Does anyone have a recommendation for a starting point of jets in a Holley 800cfm square bore doub. pump w/ mech. secondaries for a 427 BB? i am using a single plane edelbrock tarantula design manifold. I have read that left front no. 80,right front No. 76, left rear No. 76, and right rear No. 80 should be close. Also when they say "left front" Does it mean front of motor on driver or passenger side?
Also, the 800cfm carburetor came from Holley with 71H primaries and 85H secondary jets. I was under the impression that normally you should not change a carburetors factory jetting by more than 3-4 sizes or you are off track? If this is true the above jetting seems way out of line.

I run a holley 750 vac sec, rpm performer on my 427. It left the dyno with 74/77 jets. You can check out the dyno sheet on my page.

This was on pump gas.

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427 BBC Camaro
12.18 @ 113 http://www.geocities.com/mek88427

I don't think stagger jetting will work on a single plane manifold.
It was used successfully on dual plane factory type manifolds because the fuel tends to go to the ports nearest the carb venturi.
There were also fuel "tabs" added to the factory carbs to improve fuel distribution.

The single plane manifolds mix and trade fuel from cyl to cyl making stagger jetting probably innefective.

I ran the 800 carb on my Camaro 350, It has the same primaries as a 780 which uses a #68 jet on factory carbs, and a 72 on aftermarket carbs.
I think you will find your engine runs best in that range.
If you don't use a power valve, you have to go up around 5 steps. But I don't recomend running without a power valve.

76 is what the carbs come with on the secondary side. This is real close to ideal.
If you run open headers somewhere then you might try going a step richer.
David

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67 RS 327
69 Camaro Vintage Racer
65 Lola T-70 Can Am Vintage Racer

Stager jetting on a single plane works fine, and in the case of the small block victor (original) it was benifical to do so. I have not seen this as being needed on a big block though. I am not familiar with the old manifolds on the big block. It is posible it may benifit. Are the runners back out of the plenum, or in the carbs line of site in plenum? How is the floor on it? large flat surface or raised and semi directional? That is what determines if the stagger is needed. Otherwise see if you have from both power valves in car. Not needed in the rear, but leave the one in the front. Just set a power valve based on your idle in gear vac. About a point and a half to two points under. If you have the rear one pluged, use jet extensions and jet up aprox 8#'s richer than the front to componsate. Holley used #71's on the primary stock. Depending on your combination I would start close to that point and go from there. No real rule as to what to start with, motor will tell you that. And remember too that a good CD ignition (MSD, CRANE) will not usually color a plug right away. So just because it is light, it may not be that lean. Anyway that is it for now, Galen

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S/B Chevy Lover
67 Camaro street car
10:50's @ 128 on motor w/383 cid
79 Z28 w/383 9.1:1 3.73:1 Restoring stock apearance
13:40's @ 101 stock exh.& intake& Qjet
smog legal
Camaro Lover

Nice car 427, I like the clean underhood look. A little laughing gas and 10.90's? it would be fun. Galen

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S/B Chevy Lover
67 Camaro street car
10:50's @ 128 on motor w/383 cid
79 Z28 w/383 9.1:1 3.73:1 Restoring stock apearance
13:40's @ 101 stock exh.& intake& Qjet
smog legal
Camaro Lover

88 427, you needn;t stagger the jetting. In fact, this occured as a result of the center divider being milled out of the L88 manifold and the resultant cannibalization of fuel which would run #5 and #4 ( i believe) lean. And it did. in my L88 #5 was defintely lean and the plugs were various shades of toasted marshmallow.

BTW, cutting the divider out is the stupidest thing you can do. I out a diver abck in and ran paralle jetting. anyway, your car...

A single plane has less fuel signal than a dual plane. Consequently I think you'll need to jet up more than 71, but as Galen says, there are no rles here. Power valves, jetting, and squirt all combine to provide the proper A/F under various conditions.

If it were me, I'd start with 73's in front and at least an 085 PV. Again, dont know how hairy your cam is. I suspect though you'll settle in at 74-75 with a 095, and 76-78 with a 045 or 055 in back.

Again, who knows but be aware that the open plenummig require you to jet up a bit more than you'd think. The fat PV up front cuts down the low speed flats of the open design. You'll get better mid throttle response.

FWIW, I must;ve taken the 850 i run apart 10-12 times before i felt it was as dialed as it was gonna get.

knaughton, the numbers you posted for the stagger jetting are probably for a carb with power valves in the primary and secondary sides. The numbers you posted for your carb look like jets for a carb with only a primary power valve. If your carb doesn't have a secondary power valve then you will have to have much larger jets in the secondary side.

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'69 RS/SS396 pro street
427/4spd/9"