This morning I got to the bottom of a choke problem on the old Holley 8007; it would not pull off to clear once started. The electric heater would eventually crack open the butterfly so the car would idle. Also it would most often not get up all the way on the high idle cam, requiring some throttle feathering until it ran for a minute or so.

Problem was caused by a dragging lever that is actuated by a little piston, and connects to the bimetal spring. When I rebuilt the carburetor several years ago I recall being instructed to wrap the tang coupling bimetal spring and little piston with tape. Once that tape was removed things became free to move, and now she hits the high cam every time, butter fly clears as it should.

Now after running some fresh gas through the carburetor, and driving it a hundred miles or so in the last month, and readjusting idle mixture screws the car runs much better, and will idle down below 500 rpm.

Engine has been a little clattery even though I adjusted the valve lash late last summer to intake at 0.018â€￾ and exhaust at 0.021. Before making any new adjustments I measured lash first to see what if any changes occurred while car sat all winter… LOL Sure enough intake ranged from 0.016â€￾ to 0.018â€￾ and exhaust 0.018â€￾ to 0.022â€￾.

Where I don’t have a cam card specking lash measurement, I have been futzing around looking for settings that will make this engine happy. This time the settings are I= 0.012â€￾ and E= 0.016â€￾; engine is nice and clatter free just light melodious ticking.

Next came a compression test, #1 to #6: 150#, 140#, 145#, 140#, 145#, & 140#. These readings are down by 10 psi from previous testing. I attribute this fall off to tighter lash that adds to the overlap of this cam. Is my assumption on track?

Car is less peppy, in gear idle is not so hot, there is some loping at 1200 rpm, and vacuum is down. I didn’t run her up to high rpm.

Now tomorrow I plan on lashing to looser settings, and running a second compression test. Any guidance on settings would be appreciated.

A few details:
At 0.050â€￾ lift cam has 22* overlap,
Duration: Exh. = 236* & Int. = 235*.
Exh. Lift at tappet = 0.324â€￾ with center line of 113* (Total lift would be times 1.5 less lash)
Intake lift at tappet = 0.321* with center line of 99*

Mixture looks as it is burning about right, these plugs have about 3 to 4000 miles on them, also each cylinders lash and pressure:
[URL=http://s294.photobucket.com/user/wjajr/media/Dart%20Engine/002_zps42507083.jpg.html][img]http://i294.photobucket.com/albums/mm87/wjajr/Dart%20Engine/002_zps42507083.jpg[/img][/URL]

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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

Tighter lash will keep the intake valve open longer on the compression storke reducing the trapped air volume and final pressure.

As you can see, a small change in overlap really changes the low speed characteristics of the engine.

_________________
Joshua

Looks good but run more lash.....with that cam.

_________________
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

As suspected after this experiment overlap is kicking me in the pants below 4000rpm or perhaps higher.

Any suggestions on settings after looking at cam specks, or shall I just keep farting around until something works better. What would be the difference if say exhaust opening were to be shorten, and intake stayed where it is.

Overlap at 0.006â€￾ at tappet is 101*
Duration at 0.006â€￾ at tappet: exh 314* Int 315*

I see that Erson E 47000: TQ 20 M lists 0.022â€￾, & TQ 30 M list 0.023â€￾ of lash both I & E. Is this where I should be shooting for both valves in low 20 thousands?

Can you think of any cam similar to my stick? When I got the car there were two little Erson Cam stickers on the rear windows suggesting that perhaps my cam is an Erson. The guy that built the car in early nineties said he got Clifford’s biggest cam at that time…

I have looked over [url=http://users.hal-pc.org/~bwhitejr/Slant_Six_Cams.pdf]this listing of slant six cams[/url] and don’t see a direct match to what I measured a few years ago. However the foot notes are of interest describing how overlap and duration changes move power and torque up and down the rpm band, and recommendations for carburetor size and rear gear in some cases.

I wish I were closer to some of you racers and engine builders for some hands on with this car… Oh well.
Sorry I’ve rambled on too long.

_________________
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

What you are dealing with in the unknown cam is how the lash ramps are built.
Doc taught me a method for lashing an unknown cam, or any cam while we were at the track a few years ago, and it has resulted in some pretty decent results.

First, loosen each valve, one at a time, running and hot. There is a point where the valve will go from simply a noisy clatter, to a loud "TACK" Measure that lash.
Now, tighten that lash up a couple thousandths. Repeat for all the valves and record the values. It's not at all uncommon for the lash ramps to differ.
Next is a bit I'm playing with. Listening for tell-tale tight valve miss. Tighten the valve until it starts to miss on that cylinder. Measure it.

Remember to remove your tools from the rocker when listening and measuring the lash. The wrench will mess up the final lash.

What's the difference? If it misses at .012" and doesn't make a loud noise until .020" you have .008" between them. Split the difference, and try .016" on that valve. That's going to be pretty extreme, and unlikely that the lash difference is that big, but I used easy numbers to play with.

Stick it in the middle, and repeat for all the remaining valves. Check your idle quality. If it needs to improve move closer to he loose end. Just keep it a couple thousandths tighter than where it goes loose. Stay away from the tight end of the spectrum to avoid valve damage. If it's leaking tight, it will wipe out valves.

I'm yet to get a cam card with a lash setting that worked right!

Usually, whatever was suggested was too tight to run well.

2¢

CJ

_________________
Part of Tyrde-Browne Racing

Eureka! Mon Ami!

Hey Thanks CJ, this is just what I need. I knew someone out there in solid tappet land had a real world method of dialing in cam lash that is more empirical than seat of the pants.

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

Per CJ I followed his instructions to determine lash limits, and ended up with all of them set at 0.022â€￾. Engine is nosier with valve train commotion, but seems to be happier at those settings.

I have not conducted a follow up compression test, but will tomorrow.

Most improvement is how the air/fuel mixture gage reads after this latest lashing. The carb is running leaner with gage in ideal zone to lean under almost every condition, excepting steady cruse with small throttle opening on flat ground is rich, and when power valve opens up it goes to rich. Vacuum readings are up three to four inches off idle above 1600 rpm than with yesterday’s settings, and now when coasting downhill A/F gage swings lean to ideal where previously it pegged on rich. Predictable idle in gear at 700 to750 rpm, and in park 1100 rpm both are leaned out as well, no more rich mixture stink. This idle improvement allows one foot driving around town, no more feathering to keep it running. Also most of the run-on after shut-down as subsided.

Timing occasionally hangs up refusing to drop back to base setting staying around 18* which keep rpms up in park. Maybe I’ll change the light spring for stiffer one and see if that helps. I have to keep timing down to 12-13 to keep idle low enough so when shifting into R or D it does not slam into gear barking the tires. I had the distributor apart last fall to clean and lube the governor. A side note; Mrs. Wjajr strongly dislikes hard shifts during ice cream sorties…

Back to coasting downhill around 2700 rpm and if hill is steep enough engine will pull steady twenty inches, once off the hill back into steady small throttle opening cruse, gage will swing to full rich, I can smell gas and rich stink, and it will stay full rich once back onto throttle for a ¼ to ½ mile or so before acting more normal. This odd condition seems to happen on same hill during the last few test drives. Could the accelerator pump circuit be syphoning, or boosters pulling excess fuel?

Power seems to be back up, secondaries eagerly open around 3600 rpm using purple spring with a strong surge of acceleration as if the primaries are too small.

_________________
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

Some noise is fine. I like the Doc/CJ procedure for initial sweet spot. IGNORE all valve lash recommendations from all cam manufacturers, unless the cam is near stock. I always end up somewhere else...

My "final tune" is to set the lash as above or with some initial guesses, run it cold (with good carb and idle), then see if the idle quality deteriorates under hot running (up to hottest it will ever get). If idle gets worse when hot, loosen in 0.002" increments until it does not change cold to hot. This takes time! Some noise is expected and necessary.

Lou

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Home of Slant6-powered fun machines since 1988

Now you need to look at the Power Valve. At cruise, what is your vacuum reading?

Add two inches to that, and put that power valve in. That will keep you out of the power valve when just cruising around.

Once you have that figured out, you will want to revisit your primary and secondary jets. To lock the secondary out, install the black spring. Keep that sucker closed! Go drive and watch your AF gauge. Watch what is going on, and at what throttle settings and vacuum settings. Keep away from the shooter at first. When your pumping your foot, all bets are off. Look at cruise. If it goes into lean surge, bump it up. If it stays rich, bump it down. Next, go after the secondary. Go intermediate on your secondary spring. Don't go crazy.
Watch the gauge. When you wallop it, watch what happens. I like to take a helper along to watch it so I don't do something silly, like drive into a ditch.

Next, look at the pump shot. Your running a 390. right? Pink cam on #1 is a pretty good bet. Orange will usually make your tail pipe crusty. Not always. Let your instruments be your guide.

I think I ended up on a 31 or so shooter. Been a while. Went to a Carter, and only look back intermittently now. Base settings on a Carter or Edelbrock 500 with a decreased pump shot works pretty darn good!

Economy is slightly less than the Holley out on the freeway, but it just doesn't need futzed with. Ran it from negative to greater than mile high Density altitudes and it's handled it. No screwing with jet changes. I like that.

I'll grant you, I had explosive power with some of the Holley carb setups, but the car went into the 14's on the Carter. Not with the Holley. (No gaskets below the fuel level either..)

CJ

_________________
Part of Tyrde-Browne Racing

Ceej:
[quote]Add two inches to that, and put that power valve in. That will keep you out of the power valve when just cruising around.[/quote]

Would that be cruise vacuum over 2? Currently cruise vacuum is 14 to 16 inches below 2700 rpm (45 to 50 mph); it’s hard to find a flat stretch ground around here of any length for a good reading. For now I’ll SWAG cruise vacuum at 15â€￾. That translates to stock 390 PV of 6.5. I believe a 5.5 PV is installed, and it does not kick in until a substantial uphill grade is encountered. Transition from boosters to PV is smooth right when needed. Currently there is no lean surge as carburetor transitions between various circuits. Surging was a problem I had last fall when a 3.5 and 4.4 PV were installed, and I tried to correct with 28 shooter; it was unsuccessful hence the current combanation.

I had a 28 no syphon shooter installed for a spell last fall, and it was too much, now back to a stock 25 with orange cam on #1.

[quote]Once you have that figured out, you will want to revisit your primary and secondary jets.[/quote]

I have no secondary jets, just stock metering block. When all in and secondaries are open, A/F mixture meter reads Ideal; all yellow and one red (lean) and one green (rich) lights are going simultaneously.

Currently carb is running 512 jets which are out of the box stock for this carburetor. I don’t have a 52, 50, or 49 jets on hand to test.

One test I’m going to do is install black spring on secondaries as you recommend to kill the back half of carb, install PV plug, and try to figure out when boosters come on line, and how much or often it runs off of transition circuit during cruise.
Once I figure out how transition circuit inter acts with main booster, I can better tune idle/transfer mixture. Currently there is a hole drilled 3/32â€￾ in each primary throttle plate to get idle mixture screws to respond; idle is ideal to lean swinging back and forth as engine lops. What I’m trying to figure out is how this adjustment affects small throttle plate opening cruise conditions.

Also I’m trying to figure out if lope is caused by weak osculating vacuum signal messing with mixture, or solely by cam overlap. I noticed as lash adjustment opened up engine developed a rolling rpm change of 50 to 75 rpm. At in gear idle, lop is pronounced, and gage needle swings up and down from 2â€￾ to 6â€￾ caused by, I’m guessing, each overlap event as it takes place. There is no fuel dribbling from boosters during lop so I don’t think PV enrichment is playing a role in rapidly changing vacuum below PV’s rating.

_________________
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

Not sure what my brain was doing....

If your cruising at 15" HG, get a high flow 10.5 PV. You need it to come in when vacuum goes shallow compared to normal operation. The high flow is needed, as our vacuum can dump so quickly with the relatively large carburetor.
To run a PV plug, you'll have to have the primary dialed, then jet up by at least three numbers.

CJ

_________________
Part of Tyrde-Browne Racing

For the bystanders watching" the "High Flow" power valve is the version that has the larger rectangular holes in it (sometimes dealers and enthusiasts will call it the 'picture window' power valve). The other variety offered has lower flow and has a series of smaller circles instead. Also as an FYI, a couple years ago Holley cut down on some of these models so some will be available in the picture window only and some in the hole version, the 10.5 PV is available in the picture window, but Holley discontinued the 9.5 in the picture window version and now only offers it in the 'hole' version. For those using a dual value PV for mileage, they only come in the small hole version.
This only applies if racing, if the secondary spring is dialed conservatively for street (i.e. a heavier spring), it will not loose vacuum signal as fast and can also improve mileage as the secondaries don't 'flop' open as quickly (so if you dialed the car in and installed the short yellow spring, recalibrate using the purple spring instead for daily driving- install the quickchange pod and switch back to the shorty at the track).

-D.Idiot

Ceej:
[quote]Not sure what my brain was doing....[/quote]

Oh how I know the feeling.

Vacuum drops real fast below 3000 rpm when secondaries are closed dipping seamlessly into power valve with first ¼ to ½ throttle travel movement when under way.

All my power valves are the “picture window typeâ€￾.


Cj:
[quote]To run a PV plug, you'll have to have the primary dialed, then jet up by at least three numbers.[/quote]

I know jetting up is reqired, and have run this carb that way for a few weeks in the past, it was a disaster, poor fuel economy & performance, and pig rich. PV Plug is to be used as a temporary tool just to get a feel how A/F gage responds as carb cycles off idle and transitions to main jets during a short test run, and then current PV gets reinstalled.

DI:
[quote]This only applies if racing, if the secondary spring is dialed conservatively for street (i.e. a heavier spring), it will not loose vacuum signal as fast and can also improve mileage as the secondaries don't 'flop' open as quickly[/quote]

[quote](so if you dialed the car in and installed the short yellow spring, recalibrate using the purple spring instead for daily driving- install the quickchange pod and switch back to the shorty at the track).[/quote]

I have the quick change pod installed. A pet peeve of mine is why dose Holley nickel & dime us for all these stupid upgrades, just build the damn thing with them.

Currently purple spring is installed; I have run weakest yellow spring at track with no bog problem. I would run the weak yellow all the time except it starts to crack secondarys open as the load on engine increases (vacuum drop) on hills at around 40 to 50 mph. As the car goes up the grade one has to let up on throttle to maintain constant speed. It’s kind’ah weird. The car will also do this with purple spring on real steep long hills, but those hills are infrequently encountered in this area.

I did not get to playing around with follow-up compression test today, stay tuned, tomorrow will be dryer & warmer for the test.

_________________
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

More lash....more seat time and higher compression test numbers. With more lash you will have a smoother idle with that crazy cam......

_________________
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

Another pile of words:

Tuning continues.

First, I pulled PV replaced with plug, and went for a warm up five mile ride. As expected engine would fall flat on its face once throttle was opened. However, when at steady cruise on flat ground with 512 jets, a rich condition was reviled. When throttle was opened ever so slightly mixture would descend into ideal.

Observing vacuum gage closely during numerous throttle openings at different rates it does not take much opening to dip into single digits of Hg. Meaning power valve,, if installed, would be easily activated.

Once warmed up I performed an engine off hot valve lash. I know it should be running, however that thing is dancing around loping its little hart out at a low enough rpm to keep a wrench on the adjustment bolt, and get any kind of feel with feeler gages. First thing I did was check yesterday’s lash, and found some sloppy work, and correctedseveral valves to 0.022â€￾ lash, and ran a compression test. Result was higher more even cylinder pressures between cylinders. Than it occurred to me to lash to compression readings and see if they could be evened out, possibly raised figuring this would yeald the same as listening to engine as lash is adjusted; and it is not dancing. So long story short some settings are at 0.024â€￾, 0.025â€￾ and 0.026â€￾; 0.026â€￾ being the clat-clat threshold lash.
From cylinder 1 – 6:
Yesterday’s sloppy lash @ 0.022â€￾: 150#, 140#, 145#, 140#, 145#, 140#
Correcting sloppy lash @ 0.022â€￾: 155#, 155#, 160#, 150#, 160#, 155#
Fine tuning @ 0.024â€￾ to 0.026â€￾: 165#, 165#, 165#, 163#, 163#, 163#

Evening out cylinder pressures improved previous idle vacuum needle oscillations of 2-6â€￾ Hg. to 6-8â€￾ Hg. The waging was moved up 4â€￾ and damped down consiterably; a good thing. For the hell of it I tuned idle mixture before replacing PV plug to try to figure out if PV had any influence on idle mixture control. Adjusting idle mixture closer to an ideal setting was much easier than previous attempts in the last four years. Using a digital volt meter yielded easy reference voltages, and showed mixture would run rich cycle to lean than back rich, and each time it ran rich engine would change rpm or the other way around. I could not figure out which came first the chicken or the egg with the rolling idle rpm. In park idle vacuum also increase a few inches to 13â€￾ Hg,

A 6.5â€￾ PV had been installed previous to the test plug not a 5.5 as earlier reported, it did its job smoothly; I installed a 5.0â€￾ PV this time to see if this would help settle down in gear idle lope, and be under in gear wagging vacuum readings of the 5.0â€￾ power valve.

Test drive with 5.0 PV, 512 jets, purple spring seemed more docile, not as spunky off the line, secondares still gave a strong surge with no flat spot. Cruise still is rich on flat ground, and idle is harder to tune as mixture keeps changing as rpm runs up and down; lope is now less pronounced at in gear idle.

I’m out an eighth turn past 1.5 turns on idle mixture screws. The mixture change is very abrupt one eighth turn in either direction at this point will over lean or over rich the mixture. I’m wondering if throttle plate holes should be enlarged from 3/32â€￾ to 1/8â€￾, or repositioned away from idle fuel outlet below throttle plate.


After test driving six miles, engine would not idle back down to 1000 rpm staying at 1400 rpm that I had set it too. Timing had moved from 12-13* to 18*, I suspect light spring is not strong enough to keep base timing, or weights are sluggish. I had the governor out to clean and re lube last year; it’s a bit of a mystery and needs to be yanked.

_________________
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