[ponchbro]

I have been running a Qjet on my 455 that's been running good. I have a buddy running a Holley 800 Double Pumper 800 cfm Spread Bore on his 455 Olds with great success.Anyone used one on a Pontiac around here?? I like the ease of tuning!

[steve25]

If you do not have as much or more overall gearing and the same or less vehicle weight as your buddy, the 800 SB will only slow you down and its bigger primarys will reduce your cruse milage!

[goatasaurus rex]

i have one i have used in the past. great carb. easy to tune. excellent throttle response. out of production now.

[OINK 1]

I run the Holley 800 on better 1/2's 434 RA4, 6.11" lift solid roller cam motor.
Preformer RPM intake. Love it !!!

Pontiac Gregg

[71 Ventura II]

#6213 Holley spreadbore mechanical secondaries. I too have used it on a 455 build in the past with good success! JD

[71 Ventura II]

Originally Posted by steve25

If you do not have as much or more overall gearing and the same or less vehicle weight as your buddy, the 800 SB will only slow you down and its bigger primarys will reduce your cruse milage!

The #6213 has the "Small" primaries like a Q-jet which is a more fuel efficient scenario. It does however have "Huge" secondaries! LOL As with any combo you must have the proper gearing and converter to make a mechanical secondary carb work properly.

When we ran the #6213 it was on a mild 455 making 390 HP & 500 TQ in a stock weight 76 Bird with 3.73 gears and a 2200 converter. This car had tremendous throttle response; it would almost rev so fast it was hard to hit the 1-2 shift consistantly! JD

P.S. IMHO when your building a 455+ CID engine MPG is never going to be very good. Maybe if you went with an OD tranny, EFI, and friendly gears but even then it isn't going to be overly "Gas Friendly".

[Cliff R]

Some of the older spread bore units were pretty decent, but I think Tom Vaught has bought up all the desirable castings, and he's sitting on them pretty hard!

FWIW, there is nothing out there easier to tune at the track than the q-jet. I can change metering rods, hangers, pull-off or adjust the secondary spring opening rate in less time than it took to type this.

I still remember the days of catching all the fuel from the bowls on the Holley carbs we ran, then hoping we didn't tear any of the gaskets and have a fuel leak to repair before the next run......Cliff

[A.W.Dille]

I agree with Cliff in changing jets at the track, been there done that, can be a pita at times. But I have a 6213 on the shelf that I'm getting ready (as soon as I finish typing this) to put back on my 400 until I get the parts to rebuild and tune my Q-jet. A good carb when set up properly and very good carb with a four speed. My best times came with a stock iron intake with the 800 sitting on top. Proper jetting is critical with these carbs along with proper pump shot, as is the case with any double pumper Holley, but with the way the primaries and secondaries are laid out on these carbs, it's easy to overjet the secondaries. These carbs also work very well on a single plane style intake such as the Torker. Oh Cliff if you look at some previous post concerning the spreadbore Holleys, Tom really doesn't like these carbs, has said on numerous occasions that that was the worst design Holley ever made. I've had good luck with mine, and good results as far as performance, but gas mileage with these carbs sucks, but when looking at performance sometimes you can't have your cake and eat it too.

[ericwy]

Does the 6213 really flow 800 cfm? Its using a 4165 main body with with the same
1-5/8" primary and 2" secondary throttle bores as its 650cfm 4165 cousins. The only
real difference I can see is the secondary venturi diameter. 1=3/8" for the 650cfm 4165
vs 1-23/32" for the 800cfm 4156s.

Does the bigger secondary venturi diameter really allow an additional 150 cfm?

[Cliff R]

In direct comparisons, a spread bore carburetor shows a slight advantage over a square flange carburetor when used on a dual plane intake. This is simply because those intakes are designed for spread bore carburetors, and the throttle bores are well centered in the plenums.

On single plane intakes, the spread bore carburetor is at a similiar if not worse disadvantage, as they are poorly lined up with the square hole in the center of the intake. We have found in almost all cases, that a well blended spacer is required to get a q-jet to work correctly on a single plane intake.

The Torker I in particular, is the only single plane intake that was given any consideration to the q-jet. They have a "shelf" in them supposedly to help things out when they are topped with a spread bore carburetor. Specifically, something mentioned by Pete M. about fuel impingment (spelling?), nearly as I can remember.

Anyhow, the dyno testing we did with an untouched unit showed it to be down considerably on power everyplace, compared to my own iron intake......Cliff

[ponchbro]

What are the better numbers?

[A.W.Dille]

I run a 6213 and have liked it. Several years back I borrowed a 6211 to test at the track, worked really well. Like I said these carbs work real well in a manual trans application, sorry but I only used vacuum secondary carbs on automatics so can't say how one would work with an automatic if that is what you are running.

[taff2]

I used an 800 spreadbore double pumper on my 400 race motor down into the 9's,around 550hp, part# was 6910. Oh yeah,it was on a T1 inlet.

[GTO-relic]

Originally Posted by ericwy

Does the 6213 really flow 800 cfm? Its using a 4165 main body with with the same
1-5/8" primary and 2" secondary throttle bores as its 650cfm 4165 cousins. The only
real difference I can see is the secondary venturi diameter. 1=3/8" for the 650cfm 4165
vs 1-23/32" for the 800cfm 4156s.
Does the bigger secondary venturi diameter really allow an additional 150 cfm?

just diggin' around, nobody answered this ?
seriously...
assuming it was a serious question...
hell yes...
1-3/8" = 1-12/32"
so it's 1-23/32" vs 1-12/32" venturi comparison
that is 11/32" bigger secondary venturis in the 800 carb.
that's a LOT, easily 150 cfm. over a quarter inch wider venturis
.344" larger venturis
a 1-3/8" venturi only needs a 1-1/2" or 1-9/16" throttle plate to close it.
they were obviously only using the same baseplate to save on mfg. costs.
the venturi has more effect on the flow than the throttle plate.
the venturi sets the flow, that's the restriction at WOT
the throttle plate just turns it on and off tp varying degrees,
from min to max
even 1/16" bigger makes a difference,
that difference in the secondary venturis alone,
is what makes a 750 main body, into a 780/800 main body,
that and 2 or 4 downleg boosters.

4 downlegs and 1/16" larger rear venturis makes a 750 into a 780 (list 3310-1 VS)

2 slightly thinner rear downlegs and 1/16" larger rear venturis makes a 750 into an 800 (list 4780 DP)

so if you're adding 11/32" per venturi in the back, you're adding a schitload of flow.
looky here below, 650 vs. 800
pretty obvious...as easy as girlwatching actually, easy peazy, which ones are bigger

[JSchmitz]

They are great carbs. I only switched to a Q-Jet because I could control the secondary opening rate to improve 60' times. There are a few down sides. The mounting bolts are a PITA to access. The idle mixture screws are air bleeds instead of fuel control valves. They are also sensitive to overtightening. Be very conservative when tightening the mounting studs. The secondary idle shaft will binding up, and not fully return, if overtightened. I added a return spring to the secondaries that pretty much eliminated this. Mine is a List #9023. It has cathedral bowls (desirable).

[JSchmitz]

P.S. Many years ago, I found out that it's a bad idea to spray wheel cleaner on your intake manifold. It can remove carb plating! This carb would still look like new if I hadn't done it. It's the wheel cleaner with acid in it. Eagle One for uncoated wheels. Works great to brighten up unfinished aluminum. Bad for Holley carbs.