Holley 390 anyone running one?

[Keeper]

I will recheck the float level.

Squirter shoots at any, I mean any throttle movement. It was also readjusted when I moved the cam back to #2.

Advance is on the full vacuum port.

I also checked to make sure that the ported vac port was not seeing vacuum at idle, just in case.

Yes this is a part throttle hesitation, cruising along at 35, punch it, it hesitates and then goes.

 

[railroad]

Just for kicks, put the vacuum adv on the ported vacuum, double check your timing without any vac advance.
You may have to adjust your idle speed. I think that is the reason you have such a high idle with a mild cam. Not the mixture, just idle speed. Hopefully you will be happy.

 

[railroad]

I tried to edit my previous post, but waited too long. I wanted to add, this is not a shot in the dark. I run all my vacuum advances on the ported vacuum. If you want my take on this, P M me. Rather than getting into a pi$$ing match with a guy on here, which is better, I will give you both sides of how it functions. I think it will help with the hiccup.

 

[Mike]

I run all my vacuum advances on the ported vacuum.

You know, back in the day, we referred to 'ported vacuum' as (wait for it) 'spark vacuum'. Go figure... For the record, @railroad, you just may be one of the very few who understand how a vacuum advance chamber works.

If you need to hook a vacuum advance to manifold vacuum, then I question why you are running vacuum advance in the first place. At that point, the K.I.S.S. Law comes into play and you could just do away with the vacuum advance, entirely.

But then again, I suppose there are doctors that will prescribe band-aids for broken bones, so there you have it.

 

[Keeper]

haha no worries. I have always run full vacuum as I was under the impression that it was better for overall economy. My idle is sitting at around 650 in gear. I can drop it lower if needed, but it seems happy right there.

Its a simple test to flip it to the ported tube and its free!

I have also found that my "transfer slots" are pretty exposed with the settings as they are. So far no squirter changes have made a difference. I have tried the stock 25's, 28's and 31's. They all have the same stumble at the same spot. I am going to set things back to the base setting and open the secondary idle a touch to see if I can close up that transfer slot a bit.

This weekend is our big local carshow, 1500 or so cars, 3 days of fun. Figure while I am sitting around shooting the shit I can tweak the carb...lol at least there will be a bunch of folks around to help out if needed.

 

[railroad]

I guess you are updating on all the changes you have tried. I hope there is some method to the madness, but it seems like you are just throwing everything you have it, without any logic. I know from where I sit, I cannot hear, nor assess the changes. Your statement you checked and did not have any vacuum at idle on the ported idle port, made me think you did not cap it off, since it was not pulling vacuum at idle, not good. I thought you had it real close with just a little hesitation. I was hoping this is where you would try the ported vacuum on the ign advance. Just to give you a little idea, Tee a vacuum gauge in to your manifold vacuum with your vacuum advance.
When you hit the throttle watch your vacuum gauge, yepp. That is what your vacuum advance is doing at the same time. Try swapping it to ported with the same set up and watch the vacuum gauge.
If you do not get an improvement here, and you think it is still accel pump related, you might step up 2 jet sizes in the primary. I can only work with what you post. I guess you can shoot for overall fuel economy with a Hot Rod, but those are 2 different rides most of the time.
Hope some of this helps.

I really do not see the transfer slots figuring in on a part throttle acceleration hesitation.
Are you having idle problems, idle jet adjustment issues too?

 

[Keeper]

Okay let me back up a touch and explain my madness here.

If I make a change, and it makes no difference in the way it is running, I am changing it back to the base setting. This is just for me to try and keep things straight so I do not just keep chasing my tail making wholesale changes.

Couple of other comments I have made and explanation.

The ported vacuum test was to see if the ported vacuum port on the carb (the one on the metering block - in case I am using the wrong terminology) was pulling any vacuum while the car was idling. Mine does not, this was part of the testing to see if the primaries were open to much at idle as I would see vacuum at the ported port if they were. (Hope that makes sense) It is capped when its not used.

The transfer slots came from me reading my Holley carb manual (I do have one here!!) and it telling me that I should only have a little square showing on the transfer slot and not over half of the slot showing, so I adjusted the secondary idle to allow me to close that slot up. (Didn't do anything that I can tell)

No idle problems at all, it will idle smooth around 600 or so.

Here is the update for today. I tried your suggestion on the ported vs full advance, here is what I noticed, the idle had to be raised when I switched it, the idle is more lumpy (not a bad thing) but it ran exactly the same.

I really need to have someone ride along and record what I am trying to bring across in this thread.

Here is the exact scenario:

- cruise at 30MPH (1500 or so RPM), if you hammer the throttle, it hiccups then goes
- cruise at 30MPH (1500 or so RPM), lean into the throttle at medium speed, it will stumble a bit then go
- cruise at 30MPH (1500 or so RPM), slowly throttle up, it throttles up fine.
- hammer it from idle, no hesitation it will spin the tires and run
- If I am playing with the transmission in a lower gear keeping the RPM's up, there is no hesitation no matter how I play with the throttle

I know this is frustrating, I am trying my damdest to explain everything I am doing.

 

[bobs66440]

I'm not a carb expert by any stretch, but I think there's a transition circuit from cruise to wide open throttle (WOT). Maybe there's an adjustment there? Sorry I don't have an answer. Personally, at this point I'd be installing a different carb, lol.

 

[Mike]

Wait. This is a vacuum secondary carb, yes? There should be a secondary metering plate on it, rather than a secondary metering block. It doesn't have secondary main jets, does it? Unless you have a metering block with secondary idle mixture screws, there is no secondary idle circuit.

It sounds as if you have wrung out the accelerator pump circuit, so let's turn our attention to the power valve. Help me, so I don't have to read back through 48 posts - didn't you say you had a 7.5 power valve in the carb? I'm willing to wager that it is opening too late for what your combination wants. Get a long enough piece of vacuum hose that you can get your vacuum gauge in the car with you. Start it, let it warm up so it idles without the choke being on, then drop it into gear and note the vacuum level. Now, go get on a highway and run it up around 80 - 100 klicks, and on a level stretch of road with your foot steady on the throttle, note that vacuum level. What you want to do is select a power valve that is going to open about 1" - 1.5" below your lowest number. That way, you will have a power valve tipping in as needed, but not sneaking open when you are idling, or at a steady cruise RPM.

When you set the idle, it holds steady, yes? You don't notice the engine hunting and seeking, trying to keep itself idling?

 

[railroad]

Excellent update Keeper. I was going to suggest including a vacuum reading at the rpm and throttle applications you posted. Mike got that covered. To be as simple as possible, just log the vacuum reading on the same cruise test you posted, apply that to your power valve application. On the secondary idle adj, I think you just opened the butterflies ??
Just for future reference, try and observe the throttle position at your test cruising. If you can reference it to something on the carb, it might be easier. We will sit on this until you get the pv observations done.
I have been known to tape the vacuum gauge to the windshield for this kind of stuff. It puts it right up there for easy reference.

 

[Keeper]

Okay I will try those.

Yes it has a metering plate no idle screws or anything on the secondaries, I just opened the secondary butterflies a bit using the tiny little screw on the bottom of the carb.

It idles smooth no hunting or seeking at all. The only symptoms are what I described. And yes it currently has a 7.5 PV in it.

My vacuum gauge will reach inside the car already. I will get my other half to hold it and write some #'s down for me to see whats going on.

Hopefully I will have some info later on. The search continues, on a plus side, one of the guys in the club had a holley jet kit on hand with a bunch of PV's and a couple squirters. At least now I won't have to go out and spend any cash to test things out!

 

[Keeper]

Maybe I can get her to use her iStuff to record some sound/vids as well.

 

[2old2fast]

Just to throw this in, there is absolutely a sec. idle circuit in that 390 carb , it's referred to as a sec. constant idle bleed , IIRC they're around .030 each , & even though they're non adjustable , they have to be recognized as part of the fuel delivery system. Responsiveness issue's are a bear to diagnose because everything about the engine [ cam , compression , timing , port runners etc. etc. ] all play a part . Even though it's frustrating as hell sometimes , USUALLY , it can be worked out. Simple test to tell if you're rich or lean is to have someone follow you when you're testing... no "puff" when you hit the throttle on a carbed engine , generally means lean , & vice versa..
dave

 

[railroad]

Now we are cooking!! Sounds good. I did have some old pv's that did not work properly due to old age, I guess.
Hopefully your friend has some current stuff and no drilled jets.

 

[Keeper]

haha most of these jets are huge, but there was a set of 56's in there in case I needed something to try. The others were 68 and up to something silly like 100. Now the PV's were 25, 35, 45, 65, 85, 95.

Plus a couple of cams. I do not remember the colors.

 

[railroad]

If you have the tuning manual, look for a cam that gives a big shot a mid stroke. Since the engine recovers so fast, I would consider a large size shooter to get it all out there fast. Of course, I have high hopes for the pv cure.

 

[Keeper]

Okay vacuum results:

Cruising at 60-70k 1500rpm 18 inches of vacuum.

Idle at 600 rpm it is between 13-15 in gear. It bounces due to the idle being a bit more lumpy now.

Since I switched to the ported vacuum I realized that was why my vacuum gauge was all over the place in the other vids. As soon as I hooked it up today at 900rpm it was steady at 18 inches. No more bouncing. With this fixed I will take another stab at the idle screws since the steady needle will make things much easier...lol

I have a video coming of what the engine is doing, I will have to try and clean it up a bit as there is a lot of wind noise. I will try and get it up tonight.

 

[Keeper]

Okay lets see if this will work.

http://www.netquickposse.org/photos/index.php?album=bucket3&image=024.mp4

Right at the beginning you can hear when I step into the throttle. These are all while cruising around 60k.
Best one is between 10-14 seconds. You can hear it hiccup right around 12 seconds.

 

[railroad]

I could not tell much, but do have a question, what transmission are you running and are you locked in one gear for your testing? Not trying to skirt the problem, but I am hoping you are locked in second or third, not OD and the trans not down shifting during a test.
I think 900 rpm might be a little high for adjusting the idle mixture. If it will idle at 600 rpm in gear, will it not idle lower out of gear?
Without knowing more, I would find the lowest idle speed it will stay running and drop into gear without killing the engine. If you raise your idle speed to 900, this will be the reason the transfer slots look too open. 600 rpm might be too low. I would shoot for 750 rpm. You might have to go back and correct the secondary butterflies. You did count the number of turns on that little screw? If you are up to it, on the next video, put the camera in the floor. I just need to hear the engine. I might be more interested in hearing it idle, out of gear, in gear and seeing the rpm. And there was the vacuum gauge lying in the floor. How about confirming the vacuum advance is not leaking too.
Hanging in there.

 

[Keeper]

Yeah it was not the best of vids...first one. Did not think of just dropping it on the floor!

Okay, I thought I seen the 900 for adjusting on the Holley website, probably misread it. Lots of numbers flying around..lol

It will idle around 500 in Park. Right now its idling at around 550-600 in gear. I have a pretty small tach so its a close #.

Now that you mention it, no I am not in 3rd. It jumps into 4th at about 60kph and locks up soon after. 700R4 btw.

Yes I kept track of the # of turns on the secondary butterflys, only bumped them 1/2 turn.

Thanks again for this, we will get it sorted out! I refuse to put the 600 back on...lol