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426 Hemi problems.

68HemiCharger

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Ok. I have several issues with this 426 Hemi in my 1968 Charger. Engine is stock.

When I first got the car it was very hard to start when cold and the timing was too far advanced and would idle at 1800 rpm and then drop to below 500 in gear want to die.. Absolutely horrendous. I set the timing to TDC as it says on the decal on the fender, got the idle speed set to 750 and it idles good and doesn't drop in rpm when going into gear.

However the car now diesels when shutting off the ignition when in park. Won't do it when in drive. I'm running 93 octane with octane booster. Its also still very hard to start when cold.

Another issue is if I give it gas when in park the idle speed will go up to 1800 rpm and stay there or even increase on its own to above 2000 rpm. Kinda scary. The throttle return springs are good and the throttle is back down on the idle stop screws even as this is happening. It will eventually go back down by itself, or if not, if I start backing off on the idle screws itll come back down but then i have to turn the screws back in to idle at 750 to keep it running. Makes me think something may be wrong with the vacuum advance? When I disconnected the vacuum line to set the timing I had no change. Wondering if when I give it throttle the vacuum advance is stuck and increasing the rpm?

I have very limited knowledge and experience with setting timing. And am very confused by a lot of it.

Any help is greatly appreciated. If anyone knows of a good Hemi tuning guy in southeast Michigan that'd be helpful too.. but I'd definitely like to attempt fixing it myself.

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I'm not expert by any means, but here are a couple ideas. Check for vacuum leaks around the carbs, probably not the issue but always good to make sure they are sealed correctly. What I am thinking is the problem is the distributor. Looks like you are running a point distributor? so you can rule out a temperamental ECU. Distributor might be worn, causing the timing to bounce around effecting the idle and then giving you the diesel. I'd look at the distributor for the problems you are mentioning. Hope this helps, good luck.
 
Where is your vacuum advance hooked up? I believe all these carbs only have a ported advance outlet on the front if that is where it’s connected, so the vacuum advance is not activated at idle - thus no change when disconnecting it to set timing. Does your car have one of those idle compensators on the right side of the rear carb? It might be causing some of your wierd idle fluctuation issues. If you have a hand held vacuum pump you can hook it to the vacuum advance hose and pump it up with the engine idling. If it’s working OK the idle speed will increase.

The hard start when cold - if the car has been setting for a couple of days - is probably due to today’s crappy fuel drying up in the bowls. A very common problem. My friends 69 Hemi requires crazy amounts of priming fuel through the carb to get it started and keep running. For awhile he was simply using a beer bottle and just dumping it in to get it to fire but I eventually got him to get a proper priming bottle. I haven’t driven my 66 Hemi much but it definitely takes a couple priming shots of fuel to start from cold and to get it to where it will stay running. I use a bottle like a ketchup or mustard condiments bottle with a dispenser lid to prime my cars. I think my wife picked it up at a hair salon where they use them for applying hair treatment chemicals. It’s impervious to gas. You can fill the left side fuel bowl through the vent until gas trickles out and then pump the carb 2 or 3 times. Usually I just pour a little down the throat though.
 
If your vac advance is tapped into manifold vac, that could cause your rpm's to jump like you are describing.
 
If you're running points, and they haven't been replaced in some time, start with a good quality set. I always use NOS Mopar. Get your dwell set to FSM specs first, then reset the timing. Remember, point gap will affect timing but timing won't affect the gap. It really helps to know how much mechanical advance you have built into the distributor first. I prefer using an FBO limiter plate. I have 18° initial and use the 18° slots for 36° all-in. You'll want a bit more than tdc at idle. With more advance at idle you'll be able to back off on the idle speed screw and lessen the chance for dieseling and it should run cooler as well.
 
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I’ll second the FBO plate. I’ve used several of them to calibrate the distributors to where I could run between 14 and 18 deg initial advance and it really perks up an engine and helps driveability. If your engine won’t tolerate 35 or 36 deg advance on today’s fuel you can still back down the timing a little and have lots of initial advance for a good idle and strong throttle response.
 
68HemiCharger, all good info you have been given here. I look out my front window at Marine City Michigan. Unfortunately, since the border remains closed I cannot lend assistance in person.
I have driven my stock 69 Hemi Charger for nearly 40 years. I can share my experiences which are corroborated by many of the previous replies.
First, as stated get the dwell angle correct as per the FSM.
I set my timing at 35 deg. total. You will need a timing tape on the crank damper, or a variable timing light. My initial comes out to about 18-20 deg. Now, I have the advance mechanism from one of the early Super Stock transistor ignitions installed in the stock Prestolite dual point. This result can be mimicked by the total advance limiting plates mentioned previously. The vacuum advance is present, for appearance, but non-functional. I use non-resistor plugs, currently Champion N11Y's as the spec N10Y's are no longer available.
Next, in the FSM there is a detailed carb setup and balancing procedure. Make sure your carbs are in good order, follow the procedure and it makes for a sweet running Hemi.
As mentioned previously, fuel percolation from the carb bowls is an issue with modern gasolines. This is the procedure I follow to start my car. Note, the choke is present on my car, but non-functional.
I crank the engine in 10 second intervals, 10 on, 10 off (gives the expensive Prestolite starter motor a break), until oil pressure just flickers on the mechanical gauge. The carb bowls are now primed. Now, eight full strokes of the accelerator pedal (ignition off, not cranking). I know, sounds odd, but it works. Now, the car should start right up. You may have to hold your foot on the gas a little to keep it idling until warmed up.
You mention that you use 93 octane fuel. That is good, use the highest octane you can get. Octane boosters are not that effective. If you can access leaded racing fuel, or 100LL aviation fuel and ad one part to three parts of your 93 octane that will give you a better fuel option.
Good luck, you can drive one of these regularly with a little effort.
 
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Hard start when cold seems to be something wrong with the choke. When cold, engine off, take off the air cleaner and open the throttle a little. The choke plate should completely close.
If not, adjust it till it lightly closes all the way.
 
First thing take a propane tourch and open gas of course dont ignite and hold close to carb base gasket. Rpm increase? No? try hoses going to vacum brake booster. No change? Remove back carb and back off idle screw and see if butterflies close true to bore. If idle circuit slit is exposed then look at carb body for cracks. if idle circuit is tight great if not shaft is bent or butterfly is warped from back fire
 
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Distributor mechanical advance springs too light, and are all out at idle. When you try to lower idle speed, the weights pull in and the engine dies. I put a pair of Mr. Gasket light advance springs in my 426W distributor, and the exact thing you mentioned happened to me. I put one of the heavier springs back in and the problem was fixed. As far as the engine dieseling on shut down, there should probably be a shut-off solenoid on the carb. When the solenoid is energized, it sets the idle speed, then when the power is taken away, it allows the carb butterflies to close completely, thus preventing dieseling (also fixed the same problem on my 426W dual quad setup).
 
Distributor mechanical advance springs too light, and are all out at idle. When you try to lower idle speed, the weights pull in and the engine dies. I put a pair of Mr. Gasket light advance springs in my 426W distributor, and the exact thing you mentioned happened to me. I put one of the heavier springs back in and the problem was fixed. As far as the engine dieseling on shut down, there should probably be a shut-off solenoid on the carb. When the solenoid is energized, it sets the idle speed, then when the power is taken away, it allows the carb butterflies to close completely, thus preventing dieseling (also fixed the same problem on my 426W dual quad setup).
Some rhings here make good sende to me except if one spring was way too loose starting would be very hard on starter motor.
 
Some rhings here make good sende to me except if one spring was way too loose starting would be very hard on starter motor.
I don't agree. The weights have a pin, and ride in the slot in the reluctor, so a lighter spring can't allow one weight to advance any further than the other weight. The OEM spring combo (medium/heavy) will have one advance curve due to the combined resistance created by the pair of springs. The heavy/too light combo will do the same, but just at a faster rate, and the too light/too light combo will allow an advance curve that is basically too quick and will be "All Out" at idle. Also, I never had any starting problems with the different spring combinations, jus a different advance speeds.
 
68HemiCharger, all good info you have been given here. I look out my front window at Marine City Michigan. Unfortunately, since the border remains closed I cannot lend assistance in person.
I have driven my stock 69 Hemi Charger for nearly 40 years. I can share my experiences which are corroborated by many of the previous replies.
First, as stated get the dwell angle correct as per the FSM.
I set my timing at 35 deg. total. You will need a timing tape on the crank damper, or a variable timing light. My initial comes out to about 18-20 deg. Now, I have the advance mechanism from one of the early Super Stock transistor ignitions installed in the stock Prestolite dual point. This result can be mimicked by the total advance limiting plates mentioned previously. The vacuum advance is present, for appearance, but non-functional. I use non-resistor plugs, currently Champion N11Y's as the spec N10Y's are no longer available.
Next, in the FSM there is a detailed carb setup and balancing procedure. Make sure your carbs are in good order, follow the procedure and it makes for a sweet running Hemi.
As mentioned previously, fuel percolation from the carb bowls is an issue with modern gasolines. This is the procedure I follow to start my car. Note, the choke is present on my car, but non-functional.
I crank the engine in 10 second intervals, 10 on, 10 off (gives the expensive Prestolite starter motor a break), until oil pressure just flickers on the mechanical gauge. The carb bowls are now primed. Now, eight full strokes of the accelerator pedal (ignition off, not cranking). I know, sounds odd, but it works. Now, the car should start right up. You may have to hold your foot on the gas a little to keep it idling until warmed up.
You mention that you use 93 octane fuel. That is good, use the highest octane you can get. Octane boosters are not that effective. If you can access leaded racing fuel, or 100LL aviation fuel and ad one part to three parts of your 93 octane that will give you a better fuel option.
Good luck, you can drive one of these regularly with a little effort.

Thank so very much. I will look into the points and I'm actually only 25 minutes west of Marine City. Been there many times. Will have to meet up once the border opens. I will work on all the suggestions. The fuel issue definitely seems like the floats are dry. I'm not seeing or hearing fuel when pumping after a week from setting. The choke works fine but will start easily if I pour some gas down the carb. Crazy to think these engines have such a hard time starting. I have several others classics that start easily. Albeit nothing with hemi nor dual carbs.

I don't seem to have the idle stop solenoid people are talking about. What I do have is a green canister on the vacuum line. Could this be a source of my problems? I'd upload a pic but the website is giving me an error. I believe this green cannister is a California only emission device.
 
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On mine the only time I have to crank it for any extended time is after sitting more than a few days.
I can run it one day, and it fires right up the next day with MAYBE 2 revolutions , if that.

I have base timing set at about 12-13 degrees base ( have not ckd total timing yet ) When I first got it last year base timing was near 19-20 degrees and unless I ran a mix of premium and 110 octane it would ping like crazy, diesels when shut of etc etc

On hot ambient temp day ( mid to upper 90s ) and with engine temps near 190 range it will still ping slightly running straight pump gas 91 octane

I just picked up a couple bottles of lucas octane boost to see what it does,,,if anything . Before I back timing down a tad more.

But either way mine fires right up no matter where timing is set. Be if it sits a half hour or all day with zero slow crank issues
 
I don't agree. The weights have a pin, and ride in the slot in the reluctor, so a lighter spring can't allow one weight to advance any further than the other weight. The OEM spring combo (medium/heavy) will have one advance curve due to the combined resistance created by the pair of springs. The heavy/too light combo will do the same, but just at a faster rate, and the too light/too light combo will allow an advance curve that is basically too quick and will be "All Out" at idle. Also, I never had any starting problems with the different spring combinations, jus a different advance speeds.
i dont think gou unddrstand but you got clise at the end.when you said all in with light springs you were almost their.. Ok so old heavy or livht light still will as you tried to say be all in at idle. Imagine how the starter feels.
 
Do you have one of the on the pass side of the rear carb (a dash pot - I used the wrong term above).
95F1B3D3-7D7D-46D1-9CC7-D0826EF0E5DD.jpeg
They may only be on 4-speed cars. They will cause a hanging high idle speed that gradually decreases. My friend with a 69 Hemi tells me they are not driver friendly.
 
The dashpot is '69 Hemi 4spd only. I don't have any trouble with mine, because it has been missing for 40 years.
 
Do you have one of the on the pass side of the rear carb (a dash pot - I used the wrong term above).View attachment 1110999 They may only be on 4-speed cars. They will cause a hanging high idle speed that gradually decreases. My friend with a 69 Hemi tells me they are not driver friendly.

Nope. Don't have that. Mines an automatic
 
OK - that’s good. I remember having seen that green canister do-hickey thing but I don’t remember it’s function. Maybe something to do with the choke. Mrhemi probably knows.
 
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