Need guidance on what to try next to get this squared away. I here the issue 455 038 over 9:1 forged pistons with TA STG 1 aluminum heads and performer intake. TA29o cam and 67 Quadrajet carb. Was running fine but start running a little hot at the end of the season last year and finally looked at it last week. Seems the vacuum advance canister was bad on my Mallory distributor so swapped out with an MSD ready to run with V/A. The car previously would start fairly easy cold with a couple or pumps and a few minutes warm up. No problem starting hot. I did document the timing as about 19 initial and 32 full mechanical advance. Car ran fine. Swapped in the MSD and set to 30 with the 18 degree bushing which has the initial right at 14. Idle speed is set to 950 -1000 and vacuum is around 17 on gauge at idle. Set high idle screw idle at 1200 with the choke on. Car runs good, idles this way with A/C on around 650-700 in drive. Restart right up when hot with a slight pedal pressure. Carb was restored a few years ago and has been trouble free. Now the issue. I push the pedal to the floor to set the choke and crank no but thing just wont fire. Sometimes a pump with help, but it make an awful diesel, piston slapping sound like a knock until it gets to idle speed. Seems like it wants to fight getting to idle speed and stalls. I have tinkered with carb idle screws with a vacuum gauge to the last few days. Still the same and I am getting afraid of causing some damage trying to start it this way. It has at time blew back through the card.. also vapor coming back through the carb when attempting to start. I have gotten it closer today with is starting but still hard and has the knocking sound, which I think it is piston slap, but not positive. Things I tried: Lowering initial mechanical timing to 9. Any lower it barely idles if at all without vacuum advance. Adjusting fast idle screw mixture screw adjustment idle screw adjustment. Getting frustrated with this thing since it started better with the Mallory distributor. Any suggestions with help. Clyde
Is your choke closing all the way as it should when you pump the pedal once ? Does the accelerator pump give a nice shot of fuel with the smalleste movement of the throttle ? Is the power piston on the primary side of the Carb hanging up? You should not have to mash the gas pedal to the floor to set the choke, nor to get a good shot of fuel to kick the motor off cold with a duel plane Manifold! Once the motor does fire up the choke should pull open 1/8" for a motor that cid to get to high idle. If you have Vacuum advance at idle the motor will sound like a Mack truck since a cold motor can use that much timing.
X2, that's exactly what it sounds like to me. Check your firing order. It's very easy to swap the 5 and 7 wires when doing a tune up, wire replacement, etc. It will make some scary sounds when you do that. The ignition timing is not the issue. It will like lots of advance to cold start.
The firing order is correct. I checked it twice. The choke does set when slightly depressed that doesn't seem to be the issue. Today is started with depressing to set choke, few seconds of turning over no start. 2 pumps and off it went. Figure better. This evening I set the choke, and cranked it to off with the dieseling sound slight touch of the pedal and it smoothed out an up to fast idle. Getting closer just not sure what this is. Just disappointed I couldn't get a new vacuum canister for the Mallory distro and avoided all this.
Try just one pump? Before switching carbs I needed a 2 pump or 3 depending on how long it sat. After putting the new carb on and getting it set correctly, I only need a half pump. Too many and it's flooded, runs way too rich, chugging etc. Half pump sets it to high idle, fires up instantly and I kick it down to medium idle after a few seconds and let it warm up for a minute before kicking it all the way down.(For summer anyway). It used to die on me if I drove it too soon and not letting it warm up, now it is like it should be. I had vacuum leaks in the throttle shafts causing me fits on the old carb which is something you could check for also. Larry will know more than anyone on this but I'm not sure what the vacuum advance would have to do with cold starting - where is yours hooked up to? I messed around with using vacuum right off the intake rather than ported vacuum on the carb and that made my car run horribly as I didn't get the timing set accurately that way. I switched it back.
Define "cold out". Do you mean 60F or -30F? Unless it's below zero, you DO NOT need multiple pumps of the pedal. At 60F, you shouldn't even need a half-pump. No more than 10 seconds needed. Usually less. Anything more than that is for the operator, not the vehicle. Is there any fuel in the float bowl when you begin this procedure? I'm surprised you aren't flooding the engine with that much fuel--or--the engine doesn't start because the float bowl is empty. I don't know what that could be. I'd try to eliminate a failed fuel pump, though. Engine-driven fuel pumps can knock like a rod bearing when the internal spring gets weak or breaks. You're correct, there's no need for multiple pumps of the gas pedal unless it's genuinely cold out. From the moment you tap the gas pedal to drop the fast idle cam from the highest-step to the second highest step, that engine is ready to be driven with no stalls, surges, or hesitation. If you need more warm-up than that, the choke or something else in the tune-up still isn't adjusted properly.
Didn't have much time to look at but after suggestions on checking the choke it looks like it was never getting the fully closed position. Apparently my divorced choke spring was a little soft... I replaced it with a new one and adjusted and looks good now. So will try again tomorrow on the cold start. I really feel this is in the carb adjustment.. and I just don't seem to have the touch. Once it starts and warms up the thing runs good.
Captain Obvious showed up today and I though I have messed with the carb and everything with no avail.. lets start over --- starting with the change from Mallory to MSD distro. Well dug out the manual and seems the Mallory worked with the resistor wire and MSD doesn't.. not sure how I over looked it. I thought I ordered a wiring harness with that changed years ago, but now as luck would have it that one went on another car and this one was kept stock.. Maybe since I am working on wiring I just add a Ignition box. Now on to fix this non sense and go from there. DOH!
When something suddenly goes bad after you have made a change always take 2 big steps back and look over what you have done even if it seems it may not be related to the issue you are having! And never if you can help it do more then one change / mod at a time so you can prove things out and not chase your tail around for hours or days!
Looks like I got it working... spliced in the 12 volts to the coil and starts much better... the hard starting seemed to be all choke related. Once the spring was changed it started, but still labored along slowly with all the piston slap... a few adjustments with the fast idle screw and now it starts every time. Seems like I just lived with some issues for so long it took a change to bring them to the front. Thanks for the help.
