question for guys running 2-4 edelbrocks

I was wondering if anyone ever noticed any difference from how they jetted the primary jets? You can either have a larger jet with a large metering rod or a smaller jet with a smaller rod. You could dial in the AFR either way I was just curious if ones better than the other for the carb signal or power.

Mike

Me thinks you may be wrong on the results due to the area differences between a large hole with a larger step metering rod versus the smaller jet with a smaller metering rod step Try it both ways and let us know
Which type Eddy . carb are you wanting to use, the street carbs. or race carbs. part #s?

Street 1805 600cfm . The two closet settings I've tried in the past was .092 jet with a .068 X .047 rod or a .095 jet with a .073 X .052 rod.

the key is figuring jet area. once that size is determined the combination is irrelevant.

No.
Metering rods and primary jetting are 2 different animals.
That wont work.
Square jet and read plugs.

For adjustability and quick tune, I've calculated the areas of the rods and jets so that I installed a jet that allowed me to go up or down on the rod without changing the jet. Made a chart and away I go.


On the other hand, running a cross ram, I haven't changed anything for years on the race car. But I could...…..

If doesn't matter as long as you can tune it. If it was me I'd stick with what Edelbrock recommends in their tuning guide since then you can buy a tuning kit and have everything you need to go richer or leaner.

Andy since I'm running 2-1405's at 1 to 1 on a stage V manifold the chart doesn't go lean enough for light street use. It gets close and I use the chart for the 1406 which is also a 600 carb but not jetted near as rich. I just increase or decrease the part of rod that need it. Trial and error.

Area is area. That being said NO WAY square jet. Secondarys are rich enough at the factory setting or very close to it.
Doug

You are wrong. Unless you own a data logger with 8 O2 Sensors, or go on a dyno with 8 sensors, you will never know.
If you owned a racepak with 8 O2 Sensors you would see where to jet it.
Primaries run #1,2,5,6 cylinders
Secondaries run #3,4,7,8
My little small block with a sheetmetal intake was pretty close to square jetting.
If your intake manifold is semi even in distribution, you will see slight variances in jetting from front to back.
Maybe the secondaries could possibly be 3 jet sizes leaner.

Okay so your first mistake was to use the wrong carbs. Edelbrock sells carbs that are calibrated for dual carb use but evidently you didn't buy those. Since you have the wrong carbs you need to rejet them the way Edelbrock wants the dual carbs jetted. Download the instructions for the dual carb calibration and then buy the correct jets and metering rods for dual carb calibration and you should be on your way.

I believe the edlbrock "dual quad" carbs are manifold/ engine specific, or that's how I've treated it when looking at their carbs. the only dual carb issue I've found is not using a matched pair. I bought a 1406 and a 1405 for my set-up thinking simple metering rod and jet changes were all I needed. I found out the clusters/idle jets along with metering rods/jets were all different. another educational opportunity for me, but in the end a very nice street package.

In-line with this thread, have any of you used an inexpensive air-fuel ratio meter that you would recommend? "Inexpensive" means a price that is reasonable considering a one-time use or dialing in the set up on one car. If anyone knows of a used set-up, I'd appreciate your PM.

- EM

https://www.innovatemotorsports.com/products/lc2.php

Kevin

Here’s the recommended carb cart from Edelbrock mild/performance big block 2-1405 no calibration kit available.

I don't think i'd get overly lost in that chart. it's just too general. I use a ch28 with two 600's. primary jets on both carbs are .101", metering rods 71x47, orange step-up springs, .098" secondary jets (near identical to factory 1405 jetting). I have edelbrock RPM heads, modest solid lifter cam (238@.050"/.510" lift), full TTI exhaust, automatic with 3.23 gears, and factory 10 3/4" converter. I wish i'd tried this set-up years ago. very trouble free, torquey, low maintenance, drive anywhere.

I don't think i'd get overly lost in that chart. it's just too general. I use a ch28 with two 600's. primary jets on both carbs are .101", metering rods 71x47, orange step-up springs, .098" secondary jets (near identical to factory 1405 jetting). I have edelbrock RPM heads, modest solid lifter cam (238@.050"/.510" lift), full TTI exhaust, automatic with 3.23 gears, and factory 10 3/4" converter. I wish i'd tried this set-up years ago. very trouble free, torquey, low maintenance, drive anywhere. [/quote]

Thanks for your results.

A couple of things first you are right about the 1406 carb. The edelbrock tech told me that it was not just a 1405 with a automatic choke and leaner jetting, that it was an economy carb and totally different and not to be used on dual quads because it would be lean even if jetted the same as the 1405 and not a match. If you wanted an automatic choke you would add it to the 1405. If you look at the chart the 1403/1404 500's are compatible for dual usage because the choke is the only difference.

Second The factory jetting would be close for me if I was running a progressive linkage but the Stage V requires it to be 1 to 1 so it needs to be leaner because of running off both carbs and not just one down low.

Also just for the heck of it the pair of 500 they sell are setup for a small block Chevy with progressive linkage. They take the factory setting which was .086 main .095 secondary jets & .065 x.052 metering rod and change it to .086 main .077 secondary jet and rod change to .065 x .057 So that comes out to 8% less cruise and 24% less secondary jet.

Thanks for your results.

A couple of things first you are right about the 1406 carb. The edelbrock tech told me that it was not just a 1405 with a automatic choke and leaner jetting, that it was an economy carb and totally different and not to be used on dual quads because it would be lean even if jetted the same as the 1405 and not a match. If you wanted an automatic choke you would add it to the 1405. If you look at the chart the 1403/1404 500's are compatible for dual usage because the choke is the only difference.

Second The factory jetting would be close for me if I was running a progressive linkage but the Stage V requires it to be 1 to 1 so it needs to be leaner because of running off both carbs and not just one down low.

Also just for the heck of it the pair of 500 they sell are setup for a small block Chevy with progressive linkage. They take the factory setting which was .086 main .095 secondary jets & .065 x.052 metering rod and change it to .086 main .077 secondary jet and rod change to .065 x .057 So that comes out to 8% less cruise and 24% less secondary jet. [/quote]if this is stage V hemi don't put those 500's on it. I wouldn't put a 500 on a lawnmower. street hemi carbs used the same venturii and throttle bore size as the edelbrock 600's. if it's a big inch engine i'd go directly to the 750's. the 750's have the same venturii and throttle bore size as the '67 ss/b hemi cheater carbs, or '64 s/s max wedge.

I do have the 600's on it now and a pair of 750's too. The 600's are better for street driving.

If you truly square jet these carbs they are not square jetted. The rod is in the primary jet and limits flow. My combo I’m sure has distribution issues and I’m running the 800 avs, but that being said it will not run anywhere near square. I have also seen it on a hemi really liked fat primary and leaner secondary. So it’s going to take trial and error, but don’t be afraid to move off of square jetting. Track cars. Honestly thinking about it I have never done the surface area math. So taking into consideration the rod in the primary the actual flow might be square, but the jet size isn’t

I agree with Doug, you've mess up your carbs to make them run better with the same size jets front and rear
Most people on here don't know that the Carter jets are in .003 bigger or smaller increments, not .001 increments I'm not sure about Eddy jets though
Any Carter type carb with metering rods will always need a smaller jet in the rear than the front due to the rod closing up the front jet if the carb flows the same amount of air through the front and rear barrels

if the carb flows the same amount of air through the front and rear barrels
This^
It won't unless both the throttle discs and venturis match - that's only a few models, and not available in all sizes.

Primaries run #1,2,5,6 cylinders
Secondaries run #3,4,7,8
???
Is this a:
1. 360° manifold (some Offy and old Weiand)
2. divided 360° (Chrysler factory iron 2 X 4 including 350, 361, 383, 413, all Gen-1 hemi and poly)
3. 180° dual plane

Ok after getting advise from Doug member dvw the tune is very close. This is a Stage V dual 4 manifold. Front carb feeds 1234 and rear feeds 5678.

I ended up with .092 primary .086 secondary .070 x .057 rod. That makes the cruise area .0028 power .0041 and the 86 jet area is .0058.

Many possible combinations I used the rods and jets I had.

Here's a look at the manifold. Just a small equalization port between the 2.

Thanks again Doug for your time and knowledge.

The connection may not have enough X-section to flow a great deal (and not enough to be useful as a plenum) but it equalizes vacuum changes very rapidly.

That pretty close to where mine was at on the dyno with the same intake and two 800's - I run one step up from that at the track - if I go two steps its way too rich

Hopefully your running both carbs together(1x1) and not hooked up for progressive stock type use?
I used the same intake for a EFI 572 Hemi motor I built for a local customer three years ago, it has 1 to1 linkage on the 4150 dry throttle bodies on it also
You do need to be a little careful while getting use to that type linkage set up, don't bend it up (the car ) due to the better power response

Yes Cab 1 to 1

Double D thanks for sharing your results.

Mike