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Sam's Truck - from 11 to 18 MPG

Sam was looking for help with his street rod. He has a small block Chevy in a 70’s model step side pickup. The heads he’s running are alloy heads from the late 80s. The engine smelled strong of unburned fuel and was geting 11 MPG!!!

I cleaned up the ports in the heads and cut the grooves. His combination was all wrong, camshaft with too much duration, compression too low and intake plenum too large. Higher compression with a smaller cam and intake manafold should help. Combine this with grooves in the heads to increase the torque and improve drivability.

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I wanted to lean towards maximum MPG, Sam had other ideas. He wanted his truck to sound and run like a hot rod. Can we get both?

Engine specifications after modifications:

Camshaft specifications

Intake VALVE LIFT: .485"

Exhaust VALVE LIFT .505

LOBE CENTER: 108 deg.

The following timing is taken at .050" lifter rise:
INTAKE DURATION: 232 deg.
EXHAUST DURATION: 244 deg.

Bore 4.030”
Stroke 3.75”
Head 58 cc's
Gasket Thickness .040”
Deck Height .030”
Valve Pocket -5 cc’s
Displacement Cubic Inches 383
Compression Ratio 10.9:1
Intake manafold - Edelbrock performer RPM
Carburetor - Holley 750 double pumper

Fuel economy
before 11 MPG
after 18 MPG

The rings are sealing and the milage is going up!
These results are very unofficial, but noteworthy none the less. Considering the camshaft would be a better fit at the racetrack and the carburetor is antique race technology. I believe additional improvements will be realized under controlled conditions.

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Comments

Just wanted to say hi!
Written by Lola on 2010-02-07 22:46:47

What is up everyone? My name is Jessica. I am from Slovakia. I am new to the forum and just wanted to say hi.. I hope I posted this in the right section on your forum... [url=http://somender-singh.com/?28c42c78215f4af74d3ca37b6c8]http://somender-singh.com/?28c42c78215f4af74d3ca37b6c8[/url],

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Thursday, 29 July 2010