View Full Version : real life testing a 3310-1 holley vs. 4779 750 dp


450bench
08-15-2013, 01:00:06 PM
Wanted to test the differences between a good running old Holley 780 vac. sec. and a nice 2 corner Holley 750 dp 4779 that I built...Called a cop buddy with a low 12 second 2007 z06 vette and set up a test race on a local deserted road that we frequent to test stuff...It's a quarter mile so it works well...My set up is a stock body 73 RSLT with a T56 6 speed and a 3.42 gear...The motor is a 9.7 to 1 454 with a custom ground xe274 on a 108 with massively ported and polished 781 heads and a weiand stealth...Jegs headers with flowmasters...Skip White HEI with timing locked at 38...His car, by the way, ran a 12 flat last time out at 115

With the 3310-1, shifting at 5500, I got him by about a half a car but was pulling him pretty hard...With the 4779, power was way up seat of the pants wise and I got him by an easy car and a half while shifting at the same 5500 to be consistent...We were both shocked that I beat him in the first place but the 454 makes some power and I know the torque was way up with the double pumper as I had serious traction issue in the first 2 gears...One important thing to note too is that all these runs were from a 25 MPH punch.

We ran several times with each carb, all with similar results...Bottom line is, with a decent set up and combo on a street driven 454 the double pumper is the way to go...Drivability is about the same and idle quality is a bit more consistent with the dp...I never like to over-carb my stuff and it may make more power with an 850 but the throttle response I have is really good and I like that...I can't wait to get it to the track because I think 11.70s or so may be a good number, which is shocking to me with this mild set up and a relatively heavy car

Just thought I'd pass this along since there are so many vac. sec vs. dp questions on the board

Carb settings: 3310-1 with milled choke tower, 74s in front 84s in rear...6.5 power valve in front with rear blocked...4779 with choke tower and no choke, 72 in front 81 in rear, 6.5 power valve in front with rear blocked...Vacuum is around 8 inches at 750 rpm

middleagecrisis
08-15-2013, 01:08:52 PM
I've had plenty of Holley VSs and DPs over the years and always felt like I had crisper performance with the double pumpers. Only one of my many carbuerated cars was a manual trans, so I don't buy into the DP for manual trans cars and VS for the automatic equipped cars.

450bench
08-15-2013, 01:19:20 PM
I've had plenty of Holley VSs and DPs over the years and always felt like I had crisper performance with the double pumpers. Only one of my many carbuerated cars was a manual trans, so I don't buy into the DP for manual trans cars and VS for the automatic equipped cars.

Agreed...It's really a total combo thing, I think

hhott71
08-15-2013, 02:24:13 PM
The 3310, 4779 and 4780 (800 dp) have the same primaries.
The 3310 has the same size secondaries as the 4780 800 dp.
The 3310 used to be called a 780, now it's called a 750.

The 3310, is it tuned to the max as far as accelerator pump shot and diaphragm spring?
I prefer a DP over a VS even on a stock engine. A 4776 vs an 1850, the DP is the big winner and both use the same size pri and sec bores.

450bench
08-15-2013, 02:32:22 PM
The 3310, 4779 and 4780 (800 dp) have the same primaries.
The 3310 has the same size secondaries as the 4780 800 dp.
The 3310 used to be called a 780, now it's called a 750.

The 3310, is it tuned to the max as far as accelerator pump shot and diaphragm spring?
I prefer a DP over a VS even on a stock engine. A 4776 vs an 1850, the DP is the big winner and both use the same size pri and sec bores.

Yep, the 3310-1 is a 780 with downlg boosters and is tuned nicely, by me...Bought it new years ago...It runs best on this engine with a 32 squirter and a stock secondary spring with the checkball removed...The 4779-2 likes a 31 and 35 squirter with 2 jet sizes bigger on the front, which are 72s since it came with 70s and 81s in the rear...Gonna open the rear blades a bit to help with mixture screws

Bumpad_Z28
08-15-2013, 04:16:33 PM
I have and had planned on using my carb shop modified 3310 on my '78, BUT have been on the lookout for a good 4779 core for awhile ! This thread makes my looking more serious, interesting results ;)

~DaVe

hhott71
08-15-2013, 04:23:39 PM
ebay and craigslist or our local dragstrip forum, it's a great swapmeet site.

newschool72
08-15-2013, 04:37:37 PM
Ive never understood why anyone would use a vac sec carb on anything but a stock driver. To be honest, I would have thought there would be more difference than you saw. It sure feels like two different worlds to compare the two. Nice test by the way. Racing a cop on a deserted back road sound like the makings for a new car movie, LOL.

bige
08-15-2013, 04:50:23 PM
When my 383 was being dyno'ed the builder tryed several different carbs including vac. and mech. secondaries and the Holley Model 4150 HP Carburetors 0-80529-1 with vacuum secondaries made the most powr (497) and had the smoothest power curve. Am I missing something?

BondoSpecial
08-15-2013, 04:52:26 PM
No one will ever agree on "the best" carb because there really isn't one. They are just all different.

Blown Camaro
08-15-2013, 05:29:48 PM
I haven't ran a vacuum secondary carb since 1982. They are fine for mild cam street applications and near stock converters. I just prefer a direct link between my foot and the secondaries. Makes pedaling a car when you lose traction a lot easier.

I also did a back-to-back test between a 750vs and a 750dp and the dp won. This was in a sbc 4-speed combination.

Blown Camaro
08-15-2013, 05:31:25 PM
When my 383 was being dyno'ed the builder tryed several different carbs including vac. and mech. secondaries and the Holley Model 4150 HP Carburetors 0-80529-1 with vacuum secondaries made the most powr (497) and had the smoothest power curve. Am I missing something?

Did he take the time to jet each carb including HSAB's and power valves?

450bench
08-15-2013, 10:25:43 PM
I have a buddy with a super stock 69 427 Camaro. It's consistent and reliable. Runs 10.50s all day and is a 4 speed car. Obviously, you have to run the type carb that came on the car which in this case is a 780 vacuum secondary. I built his 4346 factory Holley and it screamed running 10.70s. He sent another 4346 to a shop in Dallas that specializes in super stock Holley carb. $600 later he got it back bolted it on and ran a best of 10.42 and picked up 3 mph over mine. Point is vac secs can go really fast with tweaking. I bet however a double pumper with equal work would be faster though.

newschool72
08-16-2013, 07:43:07 AM
I just like the instant control of the throttle w a mech sec. I had a vac sec on a 65 Malibu w a SBC 337 when I was in my early 20s and hated the inconsistency of the wide open throttle feel and sound. I had no idea of how to tune it, so it was what it was, but Ive been a hater every sense.

Damon
08-16-2013, 08:02:42 AM
With the stock spring in the secondary diaphragm the secondaries are not going to get all the way open, not even on a modest street performance big block.

I get why you do it in combination with the removal of the check ball (vacuum restriction), but it's hurting you on the top end.

In any case, the DP is almost always going to out-perform a VS carb from a roll like that (and in most other max-effort situations). No matter how you slice it, without a secondary side accelerator pump you can only open it just so fast without walking on the edge of a bog. Holley VS carbs always start with the secondaries fully closed and have to open slowly, at least for the first ~25% of secondary opening. Once they're half open they can flop open the rest of the way without a problem since they already have plenty of airflow through them. I should note that their vacuum supply passages involve both the primary AND secondary-side venturis for this reason.

(QJets don't work the same and use other tricks like a secondary pull-over enrichment system to allow faster secondary opening and true, full secondary throttle opening at much lower airflows through the carb.)

450bench
08-16-2013, 09:15:42 AM
Using the paperclip method, I have tested this particular 780 many times with various spring/checkball combos and the stock spring and no checkball combo opens the secondaries all the way and opens them all the way at a lower, more effective rpm than any other combo, which I like...Lighter springs, minus the checkball, open them earlier which isn't effective IMO...You're going by seat of the pants feel while checking rpm, pulling over and checking the paperclip, so it's not scientific but it seem fairly accurate as far as these things go...At the track, it's a bit easier because timeslips can't reflect changes for more tangible results...

Damon
08-16-2013, 09:28:11 PM
What RPM have you observed it being full-open by? Not trying to stir the pot- honestly just interested in your observations.

The check ball is there to slow the RATE of opening but it won't change the point at which total airflow achieves full secondary opening. That's all about spring tension.

450bench
08-16-2013, 10:08:01 PM
What RPM have you observed it being full-open by? Not trying to stir the pot- honestly just interested in your observations.

The check ball is there to slow the RATE of opening but it won't change the point at which total airflow achieves full secondary opening. That's all about spring tension.


No sweat Damon, I appreciate your comments, always...I found that without the checkball and using the stock spring, my estimation is that all four barrells are all in at roughly 3000 rpm, which is fine with a manual transmission, which is what I have...With the ball and a lighter spring, like the yellow one for example, the secondaries feel like they open at a more gradual rate beginning a bit earlier and fully opening at a higher rpm...That's strictly an opinion based on feel and traction of course...Track times would surely reveal a more accurate comparison...My car pulled so much harder with the stock spring minus the checkball and caused traction issues much like the 4779, then compared to running the checkball with other springs...Some of the other springs that I ran without the ball opened a bit too early causing some brief bogg problems...I love the 780 and think it's one of the best all around carbs ever made...The double pumper is a bit faster though, at least on my combo

Damon
08-16-2013, 10:35:55 PM
Wow, that's quite a difference. A stock/plain spring with check ball would not normally be fully open until about double that RPM (depending on the RPM climb rate, of course).

I think I'm going to have to try that out on my next vac sec Holley.

450bench
08-16-2013, 11:24:37 PM
One of my super stock buddies down here told me to experiment with and without the checkball years ago, changing springs...Hugely time consuming but fun and interesting seeing tangible differences and results...