Running an old 3310-1 rebuilt by me. Float levels, PV's, choke, idle and timing all set and perfect. No vacuum leaks. Carb is running rich and netting ~8MPG. I'm going to perform the standard trial and error method to tune the primary jets. I' curious if this poor mpg is typical of the 3310-1 and if anyone has had success in bringing the MPG up on this specific model carb.
CK5
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Holley 3310-1 MPG and jet tuning
- Thread starter rcamacho
- Start date
Beast388
1/2 ton status
I am currently running a 3310-4 on my 388. The stock #72 jets were too rich. I swapped them out for some #69's and noticed an improvement in both power and mileage. 
The plugs look like they should and the exhaust is alot less sooty.
The plugs look like they should and the exhaust is alot less sooty.
rumbly truck
1/2 ton status
What engine setup are you running? The 3310 was set up to run on bigblocks. Does your idle mixture screws change your vaccum when they are adjusted ? You may need to restict the idle mixture passage in the metering plate. You can fine tune the jetting by changing the float level. Lower will lean it, higher wil richen it.
rumbly truck said:
402 BBC with a moderate hyd roller cam, pocket ported heads and headers. Idle mixture is plenty responsive and adjusted just fine with the std. vacum guage method. I'm mostly concerned about the main jet cruise circuit which is plenty rich. PV is intact @6.5Hg. Idles @14Hg.
I'm going to step incrementally on the primary jets from 72(stock)-70-68, etc until the cruise mixture leans out and then back one or two jets. From reading on this model I'm guessing I'll end up at a 68/69. I'm a bit concerned about the primary WOT A/F after stepping down so I'll measure the PVCR's and probably resize them a bit to compensate for WOT if necessary. What fun.
Mad-Dog
1/2 ton status
FYI....there are standard flow power valves and high-flow power valves, install standard flow if it has the high-flow version, high flow valves are typically used for racing or alcohol engines.
the 6.5's may be opening too early or opening during cruise mode or part throttle so a valve/valves that open later or at a lower vacuum may be in order, usually a power valve that opens at half of the idle vacuum works fine but sometimes a little fine tuning is mandated.
64's in the front and 70's in the back are a fine place to start with base jetting and your way up from there keeping a spread of 6 jet sizes between the primary and secondary bores.
the 6.5's may be opening too early or opening during cruise mode or part throttle so a valve/valves that open later or at a lower vacuum may be in order, usually a power valve that opens at half of the idle vacuum works fine but sometimes a little fine tuning is mandated.
64's in the front and 70's in the back are a fine place to start with base jetting and your way up from there keeping a spread of 6 jet sizes between the primary and secondary bores.
beater_k20
Banned
Holley 3310... 750cfm Double Pumper... and you want to tune it for milage? 
install it on one of these intake manifolds, and you'll be all set.
http://store1.yimg.com/I/budgetpackaging-com_1861_343287
install it on one of these intake manifolds, and you'll be all set.
http://store1.yimg.com/I/budgetpackaging-com_1861_343287beater_k20 said:Holley 3310... 750cfm Double Pumper... and you want to tune it for milage?
install it on one of these intake manifolds, and you'll be all set.
3310-1 is a vacuum secondary carb. Yes, picking up a few mpg is definitely possible.
Raul, You will probably end up with around a 68. I like the 3310's for street carbs, they can clean up and run well, but with the large size of the primaries you will never get the mileage a qj can give imho. Is the 14" in gear?
Maddog, you are right about the 6 jet spread, but a 3310 is a vacuum secondary carb and doesn't have jets in the secondary metering block
Maddog, you are right about the 6 jet spread, but a 3310 is a vacuum secondary carb and doesn't have jets in the secondary metering block
Mad-Dog
1/2 ton status
I was thinking that the 3310 came as a double-pumper also, I have been wrong before. 
When it comes to mileage a high state of tune and fuel system calibration will always provide the best figures no matter what carb is used
When it comes to mileage a high state of tune and fuel system calibration will always provide the best figures no matter what carb is used
rumbly truck
1/2 ton status
Unless you install a 4150 conversion kit, which replaces the rear fuel plate with a metering block. A standard 3310 is 4160 style has fuel plates, which are availiable but are a pain to tune with.
70's in now
I just installed #70 jets this evening. I'll see how it runs on my way down to Tahuya this Sunday. Hopefully I'll have time to rig a vacuum guage in the cab prior to the run to validate proper cruise Hg vs. power valve operation.
I just installed #70 jets this evening. I'll see how it runs on my way down to Tahuya this Sunday. Hopefully I'll have time to rig a vacuum guage in the cab prior to the run to validate proper cruise Hg vs. power valve operation.
#68 Stumble a bit
#70's indicated still a bit rich on the plugs. I have #68's in now ant they seem to stumble a bit on acceleration, but cruise is OK. I'll check vacuum to veryfy PV set point before stepping the jets back to 69 or 70.
#70's indicated still a bit rich on the plugs. I have #68's in now ant they seem to stumble a bit on acceleration, but cruise is OK. I'll check vacuum to veryfy PV set point before stepping the jets back to 69 or 70.
OLD DAWG
1/2 ton status
You might need to change the ramp settings on the accelerator pump cam now or possibly change the accelerator discharges nozzles. I'd try adjusting the cam first if your not noticing any lean conditions at cruise. At least that adjustment is free (as long as you don't need a different pump cam profile). I had the same type of prob. on my Holley after leaning it out and ended up resetting the cam and changing discharge nozzles. It really helped on the throttle response/bog
OLD DAWG said:
I'm also getting poor light throttle acceleration with slow accel pedal movement so I'm inclined to think that the mains are too lean to support light throttle without engaging the PV earlier. So, net-net accel pump circuit may indeed be a bit too lean/timed and thus more exposed as an issue now that the mains are leaned out.
It's not just adjustment on the cams, there are multiple cam choices by color code. What is on there now? Don't jet for step in, if your plugs read good on cruise, stay with that jet. PV is a big adjustment, have to get cams and shooters right first.
PS your lucky, wait till you have a carb with adjustable airbleeds to throw in the mix....
PS your lucky, wait till you have a carb with adjustable airbleeds to throw in the mix....
#69 in and need 9.5/8.5 PV
Well, I took a test drive with a vacuum guage this afternoon. I definitely need the PV to engage somewhere below 10"hg. Lean misfire occurs below this range until the existing 6.5 PV kicks in. Stock 3310-1 used a 10.5 PV pri and 8.5 PV sec.
So, I'm back up to a #69 primary temporarily as a safety measure and will pick up the necessary PV's this week.
Well, I took a test drive with a vacuum guage this afternoon. I definitely need the PV to engage somewhere below 10"hg. Lean misfire occurs below this range until the existing 6.5 PV kicks in. Stock 3310-1 used a 10.5 PV pri and 8.5 PV sec.
So, I'm back up to a #69 primary temporarily as a safety measure and will pick up the necessary PV's this week.
I have 72's primary, 76's secondary, and 6.5 power valve. I also run a 46 squirter.. but this is on a 355 in a Vette.
I have done the secondary metering block conversion also.
I would try tuning with your vac advance, initial timing, and advance curve also. These can make a big difference in driveability.
Good luckl, keep posting.
