Thread: Dual quad jetting?

Tweet

Kinda hoping someone has a similiar set up.

I have a low rise Offey on my engine with dual 600 Holley 4106 carbs.
metering plates in the rear, jet's up front.
Progressive linkage.
Just wondering what size jet's you are running?
Right now I have 47's in the primary carb, and 48's in the secondary carb.
The lowest my Holley kit goes down in jet's is 46.

The plug's don't look lean (not white), and the car is not overheating.
The reason I ask is, I dialed in the curve on the distributer to come in earlier, and was wondering how much I should fatten up the jet's?
When I ran my single 4 barrel, I was at 86 and 92 jet's.
3000 stall converter.
3.42 gears.
Pontiac engine. 461
Automatic trans.
6 lbs of fuel preassure.
heads flow at 310 cfm
.510 cam lift. 2.31 - 2.40 duration 1.12 centerline. Flat tappet hydr. cam
3 inch exhaust
1.65 rockers

Hope that's all the info you need.

Sure sounds small to me. If it likes all that cfm it should like more fuel.
Probaly mid 60's primarys? What's the holley book say they came with? If
the motor likes one jetted near stock, then it'll take two the same way long as timing,cam etc a in sync.
good luck, Ron

Best way I've found to jet on dual carb set ups is with an exhaust gas analyzer...Maybe a friend who works at a shop or something could let you borrow the machine and a bit of time???? Takes all the guesswork out of tuning for jet size. I'm suffering from CRS on Holley numbers, are these the vacuum secondary carbs? If so, once you get the primary jetting correct changing the springs on the secondary diaphragm should probably be done in conjunction with re jetting.... Mike P is very good with the multi-carb set ups, he has a good thread or two on here about making them work correctly.

Yes vaccum secondaries.
I checked the #1 spark plug after my test run,and the very tip is kinda white now.
I think I am gonna change them to about 65 each.
Maybe they were both originally set at 46, if you run them to open evenly.
With the progressive linkage, I am really running on the back primaries most of the time.
What's the worst that can happen, I run to rich?
Better then running lean, I guess.

I'd start at 62's and work up.