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I am working on a 4160 3310-4 750 VS .on the rear secondary is there just a gasket and the secondary plate,that is all i have now, in the past on outher holley i have work on there was also a secondary metering backing plate what gives.

I believe the thick metering block (looks like the primary one) lets you change jets (same as the front block) whereas the thin secondary plate that you show is for one jet size. people have drilled/tapped the "plate" for using (2) screw in jets rather than buying multiple plates. Bean counters are always in play, likely the thin plate was much cheaper.

3310's come with a metering plate, not a metering block. You can add one if you like.

OK i have been looking at the conversion is it worth it just a cruiser .

Could someone give me the part number for the kit 4160 3310-4 750 VS WITH out the secondary block.thank you.

The original 3310 was called a 780, came with down leg boosters, and had a secondary metering block w/o idle mixture screws. I believe all od the 3310 after that came with a plate.

Could someone tell me what holley kit to use.thanks

I'm gonna go out on a limb & say no cuz I dont think you will be into the secondaries that much (cruiser) nor have a LM2 to dial in your AF ratio dead on but wait for the Holley guys to further/better advise you

The 3310 is and always has been Holley's most basic and economical 4bbl offering. They are good carbs on the right combo. Which is usually a milder street car. On that kind of combo, they are usually a little rich on the cruise circuit (typical) late on the power valve opening and late on the secondary opening point. All of which is fairly easy to resolve. But I have not had a 3310 on the appropriate combo that needed the sec. plates replaced with metering blocks. Remember, our 6 bbls had plates in the secondaries, too.

If you need to tune much on the secondaries or need 4 corner mixture adjustment, you may be ahead to consider a different carb that has those features and more for more precise tuning. That doesn't mean you can't make the 3310 run with some of the more expensive carbs, it certainly will. It's just that if another carb was a better match for your combo, it would require fewer parts and less tuning to get to the same place.

And remember, you will need to tune the universal metering block while your 3310's plate is already dialed in for that carb.

What issue(s) are you addressing by changing from the plate to a metering block?

Thanks Dave,not having any issue was just thinking a bout it.Can a 600 primary metering block work on my 750,I ask because I snap the vacume tube off my 750,my bad.

Why not just drill the broken port out big enough to press or glue in a different tube? Another metering block may need tuning. If you have a wide band and are comfortable with tuning, then just about any aftermarket carb can be improved in some way or other on your particular combo. After all, they are universal carbs. It is just important to get one that is as close as possible to being correct for your combo so that it would require the least parts and tuning.

The metering block (and to a less extent the plate) is where most of the magic (metering) happens. There are lots of passages and orifices whose sizes and locations are the prime determinates as to whether your engine will be happy with the carb or not.

So while another metering block may physically fit your carb, it may meter entirely differently and cause the engine to operate altogether different.

To answer the original question, you are missing the thin steel separator plate between the carb body and the metering plate.

http://www.ebay.com/itm/HOLLEY-MODEL-416...982&vxp=mtr

I believe it goes, from carb body outwards, Big gasket, separator plate, smaller gasket,, metering plate. I had to go to four hardware stores to find the #1 clutch head screwdriver for those screws. I thought seriously about replacing them with stainless flat socket head machine screws.

The secondary metering plate can be converted to a metering block using a kit sold by Holley or Quick Fuel, etc. Or at least one, maybe more, companies sell metering plates that use Holley screw-in jets.

The secondary metering isn't nearly as critical as primary. For one thing, it isn't as critical to nail the A/F ratio to make max power.

I like having the 4150 type (two metering block) carb even though it probably doesn't do a thing for me. But that's personal preference, not based on fact.

R.