Old question - you're sure of the TDC location you are basing this on? Just checking....... 27º seems like a lot to me too.

The Y-block stocker cylinder heads typically need some early low rpm advance to work well. I use 17º (10º initial plus 7º of live manifold vacuum advance) to get the best idle vacuum on my outfit. Stock "C" heads, factory cam and tuned for this arrangement. Several have told me they use 14º initial and ported vacuum to the distributor. Anyway, half of the 27º and a little bit more wouldn't be unusual.

 
 Steve Metzger       Tucson, Arizona

I marked a piece of tape with timing marks at 5* intervals up to 50* BTDC. With the engine thoroughly hot, it would go into gear without stalling immediately ONLY IF the timing was 27* or more. With that much advance, the stumbling problem also vanished.

Why could it possibly require so much advance?

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

I dropped the float as low as 5/16", double the specification. I didn't notice any difference until I dropped it that low. It became very difficult to start. When I got it started, the boosters did not flow at 1500 rpm, but had started flowing by 1800 rpm. I had to open the mixture screws up to 1.5 turns to get it to start, but once it started, it wanted them back at the usual spot of about 0.5 turns. Other than these things, every other aspect of performance was unchanged. Smooth, steady, miss-free running on the lowest step of the fast idle cam; missing and soon stalling at hot idle. Timing set to about 11* initial. Misses on the vacuum gauge involve a drop of about 0.5" Hg each. Timing light shows spark present always. Sudden throttle motion causes a stall. Blah blah blah.

At least it's consistent.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

Greenbird, thanks for your thorough and informative post. I have always intended to test and tune the advance curve. I have been waiting to sort this issue out to try it. I have assumed that the curve is not critical to hot idle issues because it is a static value (initial only) at that engine speed. I have checked and confirmed that it is indeed static at low RPM many times. A cursory study with vacuum advance disconnected shows that advance begins around 700 crank RPM and hits the second spring probably around 1800 rpm and 10* of additional advance. It looked like it maxed out around 20* of advance on top of the initial. Perhaps not optimised, but nothing highly irregular.

I was away on vacation for a week and am back to take another look at things. I decided to ignore the idle/miss/die in gear and take care of the stumble I have mentioned. I have always thought it was the accelerator pump. At first, I had an old pump in there. Then, the new one was binding in the bore. I examined the bore more closely and it had some "texture" so I attempted to polish it with my dremel tool until the new pump was moving smoothly. I put a little oil on it and installed; it wasn't binding at first but as soon as it had soaked in the gas long enough it was binding again. I removed it and put the old one back in, and ever since I have had a nice consistent pair of streams of fuel from the pump. It appears, to my eye, to be as sensitive as it ought and delivering an acceptable volume. The stumbling, however, remains. I tried all three pump rod positions, no change. I tried choking the engine manually AND maximum pump volume and still no change. To open the throttle suddenly FROM IDLE SPEED is to stall the engine. I tried completely disconnecting the pump and there was still no change in behavior.

I noticed that the main boosters are beginning to discharge at about 1500 rpm, when there is still at least 1/4 of the idle transfer slot exposed above the throttle plate. Even with the accel pump disconnected, before the engine stalls when I snap the throttle there is some discharge from the boosters. Combined with the fact that my mixture screws prefer to barely be open, I concluded that I was probably dealing with a RICH bog and not a lean one, so the float setting, though set to spec, must be too high. I lowered it 1/32" and repeated the tests with no change to ANY aspect of performance.

By the end of all of this the engine had reached that stage in its troubles where it became difficult to start. I set up my good timing light and saw a perfect spark signal as the engine spun over but wouldn't start. To start the engine, I had to treat it like it was flooded, even though there was not any fuel leaking in (above the throttle plates, at least).

After lunch, I intend to go out and continue to lower the float incrementally until I notice some kind of change. Will post back then.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

As mentioned it could be a combination of problems compounding. I would at this point start swapping parts out with known good ones if possible (carb, distributor) and if that did not fix it then start to look at other things but at least you will have eliminated then as the problem.

If I remember correctly, when I went to rebuild my 57 distributor, I found the ball bearing advance plate had wore a memory pattern in the bearing race that biased where the advance plate came to rest under vacuum advance and distorted the point gap as well. I got lucky on CL and found a NOS vacuum advance ball bearing plate. I also discovered nearly all the ground wire strands (wire from the points plate to the distributor case) were severed from flex fatigue and ended up replacing it with a new small braided ground strap that would not bias vacuum advance.

Jerome

Peeeot -One of our members - "oldcarmark" - once had a problem that I was reminded of as I read the various symptoms of your outfit. Initially, it wouldn't shift from park to drive without staggering and stalling ('56 sedan with 390 cfm Holley installed). The problem didn't turn out to be singular - it was many - and the sum result was an engine tune that didn't produce enough idle torque at low rpm. He could speed it up (to raise the idle torque) - and it would then slam into gear and stay running - no good, not a solution. He was very frustrated trying to get a handle on this - too many variables. On yours, it would seem the addition of heat decreases the idle torque further and makes the problem get worse - another variable.

His outfit had:

(1) Unsuitable spark advance - initial, increase rate, and total mechanical.

(2) Vacuum leak (excessive PCV passage in that case).

(3) Carburetor idle set-up incorrect (for his new Holley).

When a "tuner" takes on an engine/vehicle combo and works it up for a customer - they can take a "ho-hum" carbureted engine and literally make a whole different animal out of it. Most start by getting the ignition in order and going on from that. From the depth of investigation so far - you must have some useful components in hand - coil, condenser, cap, wires etc. I think you can do this tune-up yourself - just start with the distributor and go from there. For pros it is nearly always step one as the spark advance will dictate the carb tuning.

So what is the maximum mechanical advance in your distributor? - I'm assuming the flyweights are in good working order. If you "power time" the engine - determine the maximum mechanical advance by raising rpm until it stops - what is it? These Y blocks without special or reworked cylinder heads like a 36º maximum when there is no vacuum advance connected. If you set the timing at 36º (elevated rpm necessary) and allow it to return to idle - how far does the spark advance drop? This might require placing an auxiliary upper mark on the damper by measurement from the current "0".

Factory set-ups of the era had initial settings at idle of 6º and such. The engines actually produce better idle vacuum (and still start nicely) when that initial number is 10º and higher. Some of our clan are running as much as 14º+ initial with the Ford "timed" vacuum ports in use. In any case - the combination of your chosen initial and mechanical (only) should add up to no more than 36º. You will find that the engines run a bit cooler at idle when the timing is advanced as discussed here - the 6º is a bit retarded and builds water temperature from wasted heat. To get the distributor to operate in the desired advance range - from the initial you choose up to 36º - will take some alteration of stops in the flyweight mechanism. We can help you with this - the mechanical advance tuning is exclusive of the vacuum so that must be inactive.

The engine speed at which the advance can be "all in" - the rate of advance without "knocking"- is tied to compression ratio and gas quality. Swapping springs in the flyweight mechanism makes this happen. To be conservative, try to make the 36º be all in at 3000 rpm or there abouts. Getting the early spark curve correct can add many foot-pounds of torque to your engine - its worth the repetitive teardowns (if you don't know a guy with an old Sun machine). Ask Mark about this operation - he can probably field strip his distributor faster than I can explain the steps. You can get a variety of advance springs from various sources - Mr. Gasket #925D will get you a few choices.

Test the vacuum pot on the distributor to see how much advance it provides. With the engine running a fixed "high idle" speed and stable vacuum - apply manifold vacuum to the distributor and see how much it alters the spark advance. I've done this before with a long piece of tubing and another (high vacuum) "donor" vehicle running alongside. There are other ways to get the vacuum source - just try and be cognizant of the available change when it comes into play. A lot of the pots are adjustable if the upper end turns out too high when the vacuum advance sums with the full mechanical.

Next go to the carb and make sure it is in good condition to take tuning - float level correct - fuel pressure normal. Rule out every possible source of vacuum leak - my own experience has included poor fitting manifold gaskets, worn throttle shaft bushings and passing excessive air through the PCV. If you have PCV installed, a quick change is to simply plug the hose and shut it off at both ends, carb and manifold both. I used a 'Standard" '64 292 truck PCV on my outfit and it would literally run on the PCV air alone (throttle closed) - not good - had to orifice the hose to make the carb work correctly. It has to provide just a small amount of fuel to mix the PCV air - if the requirement goes too high, the mixture screws won't work in the proper range. If your engine doesn't have a PCV fitted it won't face this problem and you must look elsewhere.

This can go on and on - but the advice is to get the various "systems" functional and answering adjustment - and then optimize the next and so on. You will eventually reach the point where the engine produces the necessary torque to run at low rpm hot idle, in gear.

 
 Steve Metzger       Tucson, Arizona

Yes indeed! I would have guessed that that much initial would make things worse at idle, not better. I was playing with an MG midget just yesterday which had a clear timing "peak" which, if advanced or retarded from the peak, would result in a decrease of rpms. But I can offer no explanation for why 22 degrees would be OK on my engine. It must mean that the mixture is burning really slowly. Maybe I should try regular gas instead of premium? But I run stock timing with premium on my Chrysler and there's no issue there.

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive

You may think this is a stupid question. Just checking your terminology. Are you disconnecting the vacuum advance and plugging the carb when it is at 22 degrees advance?

Stuey, yes, I have the original style rotating-plate ball-bearing distributor. In an older post, not long after I got the car running, I had problems with stalling in gear. The problem went away (for the time) when I removed the distributor and completely cleaned and lubricated every part of it. I have not even driven 1000 miles since then. At the time, I was losing timing when I shifted into gear, but even then I was only retarding to 6*. I have made sure that the mechanical parts of the distributor are still clean and moving freely. I also made sure the oil pump shaft retainer was installed properly when I had the engine apart, so thankfully, it has not fallen into the pan!!

1954 Crestline Victoria 312 4-bbl, 3-speed overdrive