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Discussion Starter · #1 ·
I have a 1993 K1500

3.75 stroke
1 piece Rear Main
Brodix -8 pro cylinder heads
Camshaft, Hydraulic Roller Tappet, Advertised Duration 288/308, Lift .431/.451
1.6 Ratio Full Roller Rocker Arms
Edelbrock Multi Port Conversion with EGR
Factory Exhaust with shorty headers
Stock Stall with 4L60E and 3.48 rears

Checked fuel mileage after a 150 miles of pretty much 60 mph straight and it came out to 14.50 mpg. I was hoping for better than this and was wondering if anyone had any suggestions on how to get better mileage out of this? Any suggestions are welcome. Thank you
 

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My pipes are my music
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Get bigger tires! :thumbup: Really, it doesn't sound like someone was interested in mileage when they put the motor together but still, be happy :)
I'm only getting 10mpg with my 76 4x4 with 4:10's. and that's on the hwy. at 6o mph, not off road. About the only way to improve the mileage on yours is
go back to 3:08's. Maybe a mile or two if your lucky. :D
 

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crussell85 said:
I have a 1993 K1500

3.75 stroke
1 piece Rear Main
Brodix -8 pro cylinder heads
Camshaft, Hydraulic Roller Tappet, Advertised Duration 288/308, Lift .431/.451
1.6 Ratio Full Roller Rocker Arms
Edelbrock Multi Port Conversion with EGR
Factory Exhaust with shorty headers
Stock Stall with 4L60E and 3.48 rears

Checked fuel mileage after a 150 miles of pretty much 60 mph straight and it came out to 14.50 mpg. I was hoping for better than this and was wondering if anyone had any suggestions on how to get better mileage out of this? Any suggestions are welcome. Thank you
Good combo, but you're feeding a pretty big motor and a fairly large cam with 1.6 rockers. You could trade some performance for mileage with 1.5 rockers and a shorter cam, but I doubt much against the weight and aero characteristics of full size pick up.

Don't know what to say about the gears since tire size plays into overall gearing. I'll just say that 350s and 383s remind one of their size above 2000 RPM even with EFI and overdrive automatics. I expect your're getting converter lock up, that's worth a 2-300 RPM reduction against cruise speed without it.

Your exhaust isn't up to the task, though how much mileage is hiding in there above what you have might be questionable, still that's a good size engine. Shorty headers leave a lot of lower thru mid RPMs torque on the table compared to full length headers. Surprisingly, by themselves, shorties, are only a marginal improvement over the OEM's iron manifolds. A single exhaust just isn't up to it and CAT backs are a waste of money solving a non problem with pipe size and mufflers when the CAT is maxed out first. I'd add true duals with a crossover. A crossover ahead of the cats, which due to space will probably be an H pipe, will double the area seen by any one exhaust pulse, but this config tends to drop low to mid speed/RPM temps in the CATs making them less emissions effective. Either move them up toward the header if space is there or insulate the head pipes to preserve exhaust heat needed to light 'em off. Shorty header's bottom to mid RPM torque response can be improved with longer collectors, this will free up some torque numbers to be used to move forward instead of pushing exhaust, you can translate that to more speed and still get 14.5 MPG, or hold on to 60 MPH and get a bit better mileage.

As a data point for you, my daily driver is an 1989 S15 with a 350, LT1 hooked to a 4L60E, 3.08 posi, Z28 245x50, 16 tires. It weighs 2800 pounds empty and considerably more with me in it. It commutes 30 miles each way on mostly freeway which is fast in the morning so I can usually run 65 -75 but is a crawl in the evening. It gets 20-22 MPG in the summer and 18-20 in the winter doing this. Of course if I turn it loose on an Audi or Subaru WRX that mileage goes to about 14 rather easily for the rest of that tank. As soon as the engine gets over 2000 RPM it goes at the fuel supply like a 9 year old suckin' on a 48 ounce Slurpee.

Bogie
 

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Discussion Starter · #6 ·
Bogie, your awesome man, that was a lot of info. My summer tires are 33x12.50x15 and my winter tires are the stock 31 inch tires. I know the exhaust is not up to it. I just installed the engine and had to go get my camper from my uncles house which is about 100 miles away and I wanted to make sure the engine and trans was going to perform before I started with the exhaust. There is plenty of power for me, so would a 1.5 ratio rocker arm make a noticeable amount of difference over the 1.6's. I was told that full length headers would not clear the front differential on my pickup. Are you saying that the dual exhaust would help the gas mileage? I wasn't really thinking duals out the back I was thinking stacks out the bed, how would that work for gas mileage? I was trying to figure out how much further I was traveling with the 33's over the stocks but I didn't really know how to. I didn't think I was building a gas hogger, I thought I had a mild setup and thought the less the engine worked the better the mileage would be to a point. The engine is also around 10.5:1 compression ratio. I am willing to hear anything for a mile or two besides changing my gearing because thats not something I am really interested in because of the front differential. Thanks guys
 

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My pipes are my music
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With the long tube headers, it's not about clearing the front diff. it's the cross member under the transfer case. The collectors on the headers point right at it. It takes a good pipe bender to get the exhaust through the cross member like factory routing so you don't drag the pipes on the ground, or rub and rattle on the cross member.
 

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What type of tires are you running? Tread design, and the quality of the construction determine rolling resistance. Cheap tires cost you at the pump. My favorite tire of all time was the Micheline X-1, wicked expensive $89 for 185/70 R13 in 1994, but great for mileage and longevity, we got 70,000 miles off those babies. So, back to your rig. Look at the air pressure. Are you going by the door sticker?, don't. Those specs are for 1/2 load and cushy cruising. If the tires' max pressure is really low, like 35 psi, then go max, but if it is say 85psi, then go 60 and road test for handling and braking. Your braking will be affected greatly by a change in tire pressure, so expect it. your handling will improve as the tires are stiffer. If you pump them up too high without a load, then the contact patch will be reduced so be careful of that, test by driving through a puddle on otherwise dry pavement. If a tire is run at a higher pressure, then there will be less rolling resistance, and therefore higher mileage. I run my Totyota Corolla at 44psi (max) all the time and I get 36 around town, and 44 on the highway. My F250 superduty gets 16 around town. No highway specs, as it is my towing vehicle and only sees highway use in OD lockout with a big load on the ball (8,000) plus cargo in the bed. Nuff said, Tires will give you the most noticable difference. GL, repost with updates.
 

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My 2009 6.0L 2500HD with all the new factory technology and better aerodynamics only gets about 20mpg on the highway, that's with a 6 speed trans. You're using antiquated parts and expecting next generation performance. all the gearing, tire, and tuning tricks have some truth to them, but they will not get you more than a few MPG's and that is if you do all of them. To do that you're looking at an initial expense of at least a few grand for a 20% (at best) improvement in milage. If you drive your truck 10,000 miles a year it'll take rougly a decade for you to break even- and that is under a best case senario.

Always run the numbers before you chase after a project.
 

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Discussion Starter · #11 ·
I am not disappointed in the project because of the gas mileage because it is my weekend warrior. I have a 2002 Impala LS with the 3.8 Liter that I drive to work and she pulls 28-30 mpg with 212,000 miles on it. But it has been all highway miles. I was told to cut the cat out of the exhaust and run without it and I would notice an improvement or put a high flow cat in place of it. I never checked the mileage of the stock 350 that was underneath the hood to compare anything. 14.5 mpg and it tows my 3,500 lb camper down the road in overdrive without any problem. I am very happy with the performance and what I have done with the truck but I was just looking for a little bit more just like everyone else is out of their projects. I looked at buying a newer truck, but what is the fun in that, and I also figured what does it matter if I work at work to pay for a truck or if I work at work to build a truck and enjoy it along the way, if that makes any sense. I don't want to work on my car at all or be a mechanic at all but I have enjoyed my project so far and this weekend I am going to pick up a 1966 F-250 with a L6 and a manuel trans on the column. This will be a larger project. It will have a 302 built by my father (may he rest in peace) and an automatic trans if the manuel in no good. I will eventually start another post on this topic and you all better be there to help me on the way.
 
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