Check to see what power valve you are running, the power valve provides fuel enrichment under acceleration. You need to see what vac you run at idle and cruise to determine the right power valve. Accelerator pump provide fuel to respond to the sudden opening of the throttle plates.

If your can roll gently on the throttle to full throttle and it pulls well than yeah, look at your pump cam, accel pump adjustment and squirter size.

If you roll and it pulls well than starts to fall on its face then power valve or jetting need addressing.

This is why I recommend edelbrock for a daily driver, most adjustments done externally, jet changes done without spilling a drop of fuel, and set-it-and-forget-it tuning.

 

That is exactly what happens. If I ease through the throttle to wide open, it will not stumble. But if I wanna wail on the throttle, it falls on its face. I have a 35 squirter, 10 sizes larger than what I had. I also adjusted the arm to what Holley has shown to be correct.. Im using the black pump cam. Looks like I need to order the assortment of cams today off Holley.

And believe me. If I had the cash I would ditch that damn Holley and try to find a sterling on here if I could find one.

 

pump cam on mine is white.

 

Just got off the phone with a guy from our local speed shop. It's my cam. I have a blak one on at the moment and this graph will show why I am having the issue. My pump shot isnt lasting long enough to meet the transition to the barrels, thus causing the fuel cut.

http://www.holley.com/data/Products/...mpCamGraph.pdf

You called that one man. Fortunately in my large search to fix it I did discover the pump nozzle being tiny. Hopefully this evening I'll be cruising with no fear of a stumble. Now to replace my main pulley that's causing my belt belt to squeal.

 

that 35 might end up being too big. Don't go with the biggest pump cam either, edge up a bit at a time. I would bet on the white one.

 

My carb also has the white cam

 

well I researched where people were using 30 to 32 on stock ports... so far it seems to run a hell of a lot better but that doesnt mean anything yet till the cams right. I will save myself the trouble and go with the white cam first since it seems you guys have your **** together, haha. I'll give you guys an update on the performance once I get the cam on this evening. Cannot thank you guys enough for the responses and all the help. Gotta love the club community.

 

it took me 2 or 3 tries to get the accelerator pump jet right and that is with tuning on a dyno. Once you get that white jet on there if there is still a stumble, I'd look at getting a bigger jet.

 

Big update. Went to the speed shop yesterday after work. The guy told me it could be cam size or it could be the accel pump. So I bought both. When I got home I realized the carb had to come off for me to replace the pump. So while I had it off I cleaned the hell out of it, adjusted the pump arm, and replaced the parts Here it is before I cleaned it.

 

also when I took the carb off look what I found.. How I didnt see it...I have no clue. a 1" spacer. and somebody has been port matching on the intake...... Unfortunately it still stumbles. So next is rejetting.........

 

So I have a BIG street port and ported intake on a Holley 390 LOL. What size jets should I order ? I have faith 84stock will know the ways of the Holley. I cant say for the main jets what I need, but I'll bet the way it feels I need to go 2 more sizes on the secondary side.

 

at some point I'd get a RB intake if I were you. They come up on here used now and again.

 

The best thing to do for jet size it to increase the size by three. So lets say you have a 40, so you would try a 43. Having us tell you what size you need doesn't really work because all conditions are different. You will need to just keep experimenting till it works.

 

cross reference the list number off your carb, look up original spec and add 2 plus a 6.5 power valve.

 

Will do.

 

I went the wrong damn way the jetting. I pulled out 50s and went with 53s and it got WAY worse. To make things more awesome, my local speed shop can only order down to 50s.( I live in BFE redneck paradise..so dirt track is all these people know ) SO Im going to order 44s and 47s straight from holley as we speak on overnight shipping. Hopefully I get it right, cause next I'm pulling the motor and giving it a hell of a good cleaning, replacing the oil pan gasket, punting the oil metering over the hill, fixing my speedometer, replacing my throw out bearing, and if Im not too broke...rocking the MSD 6al and blasters.

 

I ordered mine through Checker in the past. You can also order through Jegs or Summit.

 

84stock kinda gave me a reminder to update.. lol. Still waiting on the 45 and 47 size primary jets to come in from summit. However I did put in a 6.5 power valve in. Hopefully the jets will be in soon...

 

Some thoughts for you... Get rid of the power valve and buy the power valve block. Don't connect the vacuum from the distributor to the Holley (overrated). Look into buying the jet kit for the secondaries it will enable to jet the secondaries. For jets you will need 68-69 on the primaries and about 70-71 secondaries (depend on port size). Don't buy the RB carb you can get your carb to run as good.

 

I'm running 50s now and its basically drowning my motor when the primary open. It's so rich it burns your eyes to be anywhere near the the *** end of the car. I tried 65s for fun and it would barely run.. There is no way a set of 68s would work on my 390

I am keeping my carb. With the help of these guys I've been able to basically rebuild the entire carb and install some vital parts I was missing. (thanks again 84stock for the diaphram) It runs really well now besides the mid cut, being the point where the primary jets are the only thing opening, then as soon as the secondaries open I'm back in business. I have a feeling i have a rather large streetport. Ive rode in stockports before and this thing is an entirely different animal.

 

jets are here !!! putting them bastards on during my lunch break, wooooo !

 

Well the 47s actually made the cut worse..... so imagine the 45s wont do **** either.. i cannot imagine going up in jets as damn rich as it is.. son. of. a. bitch.

 

Ive about had my fill of this god awful 390 and the jackass that supposedly tuned it before i owned it...ok i feel better now. So now what, lol

 

Sacrifice a pair of jets and drill them out. Sure you'll be rich but it will answer some questions. Then get idle and cruise vacuum readings to pick the right power valve. Too bad you don't live here, I could dial that thing in easy. Drill and test!!

 

I must have 60+ jet, springs galore, shooters etc etc. So easy when you already have all the **** to try.