I have a mildly modified SL6 with a Holley 390 (0-8007). If I push on the gas to get it to move a little faster it bogs and then starts accelerating like it should. Should it be re-jetted? Power valve changed?

The stock Holley Specs are:
Stock – As Delivered
Carb Specification: 390 cfm Holley, vacuum secondaries
List : 0-8007
Primary Jet: #51
Secondary Jet: #55 Equivalent
Power Valve: 125-65 (6.5)
PV Channel Restriction: 0.039
Idle Air Bleed: 0.070
Secondary Air Bleed: 0.035
Primary High Speed Bleed: 0.036
Secondary High Speed Bleed: 0.035
Diaphram Spring: Plain

What needs to be changed, if anything? Has anyone had to modify a stock Holley 390?

bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

I currently have the same carb you have on my Hpak but I have a different set of spots where it leans out than you...

Rejetting will only change things when you are in the 'mains' aka 1800+ rpm...

I think your acc. pump shot isn't enough so you'll need to get a bigger 'shooter' or try changing the screw position on the cam to #2.

If you are accelerating at any speed and your vaccuum gauge dips to 10,9,8,7" of Hg and you bog, then we need to change the power valve from a 6" to something lower (8 probably would be a nice start, 10 comes in a bit lower and hurts gas mileage).



Get a holley tuning book, it will help out a lot.

-D.idiot

Does anyone have a suggestion on a book or books on tuning Holleys?


bwhitejr

_________________
'72 Duster (Performance 360)
'83 Ramcharger (Performance 318)
'80 TrailDuster (360)
'80 D-150 Truck (See Below)
CompCams 252S, Holley 390cfm, Offy manifold
Ported, Polished and Gasket Matched
P4286813 Springs,0.040 Overbore,
0.090 Shaved Head

Super Tuning and Modifying Holley Carburators by Dave Emanuel

Holley Carburators, Manifolds, & Fuel Injection by Mike Urich & Bill Fisher

I've almost worn out the first book consulting the modifying section, the second book is a bit 'thicker' as it has sections on the nasty Holley 4011 carbs (yechhh...)

Both should be about $18.95 or so...

In the meantime, hook up the vacc. gauge, get the tach out... note where it bogs at (rpm, gear, speed, driving style, vac. reading)...

In the mean time, I'm gonna guess you need to try the screw in #2 on that orange 466 cam, and if it wakes up a bit or is sluggy a bit late, then go to your local speed shop and get the next shooter up the ladder ('27' or a '31'), then try it again, I also recommend getting the shooter with the nozzles over the regular one... you may also have to check the clearance between the acc pump arm and the spring and bolt assembly too...