holley 3310?

[VALDEZ]

hey, guys right now i have the factory q jet on my pickup and have been looking at putting a 3310 on it. i just went out and looked at one tonight and it had a front metering block and a rear metering plate. should i just hold out for one that has metering blocks front and rear or is there an advantage to the metering plates? any guidence is appreciated.

[RatPwrd72]

The 3310 will have a plate in the rear instead of the block. I like to upgrade the main body to a ProForm and ditch the plate for a Quickfuel or similar. Also, an adjustable vacuum pull-off will make tuning a lot easier.

I have one outfitted just as I mentioned on my street driven '72 with a 468 and it works really well.
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[Marv D]

Just out of curiousity,, what were they asking for the 3310?

[VALDEZ]

$100. it was my understanding that the older 3310's had plates and the newer ones had blocks

[RatPwrd72]

All of the 3310's I've stumbled upon had the plate, assuming they hadn't been converted already. I see lots of complete 3310's that need overhaul in that $75-$125 range. A new 3310 from Holley has a plate in it, also.

[Marv D]

I was just curious,, I've got a matched pair of them that Patrick worked over to make work on a 2x4 tunnelram. They were on a motor I bought from a buddy (long story) The 3310's would make sense if it was a 600+HP street motor, but not for me so they have been in a boxes on the shelf for about 6 years,, I'm such a dang packrat!!!

[Captainfab]

The 3310-1 was the only one that came from Holley with a secondary metering block and power valve. The 3310-2 and subsequent releases came with the metering plates. Also the 3310-1 was rated at 780cfm and had downleg boosters and the rest were 750cfm with straight leg boosters.

[VALDEZ]

whats the difference between downleg boosters and straight leg boosters? sorry, still kinda new at all of this

[Captainfab]

I don't think I can explain it correctly, so here is an article that explains the difference

http://www.popularhotrodding.com/tec...h/viewall.html

I'll see if I can get our resident Holley expert to post a simpler explanation.

[moggey01]

The downleg booster sits lower in the venturi. Most all builders use a "Y" drill to check the size. A lot of guys use the HP series metering blocks so they can tune the emulsification and effect the tuning that way. It is worth some power .

[prostreetC-10]

Originally Posted by Captainfab

The 3310-1 was the only one that came from Holley with a secondary metering block and power valve. The 3310-2 and subsequent releases came with the metering plates. Also the 3310-1 was rated at 780cfm and had downleg boosters and the rest were 750cfm with straight leg boosters.

John,
You pretty much nailed it. The universal 3310 that we know today was actually modeled after an original GM carb that came on the Z-16 396 Chevelle back in '65. It was a list 3310-1 and did have a rear metering BLOCK as did all the factory GM 4150 series carbs. That was the only way they could power valve up the rear of the carb. Holley decided to release the 3310 as a universal carb to the public as a 3310-2 and above.

You generally have 3 styles of boosters. To keep it simple, we'll just talk about the difference between the straight leg, and the downleg, or sometimes called the dogleg. It refers to how it comes off the rear hole in the main body. the straight leg comes off straight over the venturi. The downleg steps down into the venturi. The link you referenced goes into really good detail but to keep it simple, the closer the booster is to the smallest part of the venturi, the greater/quicker the signal. The high velocity/low pressure is the physics needed to start the siphon effect from the booster. The 3310-2 and above all have straight leg boosters to slow down the start up of the main circuit and make it a little more of a forgiving carb. Since the straight leg will flow slightly less, they give it the 750 rating where as the quicker downleg boosters that GM used all got 780 cfm ratings. Ford even took it one step further and had Holley install straight legs on the primaries and downleg on the secondaries.

The picture below shows the high velocity-low pressure part of the venturi which creates the strongest signal. It is the smallest part. This is why little 650 double pumpers will have a much snappier throttle response than perhaps a 750 and yet the 750 will outflow the 650 way up in the rpms because of the less restrictions.

I'm getting really tired........I need to stop so my info doesn't start drifting.....lol

[prostreetC-10]

Originally Posted by moggey01

The downleg booster sits lower in the venturi. Most all builders use a "Y" drill to check the size. A lot of guys use the HP series metering blocks so they can tune the emulsification and effect the tuning that way. It is worth some power .

I love the HP blocks, They have a longer usable main well and usually 1 or 2 extra e holes. It's also a nice trick to plug the factory power valve channel and drill another one right under it. The stock location actually comes in and misses the first e bleed. By drilling under it, you can get the full use and benefit of the main well and e bleeds for better atomization. Drill and tap them for 6-32 and install some changeable bleeds and really get that curve where you want it.

Bottom block is an HP where as the top one is the standard double pumper rear casting.

[Captainfab]

Thanks for helping out here Dub