[Cliff R]

+2, 3, 4, 5 and 6!!!

"As for MPG, over the last year, I've been seeing around 6.1-8.1 under most driving conditions, excluding trips where I did a lot of tuning and idling in that tank of gas, so I'd say the average was around 7.8 before. On the only tank of gas that I've run post-Qjet and post valve job that excludes tuning work, I got 12.1."

7.8 MPG average is ABSOLUTLY UNACCPEPTABLE. It tells me that something in the mix is WAY off someplace. It's often a combination of things, but I can tell you or anyone else reading this for certain, a stout 455 with iron heads, around 10 to 1 compression, and well chosen camshaft will just about double that number for fuel economy when correctly tuned.

I've had half a dozen engines in my Ventura since the late 1980's, from 406cid to 468, and gear ratios from 2.73 to 3.73, and ALL of them got over 12mpg's, and the 406 with 2.73 gears just under 20 mpg's.

Even the current 455 is very thrifty on fuel. It uses no more fuel for "normal" driving than the last 455 did. I checked the last engine for fuel economy several times, and it would EASILY make 180 miles per tank (about 14.0-14.4 gallons), and I've had a few tanks in the 200-230mile range when there was considerable highway driving involved, and the operator had enough willpower to stay out of the secondaries (seldom happens).

Even the big Holley carbs I've ran and tested, and the POS Edelbrock AFB clone would muster 160 miles per tank, which is closer to 11mpg.

Adam, I would NOT under any circumstances put the Holley back in service in it current state of tune, it is "washing" the engine for sure consuming that much fuel, running cooler or not......FWIW......Cliff