I gave another blast of carb cleaner again in the idle ports. The timing is now at 20 so there isn't much room left if any to raise it so I thought I would try it @ 22 and see if it detonates. I've seen different people on here go to 24 even with larger cams but I'll see how it responds. Its a 10.5 to 1 alum head motor with an ST-21 solid cam, 254 duration. Everything else with the way it drives is great. I'll try it again with the springs out when I check the timing. It will be Wed before I look it all again. At this point I'm at a loss if the raising the timing doesn't help.

if you are at 20 that is in the ballpark & plenty high for now, I didn't know it was already that high.

Here's a comment on a reply in this thread.

It is not recommended to run the car with the battery removed.

The sensing circuit will tell the voltage regulator to kick up to the max, say 19 - 20 volts. Any light or electronic gear on the car may fry due to overvoltage.

I once fixed a car that had been on a railcar and had to be driven off, but the battery was dead. They borrowed a battery from a passing taxi (not in the US) and used it to fire up the car. They turned on the lights, got it off the railcar, and then with engine running pulled the battery and put it back in the taxi. As they were removing the battery, they noticed all the lights burning out. The alternator also failed, developed a short in the windings. So we got to replace all the bulbs and the alternator on a brand new car.

Profit from my misadventure, don't do it.

R.

and for those guys who like to check the charging system on our old heaps with the 35 or 45 amp alternators by removing one or the other battery cables, take heed of the above. same thing can happen, especially when you re-install the removed cable and the charging system surges. as said : "don't do it". use the proper meter[s] to diagnose the problem the correct way.

Definitely on the right track with carb and fuel system. Try to get it to idle in gear even if it's at 1,100 or above. My suspicion is that the carb is losing it's vacuum signal at the lower rpm. The bouncing rods say to me that the carb is sensing an open throttle do to the low vacuum signal and trying to go into the power circuit. My roller cam 400 does the same thing if the idle falls below about 1,000 in gear. With that cam and heads you might be better served with a Holley.

I hear you on going to a Holley and will make a few more adjustments and see if I can get the Edelbrock to work with what I have. I looked at some 850's on the Summit site earlier today. I'm not ready to go that route just yet but will make the change if necessary.

No matter what it usually turns out to be something simple

That it the truth for sure and is what keeps me from throwing parts at it until I rule out some more things. Timing, vacuum leak, carb tuning, etc. I feel I am closer than I was a week ago.

Really interesting problem.

I'm inclined to also think you're running lean, or on the ragged edge at idle. (hate those step up rods) I've had problems with throttle shafts leaking, and screwing up idle quality. Other than that, you're obviously competent enough to know if the base of the carburetor is warped, or the gasket not sealing well. If you spray carb cleaner around the base of the carb while idling does anything happen?

The air/fuel mixture density in the combustion chamber will be quite low compared to when the throttle is opened appreciably. That type of mixture tends to burn more slowly, and in my experience was a primary reason for the vacuum advance, which you say you don't have connected.

I know I struggled with a warmed over 331 SBC years ago that had a Mallory dual point in it, with no vacuum advance. Played with springs, weights, on and on, and things really only got better when I installed a distributor with a vacuum advance. It really cleaned up with idle/off idle characteristics of the engine.

Update: I blocked off the PCV port with a vacuum plug, no change to speak of doing that. Started playing with step up springs from the strip kit. I went down to orange spring and it cleaned up the idle a nice little bit. I tried to yellow, the next lowest rated spring and the idle got a little worse from the orange. I went back to the orange spring and idle is back to be better than it was but I still feel there is some tuning left in it. I raised the idle speed and a little better yet even. I left the timing at 20 deg. I cant say for sure how the part throttle cruise is or more performance spirited driving is with the spring change but I'll exercise it on Saturday and report back. Overall, I feel progress was made.

Peabody: I have sprayed around the carb base and is well sealed. When I rebuilt the carb a replaced the thick spacer gasket.

We're getting closer!

Yes, slowly but surely. I appreciate the help from everyone.

I'm back to addressing the situation and have tried every step up spring in the kit, set the timing from 15 to 21, vacuum advance hooked up and I still have basically the same problem as before. I near the end of my patience here. It runs great everywhere else except the idle.

[/quote] I near the end of my patience here [quote] At this point just me I would (1) plumb a can of race gas or pump gas with no ethanol to the pump inlet & if no change then (2) borrow another carb.

I guess I'm not understanding how race gas can help but I can look into getting a few gallons. Can you explain how it can help? Thanks Robert.

the only reason I suggested race gas is that alot of areas of the US of A do not have the option of non ethanol gas at the pumps so that test would elim or confirm that the problem is the ethanol & it is infamous for causing idle problems, however obviously if you have non ethanol in there right now then we can bypass that test.

No its 10% ethanol 91 oct. That is the highest octane and only pump option for this area unfortunately. Would avgas be a reasonable thing to try?

I'm just curious too if I would run into this same situation with a 4150 Holley, like an 850 mech secondary carb.

No matter what I have done the metering rods wont stop bouncing. If I could get that corrected I would have progress I feel like. A previous post on this thread mentioned the vacuum signal being the cause and the carb is "confused" as to whether its on the idle or main circuit.

(1) I believe so. it does have differenct characteristics than race gas I'm sure but we'd at least have the gasahol out of there for a test (2) if the ethanol is the cause then likely yes, it'd act pretty much the same with another carb, the heat vaporizes it easier (not a problem in modern FI engines but problematic for us). if non ethanol does not fix it then I would borrow/try another carburetor as it might be strickly carb related/not fuel related. However when E10 was intro'd here in the 80's, cars dieing at stoplights from it were epidemic. EDIT on your 2nd post yes they should not be bouncing, can we block them all the way down (on cruise) for a test

Read up on vacuum gauge readings, might help point you.

http://www.secondchancegarage.com/public/186.cfm