Carb question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

moneyeater · 01-30-2008, 07:08 AM

I have a carter AFB 625 carb on my 350 and it works ok,but when the engine is warm it is hard to start.I have to turn it really long and pump the throttle until it starts.What may be the problem?Cold starting is real good and the e-choke works fine too! I´m thinking of getting a new carb what should be the right one? 500 cfm or 600 cfm,edelbrock or holley,mechanical or vacuum secondaries?
The carter afb is the same as an edelbrock,right?
Works fine except for the hotstarting problem and a bad gasmilage!
Give me some feedback please!

swb85 · 01-30-2008, 07:35 AM

Hot start - Fuel is most likely percolating in the bowls. Solution = phenolic carb spacer. I had the exact same issue and the spacer cured it, edelbrocks (carter afb) are notorious for this.

Bad mileage - Probably needs tuned......and keep your foot out of it.

moneyeater · 01-30-2008, 03:48 PM

My foot is a 12 how can i keep it from the throttle?

We tuned it with an emissiontester and the CO is at about 1,5%. That should be ok,or not?
For my understanding the fuel gets to warm and the spacer puts the carb higher so that the heat from the motor doesn´t warm up the carb,right?

James McClure · 01-30-2008, 08:47 PM

Money eater: You have struck a nerve here. I HATE the AFB carb's. All of them are TRASH!!! You'll only get one end of the spectrum right. Either they are ok cold or ok hot, but not both. A good Holley in the 650 CFM range would be good choice. Holley carbs are race proven. They have draw backs, but this is easily to correct through jet changes or float level re-seting. You had be a good "plug" reader though if you don't have a "CO" meter. You can use an O2 sensor but it gets tricky to get it into the whole exhaust stream so your reading all 8 cylinders not just 1 or 4. Measure voltage output of sensor (hot). It should be around 1\2 volt. Use a digital meter. It will bounce around like crazy, so just look for an average.
I would go with a "Q" jet myself. Holley's may be race proven, but the "Q" is time proven and is built by the people who built the engine. True it can be a pain to set it up, but once set properly you can forget it for 100,000 miles except the fuel filter and air filter. My truck has over 400,000 miles on it now, same "Q", but I have rebuilt it 3 times over the years and it needs it again.
Your AFB is running rich, real rich. I want you to warm the engine up to full operating temp with the air cleaner assembly off. Let the engine idle and have someone shut it down. Look down the throttle bores and look for a "fog" to develope. If it does the float(s) are set to high. If it doesen't, float(s) are probably set near correct and jet size is to large allowing the engine to suck more fuel than it needs to run. Take a look at the exhaust stream and the color of the inside of the pipe also, what color is it? Black smoke or a fluffy black deposit inside the pipe means it's way to rich. jim

wicked_sky_gazer · 01-30-2008, 10:43 PM

Quote:

Originally Posted by moneyeater

I´m thinking of getting a new carb what should be the right one? 500 cfm or 600 cfm,edelbrock or holley,mechanical or vacuum secondaries?
The carter afb is the same as an edelbrock,right?
Works fine except for the hotstarting problem and a bad gasmilage!
Give me some feedback please!

Moneyeater, I have an edelbrock 650cfm preformer series carb on my 355 in my 81 swb. I have all the same problems that you are having, perfect cold starts, angering hot starts, bad fuel milage, and my list goes on but i think you get the point. If you go with the new carb rout I would deffinately recomend AGAINST the edlebrock brand, mine has been nothin but a headach since I got it. I am now looking at replacing it with one of these Holley's, most likely the mechanical secondary one but i havent decided for sure yet. Good luck!!

http://www.jegs.com/webapp/wcs/store...0002_743726_-1

01-30-2008, 07:08 AM	#1
moneyeater Registered User Join Date: Feb 2003 Location: Northern Germany,near Bremen Posts: 684	Carb question I have a carter AFB 625 carb on my 350 and it works ok,but when the engine is warm it is hard to start.I have to turn it really long and pump the throttle until it starts.What may be the problem?Cold starting is real good and the e-choke works fine too! I´m thinking of getting a new carb what should be the right one? 500 cfm or 600 cfm,edelbrock or holley,mechanical or vacuum secondaries? The carter afb is the same as an edelbrock,right? Works fine except for the hotstarting problem and a bad gasmilage! Give me some feedback please! __________________ My little US vehicle parts business: http://www.thegearheaddepot.com/ Come have a look! ´81 GMC C 10, Spanish Red Last edited by moneyeater; 01-30-2008 at 07:09 AM.

01-30-2008, 07:35 AM	#2
swb85 On a budget like Fred Sanford Join Date: Oct 2005 Location: Topeka, KS Posts: 2,031	Re: Carb question Hot start - Fuel is most likely percolating in the bowls. Solution = phenolic carb spacer. I had the exact same issue and the spacer cured it, edelbrocks (carter afb) are notorious for this. Bad mileage - Probably needs tuned......and keep your foot out of it. __________________ '85 Silverado swb: 383 stroker, 10.5:1, vortec heads, 232/238 roller cam, RPM air gap, performer 750 carb, stainless longtubes, 3" duals/super 44's, T56/4.11 383ci build / exterior refresh thread '98 Camaro z28: 370ci twin turbo 370ci build '01 Tahoe LT 4x4: 5.3, longtubes/ory, magnaflow duals, custom tune....wife's DD Last edited by swb85; 01-30-2008 at 07:36 AM.

01-30-2008, 03:48 PM	#3
moneyeater Registered User Join Date: Feb 2003 Location: Northern Germany,near Bremen Posts: 684	Re: Carb question My foot is a 12 how can i keep it from the throttle? We tuned it with an emissiontester and the CO is at about 1,5%. That should be ok,or not? For my understanding the fuel gets to warm and the spacer puts the carb higher so that the heat from the motor doesn´t warm up the carb,right? __________________ My little US vehicle parts business: http://www.thegearheaddepot.com/ Come have a look! ´81 GMC C 10, Spanish Red

01-30-2008, 08:47 PM	#4
James McClure One shot, one kill. Join Date: Dec 2007 Location: Saratoga Springs NY Posts: 859	Re: Carb question Money eater: You have struck a nerve here. I HATE the AFB carb's. All of them are TRASH!!! You'll only get one end of the spectrum right. Either they are ok cold or ok hot, but not both. A good Holley in the 650 CFM range would be good choice. Holley carbs are race proven. They have draw backs, but this is easily to correct through jet changes or float level re-seting. You had be a good "plug" reader though if you don't have a "CO" meter. You can use an O2 sensor but it gets tricky to get it into the whole exhaust stream so your reading all 8 cylinders not just 1 or 4. Measure voltage output of sensor (hot). It should be around 1\2 volt. Use a digital meter. It will bounce around like crazy, so just look for an average. I would go with a "Q" jet myself. Holley's may be race proven, but the "Q" is time proven and is built by the people who built the engine. True it can be a pain to set it up, but once set properly you can forget it for 100,000 miles except the fuel filter and air filter. My truck has over 400,000 miles on it now, same "Q", but I have rebuilt it 3 times over the years and it needs it again. Your AFB is running rich, real rich. I want you to warm the engine up to full operating temp with the air cleaner assembly off. Let the engine idle and have someone shut it down. Look down the throttle bores and look for a "fog" to develope. If it does the float(s) are set to high. If it doesen't, float(s) are probably set near correct and jet size is to large allowing the engine to suck more fuel than it needs to run. Take a look at the exhaust stream and the color of the inside of the pipe also, what color is it? Black smoke or a fluffy black deposit inside the pipe means it's way to rich. jim __________________ 1984 K20 350M engine with 465,000 miles. Well, it's finally done!! Almost 2 years of work, but it was really worth the effort. Little stuff left to do is mount winch, wet sand & buff out and build belly pan\running boards. Body work takes lots and LOTS of beer!!!! God, Guts and Guns made America and God, Guts and Guns will preserve it! The worst thing you could do is get into my sights, but that don't matter, you'll never know it, cause you'll never hear the shotJim or Paladin whichever you choose.



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