Rich 10:1 on primary circuit

[1983zsled]

Hi Guys,

First off this is a fantastic site.
I have been reading and have learned much from others trial and tribulations.

I rebuilt carb Number 17084238 using the recipe at the back of Cliff's book for the Edelbrock carb.
and cliffs great rebuild kit.
Here is what I have done to the carb then I will explain what is happening.

Idle Tubes .038"
Idle channel restrictions .055"
Upper Idle air bleeds .070"
Main air bleeds .086"
Accel well holes .051"
lower idle air bleeds .070"
idle bypass air .104"
idle discharge holes.096"
Accel pump discharge holes .031"
Secondary air bleed tubes .036"

Secondary metering rods CH ( i will explain why)
Custom bent hangar
primary rods Cliffs custom .044"
Jet size ( now at 70)
Factory APT spring.

Mounted on a SBC 355 with 906 vortecs fresh 3 angle valve job mild bowl clean up ect......
Edelbrock performer intake ( for the Q jet) with a Lunati Voo Doo 262 cam . Old part number 60102
Headers, ect.....700R4, 2400 stall,  3:42 posi, Installed in a 3400 lb 1983 Z28.

I have a AEM Uego wide band Air Fuel monitor wired into the car.

I have a great idle at 13.5:1
I have the APT set about 2.75 turns out which gives me a great cruise a/f ratio that moves around a little 14:1 to 16:1 depending on load etc.....

Here is the issue; at WOT or even three quarters throttle it very rich 10:1 to 10.5 to 1....
I thought this was a secondary circuit problem and put in big fat CH rods and kept bending the hangar over with no change at all.......

So tonight I wired off the secondary air valve so I could see what the primaries were doing.
I found that the a/f was the same as above 10:1 range. 

Here is where I need the advice....how big of a swing do I need to take to get the a/f around 13:1 on the primary sides? I will order some jets from Cliff I'm thinking try .066" .067", and .068"
Or is there something in my carb recipe that makes it run that way?
Originally the carb had .069 jets with 43K rods.

I do have a old pair of .063" in the parts bin but I don't want to drill them because from what I've read they wont be right.

Once I get the primaries dialed in I can then work on the secondaries.

On the seat of the pants dyno the car seems to pull pretty hard for 10:1 though?

Any advice or insight would be appreciated before I order up some jets. 

[TommyK]

Do the plugs agree with the wideband? At 10:1 they should look pretty sooty.

[Shark Racer]

What's your float height set at? Any chance your float has sunk?

[1983zsled]

The float height is one quarter from the edge of the casting.  If the float sank wouldn't I have problems with idle, off idle? The plugs look OK but I haven't pulled them after a full throttle run. By the time I get home they have been operating at normal a/f . I'm going to order up some smaller jets and see what that does?

[1983zsled]

Update. I spoke to Cliff today and he suggested trying a set of fatter primary rods M series, with the .036 tip. I don't have any of these rods in my stock pile. I decided to rip the carb off tonight as per the suggestions from the Shark Racer and TommyK to check their suggestions. The float was set about a 1/16 to high so I reset it down now to 5/16 ths below the body of the carb.  Maybe that was the problem. I will test it tomorrow.  I also pulled plug number 2, pics attached, the plug was run about 5 to 7 min, after a 6 second full throttle run.  I think the color is OK around the electrode but it is very black out by the treads?

Let me know what you think?
I may be in the market for so 50M .036 tip primaries.....

[Shark Racer]

Is this a single main air bleed carb or dual?

[1983zsled]

it is a single main air bleed like this......

[Shark Racer]

That makes sense! Yep, you should be running M rods with those. The main air bleeds are quite large too, but that would be making you lean.

I didn't make the connection that "main air bleeds" in your post meant a single pair, I assumed you had the uppers and lowers sized to 086. I should have gathered it from you calling out the upper and lower idle air.

I'd stay with the 70 jets. You may find you even need to go up a bit once you switch to the M rod.

[1983zsled]

OK that is what Cliff had mentioned to try a 52M or even a 50M to get it right.....
I asked Cliff to send me some but he is out right now.
I used to have some M rods but I turned then on a mini lathe to make a tapered .044 to .040 with a small .026 power tip for another carb......
If I can find those rods do you think it will be close.....?

[Shark Racer]

No. The M rods have an 036 tip, so at WOT you'll have a different mixture.

Basic thing to remember for tuning WOT is that the jet size, rod tip size, secondary rod size, float level and engine "suck" determine how much fuel the engine will get.

M rods are 036 tip, the rest 026. That 010 difference will have a significant effect on WOT fueling.

[1983zsled]

OK excellent! Thanks for your advice!
Sorry.... my bad on the last post, it didn't come out the way it should have. So much for English Grade 12.
I should have said," will the .036 tip M rods .050 or .052 put my metering area close?
I do have some larger jets, that I can use if the 50M or 52M rods get me in the ball park.
Thx.

[TommyK]

http://quadrajetparts.com/rochester-quadrajet-parts-quadrajet-jets-rods-hangers-quadrajet-primary-rods-50m-quadrajet-dualjet-primary-metering-rods-050036-tip-later-style-p-197.html

[1983zsled]

Thanks Tommy K.
I ordered two sets...50M and 52M
I will update the post when I get them installed in about 7 to 10 days when I get them.
 

[1983zsled]

Update......
I Managed to get my hands on some 55M primary rods with the .036 tip.
I dropped a set of .076 jets in with these rods and tested tonight with the secondaries locked out.
Good news on the primary side at WOT it is now 12.8 to 13.4 to 1.
Unlocked the secondaries with a H hangar and DP rods I was 10.8 to 11.4 to 1 WOT.
Another change to CH secondary rods H hangar and I'm now 12.5 to 1 at WOT.

Do you think I can go to a different hangar to get closer to 13 to 1 or should I just bend the H hangar down a little?

Overall this is good news. The idle is fine, and cruise A/F is pretty good. At highway speed turning 2000 rpm's its around 15:1.  I do see a real lean spike when slow speed and in Overdrive and I give it just a little pedal ....17.5 to 1 at its highest but no lurching or bucking... This is low RPM 1200 to 1500 and basically just touching the pedal. If I give just a hair more it richens up to normal levels.

Those M rods sure made a difference.
Thanks Guys.
 

[Shark Racer]

Personally I'd leave it at 12.5, it'll give you a margin of safety. It may make more power there, it may make more power at 13. Only way to know for sure is on a dyno, and I'm not convinced it'd be worth a whole lot of power. (Are you building a max effort car?)

Are you saying in O/D it cruises along at 15:1 and then leans out to 17.5:1 when you lean on the pedal?