Fuel flow restriction

[travis]

Wouldn't a fuel flow restriction show up as a progressively leaner a/f as the rpms go up? Logically to me it seems that it would, but in this case it never did. 12.8 a/f across the upper rpms, it just wouldn't rev above 5600. Granted this thing wasn't built to rev, but the engine I'm building for this truck now should pull another 1000 rpms up top. I've already upgraded everything from tank to carb for the new engine.

1/4" open end wrench for scale

IMG_20240403_193211_451.jpg

[mag2555]

Are your Exh temperatures rising once the motor hits 5600

[BOOT]

Need more info, efi or carb? What was the broken part or failure?

[Ken_Parkman]

Often a fuel flow restriction will not show up til the top end in high gear. My carbed car would quit at the 1200 foot mark, fine through the gears. As a stopgap measure it would go the full 1320 with a full tank of fuel. That was with the original 6 cylinder 5/16" fuel line.

[PRH]

That’s a way bigger hole than what’s in a QJ needle and seat assy.

[Rick!]

What was the original engine in the truck?
What’s the fuel pressure at full load at 5600?
A 1/4” fuel line doesn’t usually feed a V8 with a redline over 4500rpm.

[mag2555]

G forces themselves produce a restriction.
On a starting line leave that produces close to 2 Gs every foot of fuel line running horizontally from front to rear will knock .3 psi off of your fuel pressure.

Just 8 ft of line is a loss of 2.4 psi and most fuel pressure gauges are highly dampened and you will even see it!