292 y-block distributor puzzler

[highcking]

I recently determined that the dual vacuum retard/advance unit on my ‘56 Fairlane was no longer working. I have an NOS spare that I tested and installed today. Tricky to do on the car but it came out ok. Went to start — no dice. Car behaves like the timing is way off. I did not move the distributor, and reused the same cap and rotor. I did remove the plug wires but reinstalled them using the “1” stamped on the cap and the clockwise firing order stamped on the block. If I crank the motor to TDC, it looks like the rotor is pointing to the #1 plug wire.

What gives? The shop manual is not helpful. I thought of rotating the distributor a bit - but how do you do that with two steel vacuum lines attached? I also tried rotating the plus wires one position at a time and that did not help. Car started instantly before. What am I missing? Should I surrender and go with an updated distributor?

Bill in Virginia

[scicala]

To start with, I think you said you put the plug wires on the cap for clockwise rotation. Y-Block V8's were counter-clockwise distributor rotation. Need to re-do the wires if that's the case.
I wouldn't move the distributor if it ran good before. If you do set the timing once it's running again, you need to disconnect the vacuum lines to the distributor first and plug the ends of the lines. Then set timing and re-attach vacuum lines. The spec is around 6 degrees, but they run better if the base timing is set at about 10 degrees BTDC.


Sal

[highcking]

Really counter-clockwise? I was using a Suntune Card that said “C” which I took to be clockwise! I will check on this. Thanks for the reply!

[highcking]

Sal - many thanks, started right up, no thanks to Suntune. Bad news is that the replacement advance unit seems to be doing the same as the old unit. It retards the timing at idle but doesn’t advance it at higher rooms. Timing is sitting some number of degrees ATDC at idle. Suggestions?

[highcking]

That’s higher rpms, not rooms!

[dmsfrr]

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Originally Posted by highcking

... Timing is sitting some number of degrees ATDC at idle. Suggestions?

What is ATDC? After top dead center?

At idle with the distributor vacuum lines disconnected (and plugged) the timing pointer should be 6 to 10 degrees 'Before' TDC, on the advanced side of TDC.
Example photo #2: not a Fairlane pulley but the timing marks are laid out the same way.

Check & set the points before setting the timing. If they aren't correct the timing won't be either.
.014 to .016 inch point gap, or 26 to 28 degrees Dwell.
.

[scicala]

What dmsfrr said is 100% correct. Check and reset your base timing at idle like he said.
Also, you won't really be able to see the timing advance in neutral with a timing light since the advance is based on venturi vacuum (suction) and it won't be enough without the engine under a load to see a significant timing advance.
It sounds like your timing is retarded at idle currently. Make sure the points are correctly gapped first, since a different gap changes the timing slightly like dmsfrr said.


Sal

[highcking]

Many thanks for the replies. Let me be a little clearer. The timing is set at 6 degrees BTDC with vacuum lines to the Loadomatic plugged. When I reconnect the two vacuum lines, with the engine still at idle, the timing retards into the after top dead center region. Revving the engine does not move the timing mark. I see Sal's point that revving in neutral won't advance the timing. Is it the case that the Loadomatic retards the timing at idle to avoid "ping?" I've had this car many years and never really looked into this. If this is correct behavior, then my other Loadomatic unit was OK.

The problem I've been chasing is this. The car will accelerate to say 40 mph smoothly. Then, if you squeeze the accelerator slowly, the engine just sits there at the same rpms. If you pump the acclerator a few times, the engine will respond and the car will accelerate as it should. I've never had another vintage car do anything quite like that. It's the old "carburetion or ignition" issue.

[40 Deluxe]

No, the timing should NOT retard at idle with the lines connected. And, timing should advance when revving in neutral if both diaphragms are good. After all, both venturii and ported vacuum are present at a fast idle, say 15-1800. Have you checked the diaphragms for leaks? A good old-fashioned suction/tongue test is all that's needed. If you can get a good seal with a vacuum hose, just suck on the line and block with your tongue for a few seconds to see if it holds vacuum.

[highcking]

I have tried the "mouth suction" test on the NOS unit and it seems to respond properly. Even if it didn't, I can't see how the timing retards. Let me retest tomorrow to confirm the facts as I have stated them. I am pretty clear that revving the engine did NOT result in timing advance. This is apparently the result of the design --- there is no centrifugal advance, just that weird little valve mounted on the Holley 4000.

[KULTULZ]

Deleted

[highcking]

A few extra data points on my Loadomatic system. Timing results:

No vacuum lines connected: 6 degrees BTDC
All vac lines connected: retarded into ATDC range
Ported vacuum only: same, retarded into ATDC range
Manifold vacuum only: 6 degrees BTDC

The problem I am trying to solve is a strange form of poor performance. Engine starts instantly, never misses, backfires, etc. and idles smooth. Problems? Hesitates on sudden acceleration, though I can see the accel pump jets squirting. Weirder problem is that engine rpms do not come up with pressing down the accelerator pedal slowly. (Linkage is free and moves fine by hand.) You can get all the way to the floor and be going 35 mph. If you pump the pedal, you can get the car moving to higher speeds. Without pumping, you’re dying on a hill. With a 200 hp Y-block!

Holley 4000 is a Suter rebuild from a few years back. Electric choke works fine, choke plates open when warmed up. I have another rebuild I can slap on if need be. I just can’t figure how the engine can be turning low rpms (albeit smoothly) with the pedal almost to the floor.

Bill in Luray

[scicala]

Attached is a link to a dual diaphragm schematic and text explaining the operation.
I don't understand how the timing is retarding at idle from the carb front vacuum line.
The only time it's supposed to retard the timing is on sudden acceleration just momentarily to avoid pinging (explained in the text). The inner diaphragm which is connected to the carb on the front of the carb only pulls in the advance direction.
The outer diaphragm which is connected to manifold vacuum is only for the momentary retarding of the spark on acceleration.


Sal


https://r.search.yahoo.com/_ylt=AwrJ...ZYEQ_dd0wsWrA-

[highcking]

The only explanation I can come up with is that the spark control valve on the carb is not functioning correctly. It feels like the timing is just not advancing at all.

[40 Deluxe]

Originally Posted by highcking

I have tried the "mouth suction" test on the NOS unit and it seems to respond properly. Even if it didn't, I can't see how the timing retards. Let me retest tomorrow to confirm the facts as I have stated them. I am pretty clear that revving the engine did NOT result in timing advance. This is apparently the result of the design --- there is no centrifugal advance, just that weird little valve mounted on the Holley 4000.

I found a chart showing the factory advance curve. It does not show any retard at idle. The advance begins about 500 RPM and shows 3 deg. at 1,000 RPM, 11 deg. at 1500, and 17 deg. at 2500. This would be steady RPM, not while it's revving up. So you can check it with a timing light.

[highcking]

Thanks! With everything connected, I see no advance at all. Someone commented in this thread that you won’t see any advance under no load conditions. There’s no centrifugal advance and the vacuum advance is related to lower vacuum conditions under load. It would be great if someone else could see what their car does under the timing light. I guess it’s possible I have two defective advance units.

[highcking]

I discovered with the help of my wife that the throttle linkage is slipping at partial throttle. On the linkage to the rear of the carb, there is a hefty pin that goes through a curved slot which I think is the downshift activator at full throttle. My linkage is slipping that pin at partial throttle which means the actual throttle on the carb stops moving entirely. It also explains why pumping works - the pin resets itself and allows more movement of the throttle. What the heck? I haven’t messed with that mechanism at all.

[KULTULZ]

Originally Posted by scicala

The outer diaphragm which is connected to manifold vacuum is only for the momentary retarding of the spark on acceleration.

Sal

And de-acceleration.

The trouble here is that everyone has different ideas and theories of how the system is supposed to work.You ask questions to try and diagnose and there is no answer.

The system works on a modified (continually) manifold vacuum signal The 1956 DUAL DIAPHRAM was HOLLEY's last attempt to correct problems. DUAL ADVANCE was introduced the following model year.

Sounds like the OP found the problem in the accel linkage.

[Alaska Jim]

I was going to suggest that your problem sounds like a linkage problem, if when the throttle is pushed all the way to the floor and you can only get 35mph out of it. sounds like you found the problem, now to find the "cure".

[highcking]

Jim - you’re right. See the attached picture. I stuck a piece of hose to block the kick down pin from sliding around. Car runs fine, plenty of power. Long term, I think a return spring in that area is supposed to keep tension on the linkage and it’s gotten weak after 63 years. (My Town Sedan is an original car with mileage in the 50s.) I’ll take it off and locate a substitute with more tension.

It’s amazing how this issue masqueraded as either a carb or distributor problem. If you moved the throttle lever at the carb by hand, everything did what it’s supposed to. But if you operated the throttle from inside the car ... my wife reported the throttle stopped moving and I was still pushing down! We reversed roles and I saw immediately what was happening.

Thanks to all respondents. I learned a lot of interesting things and found a problem that can’t be unique to my car.

Bill in Luray

[Daves55Sedan]

Ummm, hate to tell you this, but the reason you are experiencing slipping of that linkage is because you are missing a tension spring between the upper and lower sprags of that kickdown element.
The reason they have that slot in there is so you can punch the gas pedal and achieve intermediate gear kickdown without damaging carburetor butterfly valve shaft and associated linkage. That spring takes up the slack, but during normal driving the spring holds that kickdown element steady.
I suggest NOT using your passing gear kickdown until you can replace that missing spring and pull that piece of plastic tubing out of there. Once that spring is put back, you should be good as new.

[Daves55Sedan]

Here is a photo of '55 Ford Y-block with 2-bbl carb passing gear link. Notice the two movable plates with the spring pulling them together. That is the spring you are missing. The slot on mine is hidden on the backside.

[highcking]

I was just about to look in the '56 parts book to check on that area. A missing spring (just broke and fell off most likely) would explain the problem. I put the hose piece there just to test my theory. I've been collecting and working on "older cars" for 40 years and this was one of the harder problems to figure out, even though it's simple in a way.

Bill

[scicala]

"And de-acceleration."




The dual diaphragm '56 only momentarily retards the spark in low manifold vacuum when accelerating. Deceleration is high vacuum. The text in the link I posted earlier explains how it all works.


Sal

[paul2748]

I had a similar problem with my 56 TBird. I put and extra spring on it and it now works fine.

Originally Posted by highcking

I discovered with the help of my wife that the throttle linkage is slipping at partial throttle. On the linkage to the rear of the carb, there is a hefty pin that goes through a curved slot which I think is the downshift activator at full throttle. My linkage is slipping that pin at partial throttle which means the actual throttle on the carb stops moving entirely. It also explains why pumping works - the pin resets itself and allows more movement of the throttle. What the heck? I haven’t messed with that mechanism at all.

[KULTULZ]

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Originally Posted by scicala

"And de-acceleration."

The dual diaphragm '56 only momentarily retards the spark in low manifold vacuum when accelerating. Deceleration is high vacuum. The text in the link I posted earlier explains how it all works.

Sal

I only go by FORD info Sal, not someone's interpretation..

[scicala]

I believe that info was from Holley or Ford, and I believe it to be true from my experience. To each his own.


Sal

[KULTULZ]

Originally Posted by scicala

I believe that info was from Holley or Ford, and I believe it to be true from my experience. To each his own.

Sal

I have no idea. The referring URL you posted expired. You cannot post a SEARCH URL as it will self destruct. Remember MISSION IMPOSSIBLE?

[scicala]

I guess I don't know computers that well. When I click on the link it says it's expired, but shows a link to go to it anyway. I've tried it twice and worked both times for me. If you can't see it, maybe just google "1956 Ford dual diaphragm distributor". That's how I found it originally.


Sal

[y'sguy]

probably not helpful to have that hose laying on top of the bellcrank mechanism. I would reroute it. Just to take that out of the equation.

Good luck with the issues, These vac advance deals with the 56 Load a matic are frustrating but can be solved with a lot of patience. And unfortunately some extra money sometimes. Hang in there.

[highcking]

The fuel hose is a problem. If you route it under the bellcrank mechanism, it is getting pinched against the intake manifoold. How did the factory do it?

[Daves55Sedan]

Originally Posted by highcking

The fuel hose is a problem. If you route it under the bellcrank mechanism, it is getting pinched against the intake manifoold. How did the factory do it?

It is not supposed to be rubber hose at all. It should be metal tubing. Try to duplicate the routing shown in the '56 Ford car shop manual in various places, or you can actually buy that fuel inlet tubing (pre-bent) from various repro parts suppliers. I got all my undercar fuel and brake line tubing from a company called "Inline Tube", but they also carry a complete line of fuel and vacuum tubing for the engines.
The rule of thumb I like is: Use as LITTLE of rubber tubing as possible in fuel and vacuum systems. Rubber breaks down under heat and age and becomes damaged by contaminants in ethanol, so it needs to be checked for cracks periodically. Metal tubing lasts practically forever.
Some of your chain auto-parts stores have been offering copper-alloy tubing for a while now, so if you are creative like me, get some and bend your own for custom fit. And get new brass compression fittings too.

[Stiggy]

Originally Posted by highcking

A few extra data points on my Loadomatic system. Timing results:

No vacuum lines connected: 6 degrees BTDC
All vac lines connected: retarded into ATDC range
Ported vacuum only: same, retarded into ATDC range
Manifold vacuum only: 6 degrees BTDC

The problem I am trying to solve is a strange form of poor performance. Engine starts instantly, never misses, backfires, etc. and idles smooth. Problems? Hesitates on sudden acceleration, though I can see the accel pump jets squirting. Weirder problem is that engine rpms do not come up with pressing down the accelerator pedal slowly. (Linkage is free and moves fine by hand.) You can get all the way to the floor and be going 35 mph. If you pump the pedal, you can get the car moving to higher speeds. Without pumping, you’re dying on a hill. With a 200 hp Y-block!

Holley 4000 is a Suter rebuild from a few years back. Electric choke works fine, choke plates open when warmed up. I have another rebuild I can slap on if need be. I just can’t figure how the engine can be turning low rpms (albeit smoothly) with the pedal almost to the floor.

Bill in Luray

Just wondering ~ has the problem been found with the spark retarding (with vacuum connected ) at idle??

[highcking]

Stiggy - no. None of the reference manuals say anything about the correct vacuum readings except the reading of 6 degrees BTDC with vacuum advance shut off. But the ATDC reading may be correct anyway. In a regular system, when you check timing at idle, there may still be a small advance contributed by the centrifugal advance weights in the distributor. I’m not sure about that. There’s no obvious way to check timing under true load conditions Where manifold and ported vacuum change as soon as the engine is put under load. I’d like for others to report their vacuum reading at idle with the vacuum lines connected. I still could have a faulty unit though it seems to work ok.

[KULTULZ]

Originally Posted by highcking

None of the reference manuals say anything about the correct vacuum readings except the reading of 6 degrees BTDC with vacuum advance shut off.

Look in your SHOP MANUAL under SPECIFICATIONS and you should find the advance specs there.

[highcking]

It shows the base reading of 6 degrees BTDC for no vacuum to the advance unit. I can’t find a reference anywhere on readings for other conditions. This was a one or two year item that depended on the teapot with the spark control valve. In 1957 the whole system was dropped.

[KULTULZ]

Originally Posted by highcking

It shows the base reading of 6 degrees BTDC for no vacuum to the advance unit. I can’t find a reference anywhere on readings for other conditions. This was a one or two year item that depended on the teapot with the spark control valve. In 1957 the whole system was dropped.

I am trying to figure this out- (but I am old) ...

You went to the SPECIFICATIONS SECTION of the FORD 1956 SHOP MANUAL and under IGNITION did not find the curving and vacuum values?

I understand the LOAD-O-MATIC SYSTEM, so no need to post the description.

BTW - LOAD-O-MATIC was used on six cylinders until the 1968 model run.

[scicala]

Even if you have the specs on how much vacuum to the distributor inner diaphragm, and how much spark advance that vacuum level represents, I don't think you will be able to check it with a timing light unless you have the engine on a dyno, or the car on a chassis dyno since all the specs are based on light to heavy loads on the engine and not racing the engine in neutral. I can tell you based on my Holley carb manual that the most vacuum you will see is about 4" hg. And that is at high RPM and basicly wide open throttle. At that point the vacuum signal is mostly from venturi vacuum (suction)and not manifold vacuum. Manifold vacuum at wide open throttle will be no more than 2" hg at high RPM.


Sal

[KULTULZ]

Not to over-ride you Sal, but actually the values in the SHOP MANUAL are intended to be used on a DIST ANALYZER.

The complete system (DIST and CARB) is so complex, I don't see how anyone (without wild guessing) could calibrate one on the car as you can a DUAL ADVANCE. You might get it somewhere operational but not to spec.

The ONLY USE I can see to use the LOM if the car is a dedicated restoration. Even then (if a driver) I would have the two systems on hand if I wanted to drive it.

But the values are in the MANUAL.

[scicala]

I agree that loadomatics are probably all over the place as far as two working the same.


The specs I have are from Holley for their distributor, but they give the specs for the '56 Teapot carb vacuum, and are all based on distributor RPM versus engine load (manifold vacuum).


If it were my car, I would probably have an aftermarket or '57/later Ford distributor on it.


Sal

[Stiggy]

Originally Posted by highcking

Stiggy - no. None of the reference manuals say anything about the correct vacuum readings except the reading of 6 degrees BTDC with vacuum advance shut off. But the ATDC reading may be correct anyway. In a regular system, when you check timing at idle, there may still be a small advance contributed by the centrifugal advance weights in the distributor. I’m not sure about that. There’s no obvious way to check timing under true load conditions Where manifold and ported vacuum change as soon as the engine is put under load. I’d like for others to report their vacuum reading at idle with the vacuum lines connected. I still could have a faulty unit though it seems to work ok.

Can you do a vacuum/pressure check on both of the lines going to the
vacuum advance diaphragm? Something is causing it to go to ATDC.
I've checked vacuum at idle and there is none (500 ~ 550 rpm) The timing at idle should not change when the vacuum lines are connected..

[KULTULZ]

If one goes to the SPECIFICATION CHAPTER of the SHOP MANUAL. the vacuum signal levels will be given at the appropriate engine RPM.

Example -

DIST RPM - 200 - DIST Degrees 0
DIST RPM - 500 - DIST Degrees 3 1/2 - 403/4

So there is a modified MANIFOLD VACUUM SIGNAL @ idle. It supplies the signal to advance the breaker plate. This is why the vacuum signal is removed when adjusting base timing.

On the 1956 DUAL DIAPHRAGM SYSTEM (not all 56 engines used it), there are two signals, one modified manifold vacuum (this gives advance) and constant MANIFOLD VACUUM which operates the outer surge diaphragm (which retards breaker movement).

You can see vacuum advance operation/movement with a timing light and revving an engine unloaded. This is one of the checks performed during a tune-up. The same is true on a DUAL ADV DIST, whether using PORTED VACUUM, MANIFOLD VACUUM or a mixture of both.

If the timing shows retard @ idle, it is most likely a bad breaker plate or vacuum diaphragm.

You guys are beating yourselves to death.