Continuing troubles

[Inline6Merc]

Hi all! I've been trying to dial in mt setup for the past year. I have yet to uncover the setups true potential. I'm currently running a 200ci motor, with 10 to 1 compression, clay smith 278 (110 lobe)cam, CI head, DUI, and a Pony Carb's 480cfm carb. The rest of the drive train is a C4 tranny with custom high stall converter and 8inch rear.
Problem 1.
That the car idles at 1200 in drive. The carb idle set screw is all the way out, and the vacuum is hooked up to the manifold. Timing is set with a vacuum gauge. I get 19" in park and 14" in drive.
Problem 2.
The car seems to have a miss as the tach fluctuates between 1200-1100 or so. Along with that when idling in traffic the car starts to load up.
Problem 3.
From a dead stop if I accelerate hard (WOT) the car takes off and winds up to about 3000 rpms and falls flat to about 2600 rpms and slowly crawls up the rpm range until I take my foot a bit out of it. The thing is from a dead stop the car doesn't even light the tires up. The tires are pretty old with not a lot of traction and the rear gears are 3.50.

The Dizzy advances 24 degrees @ 3000prms according to the shipping papers that came with it. The carb came already adjusted from Pony with 43 jets in the primaries and 62's in the secondaries. Fuel pressure is around 6psi.
I've been thinking about the problems and am curious if the vacuum canister can be adjusted to lower the idle rpm. Also if timing from the dizzy or cam advancement is playing a roll in the lack of low end performance or if its carb related. If any other questions regarding the set up is needed feel free to ask. I'm looking for any help at all and thanks in advance!

-Curtis

 

[Explorer]

Bear in mind my dealings with the Duraspark have been with V8's. Using manifold vacuum is actually taking the vacuum advance out of the equation as it is advancing max all the time. I would try running on ported vac. or vacuum disconnected and plugged. Your initial timing should be set with all vacuum disconnected and plugged anyway. Then try it, hook to ported, try again, and then full manifold vac. and see what happens. I have one that prefers no vac at all. The adjustment in the vacuum can is for fine tuning on the road. If it spark knocks under load then you can reduce the signal there. Hope you understand what I'm saying, sometimes I'm not too good telling, but can show a lot easier. Here is a good link for understanding the principals of the Duraspark: http://vb.foureyedpride.com/showthread.php?t=22229

 

[WerbyFord]

Curtis,
I will try to crunch a few numbers on your car with the Gonkulator.
I had your car in the database with its old dog engine at
20.58 at 62.2 1/4-mph
Sound right?

With the new setup, a couple questions and ideas:
1. What exhaust pipes/muffs do you have?
2. Do you know the weight of the car?
3. Is the secondary of the (1.08 Autolite 4100?) opening? Paper clip test?
4. What air cleaner is on top of it? Flat base or drop base or radiused base?
5. What is your total initial+mech timing at say 3000 and above? (vacuum disconnected)?
6. Have you tried richer primary jets? 43F jets seems very lean in there.

In any case, so far the Gonkulator shows your engine making peak torq about 4700rpm and peak power about 6200rpm so something is amiss - it should be a screamer up high.

 

[Lazy JW]

..... the vacuum is hooked up to the manifold.....

Unhook the vacuum advance. Plug it off. DO NOT re-connect the vacuum advance until ALL of your other tuning issues are solved. Then hook it up to ported vacuum only.
Joe

 

[Mustang_Geezer]

If it wont idle below 1200 rpms with the idle screw on the throttle shaft all the way out you have a vacuum leak.

Did you use the Oz 250 2v intake gaskets or make your own? If you used the Oz ones, rip the intake back off and throw them in the trash and make some new ones with some store bought gasket material. They do not line up correctly with the intake and will cause a large vacuum leak.

Whats your base timing set at with a dial back timing light?? Whats the timing read at 3000 rpms with the advance light? Mine likes 38 degrees total (vacuum unhooked) @ 2800-3000 rpms.

The vacuum gets hooked up to the carb at the timed vacuum port not the intake.


Later,

 

[Inline6Merc]

It was a busy week but today I got around to messing with the Comet. Turns out Mustang_Geezer is right. There is a vacuum leak. The intake manifold doesn't have the Oz head gaskets so its fine. Its leaking from the base of the carb. I have the 1/2" adapter from CI on the intake along with a 1" spacer on top of that. I think the 1/2" adapter is a bit off because the studs aren't exactly drilled straight because I have to hassle with the carb to get to sit flush on the manifold. Im gonna order a new bottom adapter from Mike and through all new gaskets on it and see how it runs.


-Curtis

 

[Inline6Merc]

OK so I put a new gasket on today and it seemed to have solved the vacuum leak as I can spray carb cleaner around the intake and other places and the engine does not raise. I checked the timing with the vacuum advance disconnected and plugged off and I get 34 degrees @ idle. Yes at idle! I hooked the vacuum advance up to the carb rather than the manifold and got the idle down to about 900. (The idle screw is barely touching) I took it out for a test drive and from a dead stop with WOT, it spins to 3000 and drops to about 2000 or so and slowly crawls up. I feel there is a timing issue.

WerbyFord, Those numbers you have about my old engine are correct but that was only in first gear. I couldn't get the car to shift so i turned 62 mph in low the entire way. As for exhaust I have 2" all through out with Smitty's out back. The car is about 2900lbs. I'm confident the secondary's are opening, as it moves pretty good on top end. Im running a 14" by 3" air cleaner and the carb was tuned by Pony. Remember a 43 Ford jet is different than a Holley 43 jet.

-Curtis

 

[mach1 mark]

I think you're on your way. I'm glad to see someone using the Autolite 480. I've got one and I haven't put it on yet. Kind-of nervous. Anyway, I think the biggest problem is the C4. With the C4 your not going to get tire spin. And when the C4 goes into second the car seems to go flat; I believe that's just a Ford defect. Meaning that I've owned a lot of Fords and they always seem to do that; just go flat. I have a C4 and about the same set up as you. It takes off from start great and then goes into second and just kind-of flattens out. I find myself manually shifting the gears, then I get the power. I can be cruising along at 40 mph and throw it into second gear and it screams by the other cars without even pushing the accelerator down more. I don't know the engineering behind it, but I believe its the gearing of the C4 that makes the car go flat. As far as the ideal, you're not going to get a great ideal from the large cam. My car will ideal in gear at a light, but its rough. I usually just pop-it into neutral if I'm going to be at the light for a while. Good luck

 

[Explorer]

The C4 has 2.46 first, 1.46 second and 1.00 third vs manual 3 speed of 2.99, 1.75. 1.00. With your engine having a high rpm power band, the C4 gearing could be hurting you. The shift points can be changed a bit with adjusting the vac. modulator and a few other tricks I can't remember. I'm sure there are some C4 experts on here that can confirm or disagree with my thinking, plus make more informed suggestions. This is just my opinion and am by no means an expert. I'm trying to balance an engine build with my tranny and rear end ratio myself.

 

[Inline6Merc]

The lack of gearing for the transmission does not explain why the car does not take off clean from a dead stop. It wont go more than a few feet after it stumbles and I have to let off the accelerator to get the rpm's back up; but after that it takes off.Same thing when cruising, if I step down on it all the way suddenly it picks up for a second and then drops and doesn't want to accelerate until I let off a bit. I'm confused by why the timing reads 34 degrees at idle. It should be 34 degrees total advance at about 3000rpms not at 1000.

-Curtis Hanson

 

[Lazy JW]

The C4 has 2.46 first, 1.46 second and 1.00 third vs manual 3 speed of 2.99, 1.75. 1.00. With your engine having a high rpm power band, the C4 gearing could be hurting you.....

It also has a torque converter which gives almost a 2:1 additional reduction.
Joe

 

[WerbyFord]

Curtis,
I would sure figure out what is going on with that timing.
Are you sure TDC is right, etc?
Does the timing stay at 34 from 1000 to say 3000 or 3500, or does it increase even more?
I'm not sure that is causing the flat spot but I would not be comfortable until I figured out the timing.

Meanwhile I would try the following:
1. Lock the secondary shut and see how it runs. Sure it will be slower, it's just a 2-barrel now. But it should launch hard and pull smooth, just run out of power on top. Maybe that big secondary is flopping open too soon?
2. Go up about 3 or 4 jet sizes and just try it. I know a 43F jet is roughly a 47 Holley jet but that still seems lean. The 1.00" primary Autolite 4300 runs a 46F to 48F jet. The 1-1/16" primary Holley 390 runs a 51H or 52H jet (about a 47F to 48F jet). I know the Autolite 2100 "1.01"'s run about a 42F give or take, but with those big sewer pipe intake ports, a cam, and headers, I'd go richer. Worth a try?
3. Check the wet float levels. I like my 4100s 7/8" (or less, even 13/16") down from the gasket surface while sitting at idle (outside, with a fire bottle handy of course!). I always set the lid on and put two screws in loose, then fire up the car, come out and take the lid off to check the levels. Just don't play with the floats of course, they will shoot out a geyser like old faithful right above the header, or even worse far enough to pick up a stray spark. But, there is no substitute for wet float levels.

 

[mach1 mark]

Werby Ford are you using a 4100 4v on an aussie head or a Ci aluminum head, and if so what is your timing and jet size? Are you using holly jets or ford. My timing is set around 32-34 with the car in gear (set chalks under front wheels) and ideal RPM around 800. Its the only timing I can get the car to ideal OK in grear because of the C4 and the large cam.

 

[WerbyFord]

Mach1Mark,
I've used the 4100 mostly in v8's, 289, 390, 428, etc.
I don't have CI head [yet] and just learned about that and the Oz head from this forum mainly. So I am still planning, reading, learning for my falcon six build.

When I grew up, Chev was "the enemy", now it seems we are all in it together, either Detroit survives or not. So partly because of that I have a couple Brand C cars. As opposed to the more standard 390 Holley, I always thought the 4100 would make a good carb on the Chev 6. And, it does - that is where I am running the 4100 on a 250 six.

The one it likes best is a 1.12 with 54H jets pri and 62H jets sec. That is about like 50F and 58F jets by the way they flow. Basically a stock engine, iron exhaust (no headers) so with a cam and headers I'm guessing it would want to be even richer.

Ya never know with jetting, I just suggested richer to Curtis based on what he described and since it's an easy change -

 

[Inline6Merc]

WerbyFord you hit the nail on the head. I went out and disconnected the secondaries today. From a dead stop, it took right off with out a hesitation and likewise when cruising at a steady speed. Now i have to figure out what spring to replace the current one. It has a purple spring in it, which is too light. Any suggestions? Thanks for everything guys!

-Curtis Hanson

 

[JT81stang]

Curtis:

Here's the list for Holley secondary springs.
There are a number of ways to tune the moment when the vacuum secondaries open on a Holley four barrel carb. The vacuum secondaries are controlled by a diaphram and a color coded spring. Holley makes a number of different springs with different tension on the springs. You can change the springs and change the opening moment. The color coded springs run from light tension to heavy:

White - Lightest
Yellow (Short Spring)
Yellow
Purple
Plain (Steel grey)
Brown
Black - Heaviest

 

[WerbyFord]

I never stop learning!
Or maybe forgot....
I did double check and the Holley sec springs do fit the 4100. Very convenient.
I pulled a 4100 spring from a c3af-r 1.12 x 1.19carb:
Wire .036"
Total Coils 7.2
Free Ht 1.5"
I've tried several 4100s now on my 250 Brand C above, stock 4100 springs, haven't messed with those yet, and all the secondaries do open (though perhaps not fully) as evidenced by the paper clip test. And there is no bog either. I'm shifting at about 4300rpm so they must be opening before that. One of the ones I've tried is a 1.08 x 1.19 carb and that secondary seemed to open further than the 1.12 carbs.

The closest Holley spring I can find is between the plain and brown springs.
The Holley purple spring is at least a couple steps softer than the c3af-r.
Your venturis I think on the Pony Spreadbore are 1.00 x 1.19, so you should have an even stronger signal than the 1.12 x 1.19 carb. So - - -
I'd try the brown spring, and if it doesn't open soon enough, try the plain spring.
(The brown spring is taller but is only .030" wire, the plain spring is .036" wire).
Of course what I'd REALLY do is, go to the strip:
1. Run it as a 2v, locked out
2. Run the brown spring
3. Run the plain spring
I hate changing them because the diaphragm rubber gets stuck and torn in the screws. Bring an extra 4100 diaphragm for sure. And, they don't come in the kits either. I guess the rebuilders figure you only want a 2v if it's that old.....

 

[mach1 mark]

Inline6merc, how are you doing with your Autolite 4100? Did you get it running right. What did you have to do to it, Springs, jets? I just put my Autolite 4100 1.12 on, and its doing about the same as you discussed in your post. Give me some hints. I was just going to put the Holly 500 back on, but I don't want to give up.

 

[66 Fastback]

As far as idling at a high rpm with the throttle screw backed out. Make sure that the plates are closing fully and that the linkage is not binding or preventing it from closing all the way. Might as well check to see that you are getting fully open on the throttle plates too while you are at it.

Is the 900 rpm with the trans in park or in gear. 900 rpm in park is probably not far off the mark for a lumpy cam and not in gear. I am a fan of manifold vacuum as I think you can stabilize the idle with more vacuum advance which will also allow you to set the idle speed lower than ported vacuum sources will. It will also run cooler at idle.

Did you replace the balancer when the engine was rebuilt? 34 deg of static timing sounds with the vacuum line disconnected sounds a bit high. Check to make sure everything is at TDC when indicated on the balancer.
Doug