1968 Dual Vac Advance Issues

[Anonymous]

That's exactly what I am trying to figure out too, Steve.

When I sent in my old core, I got a pre-68 core rebuilt back which had the open port for the SCV. It looks the '68 1100 coupled with the proper dual advance, dual vacuum distributor should NOT have an SCV.

On my old core, the port for the SCV was never open.

I am trying to determine if my sputtering is caused by the SCV.

How does your 200 run?

 

[LEROY POLL]

HEY 'TEGOMAN


.....YOU SAID EARLIER THAT WHEN YOU HOOKED UP THE VACUUM TO THE DIST. THAT THE TIMING DIDN'T CHANGE MUCH.

.....THAT SAID IF YOU HAVE A SPARK-ADV. ON YOUR CARB.1100, THEN YOU SHOULD GET A JUMP OF MORE THAN 10* TO 12* DEGREES WHEN YOU HOOK UP AT IDLE.

.....WITH YOUR TIMING LIGHT HOOKUP CHECK TO SEE IF THE ADVANCE TIMING MOVES HIGHER OR LOWER WHEN YOU ADVANCE THE CARB. OFF OF IDLE. IF IT DIPS OR MOVE LOWER THEN YOU HAVE SPK-ADV. ON THE CARB. AND IS WORKING CORRECTLY.

.....WITH THE SPK-ADV. SWITCH ON YOUR CARB. YOU MUST UNHOOK ALL VACUUM TO SET YOUR TIMING. SET IT TO 10* AND TIGHTEN DOWN. RECHECK.... NOW HOOK UP THE VACUUM. IT SHOULD MOVE FORWARD TO A HIGHER LEVEL. ADVANCE THE CARB. AND YOU SHOULD SEE A DIP IN THE ADV. AND THEN A LARGE ADVANCE TO ALMOST FULL ADV.

....THE SETTING OF INITIAL TIMING IS MOST IMPORTANT WITH THIS DIST. YOU SHOULD ALSO BE LOOKING FOR VACUUM LEAKS TO THE DIST. THIS WILL GIVE YOU EVERYTHING THAT YOU HAVE BEEN EXPERIANCEING.

.....WITH LOW ADV. TO THE DIST. (BECAUSE OF A LEAK) YOU GET SMALL ADV. THEN AS YOU SPEED UP THE CENTRIFICAL ADV. WILL GIVE YOU SOME ADVANCE AND THEN IT WILL START RUNNING BETTER.

.....YOU SHOULD BE ABLE TO JUST BUY A NEW ADVANCE DIAPHRAM AND EXCHANGED IT OUT. YOU CAN PUT THE SINGLE DIAPHRAM ON IF YOU WANT A THAT TIME.

.....IT SOUNDS LIKE TO ME YOU HAVCE A MISSMATCH OF CARB..&..DIST. THIS IS THE MOST COMMON MISTAKE MADE BY PEOPLE..... AND EVEN PEOPLE IN-THE-KNOW. READ JACKS STICKKY AT THE TOP.

THIS MIGHT BE THE PROBLEM....WHO KNOWS?????

THANKS

LOTS OF LUCK....LOL

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

That's exactly what I am trying to figure out too, Steve.

When I sent in my old core, I got a pre-68 core rebuilt back which had the open port for the SCV. It looks the '68 1100 coupled with the proper dual advance, dual vacuum distributor should NOT have an SCV.

On my old core, the port for the SCV was never open.

I am trying to determine if my sputtering is caused by the SCV.

How does your 200 run?

Runs okay, I need to find out if it can run better. I see no difference in timing when I take off the vacuum advance hose with the car at ilde.
I'm going to blow out the vacuum advance orifices with low pressure compressed air tonight and see if that will help.

I have a vac gage and will put that on the carb take off to see if I get anything there at all. I kow the advance vac is nil at idle and the manifold is greatest at idle so I may need to put the car under load to check it somehow.

I used to see a difference at idle with and without the vac line attached to dizzy. Next step is to look at the dizzy diaphragm.

 

[CZLN6]

Howdy All:

Great check list LeRoy.

FYI-FoMoCo used the Load-a-Matic, vacuum advance only distributor with a carb with a Spark Control Valve (SCV) from the late 50's to the '67 model year on all six cylinder engines and many V8s. They changed to a mechanical and vacuum advance distributor system and dropped the SCV from the carbs. The '68 and later distributors are designed to use a ported vacuum signal from the carb. If your 1100 carb has a SCV it is a '65 - '67 version. If it has not SCV it is likely a '68 - '69, (OR a Calif emissions '66-67)

Note '68 & '69 1100s on a 200 engine only flow 150 cfm due to a smaller 1.1" venturi. '67 and earlier 1100s on a 200 engine flow 185 CFM.

Aftermarket rebuilders and marketers are very unknowing and uncaring as to the specific details of these vintage carbs. No wonder Autolite 1100s got a bad rep.

Adios, David

 

[Anonymous]

In the topic of this thread...trying to figure out what we all have...

66 conv with a 68 engine (dizzy unknown)

The dizzy has two hoses (advance and retard) I only use the advance hose. With the vacuum line off, the timing light shows an advance in timing as I rev the engine. So it must be dual advance.

When I rev the engine I get about 5" of vacuum at the carb vac line take off (which normally goes to the dizzy).

With the vac line on the dizzy, the advance appears greater at idle revving the engine. Still hard to tell with no engine load.

The carb clearly has the SCV. That's the silver buttin looking device on the passenger side ofthe carb that moves in when you rev the engine.

Am I mismatched. If so, can I plug the SCV somehow?

 

[LEROY POLL]

HELLO STEVE-O


.....I AGREE YOU MUST HAVE THE DUEL ADV.


..... TRY THIS..... AT IDLE WITH EVERYTHING HOOKED BACK UP, TURN YOUR IDLE SCREW TO RAISE THE IDLE TO ABOUT 900 RPM. YOU SHOULD READ ABOUT 6* TO 8* HIGHER. THAT WOULD BE 10* + 6* OR 8* TO AROUND 17* TOTAL. IF IT RUNS TO ABOUT 30* TOTAL YOU DON'T NEED THE PORT VACUUM SWITCH. HOLLEY MAKE A PLUG THAT SHOULD BLOCK THE MANIFLOD VAC. OFF AND JUST LEAVE THE VENTURI VAC. ONLY. BE SURE AND CHECK IT AGAIN TO MAKE SURE.

.....IF YOU HAVE BEEN RUNNING THIS SET UP WITH THE PORT SWITCH WORKING.....THEN YOU WILL NEED TO RE-TIME YOUR MOTOR. START WITH 10* INITIAL, THEN MOVE UP TO 12*, THEN TO 14*, UNTIL YOU GET THE RESPONSE AT HIGHER RPM'S YOU HAD BEFORE.

..... THIS SET UP WILL NOT GIVE YOU THE PART THROTTLE RESPONSE YOU HAD BEFORE, BUT WILL GIVE YOU BETTER W.O.T. RESPONSE.

..... IF YOU MAKE THIS CHANGE PLEASE COME BACK AND TELL US ALL WHAT THE DIFFERANCES ARE.

LOTS OF LUCK....LOL

LIVE IN GRACE

LEROY POLL

YOU TOOK A GREAT PICTURE UNDER THE PICTURE POSTS

 

[Anonymous]

TRY THIS..... AT IDLE WITH EVERYTHING HOOKED BACK UP, TURN YOUR IDLE SCREW TO RAISE THE IDLE TO ABOUT 900 RPM. YOU SHOULD READ ABOUT 6* TO 8* HIGHER. THAT WOULD BE 10* + 6* OR 8* TO AROUND 17* TOTAL. IF IT RUNS TO ABOUT 30* TOTAL YOU DON'T NEED THE PORT VACUUM SWITCH. HOLLEY MAKE A PLUG THAT SHOULD BLOCK THE MANIFLOD VAC. OFF AND JUST LEAVE THE VENTURI VAC. ONLY. BE SURE AND CHECK IT AGAIN TO MAKE SURE.

Leroy,
You're referring to the degrees advance not " Hg when you say 6* right? Or do you want me to time it based on vacuum at the manifold?

My vacuum take off is from the carb, not from the manifold, that's why I have no vacuum at idle.

The plug you wrote about, is it for the carb or manifold as my manifold plug is in place blocking that takeoff port.

Sorry for the threadjack.

Thanks,
Steve-O

 

[Anonymous]

No, problem Steve...your issues will help me solve mine!

I am going to attempt some testing today or tomorrow, I should have a report back on Friday.

Jay

 

[LEROY POLL]

HELLO STEVE, AND MONTEGOMAN

.....YES STEVE THAT STAND FOR DEGREES OF ADVANCE.

.....STEVE IF YOU HAVE LOW VACUUM AT IDLE AND JUST OFF IDLE YOUR PORT VACUUM SWITCH IS NOT WORKING. YOU NEED TO RECHECK THIS. THE CARB. WILL GIVE TWO DIFFERENT VACUUM LEVELS....FROM THE SAME PORT TAKE-OFF. I'LL SAY THAT AGAIN TWO DIFFERENT VACUUM LEVELS FROM ONLY ONE TAKE-OFF PORT. HOW IT DOES THIS IS TO SWITCH FROM MANIFLOD TO VENTURRI INSIDE THE CARB. BY WAY OF THE PORT VACUUM SWITCH.

.....THE WAY IT WAS DESIGNED WAS TO WORK OFF THE MANIFOLD VACUUM ALMOST ALL THE THE TIME. BUT THEIR IS A PROBLEM WITH W.O.T. AT W.O.T. MANIFOLD VACUUM WILL DROP BELOW A GOOD ADV. LEVEL, WHILE AT THE SAME TIME MANIFOLD VACUUM LEVELS ARE LOW THE VENTURRI LEVELS ARE AT THEIR HIGHEST. THAT IS WHY THE LITTLE PORT VACUUM SWITCH WAS USED TO KEEP THE ADVANCE LEVEL ADVANCING. THIS HAS BEEN A HARD THING FOR SOME TO UNDERSTAND HOW IT WORKS....., BUT IT WORKS.

.....STEVE YOU WILL NEED TO READ THE VACUUM AT THE PORT OF THE CARB. DON'T USE THE END OF THE LINE AT THE DIST. TO READ. THIS WAY IF THEIR IS A LEAK ANY PLACE ALONG THE LINE YOU WILL BE BYPASSING IT. IF YOU HAVE A METAL LINE COMING FROM THE CARB. TAKE THE FITTING OFF AND PUT A NIPPLE FITTING IN IT'S PLACE. YOU SHOULD READ LITTLE TO NO VACUMM AT LOW IDLE. IF YOU TURN THE IDLE SCREW TO INCREASE THE RPM'S YOU SHOULD GET ALMOST FULL ADV. MAYBE 30*+. IF THIS IS WHAT YOU GET THEN THE SWITCH IS WORKING. NOW REPLACE THE NIPPLE AND PUT YOUR LINE BACK ON AND RE-TEST. YOU SHOULD GET THE SAME READING AT THE END BY THE DIST.

.....YOU SAID YOU HAVE THE SWITCH ON THE CARB. IF THAT IS TRUE AND THE SWITCH IS WORKING AND YOU WANT TO USE ONLY THE VENTURRI VACUUM, THEN HOLLEY HAS A PLUG THAT WILL REPLACE THE PORT VACUUM SWITCH. JUST TAKE THE SWITCH OUT AND PUT THE PLUG IN. BE SURE TO CHECK THE VACUUM AT THE CARB AGAIN TO MAKE SURE YOU ARE GETTING ONLY THE VENTURRI JUST OFF IDLE.

.....AGAIN THIS SYSTEM IS TOTALLY DEPENDENT UPON HIGH MANIFOLD VACUUM TO THE DIST. IF ANY LEAK AT ALL IS IN THE SYSYEM THEN YOU WILL GET POOR PERFORMANCE AND MILEAGE.

.....TRY ALL THIS AND SEE WHAT HPPENS. I HOPE THIS IS HELPING.

LOTS OF LUCK....LOL

LIVE IN GRACE

LEROY POLL

 

[LEROY POLL]

HELLO STEVE

.....SORRY I DIDN'T MEAN 30*+ ADV. I MEANT FULL MANIFOLD VACUUM. IT HARD TO GET ANY VACUUM ADV. IF IT'S NOT HOOKED UP. THAT WOULD HAVE GIVEN YOU THAT MUCH ADV. IF YOU WERE HOOKED UP. SORRY ABOUT THAT.

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

Thanks, Leroy for the detailed help!

Here's what we did on mine and we are still experimenting:

Blocked the retard side of vac unit.

Hooked manifold vac to advance side; still going through the vac switch on the thrmostat housing.

Set idle to 900RPM.

Set intial timing to 12 degrees w/o vac line connected. Car advanced when I put vac line back on.

Result: Reduced bog to shorter duration; no ping at all. Real smooth w/o load.

Re-set initial timing to 16 degrees.

Result: further reduced bog; bog is very sensitive to the ammount of pressure I place on the accelerator. Still, no ping. Canister is almost parallel to the block.

SCV is still in the carb for now.

I checked the fuel accelerator pump and it is normal. It is set for L and the bend in the rod is just right.

 

[LEROY POLL]

HELLO 'TEGOMAN


.....I WILL HAVE TO ASK ONE QUESTION. WHAT HAPPENS WHEN YOU LEAVE OFF THE VACUUM HOOK UP FROM THE CARB AND ADVANCE THE MOTOR TO ABOUT 3000RPM IT SHOULD ADVANCE. PUT YOUR LIGHT ON IT TO SEE HOW MUCH ADV. YOU ARE GETTING FROM THE CENTRIFICAL ADVANCE.

.....IF IT DOESN'T ADVANCE ......YOU MUST HAVE A LOAD-A-MATIC DIST. .DID THE ADV. GO TO FULL ADVANCE WHEN YOU PUT THE VACUUM HOOK UP BACK ON THE DIST????

.....THE LOAD-A-MATIC HAS ONLY VACUUM ADVANCE. THEIR ARE SPRINGS INSIDE TO PULL AGAINST THE MANIFOLD VACUUM. THE LOAD PUT ON THE MOTOR WILL CAUSE THE MANIFOLD VACUUM TO DROP.....LETTING THE SPRINGS INSIDE THE DIST. TO PULL BACK AGAINST THE MANIFOLD PRESSURE. THE L-A-MATIC WILL NOT WORK WITH VENTURRI VACUUM.

LOST NO LUCK....LNL

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

Leroy,
Another great post. Learned what Load-O-Matic really means.
Thanks,
Steve-O

 

[Anonymous]

Hi Leroy!

When the vac lines are disconnected, the engine advances but sputters through low RPM until higer RPM when, presumably, the Centrifical advance kicks in.

When I put the manifold line on the advance side of the canister, not only does the car advance then (responding to the manifold vacuum) but on acceleration, the car does not sputter as much through low RPM.

A load o matic would not have the springs/weights inside correct?

My distributor has weights and springs, then the vac canister has TWO vanc lines on each side of the canister. Noramally, the carb vac goes to the advance and the manifold to the retard side.

For this experiment, I put a new distributor from MAC's/Cardone on the car. It came with the vac nipple on the retard side of the vac canister plugged with a plastic plug. So, rather than run the normal set up as the shop manual says, I was playing with the advance vacuum only swapping between the manifold vac and carb vac on the advance side of the can only.

I got a much better response from the car when the timing was set high and the manifold vac was on the advance side with not vacumm on the retard side.

I still have the SCV on the carb at this time. I am hoping when I plug the SCV or get the right '68 1100 to work with the dual vac distributor, the carb vac would be suffiicent to advance the distributor until the centrifical picks up. For some reason, I cannot get past some sputtering along the way. The only improvements I have seen is when the distributor gets more inital vac at advance I have the inital timing set almost off the timing marker at 16 degrees. Yet, I have no pinging, which tells me, and correct me if I am wrong, that the car wants more advance. Thus, the more advance I give it, the sputter duration gets less and less the farther I advance the timing.

However, the throttle response sometimes eliminates the sputter. In other words, I accelerate easy, the car doesn't sputter, but if I slam on the throlle the car sputters.

 

[mustang6]

I think the vacuum advance is still the root of your sputter problems as you suspect. Manifold vacuum does not provide the correct "signals" to the distributor in all situations- quick wide open throttle being the worst. By using manifold vacuum, you are giving the distributor the least amount of vacuum when you open the throttle fast, so you are LOSING advance right when you need it most. When you open the throttle slower, you are not dropping your manifold vacuum as much, so you are keeping more advance at the distributor and getting less stumbling. This is also why you can't make your engine ping- whenever engine load goes up, your manifold vacuum goes down, and your advance backs off. The only way you can get this combo to ping is by putting so much intial timing into the distributor that it pings on that alone.

This is why ported vacuum sources were created, to provide a vacuum advance that better matches situational egine needs- especially more vacuum advance in low manifold vacuum (but high engine load) situations. Unfortunately with the whole SCV/carburetor issue you have going on you are forced to run manifold vacuum, which will never run quite right.


As far as blocking the SCV and making the carb behave like a non-SCV carb, I'm not sure if it's possible or not. Read the sticky I have at the top of this forum, look at the diagrams of the SCV and read it's functional description. It may be possible to block off certain internal passages and accomplish it but I haven't ever thought that all the way through because it's obviously not as simple as just putting a plug in there and I've always chosen to run the correct carb rather than experiment with plugging the SCV.

 

[Anonymous]

To make an SCV 1100 act like a non-SCV 1100, take a dab of JB Weld or similar and block the venturi take off in the carb throat passenger side. May want to move carb from manifold when doing this.

In a newer reman carb, you may see a tiny brass cone sticking thorugh the plastic throat rather than being flush. You need to block that off.

Old school method is a bb stuck in from where the vac hose comes off the side of the carb. Can't tell you how well that would work.

 

[Anonymous]

This is why ported vacuum sources were created, to provide a vacuum advance that better matches situational egine needs- especially more vacuum advance in low manifold vacuum (but high engine load) situations.

Ported vacuum does not provide more vacuum under low manifold vacuum (high engine load) situations. Manifold vacuum is always greater than ported vacuum. (Venturi vacuum sources can have higher vacuum than manifold vacuum under some conditions). Ported vacuum is less because its port is located above the throttle plates or is vented above the plate. When the plates open, the ported source sees the same manifold vacuum.

Ported vacuum advance was not developed as an enhancement for performance over manifold vacuum advance. It was implemented to work in conjunction with the emission controls. Ported sources provide less vacuum and less advance at idle. This retarded the timing at idle by using a ported vacuum source and promoted higher combustion temps and less hydrocarbon emissions. To get it to idle better with reduced ignition advance, they typically had to open the throttle plates a bit further to smooth out the idle and raise the idle speed.
Doug

 

[Anonymous]

I would rather run the correct set-up, but it seems the source of my issues is the pre-68 1100 I have on my engine with the SCV on it.

I would run right out and by a Pony rebuilt, but look at Steve, he gave them his specs and he got the wrong one from them too!

So, it sounds like the sputter, whether it is the manifold or the carb vacuum hooked up to the advance, is being caused by a lack of vacuum to the advance side of the can during acceleration before the centrifical system kicks in.

So, I need to find, as was previously mentioned, a 1968 Autolite 1100 with ported vacuum internals and no scv in order to run with my dual advance, dual vacuum distributor.

 

[LEROY POLL]

HEY THERE 'TEGOMAN


.....I WILL TELL YOU THAT IF YOU HAVE CENTRIFICAL ADV. YOU ARE RUNNING THE WRONG CARB.

.....I HAVE READ THE OTHER POSTS BEFORE THIS ONE AND HAVE TO SAY EVERYONE IS CORRECT IN THEIR POINTS. THAT SAID THE PROBLEM THEN IS WHAT DO YOU WANT? I WILL NOT GO THERE ON THIS POST,.....BECAUSE WE WANT TO HELP SOME ONE FIX AND UNDERSTAND WHAT IS HAPPENNIN' TO THEIR SET UP.

.....NOW 'TEGOMAN...... WHAT SCOTT IS SAYING IS CORRECT YOU ARE GETTING LITTLE ADVANCE OFF IDLE.... SO BY INCREASING YOUR INITIAL ADV. YOU ARE OVER COMMING THE FLAT SPOT YOU WILL GET WITH MANIFOLD VAC. IF YOU GET THE CORRECT CARB. YOU SHOULD GO TO WHAT YOU WERE LOOKING FOR....PINGING....! YOU'RE GETTING TOO MUCH ADV. NOW WITH 16* +MANIFOLD ADV. YOU WOULDN'T HERE THIS PINGING BECAUSE IT IS COMING AT A HIGHER RPM. THE HIGHER RPM GIVES LESS TIME FOR THE EXPLODING GASSES TO PUSH AGAINST THE PISTON. AND TRY TO PUSH THE CRANK BACK THE OTHER WAY. THAT IS HARD ON EVERYTHING...PISTONS,..RODS & WRISTPINS,...AND CRANKS,....CHAINS,...GEARS,....PUMPS,...BEARINGS, ECT. I THINK YOU GET THE PICTURE.

.....WITH THE VENTURRI TAKE OFF HIGHER INSIDE THE CARB. THE VENTURRI WILL HAVE NO VACUUM ADV. AT IDLE. BUT AS THE CARB. OPENS THE VACUUM INSIDE THE MANIFOLD MOVE UP TO TOP OF CARB. THIS CHANGE CAUSES AIR TO MOVE RAPIDLY THROUGH THE CARB. TO THE MANIFOLD. THE VENTURRI HOLE WILL ALSO FEEL THIS MANIFOLD PRESSURE AND WILL TRY TO EMPTY ALL THE AIR IN THE LINE BACK TO THE DIAPHRAM,........MAKING THE ADV. DIAPHRAM MOVE ...PULLING THE ADVANCE PLATE TO ADVANCE. AS YOU CLOSE THE THROTTLE PLATE INSIDE THE CARB. THE MANIFOLD VACUUM WILL BUILD TO A GREATER VACUUM CAUSING A DROP OF MANIFOLD PRESSURE AT THE TOP OF THE CARB......ALSO TO THE VENTURRI PORT INSIDE THE CARB. WHERE IT WILL FEEL LESS VACUUM AND THE DIAPHRAM ADV. PLATE. THIS WILL MAKE THE PLATE NOT ADV. AS MUCH.

.....THIS IS WHAT YOU WILL WANT TO HAPPEN FOR YOUR DIST. SO GET A CORRECT CARB. OR TRY AND BLOCK OFF THE MANIFOLD VACUUM INSIDE YOUR CARB. AT THAT POINT YOU SHOULD BE CLOSE TO WHAT YOU'RE LOOKING FOR.

..... I READ SCOTTS, STEVE-OS, AND DOUGS POSTS BEFORE WRITTING THIS.

LOST OF LUCK TO EVERYONE....LOLTE!

LIVE IN GRACE

LEROY POLL

 

[Anonymous]

Thanks, for the advice, Leroy and here is the answer to your question about what I want for my set-up:

I want the correct equipment on my car today that FORD put on it when it left Lorian Assembly on March 23, 1968.

I don't want to win races, and I don't want to swap parts or gipsy wired systems.

I want the right carb, and the right distributor.

I then want to tune my car so that it operates at peak performance and is a pleasure to drive and reliable.

I want to work on and fix my own car, I want to learn this engine and these components better than others. Rather than just show off my car, I want to work on it and maintain it myself...

I have learned so much from reading this forum. The shop manual and the other service lit only goes so far. Thanks for the great learning experience.

Unfortunately, the parts market has taken me several times.

Where can I get the PROPER 1968 Autolite 1100 carb that will work with my 1968 dual advance, dual vacuum distributor just like FORD designed and how do I make sure I am getting the right carb?

I would rather purchase the right carb, and not half-azz it.

This car is only one of 20 Montego convertibles made out of 3,248
convertibles for '68 with the 200 and a three speed. I have fought off numerous know it all's telling me to get rid of the six banger and get a "5.0." I am tired of having people run up to the car and find out it is a six and then walk away disappointed. And then to be embarassed by the car when it sputters like a sick goat with those darn Corvette guys looking on with laughter.

Please help me return my 200 to its original glory and smooth performance; it deserves it.