Carburetor help

Jbland · Nov 16, 2014

Hello I am currently running an edelbrock 600 carb on my 400hp 5.9 crate engine. Is this too much or too little carb for a 400 horse 360. I can't seem to get the mixture right us my issue. I've added a pressure regulator and still can't get the sweet spot on mixture screws. Any help would be greatly appreciated. Thanks!

1969CoronetR/T · Nov 16, 2014

Maybe this CFM calculator will help:

http://www.summitracing.com/expertadviceandnews/calcsandtools/cfm-calculator

1965_belvedere · Nov 16, 2014

IMO, that is too small of carb for 400 hp. is that wheel HP or crankshaft HP? Or estimated hp?

fanucme · Nov 16, 2014

Jbland said:
Hello I am currently running an edelbrock 600 carb on my 400hp 5.9 crate engine. Is this too much or too little carb for a 400 horse 360. I can't seem to get the mixture right us my issue. I've added a pressure regulator and still can't get the sweet spot on mixture screws. Any help would be greatly appreciated. Thanks!

On a 400 HP small block , my opinion is that a 600 is way too small , especially the Eddy carbs + aren't those screws only the idle mixture anyways ? if you have the idle screw in too far they dont even matter anyways because it runs on a different metering circuit. what is your fuel psi ?
try an out of the box holley 3310 and forget the edelbrock/carter type stuff (junk IMHO) , you can tune the holleys with the jets kits or buy the ededlbrock kits with the metering rods and stuff and complicated directions

But overall , you dont really give us enough info in your post , are you tuning for idle or power ? wide open throttle ? what are you measuring your air fuel ratio with ? do you have a wideband O2 like a LM-1 or are you tuning by ear or smell or reading the plugs ?

FWIW on my 12 second at 108 mph 1970 Dart with a built 360 I ran an 850 DP, the weight HP calculator puts it around that 400hp mark

Meep-Meep · Nov 17, 2014

Getting response out of the mixture screws has little to do with the fact you have a 600 CFM carb. Check your timing and make sure it's not retarded. Also the basic idle speed setting should be about 1.5-2T from the throttle blades lightly seated. I'll agree that for optimum power you'd be better off with a 750 CFM (assuming you really do have 400 HP) but 600 CFM isn't necessarily the death of it. It's just won't RPM and therefore won't make the rated HP.

coloradodave · Nov 17, 2014

What he said^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^....

rumblefish360 · Nov 17, 2014

fanucme said:
On a 400 HP small block , my opinion is that a 600 is way too small , especially the Eddy carbs + aren't those screws only the idle mixture anyways ?

This opinion shows inaccurate. Much depends on displacement as well as many other factors. 600cfm could be right for one engine but wrong for another. How is this? It falls under what type of useage it is going to be used for.

600 CFM is enough CFM to make the power.

Truly the worst statement is "Especially the Edelbrock carbs." This just sells me you do not know how to tune them. The net and Rod kit is really not complicated. Basic math takes a few seconds. The Holley may tune with a jet kit but there is so much more to tuning a Holley than a simple jet change and anyone thinking otherwise is just fooling themselfs. Hopefully, not others.

[QUOTE/]
But overall , you dont really give us enough info in your post , are you tuning for idle or power ? wide open throttle ? what are you measuring your air fuel ratio with ? do you have a wideband O2 like a LM-1 or are you tuning by ear or smell or reading the plugs ?

The best part of you reply. And actually helping.

[QUOTE/]
FWIW on my 12 second at 108 mph 1970 Dart with a built 360 I ran an 850 DP, the weight HP calculator puts it around that 400hp mark

Click to expand...

These statements can be misleading. The OP is or could be lead to believe that his 360 now needs an 850 carb.

If this was a realitively mild engine, compression and camshaft wise, 600cfm's could very well be fine on top.

We also very much so could use some more information;
Compression ratio
Cam spec's @.050
What type of trans and if an auto, what stall converter speed is being used
Gear ratio and tire size
Intended useage of the vehicle
Track time vs. street time 90/10 - 50/50
What car again?
This engine was dyno'd? With what carb?

Many factors! But a in general question can get a in general answer.

Click to expand...

747mopar · Nov 17, 2014

What Meep said.

Lazerwolf · Nov 17, 2014

I have an Edelbrock 1406 600 cfm on my 400. It has a mild cam, aluminum heads and aluminum intake. No clue on actual HP though. Mixture screws as Meep-Meep said out 1.5 turns. Accelerator pump in middle hole. Upgraded step-up springs from stock yellow to pink. One question would be if you have the 1405 or 1406. The 1405 has jets and rods more for performance while the 1406 is on the economy side. That being said, I had to change my metering rods to 1449 to richen up both the power and cruising modes. Edelbrock has good product support if you need to call them for information. As a few others on here have mentioned several times, make sure your timing and exhaust are correct before tuning carb. Also, I had issues with the manifold. Originally I had a Perform RPM manifold on there which is for 1500-6500 RPMs. I swapped this out for a Performer manifold which is for idle-5500. Before changing springs, rod and manifold, it would struggle and almost die just trying normal acceleration from a stop. Working great now.

Mopar-Charger · Nov 17, 2014

I was running a 600 edelbrock on my 5.9 Crate. Assuming we have roughly the same engine, I threw a 750 Holley on and it runs like a bat out of hell. Chevy's just can't touch it :headbang: :3gears:

Btw, Buy a vacuum gauge. It will be your new best friend when it comes to idle mixture and timing.

coloradodave · Nov 18, 2014

Mopar-Charger said:
I was running a 600 edelbrock on my 5.9 Crate. Assuming we have roughly the same engine, I threw a 750 Holley on and it runs like a bat out of hell. Chevy's just can't touch it :headbang: :3gears:

Btw, Buy a vacuum gauge. It will be your new best friend when it comes to idle mixture and timing.

Having owned numerous fast Chevrolets I guess you just haven't run into the right guy yet. Don't worry, with statements like that, you will...

rumblefish360 · Nov 19, 2014

Jbland said:
Hello I am currently running an edelbrock 600 carb on my 400hp 5.9 crate engine. Is this too much or too little carb for a 400 horse 360. I can't seem to get the mixture right us my issue. I've added a pressure regulator and still can't get the sweet spot on mixture screws. Any help would be greatly appreciated. Thanks!

A pressure regulator should only do the job of regulating pressure. To much pressure can push the fuel past the needle and seat flooding the carb (fuel over flowing out of the carb) or filling the fuel bowls with to much fuel causing a rich condition. If you have a stock or mild HP mechanical fuel pump, the regulator is not needed.

In the Edelbrock instructions which can be veiwed and/or downloaded at Edelbrock.com, they will recomend a max. psi for the carb. Also, tuning instructions are available. As stated before, a vacuum gauge is a big help. Knowing how to read spark plugs is a big plus. An air/fuel ratio gauge is a very good tool to instal in the exhaust/header collector (not reducer)

Your engines timing is a source of running and driving ill's. Dial that in well.
I also suggest a multi sparking ignition.

Those two main screws up front on the carb to adjust the idle should be as stated above at approx. 2-1/2 turns out from there lightly seated position. Turning the screws a half turn in ether direction should show a noticeable but small RPM difference.

Swap rods before jets. The carb's come in the general ball park of what there intended for. Such was the reason for the question of just what model carb you have. Should simple Rod changes not do the trick, then a jet change is in order.

An engine capable of 400HP can use a 600 CFM carb. The difference between a 600 & a 750 can be 10 HP on one engine and 30 on another. The lack of engine specs & intended useage of the engine/car lead to this problem of getting a more exacting answer.

The one thing I'll say between the two carbs is that the smaller 600 will give you a great throttle response.
The larger carb will add top end power while at a slight loss of throttle response & a slightly lower vacuum signal.

Carburetor help

Jbland

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1969CoronetR/T

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1965_belvedere

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fanucme

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Meep-Meep

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coloradodave

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rumblefish360

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747mopar

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Lazerwolf

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Mopar-Charger

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coloradodave

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rumblefish360

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