Holley 4175 vs Avenger
Thread Starter
Burning Brakes
Joined: Jun 2009
Posts: 840
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From: Syracuse IN
Holley 4175 vs Avenger
What are your thoughts of the Holley 4175 650 cfm vs the Avenger 670? I have been running the Avenger but it does not fit the OEM air cleaner. The 4175 will fit the OEM as stated by Holley. I like the Avenger somewhat. It does run a little lean though. I have not rejetted yet. What are your thoughts??/ Al
Melting Slicks
Joined: Feb 2006
Posts: 3,428
Likes: 5
From: Japan
The 4175 has non-externally adjustable floats, and no sight plug on the float bowls to determine whether or not you've got them set correctly. They also tend to leak after awhile. It's also taller than a QJet, which means you have to run a shorter air filter if hood clearance is an issue.
The 20 cfm difference between the 4175 and the Avenger is insignificant on most smallblocks since with Holleys the real issue is whether or not it will respond to idle mixture changes. With almost any small block either one will work, unless your combination of displacement+cam is so huge that it exceeds 670 cfm at redline...
Since the 4175 is a spreadbore, it works best on a spreadbore intake, and is conceivably capable of slightly better fuel economy that a squarebore Holley, but I have run squarebore Holleys on spreadbore intakes before using an adapter plate. No issues whatsoever.
The fuel inlet on a 4175 is identical to that on a QJet, so it's a bolt-on direct swap, pretty much. It's designed to be. With a 4150/4160-type Holley you'll have to do a little plumbing work since it's a dual-inlet carb (well, the Avenger is anyway).
Essentially, the 4175 is intended as a bolt-on replacement for a QJet on a more-or-less stock 350 with a minimum of hassle. Undo the throttle cable, disconnect the line, pull the carb off, install a couple studs, and bolt on/ hook up the new carb. The 670 is intended more for the ease of tuning that makes Holleys preferable to QJets, but there's a little more work involved in hooking it up...
Hope this helps
The 20 cfm difference between the 4175 and the Avenger is insignificant on most smallblocks since with Holleys the real issue is whether or not it will respond to idle mixture changes. With almost any small block either one will work, unless your combination of displacement+cam is so huge that it exceeds 670 cfm at redline...
Since the 4175 is a spreadbore, it works best on a spreadbore intake, and is conceivably capable of slightly better fuel economy that a squarebore Holley, but I have run squarebore Holleys on spreadbore intakes before using an adapter plate. No issues whatsoever.
The fuel inlet on a 4175 is identical to that on a QJet, so it's a bolt-on direct swap, pretty much. It's designed to be. With a 4150/4160-type Holley you'll have to do a little plumbing work since it's a dual-inlet carb (well, the Avenger is anyway).
Essentially, the 4175 is intended as a bolt-on replacement for a QJet on a more-or-less stock 350 with a minimum of hassle. Undo the throttle cable, disconnect the line, pull the carb off, install a couple studs, and bolt on/ hook up the new carb. The 670 is intended more for the ease of tuning that makes Holleys preferable to QJets, but there's a little more work involved in hooking it up...
Hope this helps
