Running rich issue - Team Camaro Tech
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post #1 of 19 (permalink) Old Apr 16th, 13, 06:31 AM Thread Starter
Edm
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Running rich issue

I have a stock ZZ4 Chevy crate motor. I was running a 4150 HP and started having problems with the car running rich. Carb was getting kind of old and decided to purchase a Pro Systems 4150 750 CFM. I have adjusted this thing till my fingers bled and still having the same results. I set the timing @35 degrees @ 3000 Rpms. I was told to use a hotter spark plug, a marine Ac Delco, (I don't have the part number with me but a lot of guys use them), I did and now they just foul faster. The motor only has about 5000 miles on it. I set the valves at zero lash plus 1/8th turn.

Should I consider upgrading the distributor? If so should I use the DUI or go to the MSD set up? I have had great success with the DUI in other motors and have never used a MSD.
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post #2 of 19 (permalink) Old Apr 16th, 13, 07:18 AM
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Re: Running rich issue

Changing the ignition may help the fouling problem, but won't keep it from running rich.

You need to pinpoint the cause of too much gas.

Not familiar with a Pro Systems 4150, but am sure someone here is.

Lynn
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post #3 of 19 (permalink) Old Apr 16th, 13, 11:25 AM
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Re: Running rich issue

I would start by checking your vacuum and for vacuum leaks, along with fuel pressure. Are you running an adequate fuel filter?
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post #4 of 19 (permalink) Old Apr 16th, 13, 11:44 AM
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Re: Running rich issue

Need more information. Is it fat at idle? Rich at all RPM's? What do the plugs look like after a run on the freeway? What is your initial timing set at? Have you changed main jets? How many turns out are your idle screws? Is the carb set up for 4 corner idling?

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
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post #5 of 19 (permalink) Old Apr 16th, 13, 11:52 AM
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Re: Running rich issue

Well Ed here,s what i would do. 1 You can ghge. the ign it will help the plugs last longer ,don,t waste your time and money on MSD. This is not vendor bashing . Check out my posts on this there are valid reasons why. I dont know about Davis unified ign but have heard no complaints. I like Pertronics good stuff all of it . That won,t clear the rich though. Check your float level check for a blown leaking or early opening power valve if aplicable the next thing you might wan,t to do is down jet from whats already there . On the down jetting you need to drop 3 sizes to make a difference , so if you have 72 and 80 drop to 68 and 76 thats 3 full sizes between the two originaly used. Good luck let us know the results . Alex
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post #6 of 19 (permalink) Old Apr 16th, 13, 12:41 PM Thread Starter
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Re: Running rich issue

it has 4 corner idle screws turned out 1 1/4 turns each
Fat at idle and black plugs after all use
has picked up an exhaust backfire slightly above idle during acceleration
runs smooth when cold and picks up a miss when warm
New MSD rotor and cap
no vacuum leaks
fuel line is AN-6 w/ earls in line filter
float levels are about 1/3 up
not sure of the jets right off hand, I will look at the build sheet when I get home. It was supposed to be bolt on when I purchased it.
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post #7 of 19 (permalink) Old Apr 16th, 13, 12:51 PM
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Re: Running rich issue

Quote:
Originally Posted by Edm View Post
it has 4 corner idle screws turned out 1 1/4 turns each
Fat at idle and black plugs after all use
has picked up a miss slightly above idle during acceleration but clears out
no vacuum leaks
fuel line is AN-6 w/ earls in line filter
float levels are about 1/3 up
not sure of the jets right off hand, I will look at the build sheet when I get home. It was supposed to be bolt on when I purchased it.
What do you mean the float levels are 1/3 up? Does your carb come with a window or a plug for checking float height? What does it do if you turn the idle screws in another 1/4 turn? Carbs are rarely a bolt on. They are a controlled fuel leak that needs to be tuned to the specific engine.

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
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post #8 of 19 (permalink) Old Apr 16th, 13, 01:04 PM Thread Starter
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Re: Running rich issue

Yes it has sight windows, and turning 1/4 turn doesn't seem to do anything. The vacuum gauge is jumping around between 14 and 16.
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post #9 of 19 (permalink) Old Apr 16th, 13, 01:24 PM
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Re: Running rich issue

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Originally Posted by Edm View Post
Yes it has sight windows, and turning 1/4 turn doesn't seem to do anything. The vacuum gauge is jumping around between 14 and 16.
Does your carb have replaceable idle feed restrictors? What is you initial timing?

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
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post #10 of 19 (permalink) Old Apr 16th, 13, 01:45 PM Thread Starter
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Re: Running rich issue

Yes it has restrictors but I don't remember what the initial timing was.
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post #11 of 19 (permalink) Old Apr 16th, 13, 01:51 PM
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Re: Running rich issue

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Originally Posted by Edm View Post
Yes it has restrictors but I don't remember what the initial timing was.
Go to the next size smaller IFR. Then adjust your idle screws using a vacuum gauge. I suspect a stock ZZ4 would probably run best with 6 - 8 degrees initial. If you don't know where it is now, check it. You need to set the initial timing and then adjust the carb.

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter
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post #12 of 19 (permalink) Old Apr 16th, 13, 02:34 PM
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Re: Running rich issue

Smaller ifr will make it richer is what I learned. I was told think of it as putting a hole in a straw while drinking soda the bigger the hole the more air. Make sure the carb base adjustment is right. the secondaries should not be totally closed.http://members.tccoa.com/392bird/tuning.htm Hope this helps
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post #13 of 19 (permalink) Old Apr 16th, 13, 03:18 PM
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Re: Running rich issue

Quote:
Pro Systems 4150 750 CFM
U mean rich normal round town/ highway running....
1st that carb is way over sized for the rpms u are using.
I assume that u also have a very lumpy, high duration/ overlap cam... more designed for top end rpms...again if this is the case it is not designed to run efficiently under normal cruise conditions.
Timing.. If the cent and VA advance are in the ball park advance at the cruise rpms , not slightly retarded...it will give a poor burn.
A poor burn (wet plugs) doesnt always mean the carb is running rich....ANY of the above will cause the issue....and if big cam / big carb is the primary issue the real issue is a very old one... designing an engine with bragging rights/ ego in mine rather than designing for what the car will be used for.
A vaccuum leak will make the car run leaner.. more air less gas.
A poor spark due to bad plugs/ HT leads whatever will give a wet plug but will show lean with AFR.
Never close secondaries fully closed.. at least a hairs breath off, otherwise issues start, espec if not a daily driver of butterflies jambing in bores....bigger carbs do need secondaries closed up more for better idle
Idle mixture screws do not change to any significant degree mixtures once the car has moved off, butterflies opens up.
Intial timing (I asume not a EGR engine and therefore manifold vaccuum) is only for low load on starter and battery, easy start of the engine.. idle advance is made up of the intial+VA and should be in the 14 to 22 range depending on how wild the cam is... a good street 'rod cam usually in the 16 to 18 degree ball park.

It sounds like this engine has never been dialed in... the 'tuning specs' as one finds in the factory manuals, established.
If has a HEI then it will most proberly have to be converted in the VA and cent curves to a manifolsd vaccuum / non egr configuration.

This is all assuming float levels right, no crap in valves , jets etc...and carb has been dialed into ball park o2 AFR ball park numbers.
THEN and ONLY then can one even complentating setting up time curve specs

My Spelling is not incorrect...it is creative

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post #14 of 19 (permalink) Old Apr 16th, 13, 03:45 PM
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Re: Running rich issue

Quote:
Originally Posted by bigblockragtop View Post
Smaller ifr will make it richer is what I learned. I was told think of it as putting a hole in a straw while drinking soda the bigger the hole the more air. Make sure the carb base adjustment is right. the secondaries should not be totally closed.http://members.tccoa.com/392bird/tuning.htm Hope this helps
On a performance carb the IFR flows fuel. On an emissions type carb it flows air. His carb does have replaceable air bleeds. If he installed larger idle air bleeds it would do as you say. I think you may have the two confused. The IFR's are in the metering blocks and the air bleeds are in the throat of the carb.

From Barry Grant

Idle Feed Restrictor
The idle feed restrictor controls the amount of fuel that enters the idle circuit from the main well. This orifice controls the amount of fuel available for the idle circuit. If all other tuning results in a lean or rich idle circuit, an adjustment here may be necessary. As with any fuel restrictor, the larger the hole in the restrictor, the more fuel that will be introduced into the idle circuit. Make small changes, .001" or .002", to all four restrictors and work towards your desired tuning point.

http://www.demoncarbs.com/Assets/doc.../LIT705rev.pdf

'69 Camaro - 429 SBC Dart Iron Eagle 9.325" block, Crower crank, Crower 6" billet rods, Ross pistons (10:1), Total Seal rings, AFR 245 heads, T&D steel body shaft rockers, Cloyes Timing set, custom ground 4-7 swap solid roller 274/286 @ .050" with .704" lift, Dart single plane, Holley Dominator EFI on E85, Injector Dynamics ID2000 Injectors, Stef's #1705R oil pan, F2 Procharger, Lemons 2" primary 4" collector, ATI 9" blower converter

Last edited by Steve69SS396; Apr 16th, 13 at 04:00 PM.
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post #15 of 19 (permalink) Old Apr 16th, 13, 04:17 PM
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Re: Running rich issue

Yes I did have the two confused thanks did not mean to confuse anyone else. Also agree that carb is large. It is usable but much harder to tune because air velocity slows down with the larger venturis making for poor air fuel mixture. My car is a 496 although it is procharged it was easier to tune the smaller carb. Get an afr meter and be patient as said above no such thing as a bolt and go carb, they all need some tuning. You need to find out the afr at all rpms even wot to tune the carb best. As said above timing is also critical.
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