I have problem with my idle, it's way too rich. I was reading about solving this problem with driling holes in the throttle blades. It also said to start small, like 1/16" and go larger if needed. My question is, where would you drill this holes in regards to the mounting rod? Center, edge and if yes does it manner what side?
Do you drill on the two primaries or all 4 of them? I have newer style carburetor with four idle-mixtures screws.

Thanks
Ziggy

 

Start out with .125 or 1/8th drill bit. Start with two holes in the primaries with the hole center 3/8th from the motor front edge. After drilling the holes round the top and bottom of each hole with a larger dia. bit. So the air is smooth. Anyway you want to be able to have all four corners adjusted at @ 1 1/2 turns out at max inches of vacuum on a guage. If the 2 pri holes are not enough, do the seconds with 1/8ths .

Also when adjusting idle speed ensure that you always have the seconds open just a hair more than the primaries if the primaries are drilled. It will help with any lean spots.

 

Thanks Gkull,
I will be doing it tonight but won't start the car until tomorrow.
I wil let you know how it went.
With the big cam, it's hard to get good idle but I will try. It was so rich, it burn my eyes just by the time I was able to pull out of the garage (I have no cat either). Hopefully this will help.
Thanks again
Ziggy

 

you only need to drill the holes if you have to open the throttle plates too far and have too much transfer slot exposed. try putting .015 dia wire in each idle feed restriction. :chevy

 

My throttle plates were open very far, but I never heard of (restricting)putting wire into idle-feed restrictor. I would never thought of doing this, did you try this in the past? What kind of results did you get?

I just came back from the garage and the throttle plates are drilled :yesnod: So far I did the main only and will start her up tomorrow and see if I need secondarys too. I am hoping that this will do the trick or else :smash: some more.

Ziggy

 

it will lean down the idle curcuit by restricting how much fuel goes to it. :chevy

 

I have seen what Clem was talking about done. I just prefer not to ever have metal not secured in the system.

I was told once that the easiest way to tell if your way rich at idle is to pull the full vacuum line on the side of the carb off. If the idle speeds up and smooths out it's drilling time.

 

just bend the wire in a L shape and it can not get loose. i have done it many times in my 40 years of carb work. :chevy

 

I have done what Clem is talking about to cure an overly rich idle problem several times, mostly on double pumpers.
Never any problems with the wire coming loose.

 

IF you have a Holly with a power valve, are you sure that the diaphram is not ruptured allowing fuel to pass when it shouldn't???

 

My carburetor has the power valve, but I just took it apart and the diaphram sims to be ok. I was checking my jets and found 80 on the secondarys and 71 on the primarys. I changed the 80 to 75 and left the 71 in place. I took my car for the test drive, just to see if everything is in place, but I did not get to adjust anything just yet. I will be working on it over the weekend dou. One thing I did noticed, it was running around 13 a/f ratio, where before it was more like 12 (wot).
I only set the timing and fuel pressure and checked the float levels (not perfect but close). I also found out that I might have a problem with my fuel pressure regulator, I had no reading on my gauge when I came home and it was making some buzzzzing noises?!?!? I am kind of surprise because this is Holley regulator and very few moving parts (needle and spring) on the inside of this unit :confused:

I was talking to a X drag racer and he was talking about some tricks that some of the racers do to carburetors to make them more responsive and create more power. His "secret" was to conect the primarys and secondarys so thay move at the same time, creating much more smoother acelarations. Any ideas or coments on that?

Ziggy

 

Ziggy - who installed the 80&71 jets? If this is a new carb those were the factory jets for performance at sea level. 5 jet sizes is a radical change. The key to working on carbs or anything for that matter is to only make one variation at a time.

OK - after drilling the holes did you set the idle speed to max vacuum with a gauge? Your car should make lots of vacuum so a standard 6.5 power valve should work. Common street/strip double pumpers always have a 7-10 jet size difference from pri - seconds. Max power is at @ 12 A/F ratio for gasoline at WOT.

I use MaxJets for finer adjustments and a nut driver to R&R them. But anyway from Summit they sell jet boxes that have 2 of every size from 60 - 90 for $30. Then buy the reusable bowl gaskets.

If you can't maintain constant float level your screwed. You will be chasing your tail because jetting changes are based on the assumption that you have constant pressure on the jet and it will flow a given amount.

So anyway do it in steps. Get your idle straight. Then work on the squirter system to clear any bogs. It might require bigger cc squirter pumps or squirter holes. Then move onto primary jetting where you get the correct A/F ratio and the smoothest cruise...........................Seconda ries......................

The idea of all 4 barrels at once is more race car tech.

Did you put on an open 1 inch spacer? If you did I would suggest a 2 or 4 hole until you have your carb figured out. You threw in a big variable. Your nearly approaching single plane status.

 

If your floats are set too high, fuel can dribble over causing your rich condition. Fuel should BARELY dribble out of sight plug when removed. This the the FIRST step in setting up the carb.

 

[[QUOTE]Ziggy - who installed the 80&71 jets? If this is a new carb those were the factory jets for performance at sea level. 5 jet sizes is a radical change. The key to working on carbs or anything for that matter is to only make one variation at a time.]

Yes this is new carburetor and 80 & 71 jets were there when I got it. I guess I screw up by doing 2 things at the same time (not the first time!).


[quote]
[OK - after drilling the holes did you set the idle speed to max vacuum with a gauge? Your car should make lots of vacuum so a standard 6.5 power valve should work. Common street/strip double pumpers always have a 7-10 jet size difference from pri - seconds. Max power is at @ 12 A/F ratio for gasoline at WOT.]

Why do you say that I should have lots of vacum??? When my engine was on dyno, it only had around 8 if I remember corectly. My cam has .576 lift so it's not small cam. Reason I changed the jets 5 sizes down it's because I was told that the difference should be 4 to 6 sizes. I am not sure what size of my power valve is, but I will check next time I will take it apart.

[quote]
[I use MaxJets for finer adjustments and a nut driver to R&R them. But anyway from Summit they sell jet boxes that have 2 of every size from 60 - 90 for $30. Then buy the reusable bowl gaskets.]


I got the 60 - 90 set of jets for Holley carburetors. I will get the reusable bowl gaskets, I know that this will pay for it self in no time.


[quote]
[If you can't maintain constant float level your screwed. You will be chasing your tail because jetting changes are based on the assumption that you have constant pressure on the jet and it will flow a given amount.]


I only said that I checked the floats and they were fine, maybe the secondary about 1/8" too low, but the primary was just fine. I also must say that this was the first time since August 17 that I start up and drove my car because of the fire that she was in, so please don't hammer me hard for driving it with not so "perfect" idle. I was hungry for the power and feel of the rough ride that she provides every time I take her out. I noticed that when starting from light stop, it was "chocking", but I asume that this is part of the idle set up problem.

[quote]
[So anyway do it in steps. Get your idle straight. Then work on the squirter system to clear any bogs. It might require bigger cc squirter pumps or squirter holes. Then move onto primary jetting where you get the correct A/F ratio and the smoothest cruise...........................Seconda ries......................]

I will work on the idle over the weekend. What do you mean "squirter system"??

[quote]
[The idea of all 4 barrels at once is more race car tech.]

I am not ready for that, I was just asking if anyone knew about this.


When I had my engine dynoed, I asked about spacers and they told me that they get the best results with 1" spacer on 383s. I was not aware of the BIG adjustability problem that this might be cousing. Should I get the 4 hole one for the adjusting and tunning period??? What about eliminating the spacer all together for now??


Ziggy


[Modified by 88WHITE VETTE, 10:18 PM 10/17/2001]

 

Ziggy,

I'll bet if you tried hard enough, you could splice your EFI harness back in and run that MiniRam you aleady have. Forget about all that jet size, squirter, power valve, B.S. - All you need to worry about is pulsewidths!. ;).

Just kidding - good to hear you got it back together and are driving it again. Let me know if you need more help.

I should get mine back next week from the chassis shop with all the exhaust completed.

 

:lol: :lol: :lol:

You got me going there for a while :yesnod:

I got it out right after I put the carb on and went driving :chevy :flag :seeya
It just felt realllly good to be in the driver seat and actually driving.
I am planning on working on it again on Saturday, will also take a drive to MPG for the new regulator.

I am glad to hear that you have your car over for the exhaust. I hope to get a ride in it b4 the winter :D


Ziggy
PS,
I sold the MiniRam :eek:

 

Why do you say that I should have lots of vacuum??? When my engine was on dyno, it only had around 8 if I remember correctly. My cam has .576 lift so it's not small cam. Reason I changed the jets 5 sizes down it's because I was told that the difference should be 4 to 6 sizes. I am not sure what size of my power valve is, but I will check next time I will take it apart.

I thought that you had the 219 hydro-roller? Until I got my carb sorted out I had less than 10 inches of vac. that was bouncing all over at 850 rpm. I now have 13-14. Lift doesn't effect vacuum. lobe center or overlap is what causes + & - pulsing in the intake. With the net result of low vacuum. I have found that it is best to set up the base line idle settings with the vacuum advance disconnected. Because your throwing in another variable of smoother idle with more advance. I just choose 12 degrees initial because I have 22 degrees of mech advance. Then after drilling two holes I set the four corners to 1 1/2 turns each. The car has to be up to temp and no choke. Demons have a idle speed screws for both the primary and secondary throttle blades. Because I drilled holes in the primary blades I set the secondary slightly more open.

Now fire the motor up. Another trick is to first set your idle to say 1200 rpm. So you have a steady vacuum reading. Then begin tweaking each corner an equal amount in 1/8th or 1/4 increments in. If you see the vacuum going up and idle increasing and smoothing close the idle speed screws an equal amount to 1000 rpm. Continue to tweak the four corners to the highest vacuum reading. All four corners should end up nearly exactly equal in number of rotations open. Then reconnect the vacuum advance and lower the idle speed to what ever you want.

I just choose 850 because I have very little rpm drop when I put it in gear (auto tranny) with the brake on.

There is a formala for how to select the correct power valves. If in fact after these adjustment you have less than 10 inches you might need to get a 5.5 or so. The open spacer give the carb less signal. So it might be wise to take it out until you have everything sorted out. IMO nearly every good running Holley out there has 70 & 80 jets. Even all the ones with A/F ratio meters.

The squirters are an instant shot of gas to retain A/F ratio when you crack the throttle and vacuum goes away. Squirters have adjustments for how fast they inject the total cc volume. You have colored cam lobes to change this. the size of the squirter hole also comes into play.
:smash: HAPPY CARBING! I hope this helps. I'd like you to own a real hot rod.

I ask LARS to give additional advice because everyone including Clem have different ways of explaining.


[Modified by gkull, 11:06 PM 10/18/2001]

 

I have been reading all this. I have a 750 double pumper. I have read everything I can and have been comfortable making changes. I'm not a guru, but I do know that having nearly 10 jet sizes is the only way to get good mileage from and lean burn and when you put your foot in it the seconds kick in and fatten the mixture up to max torque. I have also learned over the years that for the same CFM carb jetting is nearly identicle reguardless of cubic inches. Within reason of course. My 355 has the same jetting as the guy with the bored out 454 and simular engine mods. I've talked to people in the staging lanes about this and that and nearly everyone of them when you ask the jet size. The answer is 70-80 71-81 71-80. GKull and his stuff is on the upper edge.

 

if you check the holley carb spec book you will see that the same size carb with different dash number after the LIST number take different jetting. the metering in these carbs is different so they take different jets. some have different size air bleeds,emulsion tube holes both number and location. running with and without a air filter can change the metering as holley carbs are very sensative to air flow over the air bleeds. i have had drag car that would not run properly till we put a mesh screen around the top of the carb to straighten out the air flow. check what the orignial L-88 had on top of the holley :chevy


[Modified by clem zahrobsky, 5:27 PM 10/18/2001]

 

88-
Clem is pretty good with the Holley stuff, and what he's saying is good advice.

A couple of other things to check:

1. before you drill the blades open more, check how far your secondaries are cracked. There is an adjustment screw for the secondary throttle blade "crack open" adjustment that is only accessible when you remove the carb and flip it upside-down. By cracking this open a little, you can get a little air bleed going on the secondary side, thus leaning out the idle a bit.

2. Make sure you have your timing and vac advance set up right. Get that intial timing bumped up to 12-14 degrees, and make sure your total timing (with vac advance disconnected) comes out to about 36. Then, make sure your vacuum advance is coming off the ported vac source (forward metering plate, passenger side).

3. A carb spacer will really screw up the idle metering signal on a street driven car. Yank the spacer, and bolt the carb directly to the manifold. If you really want a spacer, go with a 4-hole unit - not an open plenum unit.

4. Jet size on a Holley will affect idle mixture. Depending on you altitude, you can drop primary main jet size down a couple of sizes and see how (if) it affects your idle setup.