73 emissions questions

[QcodeAl]

Are you sure you wish to return to factory specifications here? You could bolt down a 1971 M-code intake to avoid the EGR and multitude of vacuum lines (which will inevitably wind up in a vacuum leak within 6 months if you use cheap vacuum hose).

-Kurt

Im with Kurt

after mucking around with my 73 Q i ended getting rid of all that rubbish and the car runs way better and still looks killer

I ve kept the original look with air cleaner assembly and standard rocker covers but upgraded intake and carb

Just out of curiosity. What did you do about the wiring for the devices you removed ? Even for me with my limited experience, if I see terminations laying around unused in the engine compartment, I wonder what's missing. There is no doubt I am the minority probably but some things like that bother me. I did consider un wrapping the harness back to where I could remove them cleanly.

Another thought I had was to discretely disable the systems but keep the original look. I have done something similar with vacuum systems in the past and just used silicone to plug the vacuum hoses in strategic places. So the hoses are there but not doing anything. I would then have to figure out how to de energize the electrical but possibly not. With no vacuum signal they may just be along for the ride.

Al,

I am out of the country until early next week...I can look for you then but the connections all look familiar. If I get a minute will look up on my wiring diagram.

Thanks Jeff !

I am traveling next week till Thursday, but will still be checking here for info and will probably have more questions also. lol

 

[cudak888]

Just out of curiosity. What did you do about the wiring for the devices you removed ? Even for me with my limited experience, if I see terminations laying around unused in the engine compartment, I wonder what's missing. There is no doubt I am the minority probably but some things like that bother me. I did consider un wrapping the harness back to where I could remove them cleanly.

The Mark V was converted from a 2-barrel factory intake to an Edelbrock 4-barrel (painted to match the block), so the EGR plate was deleted right then and there. Deleting the EGR plate resulted in the removal of 70% of the vacuum lines to start with, which were doing nothing other than diverting vacuum to operate the thing.

The other 30% were do-dads designed to adjust the vacuum response in one way or another - including a check valve on the thermostat outlet which 72HCODE will point out is rather beneficial for adjusting timing based on temperature, but I haven't had any problems using vacuum straight off the carb.

That, and I'd rather have a slightly rich mixture than a lean one from shot Chinese vacuum lines that dry rot in 6 months.

The air/smog pump was removed from the block, so that also took care of the hoses and canister that hooked to the intake manifold.

Other than running a line from the carb to the vacuum advance, and the plethora of vacuum junk for the headlights off the manifold's rear T, I don't think there's any other vacuum line running off the engine. The V has Hydroboost, so I don't even have vacuum going to a brake booster.

This is what it looked like when done. The spark suppressor is there for tests only:

-Kurt

 

[RC92234]

Here is the Q code vacuum diagram for a 73. I also have a June 73 Q code and have researched a fair amount. The 4V vacuum and sensors seem to be quite a bit simpler than the 2V cars. Happy to help if I can.

Any chance this image is still available? Sounds like what I’m looking for!

Unless it’s 3-14A. That has two solenoids.

 

[RC92234]

If I want to omit the solenoid at #5, then the middle hose from #1 will feed the single vacuum distributor advance directly. 
 

Is the #6 Spark Delay Valve still needed?

 

[Hemikiller]

If I want to omit the solenoid at #5, then the middle hose from #1 will feed the single vacuum distributor advance directly. 
 

Is the #6 Spark Delay Valve still needed?

You can safely bypass the entire system and feed directly from the PVS valve to the advance unit. 

 

[RC92234]

Music to my ears. Thank you.

 

[PeteG41]

in all honesty, the EGR and all those extra vacuum and electric solenoids is just asking for problems.

if your trying for factory concourse that is one thing or if you have draconian state emissions laws that require the car maintain all original emissions i could understand.

I you have the choice i would not start putting all that stuff back on the engine.

some things you should use, like the PVC and the Distributor Vaccum Control Valve, ported vacuum is fine, having a duel vacuum advance distributor is fine, fuel vapor canisters all fine.

but things like the EGR just clog everything up with Exhaust soot a smog pump is a nightmare and a joke.

spark delays cause ignition problems. speed sensors and extra vacuum motors with the age on the parts is asking for vacuum leaks and malfunctions.

you might want to just restore back to an early 73 setup that eliminates half that emissions control stuff it will look factory to people looking over the engine but you will have less issues and a better running engine.

if you really do have all the speed sensors and ambient temp sensor it might be cute to get them working, but understand that those were designed to keep the exhaust temp high to try to burn off exhaust gases then part of that is fed back into the motor intake for re-burning(before the catalytic converter) they will have negative effects on the motor running cool and clean internally, and performance wise. you could get a EGR block off plate and eliminate most of the controls under the hood and still have something that looks correct when looking under the hood. some of the stuff should be kept as it does some good but the rest is a short circuit and a vac leak bomb.

Thread from way long ago, but for the EGR block off plate, where did you find that?? I've read a 351c fuel pump block off plate works, but not sure if that only applies to much later years of mustangs.