Holley 390 anyone running one?

[Keeper]

Okay here are last nights results:

It does not matter what gear I am in, as long as the RPM's are in the range of 1500-2000 it will hesitate on hard accel or stumble on medium accel, easing into the throttle is smooth.
Squirter size does not seem to make a difference as a 25 or 32 acts the same.

Question, when do the secondaries come into play? Could this be the secondaries opening on me?

Sorry if this thread is getting long, but its helping me keep track of things, its my notebook for tuning!

I am going to try and pick up a cam kit to see if there is anything there that will help.

 

[railroad]

I thought you had the secondaries wired closed? The reason for wanting to stay in one gear while testing was so I could hear the engine without a downshift. Makes no difference, we will get there. I would leave the big squirter in place and for some reason I want to think the blue cam or the big red one for a 50 cc pump worked on a similiar issue. We still want to try the power valve too, one at a time.

 

[Keeper]

I did for some testing but I opened them back up. Easy enough to wire them closed again.

I am running the orange pump now, it seems to be the default for all carbs. I will see if I can track down a blue. They want $50+ for the kit up here!!

 

[Mike]

Don't fash about that kit just the now. I think you've tried enough accelerator pump changes to indicate you've wrung that circuit out. You may end up going back to it, to do some fine-tuning after we get the sag out of it, but for now, I would focus on that power valve. You had a 9.5 valve, if I recall, so stick that in there and let's see what falls out.

 

[Keeper]

Will do, for giggles I pulled the carb off tonight as I wanted to see what the transfer slots looked like. Everything looks just like it is supposed to!

PV will get swapped in and we will see what it does.

 

[Keeper]

WE ARE GETTING CLOSE!!

Yeah I know, but dammit I am happy. We now have it down to a very slight hesitation when you hammer it, the tip-in stumble is gone. No big clouds of black smoke when am heavy on the throttle.

Remember when I said I wasn't going to do wholesale changes at once? Well when I had the bowl off to swap out the PV to the 9.5 I went ahead and bumped the jets to 56's and swapped in a heavier secondary spring to see if I could eliminate them as an issue. It was more a frustration "What the hell" kind of change...

Well all these changes have done some good.

Current settings for the carb are:

56 Primaries
25 squirter (going to bump that to a 28 tomorrow)
Orange cam on #1
9.5 Power Valve
Brown spring on the secondaries

I found a cam kit laying around for $20 as well.

For those that are looking here is the cam kit sheet, took me a bit to track it down so I figure I would add it to the thread.

 

[railroad]

I find out something new with each post, tip in stumble? You know there is a secondary meter plate that you can change too, LOL. You can cure the problem with the "all-in" method, but you don't know which one masked it, by how much, or cured it.
So to be right you have to start backing out, guess what, one step at a time. The pump cams are an unknown science per application and you have to try to try again, but the orange would have been way down on the list for what I think would fix it. Try the brown. Did we every get a vacuum reading at cruise speed?, ie Mike's suggestion. This is the best way to apply the reading to pv selection, maybe 1.5 to 2 numbers lower than the cruise reading.
How are those gaskets and bowl studs holding up, LOL.

 

[Keeper]

Yeah I know the all-in method is not advised. It was more of a "Lets throw everything at it and see if it will even make a change" again it was more a "What the hell" kind of thing.

The tip in stumble started with some of the changes, it was not there at the beginning, the tip-in being from 1500rpm, if I was light and smooth on the throttle it was not there, but if I was a little heavier then I noticed it.

I am not going near the secondary metering plate...lol...at least not until I get the rest sorted out. We have an "Arm drop drag race" show coming up in a few weeks, might be a good place to get some good plug readings.

The Orange cam was the one that came with the carb, its the stock one. I did not have any others to try!

I have replacement gaskets on hand, they are actually doing pretty good!

I posted the vacuum readings earlier, 18 at cruise, anywhere from 60-90kph. 13-15 at idle. Thats what prompted the change to the 9.5 PV.

Have some storms on the way today, so no plans for any runs

 

[Keeper]

By George (and Railroad and Mike) I think we got it.

Turns out our "Storms" were 10 seconds of thunder and rain, and sunny skies to follow.

So I decided to try some small tweaks.

I went up one step in both the cam and squirter and the problem is gone. No hesitation anywhere in any RPM range. Of idle is stronger, 1500-2000 is nice and smooth. 2500-3500 and its happy as can be.

Final settings for the day, I will leave these and drive it around a bit to see if anything comes up, unlike my mileage the last couple of weeks...lol

Here is where we sit:

56 Primary jets
9.5 Power Valve
Stock metering plate
28 Squirter
Green cam on #1
Brown spring on the secondaries

After a bit more of cruising around I will report back with any updates.

Thanks again for all the help folks!

 

[Mike]

Well, the good news is that the problem has been either cured or, at the very least, covered up. The bad news is that we really have no idea which it is. Did one of the wholesale changes actually cure the problem, or did the potpourri of changes just hide it? The downside is that if you ever run into a similar problem, you won't know how to fix it, short of making this shopping list of changes.

But, hey! It's running the way you wanted, so that is a good thing, aye?

 

[railroad]

Sounds like a good day for a cruise. Not that you need to, but you can fine tune everything now for perfection.
I am looking forward to some good reports on throttle/engine response.

 

[Mike]

I am looking forward to some good reports on throttle/engine response.

He'll be giving the RCMP fits, blasting up and down the 401.

 

[Keeper]

hahaha nah I have a couple of quiet stretches of road close to home I can play on.

As for the wholesale changes, yeah I know, I kept telling myself 1 at a time, but the bowls were off and the jets were staring at me, I could not resist...lol, eventually I will dial back each change to see what happens.

I am too curious to see what fixed it to leave it alone, but now at least I know it can be fixed.

 

[Mike]

hahaha nah I have a couple of quiet stretches of road close to home I can play on.

The boy I raced with was from Arva, just north of London. We raced at St. Thomas a couple of times, but we had also traveled over to La Belle Province , to race Le Grandnational, at St. Pie a couple times. So I've logged a bit of time on the 401.

 

[Keeper]

That's a couple hours west of me. I have been meaning to get out that way. One of these days!

In the spirit of "I have to know" I decided to pop the bowl off and change the jets back down a few sizes as the jump to the 56's was 5 steps.

Pro tip - When you have extra gaskets on hand, make sure they contain the one you need......have to wait until Tues to pick up some more bowl gaskets.

At least I have the 600 sitting on the bench....lol

 

[railroad]

The 1850 carb should be the same gaskets if you have to ride.

 

[Keeper]

Okay I finally picked up some gaskets and got around to putting this one back on.

To eliminate some of the items changed earlier, I went back to these settings:

53 Primaries
25 Squirter

All others remained the same.

Hesitation came back with these changes. So I will bump the squirter back to the 28 and see if it goes away again.

 

[Keeper]

I hate it when people leaves things hanging, so here we go:

The final settings, things seem fine with these, so I am not touching them anymore!

54 Primaries
28 Squirter
Green cam on #2
Brown spring on the secondaries
9.5 Power Valve (I forgot to add this one)

 

[ellis8500]

I'm going to switch from a 600 to a 500. I can't get the idle down even when the plates are fully closed. Transfer slots let in too much for my mild ford 302 coupled with a higher than stock stall speed converter.

 

[Keeper]

Have you checked to see if the secondary plates have been opened at all? You can adjust those open just like the primaries, maybe yours have been adjusted?

There is a little screw that can only be accessed from the bottom of the carb, secondary idle scr ew. Well that is if its a Holley.