Carb help
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Cross-Country
Joined: Feb 2011
Posts: 87
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From: Yucaipa
Carb help
Ok i ended up buying a brand new holley 600cfm avenger manual choke because i took the holley 550 of to run another car i have. Ok with the catb i took of the engine rane smoothly and with the new carb installed it shakes at idle. Any ideas what could be happening. Ive adjusted the mixture screws and stuff to try and get it to run better but no luck. Im thinking of putting the other carb back on but i really don't want to because it doesn't have the kickdown hook up on the carb. The new carb i bought also doesn't have float bowl adjustments. I didn't realize i purchased the avenger until after i installed it. Another thing can i run with now kickdown hooked up without hurting the tranny in the long run?
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
You have a vacuum gauge? Did you use new gaskets? Make sure there aren't any vacuum leaks is what I'm wonderin'.
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Cross-Country
Joined: Feb 2011
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From: Yucaipa
Is the Holley 600 Avenger any good of a carb? I can return the carb at the parts store and get a different one. I know almost all the people that work in there and they wont ask no questions plus the carb has a 90 warranty. Anyways yes I used all new gaskets when I installed the new carb.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
I'm sure it's a fine carb, it just needs to be adjusted right. The most important adjustment is to choose the right size carburetor in the first place. No idea what you got or what it wants. But unless you're drag racing at WOT most, if not all, people buy way too big of a carburetor. It wastes gas, won't idle for ****, and may actually have less power. I know kickdown is CRITICAL, too. Don't guess, double check you have the right linkage and it is hooked up correctly or you will lunch your transmission.
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Cross-Country
Joined: Feb 2011
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From: Yucaipa
I'm sure it's a fine carb, it just needs to be adjusted right. The most important adjustment is to choose the right size carburetor in the first place. No idea what you got or what it wants. But unless you're drag racing at WOT most, if not all, people buy way too big of a carburetor. It wastes gas, won't idle for ****, and may actually have less power. I know kickdown is CRITICAL, too. Don't guess, double check you have the right linkage and it is hooked up correctly or you will lunch your transmission.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Yeah, they are all 390s on sale day. I'd measure the stroke, it's really the only way to tell iirc. Most likely 360. Easy to to do, use a rod to measure the total travel of a piston through a spark plug hole, from BDC to TDC.
Then decide what you want to do with it, a heavy hauler or what. Not knowing any better I bought a pretty good sized Holley 500 CFM two barrel for my truck. It never idled right and the plugs looked like they'd been spray painted black. My fault, but the clerk didn't help much. See, too big a hole up top means the fuel/air velocity is too slow, the fuel doesn't atomize well. This is what I mean by getting the right size carb.
Right now with my truck I'm shooting for about 15 and a half miles per gallon, it runs better than ever and starts and idles real good. I'm using the same stock size carb that Ford supplied. Find out for sure what your engine is, then find out what it came with - Probably an Autolite 2100 with a 1.08 or 1.12 venturi size. Maybe 4100? I dunno. One of the best carburetors ever made. Annular discharge boosters, easy to work on, parts easy to get. Webpages on how to rebuild and setup and adjust, and it will bolt right up, naturally. What's not to like? Have fun!
Then decide what you want to do with it, a heavy hauler or what. Not knowing any better I bought a pretty good sized Holley 500 CFM two barrel for my truck. It never idled right and the plugs looked like they'd been spray painted black. My fault, but the clerk didn't help much. See, too big a hole up top means the fuel/air velocity is too slow, the fuel doesn't atomize well. This is what I mean by getting the right size carb.
Right now with my truck I'm shooting for about 15 and a half miles per gallon, it runs better than ever and starts and idles real good. I'm using the same stock size carb that Ford supplied. Find out for sure what your engine is, then find out what it came with - Probably an Autolite 2100 with a 1.08 or 1.12 venturi size. Maybe 4100? I dunno. One of the best carburetors ever made. Annular discharge boosters, easy to work on, parts easy to get. Webpages on how to rebuild and setup and adjust, and it will bolt right up, naturally. What's not to like? Have fun!
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
Sounds like a vacuum leak to me. Try cupping your hand over the carb while it's idling and see if it idles better. This cuts off air going in so it's a sure sign of a vacuum leak if there is one. Not to insult you but here are a few of the top O' my knoggin'. Vacuum hose nipple on the carb not capped off since it's not in use. PCV hose nipple on carb not being used and not capped off. If there is a spacer between the carb and intake make sure you replace BOTH gaskets. Above and below the spacer.
BTW, whether it's a 360 or 390 it should handle that Holley as far as size goes. Holley loves to sell carbs with the "black" color coded secondary diaphragm spring installed. Which is the strongest one so the secondaries will open slower and maybe not all the way. Kinda makes a 600CFM carb only supply approx 500 CFM unless the engine can take the full 600.
BTW, whether it's a 360 or 390 it should handle that Holley as far as size goes. Holley loves to sell carbs with the "black" color coded secondary diaphragm spring installed. Which is the strongest one so the secondaries will open slower and maybe not all the way. Kinda makes a 600CFM carb only supply approx 500 CFM unless the engine can take the full 600.
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Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
One method I read about to check for vacuum leaks, he claims they are hard to find because most people don't check for them right in the first place. Says to throttle it down real low and lean it out with the mixture screws so it's barely idling. THEN go by with the propane or carb cleaner or what have you, and if there is a vacuum leak it will be a lot more responsive and positive test. Haven't had to try it, stands to reason though.
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Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
Wait a minute, are you using a 4V intake manifold or the original 2V intake with an adapter spacer? Only do a 4V carb on a 4V intake. And since your kick down rod is meant for a 2V and where it's placed on the engine your kick down rod will prolly be too short now. Holley makes an extension specifically for this. Part number 20-41.
What is the list number on the front of the air horn? Once you get it idling correct it may need different jets and secondary spring to dial in to your engine. Please figure out which you really have also. 360 or 390.
What is the list number on the front of the air horn? Once you get it idling correct it may need different jets and secondary spring to dial in to your engine. Please figure out which you really have also. 360 or 390.
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Cross-Country
Joined: Feb 2011
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From: Yucaipa
My truck is a 1969 F250 and original came stock with a 2bbl 6.4L 390. Te old man I got it from said its a 390 and ive known him since I was about 10years old. Im 25 now. Anyways It could still be a different size. I do still have the stock intake and 2bbl carb that came off the motor. I took the 2bbl off because it wasn't working properly. I just recently sold a 73 F250 that did have a 360 in it and had a 4bbl intake and I put a new holley 600 and it ran great. Idk I should find the #on the block and run them to know forsure what it is. Also ive ran lots of SBF and some chevys with 600cfm holleys and never had a problem with the carb being to big and all of them idled nice and smooth and had nice response. So I can see how in my mind a 600cfm could be to big for a big block.
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Cross-Country
Joined: Feb 2011
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From: Yucaipa
Wait a minute, are you using a 4V intake manifold or the original 2V intake with an adapter spacer? Only do a 4V carb on a 4V intake. And since your kick down rod is meant for a 2V and where it's placed on the engine your kick down rod will prolly be too short now. Holley makes an extension specifically for this. Part number 20-41.
What is the list number on the front of the air horn? Once you get it idling correct it may need different jets and secondary spring to dial in to your engine. Please figure out which you really have also. 360 or 390.
What is the list number on the front of the air horn? Once you get it idling correct it may need different jets and secondary spring to dial in to your engine. Please figure out which you really have also. 360 or 390.
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Cross-Country
Joined: Feb 2011
Posts: 87
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From: Yucaipa
I messed with truck a Lil today and turned the mixture screws in all the way and the engine was still running so there is definitely something wrong withe carb or a vacuum leak. I haven't had a chance to check leaks with carb cleaner but will tomorrow
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
A bad Power valve jet causes it to run on when the air/fuel had been close off.
If new Send it back. If a new used one then may be why it was sold..
I've seen a lot of Carb being resold as being from a return outlet that guys buy and flip if they have troubles.. Or put in a power valve..
Orich
If new Send it back. If a new used one then may be why it was sold..
I've seen a lot of Carb being resold as being from a return outlet that guys buy and flip if they have troubles.. Or put in a power valve..
Orich
Hotshot
Joined: Mar 2013
Posts: 14,255
Likes: 199
From: Phoenix, Az.
2X Orich. Mixture screws all the way in means carb is giving it gas from where it's not supposed too. Note, recently I bought a 80457-2 Holley carb off ebay. Thing looked brand new. Bought it to rebuild and flip. Once I got it and saw it I wondered why the seller didn't just warranty it. All that was wrong with it was the power valve was LOOSE. And I mean not even finger tight. Rear bowl float was adjusted WAY too high, and the secondary diaphragm was bad. Yours sounds like prolly the same problems. Maybe there is a lazy worker at Holley. Choice is yours, repair it or warranty it.
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