The new roller cam is great in my 454, has lots more low end and overall power. It ran good at first, idle set at about 900...but during a run to my local cruise place, I got on it hard...ran great, but suddenly started running super rich, and stalled when I came to a stop...I have done everything I can think of to fix the problem, but its still there...It wont idle below 1400 now, and even there, it runs like crap...still runs strong on the road, although smells really rich...I checked float levels, checked for dirt in the needle and seat area, set idle mixture, and did all this on 3 different carbs...it had a 750 Holley DP when it happened, and I switched to a 750 Edelbrock, same problem...then a 750 Holley Vacuum sec.....same problem again...I put in new plugs, new wires, tried a different HEI distributor, (known good one) set the ignition timing, checked valve timing, took off the valve covers and cranked it over to watch everything and look for broken parts and set valve lash...no problems there. I did a compression check, all are good, 200# plus, all within 5# of each other. Vacuum is about 9"... I have the fuel pressure set at 4# on the gauge...I had it at 7 originally, but it made no difference. It's an Edelbrock mechanical pump running thru an Aeromotive regulator. Im thinking of trying a stock pump and running it right to the carb just to eliminate that part, although if it shows 4# on the gauge, it should be 4#.. But is it?? I also checked all my hoses for a vacuum leak, but I thought with a vacuum leak, it would idle high, cause it's lean...mine is definitely rich, very rich..a little black smoke and it burns your eyes...The only thing I havnt tried is pulling the intake to see if there is a problem there with the gaskets, but I dont see how that would make it do what it's doing...but if you guys think the problem might be there, I'll give it a try. Im at a loss, I hope some of you can help!!! graemlins/clonk.gif John

John,
Try the "search" forumn above .If you type in "rich idle" you'll get tons of info with step by step procedures. smile.gif

Can you see fuel pouring out of the boosters when it idles?

first though would be powervavlve but the carb switcheroo you did didn't make a diff so that's out, if the spark is the problem the distributor swap took that out of the picture. If it won't idle below 1400 but was ok at 900 before things went bad I'd say you're probably right about the intake leak. Have you adjusted the throttle positioning screws/ idle speed screw? If you close up the throttle blade opening in an effort to lower the rpms what happens? does it want more fuel or more air to keep running? do any of the sparkplugs look different than the others oily?

Did you have to adjust the idle to 1400 or did it go there by itself.

Sounds like a blown power valve.

Do you think the distributor may have spun a little?

Happened to me before... Just a thought.

Thanks guys for all the replys...Found the problem after talking with an "old" drag racer that knows Holley carbs very well....Long story short, I just had to open the secondarys just a little to let more air in...after some experimenting, I got it right...now it runs great, idles at 900 again, doesnt stall when I stop.....all the good stuff is back!! Oh, and the vacuum advance is hooked up to ported vacuum, not manifold...that part runs better too. Thanks again for the ideas. John

glad to hear you got it figured out, it's not just the Holleys that need this, any carb with a larger cam in the motor will respond this way. The valve overlap contaminates the mixture at idle and the engine needs more air for a decent burn.

How do you open the secondarys just a little? I seem to run pretty rich too and have a holley 750 with a larger cam.

John,

Glad to here you got the problem figured out. graemlins/hurray.gif graemlins/hurray.gif graemlins/hurray.gif

How do like that new roller cam compared to your old solid? Is it what you expected? What were the specs on your new cam again?

ACLineman...look on the passenger side of the carb, where the shaft for the secondary's comes out..you'll see a cam that rests on a screw...the screw has to be adjusted from the bottom, its only accessable with the carb off...but first, run the engine till warm, then while it's idling, manually open the secondary's a little, just crack them..you should hear the idle pick up if that's the problem. Take a matchbook cover or something about that thick and put in between the little adjusting screw and the cam...see how it runs with that much in there. You'll probably have to turn down your idle screw to compensate. I had to go a little more with mine to get it to run good, but I runs much better now, not nearly as rich, and the exhaust doesnt smell nearly as much. When you get it running good, you'll have to pull the carb off and turn that set screw to open the secondarys as much as they were held open with the cardboard. That should do it if that's your problem.

Darren, runs so good now, I cant believe the difference..lots of low end, and solid right up thru the higher RPMs. I dont have the cam card right here, but it's 250/256 at .050, and .665/.654 lift, or right around there. Ground on a 108 LSA. I would recommend it to anyone, I was thoroughly happy with working with Howard's Cams. John

Thanks man, I'll check into it. Got this bookmarked !! graemlins/thumbsup.gif