Holley 4160, 390cfm on V6 - Setup/Debug

[loose_electron]

I suspect this has been covered before, so please be patient with me.

Had a vacuum leak around the throttle shaft of the carb, and decided to R&R to a new carb.

When pulling the old carb, I found a small hole drilled through the butterfly valve plates. My guess is that these were done (prior owner) to allow idle with closed plates.

In the process of setting up the new car, did not drill out the plate, and decided to try and set things up with a not modified carb.

All of that said, looking for any pointers or information on the proper setup of this carb. The issue we are seeing right now, is that even with the carb fully closed down the engine idles at 3000 rpm, and can't get it to go slower. Fuel is leaking through the system somehow, and this is a new out of the box carburetor.

 

[RootesRacer]

Many really good tuners will drill small holes in the throttle plates to force the throttles to idle earlier into the progression circuit.

This since you cant exactly redrill your progression holes where the throttle plates need to be for your idle.

Its a band-aid but a damn good one if that's what your tuning needs.

 

[loose_electron]

Many really good tuners will drill small holes in the throttle plates to force the throttles to idle earlier into the progression circuit.

This since you cant exactly redrill your progression holes where the throttle plates need to be for your idle.

Its a band-aid but a damn good one if that's what your tuning needs.

Yeah, that's about what I figured, but considering there are so many V6's in the Alpine out there, figured there might be a common set of tuning tricks for this carb out there.

 

[crs]

Do you have the Holley on line documentation on how to tune your carb?

My new Holley 390 4 bbl did not want to idle at the spec speed either and the only cure I found was to follow the Holley instructions to set the slow idle - it worked for me.

 

[loose_electron]

Do you have the Holley on line documentation on how to tune your carb?

My new Holley 390 4 bbl did not want to idle at the spec speed either and the only cure I found was to follow the Holley instructions to set the slow idle - it worked for me.

https://forums.holley.com/entry.php?429-How-To-Adjust-The-Idle-Mixture-On-Holley-Carbs

That procedure seems to be the one that most folks point to. Something different?

 

[John W]

Bout 15 years ago, Jose tuned my Weber on a 1600 about as good as it had ever been. Dan has designed headers for the V6 that don't drag, and everything better, really, as things go naturally, Bill wants Jose to prove 200 hp, Jose used names I'd never use. Gemstone and Jan are Yankees for perpetuating that salt flat April 1st Ian wicked otherwise normal guys stuff. You should get Jose's number. And I hope Jose doesn't quit posting here. All that said, best I can think of is carb linkage is catching or something.

 

[John W]

I apologise for calling anyone a Yankee. Even if they are one.

 

[Bill Blue]

In order for an engine to idle at 3000 it needs air - lots of air. The first question is "Is the air going through the carb?" Are you sure the throttle plates are completely closed? Have you tried looking for vacuum leaks?

Bill

 

[crs]

Jerry,
The procedure looks similar but not the same;not the same source and without vacuum testing. I just used the engine sound and tach reading.
I printed it out directly from the Holley web site and saved it and will look to see if I can locate it.

 

[loose_electron]

In order for an engine to idle at 3000 it needs air - lots of air. The first question is "Is the air going through the carb?" Are you sure the throttle plates are completely closed? Have you tried looking for vacuum leaks?

Bill

Agreed - since the last post it was found that the throttle plates were sticking open. Brand new carb so still working on it.

 

[Bill Blue]

Agreed - since the last post it was found that the throttle plates were sticking open. Brand new carb so still working on it.

Sometimes it is necessary to loosen the throttle plate screws a bit and wiggle the plates around while the throttle is closed. That allows the plates to align properly and close completely.

Bill

 

[loose_electron]

Sometimes it is necessary to loosen the throttle plate screws a bit and wiggle the plates around while the throttle is closed. That allows the plates to align properly and close completely.

Bill

That is very useful information! Thanks!

 

[DanR]

If they are on the car "Don't drop a screw"

 

[Bill Blue]

If they are on the car "Don't drop a screw"

No need to remove them, just loosen. But yeah, don't drop a screw.

Bill

 

[loose_electron]

No need to remove them, just loosen. But yeah, don't drop a screw.

Bill

I made that mistake, once, back about 1974, so had that "learning experience" many moons back.

 

[kmathis]

lessons learned

So, recently I have learned a couple of things about tuning these Holley 390s, I would like to share for those interested; On my first engine, when my Holley was brand new out of the box, it had #51 primary jets and fixed jets on the secondary side. I got rid of the fixed jet block for one that I can replace jets as needed. When I dyno'd my car we bumped up to #54 jets on the primary side and I don't remember what the secondary ones were, but all through the power band I had very good air/fuel mixture. The car ran great.

Second engine, much higher compression, my engine ran terrible and wouldn't idle. Same Holley as before, so, after I adjusted my timing to the highest vacuum at idle, I was getting 9" HG at idle; I then realized that my power valve was opening just off idle and dumping fuel in prematurely. The stock power valve was a 6.5"HG (meaning that it opens at 6.5" HG vacuum and below) so I ordered a 4.5" HG power valve and what a difference that made. I don't smell gas anymore, and the exhaust doesn't clear the neighborhood.

A Youtube video suggested that my idle vacuum divided by two is what my power valve should be. Mine was 9" HG at idle, so the 4.5 did the trick. I increased my primary jets to #56 since the power valve is opening later. Just now the car runs fantastic, the best it has run since rebuild.

Hope that might help someone, I have never messed with these carbs too much, but this really made a difference on how my engine runs. The vacuum gauge is the key.

 

[DanR]

Kelly, you may be on to my problem with idle.

My car will not idle below 1200

It has no vacuum below 1000

While driving today with my "new" vac gauge installed it was always below 5lbs unless I let off the gas, it would them jump up to maybe 10.

I will study your comments further and try to figure it out.

Also today I notice it did not have the power as the last trip out on the road...

Thanks for your post,

DanR

 

[loose_electron]

Interesting - I will pas along the info to the guy I got who is going to tweak the carb for me. All the shops here in San Diego that work on customs-classics recommend one shop for this so I made an appointment with the "carb god" and will pass on what I learn in the process.

You can throw time or money at it, right?

I want to get the power train dialed in so I can get started on the electrical stuff.

Jerry

So, recently I have learned a couple of things about tuning these Holley 390s, I would like to share for those interested; On my first engine, when my Holley was brand new out of the box, it had #51 primary jets and fixed jets on the secondary side. I got rid of the fixed jet block for one that I can replace jets as needed. When I dyno'd my car we bumped up to #54 jets on the primary side and I don't remember what the secondary ones were, but all through the power band I had very good air/fuel mixture. The car ran great.

Second engine, much higher compression, my engine ran terrible and wouldn't idle. Same Holley as before, so, after I adjusted my timing to the highest vacuum at idle, I was getting 9" HG at idle; I then realized that my power valve was opening just off idle and dumping fuel in prematurely. The stock power valve was a 6.5"HG (meaning that it opens at 6.5" HG vacuum and below) so I ordered a 4.5" HG power valve and what a difference that made. I don't smell gas anymore, and the exhaust doesn't clear the neighborhood.

A Youtube video suggested that my idle vacuum divided by two is what my power valve should be. Mine was 9" HG at idle, so the 4.5 did the trick. I increased my primary jets to #56 since the power valve is opening later. Just now the car runs fantastic, the best it has run since rebuild.

Hope that might help someone, I have never messed with these carbs too much, but this really made a difference on how my engine runs. The vacuum gauge is the key.

 

[kmathis]

Kelly, you may be on to my problem with idle.

My car will not idle below 1200

It has no vacuum below 1000

While driving today with my "new" vac gauge installed it was always below 5lbs unless I let off the gas, it would them jump up to maybe 10.

I will study your comments further and try to figure it out.

Also today I notice it did not have the power as the last trip out on the road...

Thanks for your post,

DanR

Mine idles at about 1100 RPMs, but I am happy with that...engine mods have their cost, and idle may be one of them. It did make a huge difference changing out that power valve and re-jetting, the motor accelerates very smooth and idles with about 9-10 in HG, and drops significantly off idle.
I am running about 26 - 28 degrees of timing static. Seems crazy but that is what it likes. No detonation, dieseling or difficulty starting. Not sure if your situation is the same, but there it is.