ATM/Holley verses Carter 625 AFB

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Newbomb Turk

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Here is a comparison graph between these two carbs. One is one of my ATM carbs for my tunnel ram with a WAG tune up.

The other is a 625 Carter AFB. The Carter LOST 29.11 on torque and 37.45 on power. I have a bunch of time tuning the AFB and it shows in the A/F ratio. There is more in the ATM carb if I want to keep tuning on it, which I’m not doing. I don’t want to wander any further from my TR tune up than I already have.

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are you running a single top tunnelram? damn i just bought 2 650AVS2 for my 360 magnum tunnelram. didnt want to spend close to $1800 for the ATM carbs at this time.lol
 
PRH said:
A 1.420 x 1.750 carb with a modern chokeless main body would be closer to 850cfm.

Carb flow testing - Don Terrill’s Speed-Talk

The real question in my mind is…….how does the ATM carb compare to another similarly sized, “known good” carb.
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I’ll read that in a bit. I figured about 830ish. The ATM beat my true 750 dyno carb by 15 or 18, but like I said I need to do more tuning on my carb but I’m not going to do it because I’ll have to undo it for my stuff.
 
Newbomb Turk said:
I bought builders kits but the carbs I bought retail for 710.00 each.
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I bought both the 650AVS2 for $600 or 650. I bought then when they went on sale. The ATM look like nice carbs. Can you post a build up of your engine build
 
A different Holley v Carter test, apples to apples. 600 cfm Holley v 625 cfm Carter AFB.
AFB made: 17 ft lbs more tq, 17 hp more....& used less fuel doing it.

img203.jpg
 
Bewy said:
A different Holley v Carter test, apples to apples. 600 cfm Holley v 625 cfm Carter AFB.
AFB made: 17 ft lbs more tq, 17 hp more....& used less fuel doing it.

View attachment 1716208041
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My test is apples to apples. Put your best Carter in a box and ship it here. I’ll test it.

Also, I did mention my true 750 dyno carb beat the Carter but not by as much as my carb did. And as I said, there is more in my carb yet.
 
Why not test a Holley and Edelbrock 600? A 1405 to a tried and true 1850.
 
I could be way off base here, but my guess is the main purpose of the test was to try out the new carb.

I’ll just throw this out there……..
I’ve done countless carb tests on the dyno.
Usually it revolves around quantifying that the engine owners carb isn’t a power robbing turd.
So it gets compared to a known good carb.

I’ve tested many custom carbs, and carbs that come from carb specialty shops.
There might be a few instances that have slipped my mind, but I can’t think of any at the moment where some high end carb beat another similarly sized, known good carb by like 15-20hp.
Sure, they often do some things better than the test piece(better fuel curve, better throttle response, etc), but it’s pretty uncommon to see a 10+hp spread.
I’m not saying it can’t happen, I’m just saying in my experience……..it’s rare.
I’ll also say that what’s less rare is…….having the fancy new carb not be any better than the test piece……or even end up not as good.
 
RustyRatRod said:
Why not test a Holley and Edelbrock 600? A 1405 to a tried and true 1850.
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For one, I don’t have a 600 Holley. I can’t think of a single instance where I’d use one.

The Carter is a Competition 625 that I think I have close to 20 hours in tuning time on. That’s why the A/F ratio curve is so flat.

I originally tested the Carter against my 750 dyno carb. It needs more work, but I’m seriously considering buying another ATM carb and using that as a dyno carb.

IMO, many guys have a 625 Carter in some form and the general swap is to go to a 750.

I used one of my carbs to qualify my thinking. My carb has more power potential than the dyno carb if for no other reason than the boosters I use are the best on the market.
 
PRH said:
I could be way off base here, but my guess is the main purpose of the test was to try out the new carb.

I’ll just throw this out there……..
I’ve done countless carb tests on the dyno.
Usually it revolves around quantifying that the engine owners carb isn’t a power robbing turd.
So it gets compared to a known good carb.

I’ve tested many custom carbs, and carbs that come from carb specialty shops.
There might be a few instances that have slipped my mind, but I can’t think of any at the moment where some high end carb beat another similarly sized, known good carb by like 15-20hp.
Sure, they often do some things better than the test piece(better fuel curve, better throttle response, etc), but it’s pretty uncommon to see a 10+hp spread.
I’m not saying it can’t happen, I’m just saying in my experience……..it’s rare.
I’ll also say that what’s less rare is…….having the fancy new carb not be any better than the test piece……or even end up not as good.
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Lol, yep. I’ve seen way more high dollar carbs fail than succeed.
 
None of my dyno mule carbs are anything too special.
But they are drama free when breaking in a new engine.
I have 3 that I use most of the time.
4779 750, 4781 850, home built HP950.
Those have me covered for most builds between 400-700hp.

There’s also a pretty good working 1150 Dominator at the dyno for the bigger cube/higher hp stuff.
 
Newbomb Turk said:
My carb has more power potential than the dyno carb if for no other reason than the boosters I use are the best on the market.
Click to expand...
Please explain how the boosters you have will make more power and what makes them the best on the market?
 
So let me see if I understand this 'apples to apples' test.

One carb was 625 cfm & the other 750 cfm. Used on a 360 engine that came from the factory with an 850 cfm carb [ TQ ]....but said 360 is now making more hp than stock because of a bigger cam.

Ans surprise, surprise the engine made more HP with the 700 cfm carb.
.....And the silly poster wants to imply that the Carter 625, down more than 200 cfm from the factory carb, is somehow not as good as the bigger carb tested....because it was down on power...
Everybody, down to the bottom of the garden NOW looking for fairies.....
 
Bewy said:
So let me see if I understand this 'apples to apples' test.

One carb was 625 cfm & the other 750 cfm. Used on a 360 engine that came from the factory with an 850 cfm carb [ TQ ]....but said 360 is now making more hp than stock because of a bigger cam.

Ans surprise, surprise the engine made more HP with the 700 cfm carb.
.....And the silly poster wants to imply that the Carter 625, down more than 200 cfm from the factory carb, is somehow not as good as the bigger carb tested....because it was down on power...
Everybody, down to the bottom of the garden NOW looking for fairies.....
Click to expand...

Build the best you can, send it here and I’ll test it.

In fact, the next time I run the engine I’ll put the air hat on it and we can see what the air flow says.

Did you forget the 340 came with an AVS that had a similar flow rating?

And it is apples to apples because like I said, a swap from a 625 to a 750 is a regular occurrence.

I’m not doing an 1850 Holley test because they are door stops at best, right along with the AFB.
 
Hysteric said:
Please explain how the boosters you have will make more power and what makes them the best on the market?
Click to expand...

I’ll tell you what I know, because…well…that’s what I know. If you want the science behind it you’ll have to call Mark Whitener at Lightning Racing Carbs and ask him.

I can’t remember for 100% sure but IIRC these are 22 hole boosters. They may only be 20 hole, but I didn’t count them. My memory says 22 holes. So that’s a thing right there.

The other thing I know is that unlike other (I guess you could say all others) annular boosters these do not restrict flow.

And the last thing I know is these boosters have more gain (without dropping flow) than any other booster out there.

IIRC, Mark has a 70 inch manometer and his boosters will bury the manometer. No other booster gets close.

So with 20-22 holes, no flow loss and a huge signal gain these boosters make it so you can use a bigger carb not lose any flow. Of course, with booster gain like that atomization goes through the roof.

I have 70 and 80 main jets right now. By the time they are done and ready for my tunnel ram I’m pretty sure the jetting will be in the 64-65 and 72-74 range. Where I end up with a main bleed I’m not sure. I’m thinking for emulsion it will only take one hole. The size and location will have to be tested.
 
Bewy said:
So let me see if I understand this 'apples to apples' test.

One carb was 625 cfm & the other 750 cfm. Used on a 360 engine that came from the factory with an 850 cfm carb [ TQ ]....but said 360 is now making more hp than stock because of a bigger cam.

Ans surprise, surprise the engine made more HP with the 700 cfm carb.
.....And the silly poster wants to imply that the Carter 625, down more than 200 cfm from the factory carb, is somehow not as good as the bigger carb tested....because it was down on power...
Everybody, down to the bottom of the garden NOW looking for fairies.....
Click to expand...

69 1969 DODGE 340 CARTER AVS CARB CARBURETOR 4612 SA DART 4612SA AUTOMATIC | eBay

Here you go. I did a quick search and came up with this. Buy it, do your voodoo **** and send it here. It will lose too, but give it your best shot.

Edit: don’t forget it LOST 37 HORSEPOWER. You think that was all airflow? Not hardly. We could drop an out of the box 4781 850 Holley on there and it wouldn’t gain 37 horsepower over the Carter. It’s not just about airflow. Even you should be able to grasp that.
 
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