86Stevo

hey guys im trying to adjust my carb to what i need its alot i know but im going to try to break it down

The issue
i raced my friend in his mustang 07, i have the GM 290hp crate in camaro every gear he pulled on me. the second my car hit about 35-4000 RPM its like my friends car kept pulling and mine slowed down we started out even (yes i no my Friend wasn't just half throttle and then full i have driven his car and mine). I pulled my plugs they looked brand new no blackness or anything and i have driven the car a few thousand miles there suppose to be a little black/ almond color.

now i want to make it richer because the motor was dyno`d according to the instructions that came with the motor with a 670 holley well im 70cfm shy and running lean

my questions are

Can a metering rod restrict the flow of a jet at WOT? If so how do i know if a jet is maxed out?

The metering rod measurements (.075x.047) what are they of?? and witch ones are what ?

do metering rods only effect fuel delivery while the gas pedal is being pressed ?

Springs that the rods sit on.. i forget here names... the stiffer they are the slower the metering rod opens ?? or is it the other way around?

and Finally edlebrocks 650 AVS carb how come it runs .095 prime jets .098 seconds with a .068x.047 rod
But my carb the 600 performer is running .098 primes and .095 seconds with a .075x.047 metering rod?? cant i just put in the jet sizes and rod size that the AVS has ? the jets work for both performer and AVS series im not sure about the rods.


thanks alot guys i no its alot of stupid and technical questions but i couldn't find all my answers and i don't have any one to explain it to me ill let u guys know how i make out maybe post a vid of me beating my friends stang!

Apeiron

That's the function of the metering rod, they control the flow through the jet. Jets don't really "max out".

The diameters of the rich and lean portions of the rod. Normally the lean portion is in the middle of the jet, but when manifold vacuum drops under load the step-up spring pulls the rod up until only the rich tip is in the jet, which increases the area available for fuel to flow through.

They affect it any time the car is running on the mains.

The step-up spring works against manifold vacuum, so the weaker the spring, the longer the mixture stays rich as vacuum decreases under load.

Jets and rods are interchangeable between any of the Edelbrock AFB or AVS style carbs of any size. Whatever rods and jets a carb comes with are only a starting point. Follow the tuning procedure in the manual to determine which rods and jets are best for your application.

86Stevo

That's the function of the metering rod, they control the flow through the jet. Jets don't really "max out".

how do i know when i need to move to a smaller rod or a bigger jet? that's what i ment by maxing out i guess.



The diameters of the rich and lean portions of the rod. Normally the lean portion is in the middle of the jet, but when manifold vacuum drops under load the step-up spring pulls the rod up until only the rich tip is in the jet, which increases the area available for fuel to flow through.

so the smaller the numbers the richer the carb will run? and the smaller number is the rich side and the lager is the lean side correct?


The step-up spring works against manifold vacuum, so the weaker the spring, the longer the mixture stays rich as vacuum decreases under load.

so i would change the step up springs more according to timing? for instance if i change the timing curve but im running the proper a/f mix at wot i would change the springs to have the rod richen up the motor sooner if my timing comings in sooner. or some situation like that


Jets and rods are interchangeable between any of the Edelbrock AFB or AVS style carbs of any size. Whatever rods and jets a carb comes with are only a starting point. Follow the tuning procedure in the manual to determine which rods and jets are best for your application.

okay but if i do use the same size jets n rods that they did for the 650 AVS does that mean ill be running 650CFM threw a performer carb?


thanks for the quick response you explained alot just want to understand how it works before i change it

Apeiron

If you're lean you need more fuel flow area, if you're rich you need less. The flow area is determined by the difference in the outside diameter of the rod and the inside diameter of the jet.

Yes

The enrichment point is more of a driver-preference thing, like power valve selection on a Holley. If the car feels sluggish on part-throttle aceleration and you feel like you have to put your foot too far in to it to get it to accelerate, use a stiffer spring to bring the enrichment in sooner. If it feels touchy and burns through gas, use a weaker spring to delay enrichment.

CFM refers to the volume of air that flows through the carb under a constant pressure differential (1.5 inHg for 4-bbl carbs). Nothing to do with fuelling.

86Stevo

Alright thanks, you explained it awesome i feel like i have a better idea of how to change things and what does what. thanks ill reply to this if i have any issues im getting a calibration kit tomorrow probably mess with it Sunday

Apeiron

Don't just get a calibration kit and start swapping things all over the place without a plan. The Edelbrock manual has one of the best descriptions of a systematic tuning process that you'll find anywhere. Follow it exactly, and you'll end up with a very good tune.

86Stevo

yea i have that chart in my owners manual. i have a few numbers im going to try but at least i know no what im changing and what to look for. like i siad ill keep you posted and thanks for the explanations

Apeiron

Don't just look at the chart, read the whole manual, and follow all the steps. Every question you asked here today is covered in the beginning, even.

86Stevo

Thanks i went 1.5 stages higher power and cruise mode on the chart and it worked out great it runs alot better im going to use this set up and see how my plugs come out i tried putting in smaller rods but it was to rich car bogged down a little bit so i went back to my 1.5 stage

thanks for all the help and the quick reply i did read the manual but it was confusing a little bit on how they worded it

you explained it very clean thanks

next is timing curve hopefully pull a few more HP outta my car next week Thanks again

86Stevo

after Driving my car for a bit with the new rods in im getting horrible gas mileage i went from about 18-20 to 11ish... i only went up 1.5 stages is it really that big of a differance ?? or should i put the stock rods back in and switch out the secondary jets so i save gas when i dont hit it and when i do hit it i get the power out of the carb

cabsclassics

oops wrong post

nascarhodge3

Try going to no2 in the manual this should give you more fuel in power but not change the cruise side of things.also don't be afraid to step up the secondary's by a step or 2 this will not change your cruise side of things.this should keep the milage up but give you the extra fuel you need under power.the beautiful thing with Edelbrock is it does not take but a few minutes to change things around if it don't work right