no

The primary throttle is linked to your foot. So if you've floored it, the locking mechanism for the secondary throttle is out of the way.


If you've only given it half-throttle, the locking mechanism is probably engaged, and the secondaries won't open no matter what rpm...

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

The vacuum diaphragm that operates the secondary throttles is done through a passage that's a port in one of the primary venturis.

The vacuum created has to overcome the spring.

This vacuum is proportional to the airflow going through the primary barrel.

So a smaller engine needs more rpm to get the same airflow than a larger engine.

What size engine are these springs rated for?


As a first time guess, I'd multiple the given spring rpm by 1.5 to get the spring rpm for a slant...... (roughly a 225 vs 340 engine)

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

SV162:
Your car, depending on gearing, likes to start opening secondary at about 60 mph. --- lower rpm with tall gear, and higher rpm with short gear. My car is running a 3.55 which runs about 60 mph at 2800-3000 rpm mid way between a 3.24 & 3.7 gear.

Emsvitil: AV162, I revisited Mike Urich’s spring vs. opening chart that uses a 350 cid & 402 cid as examples. Using Emsvitil’s 1.5 correction factor for a 225 cid engine the opening rates come real close to the rates you listed:

Urich also found the black spring would not allow full opening on both 350 & 402 engines.
Based on these bits of data I shall install a purple spring to keep that secondary closed at and below my general cruse speed. Hopefully this will reduce fuel consumption.

Contrary to previous seat of the pants SWAG analysis, the car is still swilling fuel at an alarming rate yet to be calculated; half tank, by gage, in 120 miles… Granted, some of the last 30 miles have been hot dogging it while trying to ascertain operating characteristics of that 390, but half a tank is not so hot.

DI, I’m holding off on the LED indicator light for now, a good idea, and grandpa’s super simple coat hanger method, which I really like, only because we have just wooden & plastic hangers. As well, Ted’s vacuum tap is on hold. I’ll just make a few spring changes.

Emsvitil:
I’m always dipping in past half throttle, so with the lightest spring installed, the secondaries must be cracking open often where 2400 rpm yields around 40 mph in top gear, not to mention first & second’s generous helping throttle.. Also, this a point where the converter is not always locked, and I can get 2 to 300 rpm of slop depending if going up hill, or on flat ground. So I think for now, moving the opening rpm to around 3000, will stop most unwanted activation in the name of economy.

We'll see.
Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

You may not be dipping into the secondaries, but dipping into the power valve on the primaries...............

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

That is why you need to drive by the vacuum gauge. You can watch when the power valve opens and the secondaries.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Ed:
You may not be dipping into the secondaries, but dipping into the power valve on the primaries...............

Ted:
That is why you need to drive by the vacuum gauge. You can watch when the power valve opens and the secondaries.

Power Valve is currently plugged, how will vacuum gage react when secondaries open?

At WOT, vacuum gage is parked at or damn close to zero inches. I do know from previous testing, once rpm gets into mid 4000 rpm range, vacuum bumps up 3 or 4 inches during steady cruse over 3000 rpm cruse. But, that is manifold vacuum, not venturi vacuum.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,

Since you have the power valve circuit plugged, if your cruising along at 3000 rpm and seeing 18" to 20" of vacuum and you push down on the throttle a little, the vacuum will start to drop quickly as the back barrels open and may cause a sag in the response if the spring is too soft like the short yellow spring. It depends on if you give it a quick blip or just mash the throttle. It may be more pronounced at a different rpm, say 2000 or 2500 vs 3000. Obviously the the higher the rpm the less you may see on the gauge. That is why I mentioned plugging your gauge into a fitting on the secondary housing for easier monitoring. Locking it into second gear will make the test easier since the transmission won't be able to kick down and throw everything off by going to zero vacuum.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

Some of you may have been following the continuing saga of my, now almost identified, race cam over in “Otherâ€￾: [url=http://slantsix.org/forum/viewtopic.php?t=41613] Got the Poop…[/url] thread. By loosening the lash on intake to 0.024â€￾, and keeping exhaust lash at 0.026â€￾ I have been able to pick up a bit more vacuum at idle and at road speeds.

The last tank of gas that saw a lot of testing, jet size adjustment, and hard driving, it yielded a crummy 14.2 mpg. Today I took the car to a car show on a 200 mile round trip on two lane 45 – 60 mph roads. This tank saw 17.5 mpg with power valve blocked off, and 57 jets. I know these are small mileage samples, but that is a 25% increase over the last tank, and very close to what I was seeing with the 2.5 power valve in place & 51 jet combo that I started with before all this jet tomfoolery took place.

I would like to see better fuel economy, but I don’t think is in the cards with this aggressive cam. To put this in perspective, my first Dart that I had in the early seventies, had a 273 V8, three on the tree, 13 inch tires, and 3.24 rear gears, and it would only get about 16 mpg on a good day, and wasn’t near as quick as this car is 40 to 80 mph.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I finally picked up a replacement 2.5â€￾ Hg Power Valve, installed it in place of the plug, and test drove the Dart. There is now stronger 3000 to 5000 rpm range power, but no improvement idle to 3000 rpm with this properly operating valve.

By increasing in park idle to 1100 rpm, and that, in turn, increases in gear idl rpm to 700 to 750 the vacuum needle stays above 3â€￾ Hg 90% of the time when ingear.

Now an interesting phenomenon exhibited by this engine is the “in gearâ€￾ idle sometimes will bump up a few hundred rpm after a little power braking & WOT. Than without notice, idle will settle back a few hundred rpm for a few days until the next pounding. The advance in idle speed is not incremental at a stop in gear it will be putting out 550 rpm (before this power valve installment), give it the boot and the next time she comes to a stop the idle is up, and no blipping will knock it down. I don’t think my throttle cable is hanging up, and keeping throttle plates cracked open a little more than they should.

Would a sloppy harmonic balance cause the timing to shift just enough to advance timing thus the rpm? Remember my timing is flat until 1500 to 1600 rpm where it begins to increase.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Bill,

Did you ever solder up the holes in your throttle plates? If not, that might help stabilize the idle.

_________________
Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

[quote]Did you ever solder up the holes in your throttle plates?[/quote]

Ted, I did not.

I’m trying one alteration at a time with this baby. Now that I know I can pull 13â€￾ Hg @ 1100 rpm, and 6â€￾ Hg or so in gear idle, keeping that 2.5 from pumping open & closed to the beat of the vacuum needle, I shall plug the drill holes in the throttle plates. My guess is that I’ll be able to turn in the idle mixture screws in a bit more when less air is passing those plates. As for idle quality, we’ll see…

Now to locate my solder, flux, and soldering iron that is still packed in a moving box somewhere in the man cave... This may be more of a project that I bargained for.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Your idle (pwr brake, up/down) observation might be the mechanical advance changing timing quite a bit in the 500-1000 RPM range. This will cause very erratic idle and vac readings. Have you mapped your timing curve?

Lou

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Home of Slant6-powered fun machines since 1988

Lou,

[quote]Your idle (pwr brake, up/down) observation might be the mechanical advance changing timing quite a bit in the 500-1000 RPM[/quote]

Not power brakes for stopping, but power braking for burn outs. The car has manual disks.

[quote]Have you mapped your timing curve?[/quote]

Yup. There are several threads in the “Engine Sticky FAQ’sâ€￾ under "Re-curve" of my re-curve ordeal, guided by AgressiveTed, with advance curve data, for your viweing pleasure.

Bill

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

I understand you meant power braking for burnouts. OK, I assume you have checked that your mechanical and vacuum advance are not changing in the 500-1100 RPM range. If either one is changing, that will cause poor idle. With that low a vac reading at idle, if the vac advance is plugged in at all it could be moving your timing all over.

Lou

_________________
Home of Slant6-powered fun machines since 1988

Lou,

Haven’t plugged in the timing light for a while, but timing was rock solid until about 15-1600 rpm by design due to this radical cam that is most likely designed for use in conjunction with a standard transmission.

My dilemma, worded a different way, because perhaps I wasn’t clear previously is; for several starts, or just driving around in traffic after I have set the in park idle to say 1000, which will yield 600 or so in gear. The idle will drop 200 rpm or so for no apparent reason and stay the way, than after a little Hot Roding it will bump up 200 rpm or so for a period of time. I never know how the engine will be ticking over when I come to a stop sign, 450 rpm or 650 rpm. At 450 the engine is apt to stall after a long run on the road, at 650 it idles with a great lope, but won’t stall.

If I’m driving with hearing protection (this car is damn loud with the top up in that mid 2000’s rpm drone) , and don’t watch the tachometer, and come into an intersection for a landing at 450 rpm, it stalls every time, because I can’t always hear the engine once it idles down.

I guess I need to inspect my throttle cable & the bracket that attaches it to the base of the carburetor for movement. I now suspect that it is swiveling a wee bit after a heavy footed WOT, something it was doing when I first cobbled up the kick down cable & throttle cable connections.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC