Quote:
Originally Posted by ScumOne
I did a mild buildup of my 400 in my 69 Bird last year...10.6: 1, Kauffman heads, recommended cam/roller rocker arms, RA exhaust manifolds. Went to the Holley 750 with vacuum secondaries instead of the Q-jet (since rebuilt by SMI for 5500 ft elevation).
The Holley is just a gas hog, plain and simple. The Q-jet got 11/12 mpg around town and 15 mpg on the highway doing 80 mph with the AC on.
The Holley was so bad I did a test driving 52 miles, 1/2 city, 1/2 highway. I drove like an old lady. And I mean slow AF. It was torture for me to drive the Bird that way for 52 miles. I filled it up after that and it took almost 7 gallons to drive, which was 8.3 mpg.
The Bird is back in the shop to get that dialed in. My mechanic hates Q-Jets, but this Holley has been a huge disappointment compared to the Q-Jet. The Q-Jet was better on mpg and it launched and accelerated quicker at high speed, too.
Just my .02
Jim
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Maybe check the sparkplugs color and a jet change. go at least 2 sizes down.
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1968 Firebird 400 RAII M21, 3.31 12 bolt, Mayfair Maize.
1977 Trans Am W72 400, TH350, 3.23 T Top
Everyone you will ever meet knows something you don't.
Bill Nye.
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