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Re-jetting an Edelbrock AVS Thunder 650 cfm

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Re-jetting an Edelbrock AVS Thunder 650 cfm

deemann deemann
User | Posts: 57 | Joined: 02/09
Posted: 12/02/13
02:00 PM

1969 Chevelle

This is a GM Crate Motor Manufactured for Chevy Trucks with the Mexico Cylinder Heads.  4 bolt main, 2 piece rear main seal  76cc combustion chambers  8.5:1 compression  -  advertised power:  260HP  304TQ

I upgraded this engine with:
1.  Edelbrock EStreet Aluminum Heads  70cc combustion    185cc intake runners and  2.02 and 1.60.

2.  Edelbrock RPM Air Gap Manifold

3.  Lunati Voodoo  .468/.489  219/227 duration  RPM Range:  1,400 - 5,800

4.  Edelbrock AVS Thunder #1805  650cfm

I had a problem with it coughing/spitting when I floored it, so I adjusted the front lever to allow for the maximum shot of fuel.  This made a huge improvement, but I still get a slight amount of hesitation right at initial takeoff when I floor it or anytime I'm cruising along and then really get on it.

The AVS Thunder carb has all the factory setting except for the lever I adjusted for the maximum shot of fuel - do I need to look into re-calibrating (re-jetting) the carb by using an Edelbrock kit with different jets, springs and rods?

If so, can someone recommend which size jets, rods and color springs?  Thank you.  

wayne712222 wayne712222
User | Posts: 198 | Joined: 10/13
Posted: 12/02/13
09:31 PM

does your exhaust have any provision for an oxygen sensor.. so you can run an air fuel ratio display..  this way you will know which way to go with your tuning..

a few things..
what happens with the engine when you slowly accelerate off idle..? does it stumble and sometimes pop???

what happens when you have it up and about 3000 rpm.. and slowly back off the throttle and stabilize  around 1200 to 1500 rpms.. does it stumble..

if it does.. then you will need to verify the idle feed restrictions are not clogged or restricted..

one way to clear these is to remove the idle mixture screws.. spray some carb cleaner into the holes with the spray nozzle.   then as quick as you can.. some compressed air.  this will sometimes clean out the various air bleeds and the idle feed restriction...

also.. is your primary throttle setting as far closed as possible..  so the idle transition slots are almost fully covered.. just a fraction of the idle transition slot exposed.

Idle Transition Slots Setting Zps7bcc767a

AFB AVS Booster Assemblies Zpsc75bdda8

35D5824f C301 4A1e 9D64 0Dbfe2c6dd71 Zps98f001e9

why.. because above idle.. and below the point where the mains take completely over. the idle transition circuit is supplying the fuel...

Idletrasnitionmains Zps1a151b85

90C08742 E8aa 4197 8E7a 68837E4e7447 Zpscd75c134

all this that i have mentioned.. is just for idle transition..  not on the mains or secondaries...  

deemann deemann
User | Posts: 57 | Joined: 02/09
Posted: 12/03/13
12:00 PM

No provision for an oxygen sensor.

When I slowly accelerate off idle - it does NOT stumble or pop.

From 3000 rpm then down to 1200 - 1500 no problem there either.

Yes - the primary throttle setting is a far closed as possible.  

wayne712222 wayne712222
User | Posts: 198 | Joined: 10/13
Posted: 12/03/13
03:39 PM

how about playing with the AVS thunder.. secondary air door adjustment..

edit.. the edelbrock factory adjustment is 1.5 turns from the blade closing with just spring tension..

ONE SIXTEENTH of a turn at a time...

go tighter.. slightly...

Edelbrocksecondaryairvalveadjustment Zpseafa7b90

this adjustment is talked about in the tuning manual from edelbrock..

you want it tighter if you have a bog when you stomp into the secondaries..

but trial and error a fraction of a turn at a time..

just for kicks.. on quadrajets.. with a different type of spring..

the adjustment is between 1/2 and 15/16th of a turn 1/16 at a time.. so 1/2, 9/16, 5/8...