I have a holley 3310 750 on a mopar 380 horse crate motor. The secondaries will not open. I have the quick change spring kit on the carb. I have changed the diaphragm, tried it with and without the check ball, tried all springs in the holley spring assortment. I currently have no check ball in the vacuum housing and the white spring installed. I have made sure the vacuum housing has no leaks and bench tested the secondaries by blowing air with a blow gun through the front right venturi. With the carb installed I have used the paper clip on the diaphragm rod trick to check the secondaries. I have run the car full throttle through all the gears and also just left it in drive and gradually accelerated to full throttle but the secondaries never open. Does anyone have any ideas on why the secondaries won't open? Could it be the carb is too big for the application? 67 barracuda with auto, 10 inch converter, dougs headers. 3:55 rear.
secondaries won't open on holley 3310
- Thread starter 500duster
- Start date
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I would remove the secondary diaphragm and make sure the vacuum port int he carburetor is not blocked. You can use mechanic's wire. Do the same thing to the matching port in the diaphragm.
I have made sure the vacuum passage is clear. I have bench tested the secondaries by blowing air past the vacuum hole on the right primary venturi while holding linkage open and the secondaries open. For some reaon they don't open when the carb is on the engine and in use.
Inertia
Well-Known Member
Is there a chance of gasket interference.
Your description wasn't clear if you test on/off car.
Your description wasn't clear if you test on/off car.
Inertia
Well-Known Member
If it has choke linkage, it won't let sec open "cold".
Adjust as nec.
Adjust as nec.
Demonic
Well-Known Member
There's a passage to the primary and secondary venturi. I wonder if a really big shop vac could do a dry test? You couldn't have any fuel vapor of course, unless you're filming it for YouTube.
So you tested the operation by blowing past the hole in the primaries while the carb is off the engine. Try doing this while the carb is on the engine with everything hooked up. If it does not work, then take your linkages off one at a time & retest to see what has changed. If it still does not work with everything disconnected, you must look at gasket/manifold interference.
Once you install a larger camshaft Vacuum carbs are a pain in the ***. If you decide to go big camshaft there are 4 No's to consider
No Power brakes
No Vacuum advance
No low stall converter 3500 and higher only
No Vacuum secondary carb!!!
You should have bought this. Your problems would have never appeared.
Quick Fuel SQ-750 Street-Q Carburetor, 750 CFM
Many people put a cam in because they want the lumpy sound. They don't go the full distance. And then they complain about the engine not having any torque with the rest of the junk parts they used. Compression ratio is the number one fail of large cam engines. Overlap will kill the performance of a low compression engine. LOW VACUUM !
Many want to run pump gas and have the sound of a race car.
No Power brakes
No Vacuum advance
No low stall converter 3500 and higher only
No Vacuum secondary carb!!!
You should have bought this. Your problems would have never appeared.
Quick Fuel SQ-750 Street-Q Carburetor, 750 CFM
Many people put a cam in because they want the lumpy sound. They don't go the full distance. And then they complain about the engine not having any torque with the rest of the junk parts they used. Compression ratio is the number one fail of large cam engines. Overlap will kill the performance of a low compression engine. LOW VACUUM !
Many want to run pump gas and have the sound of a race car.
Disagree with saying vacuum carbs are a no-no on big cam engines. We are not talking about vacuum at idle, but when the engine is revving up and demanding more fuel. With him changing his secondary spring to white, the secondaries will start to open at a very low RPM. In fact, they open so fast he would notice a "bog" as they do so. No, no double pumper needed.
Well it doesn't look he is having much success with springs. Vacuum secondary carburetors are great for a replacement of a factory carb on a Street engine built to factory specs.
Once you start building bigger they are a loss in performance . Nothing is better then mechanical. There is no wondering if your secondaries are working at wide open throttle. Vacuum secondary Carbs are for passenger cars , Trucks and RV's . Not for built high performance applications.
Most people drive on the 2bbl . When they use the 4bbl it is usually pushed in the wide open position.
Inertia
Well-Known Member
Secondary opening is by venturi vacuum .
Opinions about VS or DP are infinite. I guess DV's opinion about VS on a street/strip car is wrong too.The bottom line here is what the OP is dealing with. The 3310 will work just fine for him once all the hindrances are dealt with.
dano
Evil Handy Man
When its installed, have you been able to manually move the secondary blades? I hd this issue on a 3310 and the secondary blades for some reason we're stuck, Once I moved them a bit manually everything was fine.
I will check for gasket interference tonight. The 750 vac secondary is what mopar suggests for the crate motor. I had a 750 double pumper on engine last several years but when i tried starting car after winter storage it ran like crap. Took carb apart and fuel bowls and metering block are full of white crystal like substance that ate into the metal. I figure it is due to junk pump gas. I had the 750 vac as a spare so i rebuilt and installed it.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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I have run that 3310 on my 292/508 equipped 367. it worked as expected. Like said, it works on venturi vacuum.
remove the pod, and spray thru the circuit with something like Brakleen, to see where it comes out.... or doesn't.
Also like said; If the choke does not come off or does not stay off, it will disengage the secondary linkage. If the choke has been removed, but the mechanism has not, well then there you have it, get rid of the interfering non-functioning parts.
on the street, a DP is overkill.....especially in first gear, which is why my engine has one, lol
remove the pod, and spray thru the circuit with something like Brakleen, to see where it comes out.... or doesn't.
Also like said; If the choke does not come off or does not stay off, it will disengage the secondary linkage. If the choke has been removed, but the mechanism has not, well then there you have it, get rid of the interfering non-functioning parts.
on the street, a DP is overkill.....especially in first gear, which is why my engine has one, lol
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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That powder is what's left after certain alcohols attack the metal. It can be chemically removed. But if the cuircuits have been ruined in the metering blocks, that is another matter.
I will check linkages tonight also. I will try blowing air through right primay venturi with throttle open and see if secondaries open with carb on car. I did this on bench and all was good but did not try with carb installed.
So the last several years the DP worked fine . But now all of the sudden Mopar tells you Vacuum secondaries is better because you parked the car with ethanol in the carb. And you just so happen to have one as a spare.
Then you disagree with me telling you that the DP is a better choice. You'll open your eyes and toss the VS carb after a while.
Why do you think they are the cheapest holley style carb you can buy? They sell the parts to make them work and people spend the money. After they can't get it working they'll sell you a DP.
When ever I open a hood and see a VS I ask myself . Why the hell didn't they just buy an Edelbrock for the street? Oh yeah , For the look of the Holley to go with the thump of the Cam.
Did you know and engine with a Bigger cam and a holley should be idling off the secondaries after squaring the primaries. Or holes need to be drilled in the ventury blades as in the 4th picture. The carb you have doesn't have a secondary idle screw. The primaries should never be opened past square to obtain idle.
Inertia
Well-Known Member
Depends on application, but he's right, the first Mopar Hustle Catalog recommended 3310, LD340, and Hooker underchassis headers as first recommendation.
I wouldn't put a double pump on a 2:76 geared vehicle, would you ?
I wouldn't put a double pump on a 2:76 geared vehicle, would you ?
MopaR&D
Nerd Member
Not sure about the vacuum advance part, might not work "ideal" but at cruise your vacuum will be the same whether or not your engine has a big cam... works fine with my car that has a somewhat lumpy cam but it's only 222* @ .050" and pulls about 14" Hg at idle. I have VA hooked to manifold vacuum.
I guess it depends on definition of "lumpy cam" and what exactly "low idle vacuum" is. To me anything that doesn't idle with all cylinders firing evenly is "lumpy".
I wouldn't put a High stall or a larger cam in a car with 276's either. That is the problem with some builds . They want the race car sound . The race car look. But they want to run on pump gas and get good fuel economy.
OMM: His eyes *are* open and he wants his 3310 to run... and it should when following the recommendations given. The rest of your post is nothing but rhetoric, which is not germaine to his issue.
And you can't have it all. Well a little of it all with a 3.91 gear and a overdrive. Mild cam and a Thermoquad.
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