2x4 dual quad - holley 450's or 465's?

Go joe go! · #1 (**permalink**) 05-15-2004, 10:59 AM

I have a blue thunder 427 medium riser intake and was going to use twin 450's (0-9776). But I have a chance to buy a matched pair of holley 1848's (465 cfm). I've been told that the stock linkage kit will bolt up easily to these. 450's have mechanical secondaries while the 465's have vaccum secondaries. Any one running dual quads, please let me know what you think is a better choice. Thanks

Excaliber · #2 (**permalink**) 05-15-2004, 11:07 AM

If I had a choice I'd go with Vac secondaries for sure!

mr0077 · #3 (**permalink**) 05-15-2004, 12:49 PM

Joe, I'm not sure the mechanical secondary carbs will fit your manifold...have you tried fitting the 450s on the manifold? Maybe Blue Thunder makes their manifold with a little more space so the secondary metering block will fit, but on my Fomoco manifold you HAVE to use vacuum secondary carbs, and you HAVE to turn them around backwards to clear the distributor...

Go joe go! · #4 (**permalink**) 05-15-2004, 12:56 PM

Ken, I do have the 450's on the blue thunder 427 medium riser. They seem to fit fine. I have only placed them on as I have no linkage yet. The 450's have a metering plate not a block.

lineslinger · #5 (**permalink**) 05-15-2004, 03:39 PM

I plan on using a pair of Holley 1850's (4160 series) mounted on a dual plane medium riser intake manifold, ford part #C5AZ-9424-G.
This configuration is topping off a 427SO with Edelbrock RPM heads using hydraulic rollers. Anyone else have or know of a setup similar to this?
Mark

mr0077 · #6 (**permalink**) 05-15-2004, 05:47 PM

Joe, I just checked the Holley site to see how that carb works...with no secondary shooter, does the primary pump squirt for the secondaries when they open? Interesting, I thought (until now!) that mechanical secondary carbs all had metering blocks and accel. pumps! Ah, well, ya lives and learns...
But ne'er the less, I have also heard the 450s are a good choice.

Excaliber · #7 (**permalink**) 05-15-2004, 06:20 PM

Mine are "660's". They have ONE (50cc) accell pump the squirts fuel in the CENTER of the carb to all four barrels at once. The primaries don't open very far before the secondaries are right behind them.

,,,,with careful tuning and driving I'm getting 8mpg, UP from 6.

kountzecobra · #8 (**permalink**) 05-15-2004, 07:42 PM

Ken, the thinking behind the 450 not having a secondary accelerator pump is that the very small venturis have such a high flow velocity that they instantaneously pull fuel as soon as they open with no "hole" to need filling by the pump shot. Did that make sense?

What I am trying to say is in a large carb, the secondary pump shot is used to cover up the hole left by the low velocity when the throttle plates first open up. Little carbs have a very high flow velocity so they can flow more efficiently. That will give you something to think about. I'm through now!

mr0077 · #9 (**permalink**) 05-15-2004, 08:04 PM

Yeah, and NOW yous guys tell me!!! Not only do they have more flow, they're $100 cheaper than my beyutiful 390 CFM carbs! Ah, my little 390s are workin just fine...but the explanation on the lack of a secondary shooter makes sense.

427 S/O · #10 (**permalink**) 05-16-2004, 04:06 AM

David is right Ken, a much stronger signal
with the 450's, comparison would be like blowing through a straw and blowing through a 4" pipe. I like using my foot to operate the secondaries, you learn at what RPM to open them up.

Go joe go! · #11 (**permalink**) 05-16-2004, 04:06 PM

Well thanks for the imput guys. I have won the auction on ebay for a pair of holley 465's (0-1848-1). They were $425 used but in nice shape. The fact that they were on an origional factory 2x4 intake is nice but it's performance is more important. Plus they have vaccum secondarys and I've been told that the 427 linkage will bolt on flawlessly, We'll see! I returned the new 450's I had bought from summit. I hope I made the right move. Any one running 465's?