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Bill-E-BoB 03-15-2010 04:02 PM

carb advice
I've been tinkering with my '69 Camaro lately & up next on the docket is the carb. I've got a 350 with headers, HEI ignition, aluminum intake, and a 750 cfm Carter AFB carb. Its running way way way rich, like nauseatingly rich. Even turning the mixture screws all the way in, its still rich. From what I understand, it should totally stall out by that time, shouldn't it? Stumbles on hard acceleration under load, but has great throttle response in neutral & smooth to moderate acceleration. So the obvious solution to me is that the carb needs to be rebuilt. 11 years ago I rebuilt it in my highschool autoshop class, it was my first carb rebuild, and it's been sitting in storage ever between the varnish & the likely screwups of a highschool kid learning how to rebuild a carb, I'm sure that's not a bad idea.

But then, I'm getting other opinions from some local guys who don't think very highly of Carter AFB carbs & think I should use this as an opportunity to scrap it & get a 600 CFM Holley on there anyway. Their opinion is that my motor is close enough to stock that it shouldn't have more than 600-650 cfm anyway, and no amount of tinkering will make that carter as good as a Holley. Are they right? There's a seller on ebay that sells Holley # 80457 for $189, which is nice & cheap if its going to be a good carb for me to run. Is that going to be the carb I want? Will it perform well? Bolt up easily to my Edelbrock Performer RPM manifold?

So what do you think, rebuild the Carter 750 I've got, buy the Holley 600, or buy something different?

T-bucket23 03-15-2010 05:35 PM

A 600CFM Vacuum secondary is really all you would need.

Fast 4 Door 03-15-2010 05:56 PM

600cfm holley OR edlbrock.. I have had good luck w/ both on my 350 stockers

techinspector1 03-15-2010 06:00 PM

Have you monitored your fuel pressure? No modern 4-bbl carburetor needs more than 5 psi at the carb inlet. Get the pressure under control before you do anything else or you'll be chasing this forever.

Fast 4 Door 03-15-2010 06:11 PM


Originally Posted by techinspector1
Have you monitored your fuel pressure? No modern 4-bbl carburetor needs more than 5 psi at the carb inlet. Get the pressure under control before you do anything else or you'll be chasing this forever.

Hey Tech, I admire your thought process, You really don't take any chances do you? ( I read a thread where you said you don't have any good luck) Right on !

cobalt327 03-15-2010 06:35 PM

After the fuel pressure is OK, the next thing to check is the float level.

kleen56 03-15-2010 07:52 PM

Carbs are only good when they calibrated correctly to your specific engine. Holley's are always a popular choice and have great performance. Edelbrocks are easy to work on and dependable. I agree with the others that a 600 CFM or 650 would be all you need. I personally like Holley's but the double pumpers and not vacuum secondaries. Just my opinion. Be careful buying used carbs. Some people think they know how to modify them and can really mess up a good carb.

Bill-E-BoB 03-15-2010 10:36 PM

ok, so dumb do I test my fuel pressure? If it makes the difference, I'm using the stock mechanical fuel pump, so I can't imagine it'd be building up too much pressure...

For float level, I assume the only way to check it is to take the top back off the carb, flip it upside down & measure the distance to the floats like you do when rebuilding it right? Can I leave the carb on the car & just take the top off, or do I need to pull it out & really disassemble?

From what I can tell, appearance wise & based on rebuild kit part numbers, it seems a Carter AFB 9000 series (my carb) is the same carb as an Edelbrock Performer. So if a Holley or Edelbrock is the way to go, is there any real advantage to the 600 or 650 cfm Holley vs my 750 carter/edelbrock? I mean, I understand 600 may be all I need, but does that mean 750 is too much? Am I going to spend $200 to decrease performance instead of 50 bucks to rebuild an otherwise superior carb?

kleen56 03-15-2010 11:28 PM

If your using a stock mechanical fuel pump, your most likely OK with fuel pressure, unless the pump itself is defective. They sell inline fuel pressure gauges which simply go in the fuel line going to the carb. When you start the engine, you see the fuel pressure going to the carb.
The Carter is similar to the Edelbrock and float adjust can be made with the carb mounted. Top of carb needs to be removed and turned over as you stated.
The difference on a 600 CFM and 750 is the venturi sizes. If the carb is too big, performance will be affected. Symptons like a bog, hestitation, too rich of mixture are all part of being over-carburated. Sometimes a smaller CFM carb will run more efficient, get better mileage and run hard. Bigger is not always better when it comes to carbs. The choice is yours. Important note, no matter what carb you go with or purchase, regardless of CFM, brand, the carb will need to be calibrated to your engine (ex. idle mixture, jetting, etc.)
Here's a good website for you to read. It also has a carb calculator to see what CFM's are appropriate for you application.

techinspector1 03-15-2010 11:35 PM


Originally Posted by Bill-E-BoB
how do I test my fuel pressure?

Tap into the supply line at the carb inlet and run a small 1/8" nylon pressure line back to the firewall, up between the lip of the hood and the top edge of the firewall, to the grillework in front of the windshield. Temporarily mount a mechanical fuel pressure gauge to this grillework so you can observe it through the windshield while you are driving. Duct tape it down, ziptie it down, whatever. It's just temporary.

Bill-E-BoB 03-16-2010 11:21 AM

Thanks guys, I'm about 90% sure I have a pressure gauge that came in a kit with my compression tester at home, so assuming I do, I'll double check the fuel pressure first chance I get to tinker for a few minutes.

The calculator on that page & the opinions of pretty much everyone who's more knowledgeable than me (such as you guys) seems to all point toward getting a 600 cfm carb.


Originally Posted by kleen56
If the carb is too big, performance will be affected. Symptons like a bog, hestitation, too rich of mixture are all part of being over-carburated.

Check, check, and check. :)

So, here's the carb I'm thinking about, its remanufactured but dirt cheap & the seller has great feedback ratings. Added bonus, it has an electric choke (which I'll be asking you guys how to wire) and all the linkages for the kickdown in place, which my Carter is missing. This looks like the right beast to me, yes?

cobalt327 03-16-2010 11:41 AM

This is the newer style 'shiny' 4160 600 cfm (80457-2 is shown).

Unless there's an issue w/the 'shiny' part, it should be fine.

I see that it comes from Holley w/a black (heaviest) secondary spring in it. You might want to swap that one out for a plain or purple colored spring to get a quicker secondary opening.

454C10 03-16-2010 12:34 PM

if the idle mixture screws don't do anything then that is a sign the throttle blades are open past the transfer slot at idle.

the engine may need more timing at idle to increase idle speed which would allow the throttle to be more closed at idle (not past the transfer slot).

Or more air needs to be let in other than the front throttle blades. (crack open the secondary blades or drill small holes in the front primary blades)

here is a nice "how to tune a carter/edelbrock carb" write up.

I would use a holley.

eric32 03-16-2010 03:46 PM

Well to help you out on a decision I have a holley 1850s 600 cfm carb on my 350 sbc and it pushing 400 horse power and I have tuned it to work really well with my setup. I found out about the carb your wanting on ebay cause my Dad got the same carb for his ford 302 engine and it ran like a charm just bolt on and a little tuning and away he went.

He also got it from national carburetors the exact one you have in the link and they look and operate like brand new carbs. I recently rebuilt one for my brother on his 305 chevy and it did excellent. The holley 600 carb will out do any edelbrock 600 in my opinion as I used to have one but sold it after I learned many things about holley's and how to fine tune them.

I would get that one from ebay in a heartbeat if I needed a new one. I am not saying your carter carb is junk or anything just after many years its just better to get a new carb or one that has been refurbished like the one I got. National carburetors are very good with there carbs from my experience. Good luck


Bill-E-BoB 03-17-2010 12:15 PM

Alright cool, that definitely sounds like the carb I want. One thing though, I called 'em up & they said it comes with a Ford Kickdown instead of GM. My kickdown cable isn't currently connected so I don't know exactly what I need in order to connect it. the cable is attached to the transmission as it should be & comes through to the bracket on the back of the motor as it should be, then the end of the cable is just hanging free. Does that one on ebay have the right linkages to connect my kickdown to or not? I'm assuming I just put a bolt in a hole somewhere on the throttle linkage & put the end of the cable on it & adjust to where it pulls the cable out as the secondaries engage...right?

Anybody with a 350/TH350 and their kickdown installed correctly have a picture of how this installs? I'm havin' a tough time visualizing it...

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