Tips for adjusting dual quad set up - FE

DanEC · #1 (**permalink**) 02-16-2013, 11:50 AM

I've just started my motor in my chasis for the first time and for the most part so far, so good. This is my first multi-carb motor and I'm looking for tips to get it set up to run smoothly - particularly at idle.

It's a Keith Craft built 459 FE that was built to be pretty mild and streetable. It has heavily reworked steel heads, 9:1 compression, dual point distributor, LR Ford 2x4 intake and 600 Holley carbs. Cam flat tappet hydraulic and is custom ground and thought to be fairly mild wjtb .563/.575 (I/E) lift with 280/290 duration at .006 lift. Lobe separation is 112 deg. it was broken in and run on KC's dyno. At the time it struck me that it didn't have as good idle characteristics as I was expecting but I figured they didn't spend a lot of time on that.

I ended up with 32/33 deg dwell when I started it and decided that was good for now and I set the timing on the white line KC marked on the damper for initial timing but I'm using a different distributor than he used so I don't have that quite dialed in yet. My distributor has 11/22 deg mechanical advance built in so I need about 16 initial for a total of 38. KC ran it at 40 deg total because of the low compression and recommended that.

Despite the timing which I've moved up and down a little, the best I'm getting is a pretty lumpy, not real stable 950 rpm idle. I'm having a charging problem that I'm also working on and the weather is cold so I haven't been able to do a lot of testing and and I haven't checked vacuum yet. The battery is holding up only so long. It's on a charger currently.

After all that background - what's the best way to set up the carbs at idle. Both carb idle circuits are functioning at idle - correct? So, I need to adjust idle mixture and idle setting on both? Best to use vacuum or tach? Adjust the front carb for best response and then adjust the back one. And then go back and fine tune the front one again?

I have a 66 Corvette with a 12:1 L88 motor and a lot more cam than this thing and I have a fairly manageable idle of about 850 rpm when warm. I would expect this thing to do better than that.

ERA Chas · #2 (**permalink**) 02-16-2013, 12:30 PM

Dan-
Use a vacuum gauge on each carb at idle. Motor should be operating temp-about 160 water or higher. First baseline the mixture screws at 1 turn out. Then do one at a time in 1/4 turn increments and see where highest vacuum wants to be. Go 1/4 turn past best reading to confirm and then go back.
Assuming idle has picked up and steadied, reset idle speed screw and see if you can get 800 smooth(er) idle.
For advance, I'd use more initial (18 or more) and about 38-40 total. That too will raise idle so readjust speed when it's stable.
Edit-Make sure float levels are good first-I'd start with fuel at the very bottom of the hole.

DanEC · #3 (**permalink**) 02-16-2013, 03:27 PM

Crud - I just remembered that that mark Keith's shop put on the damper was to use to power tune full advance of 40 deg - not for the initial advance. I forgot that over the last 2 years. So I have to pull about 22 degrees of initial advance out of it. Damn impossible to read the stamped marks on that black balancer from above. I'm going to have to get underneath and mark the TDC and other major timing marks on it. That explains my complaining starter motor but what's the thing going to idle like with all that advance pulled out of it. Something seems out of whack. Since I've only been running it at idle and winging the throttle slgihtly a few times - no harm.

Chas - that's pretty much how I adjust my Plymouth and Corvette so nothing new on that. I guess you just go through the same process on both carbs - one at a time and go back and forth from one to the other a couple times until it's kind of wiggled in as best as possible.

ERA Chas · #4 (**permalink**) 02-16-2013, 03:46 PM

Quote:

Originally Posted by DanEC

Chas - that's pretty much how I adjust my Plymouth and Corvette so nothing new on that. I guess you just go through the same process on both carbs - one at a time and go back and forth from one to the other a couple times until it's kind of wiggled in as best as possible.

Yes that's about it but you will get a stable level when it's right and pretty close. My cam and big valves only allowed 7 1/2" vacuum but it was consistent.
You give you cam's spec at .006"-what's the .050" duration?? I can relate easier to that.

DanEC · #5 (**permalink**) 02-16-2013, 03:51 PM

Quote:

Originally Posted by ERA Chas

You give you cam's spec at .006"-what's the .050" duration?? I can relate easier to that.

It's 231/236 at .050 lift according to the cam grind sheet.

Thanks

Dan

ERA Chas · #6 (**permalink**) 02-16-2013, 04:01 PM

I think you'll pull 12" or so of vacuum with that.

DanEC · #7 (**permalink**) 02-16-2013, 04:05 PM

I'll check vacuum tomorrow. Might have some sort of vacuum leak. With 459 cu inches I was expecting a pretty mild idle with this cam and from Keith's comments.

ERA Chas · #8 (**permalink**) 02-16-2013, 04:08 PM

It will be a mild idle. Those big inches have the effect of making your cam slightly 'smaller'.

DanEC · #9 (**permalink**) 02-17-2013, 12:28 PM

After I pulled the excess timing out of it and adjusted the carbs idle mixture it settled down quite a bit. It was left rich from the dyno work. It's pulling betwen 11 and 13 inches vacuum depending on where I set the idle speed - around 12 at 900 -950 rpm.

Here is an ignorant question - especially since I've owned, worked on and restored 4150 Holley equiped Corvettes over the years - where do you check the bowl fuel level on these 4160 600 carbs? There isn't a side port to open to check level and there aren't any top-side float adjustments screws????

racco · #10 (**permalink**) 02-17-2013, 12:46 PM

Quote:

Originally Posted by DanEC

I've just started my motor in my chasis for the first time and for the most part so far, so good. This is my first multi-carb motor and I'm looking for tips to get it set up to run smoothly - particularly at idle.

It's a Keith Craft built 459 FE that was built to be pretty mild and streetable. It has heavily reworked steel heads, 9:1 compression, dual point distributor, LR Ford 2x4 intake and 600 Holley carbs. Cam flat tappet hydraulic and is custom ground and thought to be fairly mild wjtb .563/.575 (I/E) lift with 280/290 duration at .006 lift. Lobe separation is 112 deg. it was broken in and run on KC's dyno. At the time it struck me that it didn't have as good idle characteristics as I was expecting but I figured they didn't spend a lot of time on that.

I ended up with 32/33 deg dwell when I started it and decided that was good for now and I set the timing on the white line KC marked on the damper for initial timing but I'm using a different distributor than he used so I don't have that quite dialed in yet. My distributor has 11/22 deg mechanical advance built in so I need about 16 initial for a total of 38. KC ran it at 40 deg total because of the low compression and recommended that.

Despite the timing which I've moved up and down a little, the best I'm getting is a pretty lumpy, not real stable 950 rpm idle. I'm having a charging problem that I'm also working on and the weather is cold so I haven't been able to do a lot of testing and and I haven't checked vacuum yet. The battery is holding up only so long. It's on a charger currently.

After all that background - what's the best way to set up the carbs at idle. Both carb idle circuits are functioning at idle - correct? So, I need to adjust idle mixture and idle setting on both? Best to use vacuum or tach? Adjust the front carb for best response and then adjust the back one. And then go back and fine tune the front one again?

I have a 66 Corvette with a 12:1 L88 motor and a lot more cam than this thing and I have a fairly manageable idle of about 850 rpm when warm. I would expect this thing to do better than that.

it should be able to idle at 650 rpm is it has a street cam.

ERA Chas · #11 (**permalink**) 02-17-2013, 01:09 PM

Dan-the vacuum is right where I thought. Don't be concerned about 900+ RPM idle. Now get initial around 18 and readjust idle speed as needed.
Show me a picture of the 4160-I forgot where the level is. I think you must remove the bowls and set the floats while inverted by bending the tang-to the Holley drop spec.

DanEC · #12 (**permalink**) 02-17-2013, 01:15 PM

Quote:

Originally Posted by ERA Chas

Show me a picture of the 4160-I forgot where the level is. I think you must remove the bowls and set the floats while inverted by bending the tang-to the Holley drop spec.

That's what I'm thinking - no external adjustments. I'll send a picture this evening. These are obviously not original series carbs but I knew that.

Thanks

DanEC · #13 (**permalink**) 02-17-2013, 05:34 PM

Chas - I went to take close up pictures of the carbs and found I didn't have a card in the camera. Here is an older photo that shows the carbs to some extent.

ERA Chas · #14 (**permalink**) 02-17-2013, 06:25 PM

OK - if you buy a Holley Zip kit (Summit) it will have a diagram for the float drop dimension in the instructions.
To avoid that PIA in future, I'd buy 2 pairs of float bowls which have the sight port and adjustable needle / seat screw in the top-like your GM and Mopar carbs.
Here's mine:

Also, why do you feed fuel from the rear? The pump is on the driver front corner of block...

DanEC · #15 (**permalink**) 02-18-2013, 05:38 AM

Actually one of my down-the-road projects was to buy a set of correct code carbs. I'll run these for a little while and see how they do.

Thanks Chas

DanEC · #16 (**permalink**) 02-18-2013, 02:52 PM

Chas - one more question. Anything particular you did to set the idle speed? I pretty much set it by the front carb and then adjusted the second carb until the idle started to increase. Then I backed off the second carb just enough to bring the idle back to where I started.

Or should I set the idle a little low by the front carb and then use the rear carb to bring it up to where I want it?

I don't want to run the rear cylinders lean.

Dan

DanEC · #17 (**permalink**) 02-20-2013, 11:34 AM

Anyone have an idea what Holley furnishes for power valves in stock 600 4160 carbs? I had a buddy suggest that with 12 inches vacuum that I may need to install lower rated power valves to settle the idle down.

ERA Chas · #18 (**permalink**) 02-20-2013, 11:53 AM

Quote:

Originally Posted by DanEC

Chas - one more question. Anything particular you did to set the idle speed? I pretty much set it by the front carb and then adjusted the second carb until the idle started to increase. Then I backed off the second carb just enough to bring the idle back to where I started.

You can if you know that the rear is not already
contributing to idle speed.
I took all the rear out of the idle (backed screw off the arm) then set front only and just added enough rear to touch the arm. But I have a single plane plenum-feeds all cylinders. With your dual plane you may have to set each carb the same because you're feeding half the cylinders at a time with front and rear primaries.
Can't help on PV's-I run 3.5's on 7 1/2" vac.
Go by the formula off your true vacuum reading-like 1 1/2 numbers lower than your vac.?? I forgot the formula but it will get you close.

DanEC · #19 (**permalink**) 02-23-2013, 04:07 PM

I carefully adjusted the idle speed setting on both carbs today so at idle they are equally contributing. I backed both off until they were just starting to make contact with the throttle blade shaft arm and then opened them up equally. Also marked my balancer and was able to put in a couple more degrees of initial timing. This all helped quite a bit as it still has a pretty good rump rump idle but will run at 700 to 750 rpm now without too much drama.

ERA Chas · #20 (**permalink**) 02-23-2013, 05:05 PM

Nice work Dan. It was worth it all.
Bear in mind, when you're out driving around and the motor's all hot, that you may want 800 or 850. The cycles of stop and go plus temp may need bit more stability.
As far as the lope, enjoy it and show it off. Glass smooth idle is for Civics and Corvettes....