fuel economy build
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Teching In
Joined: Jan 2024
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fuel economy build ok i have a 2002 avalanche with a 5.3 with about 300 thousand on it. still running good but i want to rebuild the motor. it has 706 heads i have heard they are good heads but i want to replace with 799 heads wth better flow and put flat top pistons. losing a little compression i know but again im building for fuel and not lose the power. I'm putting 1 3/4 long tube headers and a better breather for good airflow. what do you guys think? the cam, do i go with a little more power or us a truck cam for lower torque? I'm not towing anything big. just trying to get better then 14 miles to the gallon and still have a little power so im looking at this cam any thoughts you guys? New Stage 2 Truck Low Lift Cathedral Camshaft GEN 3 / GEN 4
Cam Specs: 212/218, .553/.553
Cam Specs: 212/218, .553/.553
Last edited by learning101; Feb 1, 2024 at 10:17 AM.
TECH Senior Member
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From: Central Cal.
You lose compression, you lose efficiency, plain as that.
Keep the 706 heads but do a good valve job on them plus do a bowl blend (or pocket port as it's sometimes called).
Get .040 head gaskets to get your quench better, plus mill heads about .020 to get compression a bit better but still use regular gas.
I think you want fuel economy, but not afraid of gaining a little power if it happens.
Headers are a good move for both (you must not be where smog testing is done... )
If you must have a bit more cam, do the Summit Torkinator (200/205, .550/.550, 113+4)
Or the Scoggin Dickey Truck Torque (205/210, .550/,525, 115)
Either of these boosts low end torque.
The 5.3 is working hard to push a barge like the Avalanche around.
I had a 2004 Tahoe with LM7 w/ cold air intake and catback and still never really got more than 14 city/19 highway.
Keep the 706 heads but do a good valve job on them plus do a bowl blend (or pocket port as it's sometimes called).
Get .040 head gaskets to get your quench better, plus mill heads about .020 to get compression a bit better but still use regular gas.
I think you want fuel economy, but not afraid of gaining a little power if it happens.
Headers are a good move for both (you must not be where smog testing is done... )
If you must have a bit more cam, do the Summit Torkinator (200/205, .550/.550, 113+4)
Or the Scoggin Dickey Truck Torque (205/210, .550/,525, 115)
Either of these boosts low end torque.
The 5.3 is working hard to push a barge like the Avalanche around.
I had a 2004 Tahoe with LM7 w/ cold air intake and catback and still never really got more than 14 city/19 highway.
TECH Fanatic
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Maybe way off base but bore and stroke the 5.3 to 383 cubes? More torque and hp so you can use less throttle to get the same results?
My 20 Silverado has a 6.2/10 speed combo and it will easily do 22 mpg at 60-65 mph.
A lot depends on if you are going the keep the Tahoe forever or trade up in the next few years.
My 20 Silverado has a 6.2/10 speed combo and it will easily do 22 mpg at 60-65 mph.
A lot depends on if you are going the keep the Tahoe forever or trade up in the next few years.
Thread Starter
Teching In
Joined: Jan 2024
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i noticed the cam i was looking at needs torque converter. i dont want a hot rod but im rebuilding the 5.3. so what is a good truck cam so i dont have to change converter? should i stay with a stock cam?
Gary A. is spot on about compression. High compression....is one reason why diesel engines hold all the cards on efficiency, and torque. As Scott said, you can also do a lot with a tune. On my 2000 A4 C5 Corvette, I did a bunch of bolt ons, and had good results. Each one helped my ET by 1/10 second here, another 1/10 there. But the tune alone gained 3/10 or 4/10 by itself. This was only an educated guess tune. I started at 13.70s, and ended with a 12.50@114mph!! Totally stock internals LS1. Never even pulled the plugs.
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Verdad Gallardo Compression is the best (quite possibly the only way) way to increase mileage by doing it mechanically vs. electronically through the tune. The only way to make a gallon of gas “go further” is to squeeze it harder via compression. It’s why the OEM’s are upping and upping compression in their junk.