Carb problem
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Carb problem
Ever since I installed a new out of the box 600 cfm Holley I've had a couple of problems.It seems to idle very rich,and it tends to surge when I first take off. I adjusted the carb with a vacuum gauge and it turned out to be about one and one quarter turns out to the highest vacuum reading. I idle at about 750 rpms and I get black smoke and of course fouled plugs.I lowered the idle mixture screws each to 3/4 turns out and didn't seem to make much diffence. I also checked float levels and they are correct. The engine is a stock 327 350hp except for a new Mallory dual point dist. and a set of headers. The advance is set to 36 degrees at 2900rpm. The fumes are so bad when I idle in the garage I'm afraid I'm going to kill my cat. Thanks for your help in advance......Gary
Instructor
Joined: May 2007
Posts: 105
Likes: 2
From: West Paterson, NJ
A new Holley out of the box, while not tuned perfectly, should be acting better than you describe. 600 cfm should be fine for a 327 too.
I'd go back to your new distributor and make sure it's in tune. Check firing order, set dwell, set static timing to spec @ about 550 RPM before the centrifugal advance kicks in. Do this with vac advance disconnected if so equipped. (I'm assuming the new dizzy should be set to stock specs, can't speak from experience on the dually points...)
When all that checks out, check your carb installation for vacuum leaks. Then go through idle, mixture, and fast idle/choke settings.
Is this a vac secondary carb or double pumper? Jet size?
Hope you're leaving the garage door open during idling
I'd go back to your new distributor and make sure it's in tune. Check firing order, set dwell, set static timing to spec @ about 550 RPM before the centrifugal advance kicks in. Do this with vac advance disconnected if so equipped. (I'm assuming the new dizzy should be set to stock specs, can't speak from experience on the dually points...)
When all that checks out, check your carb installation for vacuum leaks. Then go through idle, mixture, and fast idle/choke settings.
Is this a vac secondary carb or double pumper? Jet size?
Hope you're leaving the garage door open during idling
Melting Slicks
Joined: Oct 2005
Posts: 3,073
Likes: 3
From: New Jersey. The deer ate my Garden State.
I had the same problem with my '66 327 300hp coupe. I adjusted everything that I could adjust then, finally I broke down a purchased the correct Holley for my car. After some small adjustments, the car runs perfect. The aftermarket Holley carb always had some vacuum leaks that I could never seem to solve. Do you have the correct base plate?
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
The carb has vacuum secondaries and it seems like if it had a vacuum leak it would run lean. The vacuum gauge doesn't indicate a leak. This is a brand new 2818 which is the correct carb for my motor.Really has me stumped. Could it be a timing issue?
Melting Slicks
Joined: Jul 2004
Posts: 3,493
Likes: 123
From: Kissimme now from LI,NY
I don't think there are any NEW 2818's.. It should also be a 2818-1, and if you really did get a new one, then good for you!!!... I got a rebuilt 2818-1 and it ran like sheet until I found out that the moron glass beaded it and one of the beads hung up my float intermittenly. It was also in my metering body... Where did you get it and or who rebuilt it... You didn't happen to buy this from flea bay did you??? I saw that carb on there??
/joe
/joe
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Yes the carb is a 2818-1 and it is brand new. Holley is now makeing them again and most vendors(Corvette Central) are selling them for 595.00. They are not date coded but they have 2818-1 stamped on them and I think the GM part number. Thanks for your help. I guess I will have to tear it down and see maybe if I picked up some dirt or somethig.
Race Director
Joined: Oct 2000
Posts: 15,044
Likes: 79
From: central FL, near the beach.
i used to have frequent dirt problems in my 72 despite a big filter(fine rust dust still gets thru).
after i changed the tank & all lines in '99, no more CRAP! like a new car!
after i changed the tank & all lines in '99, no more CRAP! like a new car!
Last edited by Matt Gruber; Jun 12, 2007 at 02:25 PM.
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Team Owner
Joined: Oct 2000
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From: Washington Michigan
Throttle plate is too far open, and it's idling on the transfer slot instead of on the idle mixture screws. Back the idle speed screw down, make sure your throttle linkage is properly adjusted so the lever on the firewall isn't holding it open, and re-adjust the mixture screws. 
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Thanks John. Thats got to be my problem. I've tried everythig else. I'm not quite sure what you mean by transfer slot. I will make the adjustments first chance I get and post the results.
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Well I just finished checking my throttle and it is closed. The idle adjustment screw doesn't even touch and is not even in play. It appears that at idle, I'm running on my idle mixture adjustment only..... which now is 3/4 turn out each. One thing I did find out today,I checked my vacuum and it was 12 hg at idle and steady. Seems low to me. I swear the last tlme I checked it,it was 16 hg and steady. Hmmmm might be a clue there. Oh well, tomorrow is another day.
Navigator
Joined: Feb 2007
Posts: 9
Likes: 0
From: 68 Years in Wooster Ohio
After you first installed carb, prior to adjusting, did the engine backfire at any point ? If so, your power valve can get damaged very easily. Swap out a new one of same size & life will be good. Happened to my 64 365hp several years ago. Good Luck..........Heavy on fuel at idle.......
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
After you first installed carb, prior to adjusting, did the engine backfire at any point ? If so, your power valve can get damaged very easily. Swap out a new one of same size & life will be good. Happened to my 64 365hp several years ago. Good Luck..........Heavy on fuel at idle.......
Burning Brakes
Joined: Oct 2004
Posts: 1,210
Likes: 1
From: fighter pilots make movies, bomber pilots make history
John Z suggestion is probably right 90+% of the time; however, the secondaries can be cracked open slightly as well and slobber excess fuel. The secondaries may not be closing completely and need to be corrected.
Joe
Joe
Thread Starter
Melting Slicks
Joined: May 2007
Posts: 3,461
Likes: 18
From: cooper city florida
Thank you devil dog. I just got off the Holley tech line and they suggested the same thing. I turn the idle mixture screws all the way in, with the throttle completely closed and the engine still idles. Holley said its has to be getting fuel from somewhere and the secondaries are a good bet. I will check it out as soon as the rain stops and advise.
