I'd stop and put a dollar's worth of gas in it. It wasn't enough to move the gauge off of empty but I knew I could drive 50 miles without getting gas again. At about 30 cents a gallon ( in the very early 70's gas was even cheaper) I was getting about 15 miles per gallon in a full size Chevy. This was all local but country road driving.
So there you have i, one dollar for every 50 miles of driving.
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