BLKMGK Posted September 13, 2001 Share Posted September 13, 2001 Okay, took the car out tonight for the longest drive yet. No jumping on the gas just a cruise to a local Z club meeting. Yeah, the Holley blue is LOUD! Work on that later. Question - at part throttle the car bucks and pops. RPM doesn't seem to matter, part throttle is miserable. Give it gas and it takes off pretty good till I let off. Feels liek it might be missing some too as it Rs up but I'm not sure it's ignition making it jump around. What's making it pop and jump? Lean? Rich? Would it be running on the idle circuits at that point - 3K rpm or so? Power valve? Haven't checked vacuum at idle since I got all cylinders running but it's still idling at about 1500RPM (sigh). Appreciate any ideas, going to read the Car Craft carb tuning guide tonight too Just need some ideas to smooth out the part throttle and want to get the idle down. Otherwise the drive was fine. Exhaust booms and drones a little but the pump is loudest when the windows are up (lol). Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 13, 2001 Share Posted September 13, 2001 High idle may be due to too much initial timing. My car idles at 1500 with ingition locked at 34 deg. Car may also idle high because the butterflys are open too much. If this is the case the idle circuit is exposed and will not work. Take the carb off and look at the position of the butterflys relative to the idle transfer slot. No more than .040 of the slot should be exposed. If more is exposed you may solve the problem by drilling a small 1/8 hole in each butterfly. Or yo can open the rear butterflys up a bit by the idle adjustment screw on the bottom of the carb. The above will make off idle transition a nightmare. Make sure that the accelarator pump arm is properly adjusted. Follow the step in the Car Craft artical. It is a good one especially for checking lean or rich condition at idle. It has some tips that I have never read before. After adjusting make sure the car after properly warmed will rev in nuteral. It is does not it certainly will not in gear on the highway. My car will go from 1500 to 6500 quicker than you can lift your foot. Go the the Jet intranet site or to barry grant site for better tuning tips. These have helped me out very much, but are fairly advanced and can get you into trouble in a hurry if not carefull. Make note of all changed so you can go back to your base setting. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 13, 2001 Author Share Posted September 13, 2001 Will try to look at the idle slots tonight. Idle is as high as it is becasue I've had to turn the idle screw in to keep it up. If it gets down around 1000RPM it dies and I don't think the cam is that radical. If I turn down the advance from about 18BTDC the idle gets erratic and it dies. Will try turning the idle screw down and adjusting idle circuit for highest vaccum. What should base timing be approx.? Fords are about 10 or 12 so being as high as 18 has had me worried The Car Craft article mentioned as high as 20BTDC I think Chevies are weird! Car Craft article also seemed to call into question the power valve. I'm not sure what number I'm running right now or what my idle vaccuum is but I'll be checking that too. Quote Link to comment Share on other sites More sharing options...
Tim240z Posted September 13, 2001 Share Posted September 13, 2001 I had a similar problem, WOT was great but anything less was terrible...turned out that the needle and seat was not sealing (little dirt in the float bowl), so at anything less than WOT it was flooding slightly. This could also happen if fuel pressure is too high, forcing fuel passed the seat...Holleys like volume not pressure. Easy to check for this...look down the throats of the carb at idle and see if fuel is bleeding in the secondaries. Hope you get your beast debugged soon, sounds like you are having an epic battle Tim Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 14, 2001 Author Share Posted September 14, 2001 Hrm, it's better! Got the float level set a little better first. Then I lowered th eidle as far as I could with th eidle adjustment - the idle circuits were NOT responsive previously. Once th eidle was down I turned one of them to the right and the motor nearly died - good we have adjustment! I then went back and forth turning the screws OUT. I think th emechanic at the muffler shop may have turned them in some but with the idle as high as it was it did nothing. As the idle circuits were twiddled the idle speed went up and I lowered it with the screw. I actually got it to the point where the idle screw is all the way out and the idle was still above 1K. I checked the timing and turned it back some. I believe the initial is now closwer to 15 but typing this I've just realized that the vaccuum hose was hooked when I did this (doh!). Fix that tomorrow I guess, dammit. Anyway, it seems to idle a bit better but vaccuum is around 15 tops and a little rough. Will adjust timing better tomorrow and see how the idle circuits are setup. At this point I'm betting my power valve needs to be looked at too. Getting there, appreciate the suggestions, keep 'em coming! Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 14, 2001 Author Share Posted September 14, 2001 Aw geez! I went out there tonight before heading for bed to look for my Water Wetter to put in. Couldn't find it but I spent a few minutes looking things over - puzzled that I'd had to fiddle with the idle screws so much and still had such low vaccuum. I'd also been wondering why my brakes still seemed odd - hard sometimes, softish at others. Well, I happened to notice that the blue hose for my brake booster was routed along my firewall and was straight.... except that it's supposed to curve down into the port on the carb! I followed it and found the open end. I checked the port on the carb - yup uncapped!! Someone working on the car, NOT ME, unhooked that sucker and put it under a clamp on the firewall. They never hooked it up and I never noticed. Worse, I sprayed carb cleaner under there and while it sometimes seemed as if the idle changed it was so little that I thought I was imagining things. Kripes, with a leak like that I'm surprised it ran at all! When I had the idle screw all the way out and it still idled high I wondered about a leak and even poked around some but never spotted this. I'm an idiot! I'm now going to have to retune this sucker - I'll bet the idle circuits are full rich now (sigh). Geez, when this is done it's going to run like a raped ape Hrm, I might actually be starting to understand this carb stuff too. If I hook up the A/F gauge maybe I can tune the rest of it too.... Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted September 14, 2001 Share Posted September 14, 2001 TTTT Thats GREAT! I know it will run now! Please share the results. I have never seen a raped ape but it is probably similar to a kerosened cat. I am glad to know that you whipped it! Quote Link to comment Share on other sites More sharing options...
Lewis Maudlin Posted September 14, 2001 Share Posted September 14, 2001 I concur with Tim240. I had the same problem. The float was not sealing. I had a little dirt in there, but the main problem was too much fuel pressure from the Holley Blue. How much pressure are you running? I finally got rid of the dirt (rust) and put the Carter pump on. Now I idle about 800 and cruise smoothly down the street. Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 14, 2001 Author Share Posted September 14, 2001 I've got the blue turned down around 6PSI if I remember right. Had to fix a leak at the regulator last night too I've learned nto to ignore "small" fuel leaks. Need to check over the pump fittings in back too just to make sure nothing is loose - was fine last I looked though. All in all some of the problems I'm finding have been pretty silly. I figure I'll turn the idle mixture screws in about three turns, turn the idle speed screw in a bunch, prime it, and fire it up. Will see what the idle vaccuum is, check the timing sans the vac advance, and then tune from there. I probably did more harm than good last night but between the Car Craft article and the Holley instructions I'll get it back on track. I've not looked at jets or PVs yet, might try to tune jets after getting an O2 sensor and temporarily hooking up an A/F gauge. Fun 'n games! Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted September 15, 2001 Author Share Posted September 15, 2001 Sweet! Idle is down around 900RPM but a bit lumpy at that speed Idle screws don't seem to have too much authority but I think it's as good as it's going to get. Idle vaccuum is around 12PSI but that seems to be enough to run the brakes. Car even pulls when lugged down in 6th gear Tip in is fine but I suspect it's still running rich. An A/F meter ought to allow me to check that. Overall, 100% improvement in driveability now. Looks like the Saturday drive ought to go well. Hope to setup the speedo beforehand too. Once the CVs are in I hope to drive the wheels off of it Quote Link to comment Share on other sites More sharing options...
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