Holley 3310 idle problems

[greyhounds_amx]

I expect that any warranty they provided ended 10-20 years ago. It's been rebuilt twice that I know of since CS had it.

Plus I like to learn and this is a tough one.

[JDR Performance]

You had mentioned a couple of times that you were ruling out a bad power valve because fuel wasn't coming out of the boosters. It wouldn't, it would let fuel run through the bad power valve and through the hole in the main body and base plate. You wouldn't see it from the top side of the carburetor.

[pamotorman]

I expect that any warranty they provided ended 10-20 years ago. It's been rebuilt twice that I know of since CS had it.

Plus I like to learn and this is a tough one.

they may have the specs it was built to and you could see if there has been any mods after they built it.

[greyhounds_amx]

You had mentioned a couple of times that you were ruling out a bad power valve because fuel wasn't coming out of the boosters. It wouldn't, it would let fuel run through the bad power valve and through the hole in the main body and base plate. You wouldn't see it from the top side of the carburetor.

That's true I suppose. But for that to happen either the diaphragm in the PV would have to be ruptured or the gasket under the PV would have to be providing a leak path. Each time I take the carb apart and check it the PV diaphragm is good and the gasket is as well, so the PV isn't the issue in this instance.

[greyhounds_amx]

I just finished checking the metering block surface and the mating surface on the carb main body. The body surface is flat, and the block surface is warped. I'm finding areas with about 0.018" gap under the mini straight edge I'm using.

The reason it's warped is interesting. The raised cast boss in the center of the metering block used to transfer accelerator pump shot to the main body is about 0.018" higher than everything else on the metering block. The corresponding boss on the main body is flush with the rest of the gasket surface, but not so on the metering block, so when you tighten everything down it bends the metering block.

I always though it was strange that Holley would have some carbs with the cast accelerator pump transfer passage like the 3310 and then some with the brass transfer passage tube with the pair of o-rings on it. Obviously it costs more to make the brass transfer tube and for the extra machining operations on the main body and metering block in order to use the tube, so Holley must have had a good reason to make that change. I'm thinking that this warping issue was probably the problem they were solving with the tube setup.

[cjperformance]

Did you match the IFR in the secondary metering block to what the metering plate had? I should also ask if it was converted to 4 corner idle ? I dont think i saw that anywhere.

[greyhounds_amx]

That's a great idea. I've used the Holley generic secondary metering blocks for decades and never though to modify the IFR. I've always assumed that the primaries would end up compensating, but matching those (assuming the stock IFR size is good) would probably help idle quality.

Here's a new question now, knowing what we do about this metering block:

Should I replace it with a stock 134-131 metering block or go with a billet block. I do intend to mess with the PVCR sizes in the future so adjustable jets there would be nice.

Thanks!

[77cruiser]

Have you tried plugging the idle air bleeds to see if it's better or worse?

[cjperformance]

That's a great idea. I've used the Holley generic secondary metering blocks for decades and never though to modify the IFR. I've always assumed that the primaries would end up compensating, but matching those (assuming the stock IFR size is good) would probably help idle quality.

Here's a new question now, knowing what we do about this metering block:

Should I replace it with a stock 134-131 metering block or go with a billet block. I do intend to mess with the PVCR sizes in the future so adjustable jets there would be nice.

Thanks!

Do you know what part number sec meterung plate it had?
If you intend to play around with PVCR just go for a billet block, unless you want to mod your block. screw un bleeds, pvcr etc are just so much nicer to mess with

[greyhounds_amx]

It had the stock 134-21 metering plate, which would have 0.081" main orifices and 0.040" idle restrictions.

But I'm looking at the generic Holley secondary metering block that I have that came as part of the 4150 conversion kit they offer, and I just don't see any restrictions in it at all. The block is stamped "4100". Here's pics of what I'm seeing:





There's no idle mixture screws, but I was under the impression that it allowed a very small amount of idle fuel flow in order to keep the secondary fuel fresh. With no restriction wouldn't it let a bunch of fuel through? Or does the fact that there's no mixture screw in the system resolve that concern?

Thanks everyone for the help.

[cjperformance]

20180518_094810-800x600.jpg

The IFR in that metering block is under the plug im pointing to in the pic, one ifr on each side

[greyhounds_amx]

Ok, thanks for pointing that out. With that metering block i should probably just not mess with the IFRs then I guess. Unless someone has specs on the part number 4100 metering block, then we could check the IFR size I suppose.

Thanks!

[DrillDawg]

Helped someone with the same problem on a 1850, found the screws on the secondary plate loose, tighten them and it fixed the problem. I would go with two billet blocks and switch to a 750 DP as you can use the same blocks with it.

[greyhounds_amx]

If you have a gasket between the main body and the baseplate that is intended for an 850, it will block off the idle mixture passages of the 3310 baseplate. That will make the idle mixture screws ineffective ,and require opening the butterflies enough to idle on the transition slot fuel .

And it's NormS for the Win!

It appears that I put the wrong gasket on and it's blocking some of the passages between the main body and throttle plate.



In the upper right corner you can see a good example, in that the gasket impression from the passage in the main body doesn't quite reach the hole in the gasket, and then the hole in the gasket goes nowhere anyway as it's blocked by throttle plate. The correct gasket has those holes pulled in toward the bores a little bit so everything lines up.

New gaskets are on the way along with some blank emulsion / IFR jets for the new main metering block. Thanks again for the help everyone - this one really had me stumped.

[JDR Performance]

You also have something upside down.