[spawn_x]

Gents, have a question.

Im having odd behavior with part throttle/transition. Also now I see fuel in the vacuum port (not timed vac) Found this thread

https://forums.holley.com/forum/carb...ing-block-fail


Guy says this block cant be used. They do indeed look a bit different, ie. emulsion well is further down.

However looking at both side by side, the emulsion well is covered by a gasket. Gaskets on stock and the billet block are same.

"can see that the bottom of the emulsion well is in a different position, (further down) on the red block. Complete mismatch at that point. The main well will then discharge straight into the idle discharge port, instead of the "up and over" loop. You cannot use that block. Gary"


Is he correct? Are these not interchangable? I dont care about the ported vac advance, but the 34-8qft looks different, pic attached. One less emulsion hole.


Pics attached of mine side by side. I do not know enough about this so hoping someone does.

Thank you

[Dragncar]

That looks like a metering block a bought from jags many years ago. The stock one ran better.

[steve25]

There can be problems with not only used blocks that have been filed level to get back to being flat, but even with new Carbs and there blocks.

Heres two things to check out .

Set the block on the main body without the gasket and make darn sure that the dowl pins do not stop the block from compressing the block gasket to seat enough to seal as it should.

Sometimes the locating dowl pins are not driven in as deep as they should be either, or the blocks pin holes are not drilled deep enough and or the pins are not pressed in deep enough or there a touch too long.


Another maylay that has accured is that the main body casting right behind the power valve will be too proud .

This will cause a corner of the power valve to hit it.
This will also keep the metering block from sealing as it should

If this is taking place you will find a whiteness mark on the main body where the two have been touching .

[spawn_x]

Ok, so there are no issues with the location emulsion well on the new block compared.to the old??

[steve25]

That question I can't give a definitive answer to I am sorry to say.

[Tandyman]

To allow the extra emulsion on this block the main well to idle well passage had to be moved down and it is now overlapping the position of that the ported vacuum passage is on the 3310 main body exposing it to motor vacuum when the throttle plates open uncovering the port . To use this block you need to block the ported vacuum passage in the main body or baseplate. I would drill and tap it and use a set screw. This means you will not have ported vacuum when using this block.

Glenn

[chiphead]

Not sure what carb your're trying to retrofit. I swapped proform blocks onto my QF 750HR 4150 double pumper. Works great. Check the gasket openings between the block and the main body. The block to body gasket should seal off the spot on the block where the main well transfers fuel to the idle well. That transfer spot should not overlap with any opening in the gasket.

You'll need to tune that billet block to work correctly. Typically move the IFR to the lower position, and block all but 2 of the emulsions to mimic the behavior of the old holley configuration. Thats typically a good place to start.


https://forums.maxperformanceinc.com...ight=quickfuel

[Tandyman]

Chiphead,
Any holley carb that originally provided ported vacuum thru the primary metering block will have this problem with the 4 emulsion block.
Your 750HR likely provides ported vacuum thru the baseplate like most QF carbs. Moving the IFR to the lower location is highly recommended but it will not fix this problem with the 3310 holley.
Glenn