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#1
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My 440 has had a miss in it for some time now that I have been trying to sort out. It is at all RPM and now it some times lets out a loud backfire out the exhaust when idling. It just doesn't run as smooth as it should, rpm varies and you can here a miss.
Here is what I have done so far: 1)replaced the distributor with a new billet alum. 2)couple different sets of plugs 3)changed plug wires 4)3 different ignition systems and coils (2 jacobs and 1 MSD) 5)different timing setings 6)new distributor drive gear Tonight I am going to readjust the rocker arms again and try a differnt brand of plugs and see what happens. The only thing left is the carb, could something bad in the carb cause a problem like this? It seems like it should be an ignition problem. Any ideas out their, I have run out of them. |
#2
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Mudder
It could be a bad exhaust valve. Just a quick thought Christian ------------------ 68 'Cuda 383 Formula S recreation Working on adding EFI 69 'Cuda Race Parts Car 76 Duster 273 recent transplant 95 Neon 2.0 SOHC best of 16.96 84 Dodge Ram D50 transplanting 360 |
#3
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Anything is possible but I just refreshed the motor with all new bearing and rings after spinning a rod bearing. The valves all looked great and are one piece stainless units. Before the refresh I had 150 psi on every hole and it had the same miss before and after the refresh. I suppose a sticky valve maybe? Wouldn't thinks so running double springs on a solid roller cam, no noise to indicate a bad valve.
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#4
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You see to have gone through just about all the electrical, but could it be a timing issue in the mechanicals? Is the cam lined up in the right place or something like that? Something other than a timing problem I experienced once was when my coil would get heat-soaked and start leaving out a spark or two, causing a backfire out the tail pipe, but it sounds like you dont even get up to temperature before you have problems. Could the cam be installed to far advanced or retarded? The great thing about Mopars is that you are either right on, or 180 off with the distributor, so could it be in the cam alignment?
Just a couple thoughts. [This message has been edited by dartboy71 (edited July 26, 2000).] |
#5
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I degreed the cam when I put it in originaly and checked it again when I had it aparts. It is suppose to be at 108 and it degrees out at 109 I had to use the advance (or retard, don't remember now) on the crank gear to get it at 109, it was 4 degresse off intalled at "0". But regardless it didn't have the miss in it when originaly installed.
Boy isn't this fun, may have to find someone with some sort of supper computer to hook up to it!!! |
#6
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Just a thought, have you checked the valve lift on the cylinder that has the miss? I had a cam that was going flat on one lobe and caused a miss.
Regards, ------------------ Cameron's Racing Division of GOT NUTZ? MotorSportz 66 Belv 2 440 auto 10.76 @ 125 69 Road Runner 426 wedge auto 9.74 @ 138 99 Dakota Pro Stock type truck (under construction) 79 Lil Red Express Truck 96 2500 Ram 5.9 99 Durango 5.9 |
#7
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this is going to sound so stupid as to probably insult you--But do you have the plug wires correct?? if you have two swapped it would cause just what you describe.. A comp test would show up valve problems-bent pr's etc. If all is well after that then disconnect one plug wire at a time untill it doesn't make it any worse.. that will tell you which cyl is the culprit.. beeper
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#8
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Try a check to be sure your plug wires are in correct order. then disconnect each plug one at a time and see which one DOESN'T make it worse. If it is not specific to a particular cyl then it isn't valves etc. From here you are on your own.. Sure sounds like ign to me!!
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#9
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I'll bet I have gone through them wires a hundred times thinking the same thing that they must be wrong. The cam is fine and they are roller lifter so their are no bad lobes. I haven't tried pulling wires off beacuse it doesn't seem to be specific to any one cylender when checking the plugs. Before taking the motor apart I had from 150-155 lbs on each cylender, haven't check it yet since putting it back together, but it missed before I took it apart.
Just a though but has anyone ever had problems with the spark jumping inside the cap? Dodge runs a pretty small cap compared to GM and I have seen a distributor to change to a bigger cap if you have such a problem with spark jumping between the pickups in the cap. But I have never heard anyone say that they have expierenced this so I haven't given it much thought |
#10
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Just a couple more things to check-- IF it is not cylinder specific. Check the phase relationship between the reluctor and the dist cap .. There are articles that describe what it should be. Next, and this is a f-u that I was guilty of..Make SURE the hook-up from the dist reluctor output is correct. If its backasswards it will run but the initial pulse polarity is wrong and the Ign system will wait to fire on the second cycle of the pulse. We WILL get to the bottom of this if I have to come to Rice Lake and figure it out!!! BUT FIRST you must determine if it is cylinder specific ( hopefully not ) or if it is an intermittent miss on all cyls. Keep it touch Wi needs all the Moparites we can get in this morass of bowties and mustangs. Comming to the show in Green Bay this Sat??
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#11
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I will check the distributor hook up to make shure that I have them right, it is possible. Wont be going to green bay no, was at Iola a couple weeks ago though.
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#12
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Another good though but I just put in new cam bearings and the old ones were in place. The problem was before and after the bearings were installed. I just know this is going to be some stupid little thing that I am going to kick myself for!!
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#13
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Based on all the other things you tried - this sounds like it could be an intermittent electrical problem - like the 12v supply to the ignition system is intermittent - could be a bad or intermittent ignition switch or a short or ground that kills the ignition for a short time (ie a feed wire that is worn thru and grounds once in a while due to vibration etc). Also poor connections to the ign box or thru the firewall connectors (what ign box etc are you using???)
I had an ign switch with similar simptoms that progressivly got worse until the car would start but would not run. I went down all the other routes first - after all the switch never fails! Right!! You could try bypassing the ignition switch and other portions of the electrical system by feeding directly from the battery with a separate wire. Just my $0.02...... |
#14
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It is a Jacobs Pro Street system. The power for the box itself is hooked direct to the battery and their is one wire that is hooked to the igntion to turn it on. I will hook that wire direct to the battey once and try it. The ground is direct also. That wire that turns it on is the only "original" wire left. If it is turning on and off I think the two ignition LED's on the dash should give me some kind of sign, but maybe not.
Its another good idea, I will give it a try. Will have to wait till tommarow night, have to take the wife to the airport tonight to get rid of her for the week end. |
#15
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You best hope she NEVER sees this website or engine problems will be WAYYYYY down on your list of agrivations. If you had this problem before and after the rebuild--what is the one thing that didn't get redone ??
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#16
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That is why I was thinking the Carb, the only thing I haven't tuched. I am going to steal another carb from a buddy this weekend and give it a try to see what that does.
As for the wife, she lets me get away with way to much in the garage. But the cat is away this week end so we are going to get this baby humming so I can play next week end!! |
#17
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Hey, if she's anything like my lady, she knows that she is safe in leaving you for the weekend because she knows the other lady is a Mopar
Good luck with the tinkering. |
#18
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Man i know whats it like!? Well just wanted to ask if the carb helped! Where you running a Holley before! Could have been a blown out power valve!
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#19
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I put another carb on yesterday and reset the valve lash. The valve lash did seem to make some improvement. And the different carb might have made a slight change but not much. I know it is running rich so I changed the primary jets from 78's to 74's and a 6.5 power valve (smallest valve I had at the time). I have a air/fuel meter and for some reason it shows richer now with the smaller jets so I am thinking that valve might be bad. I am headed to town right now to see what I can find for a valve. Both carb were 750 vac secondary holley's. I have the vavle lash set at .027, the cam calls for .026. On another note the plugs are wet when I take them out like their is too much fuel. Funny thing is that I haven't changed the jetting from when I had the .455 lift hyd cam in and the plugs looked great with that cam. You would think the bigger roller cam would want more fuel not less. Plus I raised the compresion from 9:1 to 10:1. I have bettween 160-165 psi on all cylenders. Well back out to try some more things.
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#20
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Didn't see it addressed, but have you re-checked your plug wires for proper routing? My experience is that stock big-block wire routing on some engines will cause a cross-fire from induced voltage.
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#21
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Have you adjusted the idle/air mix! Maybe try leaning it out! I hope you know how, i'm not even gonna try to explain, i can do it but can't explain! Well hope it helps!
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#22
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If you are running 5" vacuum at idle with a 6.5 power valve --your power valve is open at idle !!!! then as you pick up some rpms your vacuum will increase to where your power valve will shut thus leaning it out...You must have a power valve that is BELOW your idle vacuum!! Try the 74's with a 3.5 or so power valve. Personally I've never been able to get a vac sec carb to perform on a semi radical engine with a single plane manifold. The Holley techs tell me it has to do with " standing wave reversion " which screws up the signal to the vac sec signal passage. If you stop and think about it for a minute-- why do you suppose at every swap meet there is a boatload of vac sec carbs for giveaway prices and damn few dps ?? And even if you can score a dp it has usually been messed with. In my opinion a used carb is like a used comdom-only slightly better than nothing. unless you trust the history behind it.. When you get this right you should see 10" vacuum @1100rpm .25 degrees initial advance, 38 degrees at anything above 2000 rpm. beeper
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#23
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Here are the vacume readings:
900 = 6 1500 = 11 2000 = 15 3000 = 18 I got a 5.5 valve (smallest NAPA had) and ran it with the 74 jets. I realize the power valve I had was to big, it was just all that I had at the time and nothing was open. The 5.5 with the 74 made no difference. The plugs still looked a little dark to me so I put in a set of 72's. This made the backfire out of the ehaust worse, the backfire only happens below about 1500 rpm and is out of both sides. I pulled the plugs and after a short 2 mile trip they were all white and dry, looks to me like the 72's are too lean. I put on another new cap a rotor and amazinly the back fire was gone, shut it off for a couple minutes and started it back up and the back fire was back, I changed nothing. The timming is at 36 deg total and all in by 2500. I had it at 38 but had a slight ping. Also now it has started deisiling with the leaner jets. I also through on a whole nother set of plug wires to make shure none were jumping but it didn't help. With the 5.5 power valve and I had the idle set at 1000 wich gave me 8in of vacume it should not be causing a problem. Oh yea the intake is a dual plane Performer RPM, not a single plane. And I have been adjusting the idle mixture with each change, but for highest idle, highest vacume and by the readings on my fuel ratio meter. I think I am going to go look for some perfesional help tomarrow from someone who has some tesing equipment to hook up to this thing. |
#24
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When you leaned it out you picked up the exhaust backfire again-- I think you are still to lean.. If you have one -plug the power valve and start over.. that way you only have one variable with respect to mixture. A sure sign of being to lean is HOT headers and I mean HOT.. another sign is if you stab the throttle from idle and it barks somewhat louder and then goes flat-- it means your engine liked the extra shot from the acc pump. keep the faith--
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