440 runs terrible at higher rpm and load

[superbee_68]

There are more problems than I thought. These cars really don't like to sit unused, lesson learned. I will try to present the facts as organized as possible:

Full advance is set to 30 degrees, base timing is around 12 degrees
1,000 rpm idle, drops to 900 rpm when the fans kick on
Vacuum at idle ranges from 9 to 11 inches depending on if the electric fans are running
The fuel pressure is set at a constant 8 psi and does not drop when the engine is revved
The fuel level is about slightly less than halfway up the sight window on both fuel bowls
The alternator is a 300 amp high output that is putting out 14.5 volts at idle

I have discovered new problems last night. My 1 year old rebuild on the heater control valve is leaking anti-freeze, oh joy, the exhaust is now rubbing the crossmember near the transmission and vibrates at certain rpms, how the heck does that happen, and the car will not start when its warm. It fired right up last night, I measured everything, let the car warm up completely, then shut it down for a brief moment. Then, the starter would barely turn over the engine, acted like a dead battery. I waited 15 mintues, then it finally started again. I played with it for a few more minutes and shut it down again. The car then started with the bump of the key, at which point I was started to get pissed. I kill the car, go inside, tell the fiance I am going for a test drive, walk back out, and the thing won't start again, same thing, acting like the battery is dead. I wait 15 minutes, fires right up. I go for my test drive, the car will not handle any load whatsoever. Cruising is fine, just cannot get on the throttle at all. Cuts out, pops, sputters, you name it.

I think I either have an intermittent connection going to the starter, or faulty starter.

I need another rebuild on the heater control valve.

I need to visit a muffler shop

I think I am going to pull the carburetor next. It needs to be gone through even if it's not the problem.

I will definitely check the distributor for proper clearance, that's a great tip Kern Dog! I might also try upgrading the distributor to bring on full advance at lower rpm later down the road, but I don't want to change anything else until I figure out this problem. Thanks for the help guys!

 

[440beep]

As part of your trouble shooting, perhaps get a new starter relay and see how that works. Always good to have an extra one just in case if it checks out fine.

 

[coloradodave]

superbee_68: "The more you apply the throttle, the more the vacuum should approach atmospheric pressure, essentially decreasing vacuum. This is why it's important to hook up the vacuum advance to the correct port on the carburetor. One port will increase vacuum with load, used to run vacuum secondaries. The other port decreases vacuum with load, used to run the vacuum advance. Depending on your camshaft, you can adjust vacuum advance to be sure it will fully apply with the vacuum supplied by your specific parts combo by adjusting the allen screw built into the diaphragm."

Hate to be the accuracy police, but most of THIS information quoted from your post is incorrect. I don't feel like writing a book here as the correct information on engine vacuum can be easily found on the web. Not trying to be an a**, just want those reading these posts to get correct information.

 

[SlinktRR]

The 15 minute no-start is not likely to be a starter problem. When this has happened to me it was from flooding or too much initial advance. Flooding for me was either too rich, floats set too high, pieces of fuel line in needles/seats, or heat soaked carb bowls boiling fuel. 8 psi seems a bit high, you could try regulating that down but I would go through the carb. It doesnt take long to gum up a carb with todays gas.

 

[superbee_68]

As part of your trouble shooting, perhaps get a new starter relay and see how that works. Always good to have an extra one just in case if it checks out fine.

The starter relay was changed Monday along with the ignition box and plugs, but I guess it could be a defective new part. The no start for 15 minutes could be too much initial timing, but the first time it happened, I loosened the distributor and backed off the timing a little at a time and the car still wouldn't start no mater how much I backed it off, still sounded like a low battery. When it finally did start, I reset the timing back to where it should be.

This is why I am thinking starter or corroded connection somewhere in the system, and hopefully a properly rebuilt carburetor will eliminate flooding or float height. The two batteries are in the trunk, run through a kill switch in the side of the battery box, and up through the car to the starter. I then have a 4 gauge wire running from the starter to the starter relay junction, and another 4 gauge wire running from the starter relay junction to the alternator. My big giant alternator would have destroyed (overheated) the two feed throughs in the bulkhead on the firewall, as well as burning up the ammeter so the giant wires bypass all of it. The fusible link gets power from the starter relay junction. The alternator chassis, as well as the engine block both have 4 gauge grounds to the vehicle chassis. The batteries ground to chassis in the trunk. The stereo gets power through a 1/0 cable, but first goes to a 4 farad capacitor, then to the amplifiers. The capacitor definitely helps keep more stable voltage when there is a hard hit in the music, and doesn't stress the alternator with huge instant power demands. The only thing missing is an isolator switch so I don't kill both batteries when listening to music with the engine not running. It's total over kill with two batteries, 1/0 wire from the trunk with a kill switch, and 4 gauge every where else, but it definitely works. The giant electric fans, fuel pump, air conditioning, and big stereo need all the power they can get. And I got tired of burning up factory style alternators every few months. This setup has been working for 6 years now. But there are a lot of potential corroded connections, or a possible bad battery switch. I will just have to figure it out.

The starter is a parts store reman I looked up using a late model dodge dakota with a 360 in it. Technically a mini starter, without paying the big price for "mini starters" sold from old car parts suppliers. You just have to remove the extension bracket that relocates the power feeds, it hits the block on a big block. I am thinking the junk reman has failed again. Need to think about buying new this time maybe.

I put the big stereo in when I was 16 and big stereos were cool, especially in the 2006. I also worked as an installer at the long gone Circuit City when I was 16 doing car alarms, stereos, and satellite radios, so the discounts were deep. To be honest, I could care less about any of it now. If I just had four speakers and a radio that worked I would be good now. Back in 2006, the car also had 17 torque thrust wheels, super dark window tint, no working a/c or heat, no reverse lights, no speedometer, leaked power steering fluid, leaked oil, had a 68 hood with 69 dual scoops painted yellow, had air shocks with a jacked up in the rear stance, and I ran the exhaust cutouts open all the time terrorizing my home town. Oh how things change when you grow up, and yes all of that has been fixed/changed. Although not all of my "adult" parts choices are factory correct, hood and center caps for example, they are so much better! When my dad bought me the car, it was a green on green 318 auto with one quarter panel knocked off, the front had smashed into a pole, no driver window or driver door handle, slashed tires, big dents all over from vandalism (crazy ex girlfriend), harley davidson floor mats with a duck tape front seat cover, and I found a joint in the ashtray from the PO. It has come a long way.

I am taking the fiance to the national finals rodeo in Vegas this weekend. She is a barrel racer and it has been her dream to go for many years. We bought dirt cheap tickets from southwest and bought some nosebleed tickets to the rodeo. It's our first time in Vegas, any advice? I'll get the carburetor and heater control valve off next week when we get back. I am running out of time!

 

[bigmanjbmopar]

I'm gunna just drop this right here, Have a great weekend fellows!


http://www.mopar1.us/engine2.html






:headbang:

 

[superbee_68]

I'm gunna just drop this right here, Have a great weekend fellows!


http://www.mopar1.us/engine2.html






:headbang:

That is a fantastic tuning guide, I love the method of adjusting the vacuum advance with a manual vacuum source and watching timing with the light, so cool! I only have one more thing to add. Where to hook up the vacuum is advance important. Manifold vacuum is the correct place to connect the vacuum advance for a street car. The ported vacuum port does have some uses, and has been used successfully by some to add advance just off idle, but is more of a relic from the emissions band-aids era. If you are using the curb idle to get the car to idle, and have adjusted it open to the point where the ported vacuum port is below the throttle blade at idle, then you have essentially created another manifold vacuum port and the argument between the two is pointless. But if you are have adjusted the curb idle this far, you have less control over idle mixture and could create off idle stubmles or flat spots.

I will try to get the vacuum advance to work properly one more time after I clean and rebuild the carburetor since the advantages are numerous. We will see if my big cam and low idle vacuum will cooperate.

For more explanation on manifold vs ported vacuum, see the quote below:

Excerpt from John Hinckley's "Timing 101" (John Z).

Now, to the widely-misunderstood manifold-vs.-ported vacuum aberration. After 30-40 years of controlling vacuum advance with full manifold vacuum, along came emissions requirements, years before catalytic converter technology had been developed, and all manner of crude band-aid systems were developed to try and reduce hydrocarbons and oxides of nitrogen in the exhaust stream. One of these band-aids was "ported spark", which moved the vacuum pickup orifice in the carburetor venturi from below the throttle plate (where it was exposed to full manifold vacuum at idle) to above the throttle plate, where it saw no manifold vacuum at all at idle. This meant the vacuum advance was inoperative at idle (retarding spark timing from its optimum value), and these applications also had VERY low initial static timing (usually 4 degrees or less, and some actually were set at 2 degrees AFTER TDC). This was done in order to increase exhaust gas temperature (due to "lighting the fire late") to improve the effectiveness of the "afterburning" of hydrocarbons by the air injected into the exhaust manifolds by the A.I.R. system; as a result, these engines ran like crap, and an enormous amount of wasted heat energy was transferred through the exhaust port walls into the coolant, causing them to run hot at idle - cylinder pressure fell off, engine temperatures went up, combustion efficiency went down the drain, and fuel economy went down with it.

If you look at the centrifugal advance calibrations for these "ported spark, late-timed" engines, you'll see that instead of having 20 degrees of advance, they had up to 34 degrees of advance in the distributor, in order to get back to the 34-36 degrees "total timing" at high rpm wide-open throttle to get some of the performance back. The vacuum advance still worked at steady-state highway cruise (lean mixture = low emissions), but it was inoperative at idle, which caused all manner of problems - "ported vacuum" was strictly an early, pre-converter crude emissions strategy, and nothing more.

What about the Harry high-school non-vacuum advance polished billet "whizbang" distributors you see in the Summit and Jeg's catalogs? They're JUNK on a street-driven car, but some people keep buying them because they're "race car" parts, so they must be "good for my car" - they're NOT. "Race cars" run at wide-open throttle, rich mixture, full load, and high rpm all the time, so they don't need a system (vacuum advance) to deal with the full range of driving conditions encountered in street operation. Anyone driving a street-driven car without manifold-connected vacuum advance is sacrificing idle cooling, throttle response, engine efficiency, and fuel economy, probably because they don't understand what vacuum advance is, how it works, and what it's for - there are lots of long-time experienced "mechanics" who don't understand the principles and operation of vacuum advance either, so they're not alone.

 

[slepr1]

I'm not sure about your carb but mine, a Holley 850 DP, doesn't like high pressure. I set mine to 7.

 

[badmopar67]

Just a thought had the same problem when I built my 440 which is similar to your specs, I was running a regular air filter it was chocking it out at high rpm's went to a K&N and that took care of the problem.

 

[hangn0ut]

Can be difficult to get a good ground in the trunk. Grounded to the sheetmetal is suspect. Thru the frame rails will collapse the rail when its tight. I put a heavy spacer inside the rail to keep it sound. Then tighten it up tight.

 

[dvw]

Do you know how to do a voltage drop test? Measuring circuits this way will check them under loaded conditions. Obviously if the starter is not faulty it has insufficient voltage/amperage/ground. It's an easy check with a voltmeter.
Doug

 

[superbee_68]

I have been so busy prepping for the wedding, the car fell to the back burner. I finally picked up a rebuilt heater control valve and a carburetor rebuild kit Friday. I also picked up a 4.5" power valve. I got the carburetor off and apart. As far as cleanliness is concerned, the thing looked brand new and perfect inside. No gum, varnish, deposits, nothing! I did find something horribly wrong. The primary jets were 84's and the secondary jets were 76's. I have no explanation for how this happened. I was pretty sure I had never taken the thing apart. I need to look up the list number on the carburetor, make sure what cfm rating it is, and put the standard jets back in. I found all the specs on Demon's website so I'll be able to put it back exactly the way it was built. I'll be in the shop all night tonight after work. I sure hope I found the issue.

I'll do a voltage drop test on the starter circuit once I get it back together.

 

[Danomt]

What is the list number of your carb. Most of the 750's come with 72 front and 76 rear, but the number will help. With headers and more motor it may have to go up a little. they usually run fair right out of the box...

 

[superbee_68]

The list number on the carburetor is 1402010, it's a Demon 750 CFM twin squirter according to their website. The carburetor went back together beautifully. The thing came with 76 primaries and 83 secondaries, so that's what I put in it.

So I have great news, the car is almost fixed, woohoo! I swapped in the new heater control valve and fixed the water leak. I also got the carburetor dialed in, then set the timing, and finally got the idle mixture spot on. I was still having hot start issues. Turns out I had a bad engine block ground. It was causing the hot start issues. I also had a corroded connection at the bulk head where the fusable link feeds the car power. I cleaned the connections and added some grease to keep out moisture. The alternator is still perfect, over 14 volts with lights, fans, and fuel pump running, with almost no a/c voltage, my fluke meter read 0.

The bad ground was most of my problem. The car is running nearly like it did when I first put her together. The car hot starts with the bump of the key and idles fantastic, with the vacuum advance hooked up!

I still have one issue. In the primaries, the car hauls ***, as long as I don't slam the pedal to the floor. A quick roll in feels nice. If I slowly roll into the secondaries all the way to full throttle, the car keeps pulling. But, if I slam into the secondaries or roll in quickly, the car will sputter and fall on its face a bit, but does eventually rev up there. My guess is I need a bigger squirter, and/or bigger jets in the secondary. How the heck can I figure out what it wants?

Again, any help is much appreciated. And thanks for all the tips so far, I might just be able to drive off from the wedding in this thing!

 

[Kern Dog]

"I still have one issue. In the primaries, the car hauls ***, as long as I don't slam the pedal to the floor. A quick roll in feels nice. If I slowly roll into the secondaries all the way to full throttle, the car keeps pulling. But, if I slam into the secondaries or roll in quickly, the car will sputter and fall on its face a bit, but does eventually rev up there. My guess is I need a bigger squirter, and/or bigger jets in the secondary. How the heck can I figure out what it wants?"

I installed an Air/Fuel meter made by AEM. It uses an oxygen sensor in the exhaust system. The guage looks like the one on the right...

 

[Bigal75]

I'm pretty sure Demon carbs have transfer slots as well. The primary side slot should be adjusted so only a small square is visible from underneath (0.020). If you need to readjust your idle use the secondary adjustment. Or it may need a larger squirter on the primary side.

 

[furyus]

Try different squirters as said above. Also try a little more timing. Make sure you mark the distributor so you can easily go right back to the original setting.

 

[superbee_68]

I know this is an old thread but I finally got this last problem solved, the problem where the car would spit and sputter under a heavy load, pretty much anywhere in the secondaries. I grabbed an old MSD 6AL ignition off my uncles wall the other day, and I mean fairly vintage. It is probably from one of his race cars from the early 90's. I bolted in the box, wired up the power, ground, switched ignition, and distributor pickup wires to the stock mopar electronic distributor. The car fired up better than ever so I took it out for a spin. To my surprise when I pinned the throttle to the carpet the tires lit up and the revs nearly hit the rev limiter. I did a few 2nd and 3rd gear pulls and the car performed great, I couldn't believe it. My car is finally back to life! I don't know if it was the Napa ignition box, engine wiring, or just not enough spark for my combination of parts. Same coil, same spark plugs, same plug wires, only thing I did was add an old dusty MSD box. Just thought others who look back on this thread when searching might want to know the resolution to the problem.

I did create a new issue, a horrible buzzing feedback noise in the stereo that goes up and down with revs. Definitely electrical noise from the MSD. I will need to add a bi-pass filter where the RCA's plug into the amp to help fight the noise.

Also, the car did fire up on wedding day even though I had not gotten the final problems figured out yet, and my new bride and I drove home in it with a working heater, just no full throttle pulls on the way. Thanks to everyone who chimed in on this thread years ago, I appreciate the help!

 

[kiwigtx]

My car is finally back to life! I don't know if it was the Napa ignition box, engine wiring, or just not enough spark for my combination of parts. Same coil, same spark plugs, same plug wires, only thing I did was add an old dusty MSD box. Just thought others who look back on this thread when searching might want to know the resolution to the problem.

I was just going to post a few thoughts ....basically echoing what others have said. My first thing to check would be the carb - fuel starvation can be a problem. Next would be the ignition system.
Since I installed a Rev-N-Nator Ignition system in my car it has gone way better than ever before - revs are free to take, and top end is only limited by the road, traffic laws, and ball bag twitching.
Thanks for updating the thread....I'm sure a few people will get tips from here as a result.