Vacuum delay valve?

[jmcleek]

Have installed the carborator, 1403 ederbrock 500cfm eletric choke, and working on some vacuum lines. I would like to know if any one has needed to use a vacuum delay valve, and what the part number is and has anyone needed to use any coolant controled such device?Has singal port vacuum advance, stock 302.

 

[dangerranger83]

Never heard of a vacuum delay valve other then using ported vacuum but even then I don't use that, I use the manifold vacuum port on the carb for my dizzy since computer controlled vehicles use the ported but I have also hard if prior using the ported with good results.

What are you using that needs a vacuum delay?

I'm running the exact same carb but my current issue is starting my truck, I have to pump the hell out of it to get it to start but in the winter, two pumps and she would fire right up (think my choke needs adjusted too stay closed longer due to the warm weather).

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[dangerranger83]

Should have two advance ports. Looking at it from the front, the left is manifold vacuum and the right is ported. The center is for your PCV valve hose.

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[kimcrwbr1]

Use the ported vacuum on the carb where there is no vacuum at the distributor until you open the throttle. I think what you thinking is the vacuum switch that runs on engine temp. Actually I have one on my 2.8 V-6 and I just though of trying something.
http://www.ebay.com/itm/Tomco-13312...Parts_Accessories&hash=item5655490f58&vxp=mtr
What I havent tried yet is switching from manifold vacuum advance when cold to ported vacuum on the carb when warm. I think mine switches around 135 degrees the center port is the common and it switches from one to the other.

 

[RonD]

Yes, you want to run a distributor with vacuum advance from a vacuum port above the throttle plate(ported), also most 0 vacuum at idle, not from the intake manifold, full vacuum at idle.

The Ford "distributor vacuum control valve" was mostly for cooling, when the valve gets hot the manifold vacuum is used which advances the timing and increase idle RPM, increasing fan speed and coolant flow, like sitting in traffic with A/C on and with an automatic, a pain to rev engine.
I didn't think they switched to manifold vacuum until they got to about 225deg, and as soon as coolant temp dropped, you were back to ported vacuum.
So it is pretty much only used when idling.

This was used because of emission standards at the time, they had to retard the timing to meet the standards at idle, run hotter, but they could, legally, advance timing if overheating in long term idle was an issue.

 

[jmcleek]

Thankyou for all of your respones. I have been reading a few things online that I will share with you.
http://grantorinosport.org/BubbaF250/perf/perf02c.html
http://www.fordmuscle.com/archives/2000/03/timing/
Yes, you want to run a distributor with vacuum advance from a vacuum port above the throttle plate(ported), also almost 0 vacuum at idle, not from the intake manifold wich is full vacuum at idle.
That was my thoughts too.
The following is from one of the above cites:


The vacuum signal from the carburetor spark port can momentarily spike when the throttle plates begin to move. Generally, this is more likely to occur when the throttle plates are closer to being closed (at or near idle).

To prevent pinging problems caused by such a vacuum signal spike, Ford used vacuum delay valves inline between the carburetor spark port and the vacuum advance canister on many engines. The vacuum delay valve is just a metered orifice that slows down the transmission of the vacuum signal, effectively buffering out any spikes in the signal.

You may need a vacuum delay valve if your engine has persistent problems with off-idle pinging, or momentary pinging at part-throttle acceleration, even when vacuum advance sensitivity is reduced to its minimum.

Back in the day when carbs where common , it wasn"t uncommon to have a summer choke setting and awinter choke setting.

 

[RonD]

My summer and winter choke setting was a wooden cloths pin on the "automatic" choke plate, manual chokes didn't require such fancy mods, lol.

302 compression ratio is 9:1 so I doubt you would have a pinging issue with a spike in the vacuum advance, even with regular gas.

And a vacuum delay can be added at anytime if you feel there is an issue that might be solved by using one.
These come with different delay times as well, too much delay and you will have sluggish off the line acceleration.

 

[jmcleek]

My summer and winter choke setting was a wooden cloths pin on the "automatic" choke plate, manual chokes didn't require such fancy mods, lol.

302 compression ratio is 9:1 so I doubt you would have a pinging issue with a spike in the vacuum advance, even with regular gas.

And a vacuum delay can be added at anytime if you feel there is an issue that might be solved by using one.
These come with different delay times as well, too much delay and you will have sluggish off the line acceleration.

thanks RonD. Was not sure if tha was needed.

 

[dangerranger83]

I may have to check and see if it has a summer and winter choke setting.

I do notice that Im when I get too the higher rpms, the power drops off very fast so I may be maxed out on my vacuum so I may try ported this weekend.

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[jmcleek]

I may have to check and see if it has a summer and winter choke setting.

I do notice that Im when I get too the higher rpms, the power drops off very fast so I may be maxed out on my vacuum so I may try ported this weekend.

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Sorry clarify, it was not uncomon to have to reset the choke from winter to summer in my area winter can get below -20 , summer or above +110.

 

[RonD]

Electric chokes are a little different in that they are time based so engine temp doesn't matter.
And they vary with voltage, if alternator is maxed out at 14.8v then they warm up faster, than at 13.8v, and on very cold days battery takes longer to recharge from startup so alt is maxed out for a few minutes.
Not much of a difference though, lol.
Electric chokes are usually fully open in 3 to 4 minutes.

I believe some people have used variable voltage on electric chokes to slow the warm up time, to have the choke working longer.
Like the older coil systems that got 12v when cranking then 6-8v via a ballast resistor(or resistor wire) while running.
You might be able to setup a similar two voltage system, winter(lower volts to choke) and summer(full volts)

never done this, just thinking out loud


And just as a note, when getting the 12v for the choke make sure you get 12v when key is in RUN position and no 12v when key is in accessory position, otherwise if you decide to listen to the radio for a few minutes(accessory position), the choke will be fully open when you try to start the cold engine.

 

[pcdoc2001]

Vacuum Delay Valves And What They Are Used For:
First off anyone who tells you to use ported vacuum for a vacuum advance is WRONG. Set the base timing, check the mechanical advance, (normally 34 degrees of advance at about 3600 RPM but varies engine to engine. My old Mercedes doesn't get full mechanical until 4600). Then hook up the vacuum advance hose to MANIFOLD vacuum. Your vacuum advance should rise up by about 11 degrees, Making for a smooth idle and more complete combustion of a lean mixture of fuel. That means that when you are going down the road about 50 MPH with very little throttle and high vacuum in the manifold you will get about 47 degrees of TOTAL advance, (usually about 45 because there will be a slight loss of vacuum from the throttle opening. Light throttle higher RPM, so you have the RPM giving you the mechanical advance 36 degrees and about ten more from the vacuum advance= 45-47 degrees.
As you approach a hill with the same throttle opening the vacuum drops because of the lower engine speed and increased throttle opening. The sudden drop in vacuum makes the vacuum advance drop out as well. The vacuum delay valve delays the speed at which the vacuum pot on the distributor loses vacuum. The vacuum advance decreases at a slower rate, it will still come down , just not as quickly. That's one way that they were used but not the most common way.
In a manual shift car they were often used backwards of this. When you shift the car, you drop the throttle between most shifts, The drop in throttle increases manifold vacuum suddenly and the vacuum advance maxes out the VACUUM timing. Your throttle pedal normally goes immediately back to the same position but the delay in the vacuum advance mechanism returning is slow. This leaves you with too much timing for the throttle percentage and the engine would ping. By using a delay vale to slow the vacuum advance down you could shift and return to the throttle opening before the vacuum advance reached it's full travel.
In a car with an automatic transmission, when the vehicle shifts you have a vacuum drop from the shift, (engine RPM drops, manifold vacuum drops). As the engine accelerates the mechanical advance works to advance the ignition, vacuum quickly rises with the accelerating engine so the vacuum advance begins to also add timing, sometimes too quickly for the higher gears, especially at lower throttle openings. The vacuum delay valve keeps the vacuum advance from returning as quickly to allow the engine to get into the upper RPM range before timing is returned. This reduced after shift pinging in higher gears but still gives you full timing at cruise speeds and was a VERY useful little tool. I hope this helps someone better understand this often thrown away little valve.