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Rebuilt 400 HO suddenly runs rough
I posted this over in the ‘67 GTO forum’ but I think this is probably the better place. My 67 400 HO has only 250 miles on it since a full rebuild. It is .040 over with a roller cam and ported 670 (Gessler) heads. Everything on car (tank, lines, pump, filter) is brand new.
I drove it today and about an hour into the drive I noticed it suddenly stumbled. It had been running perfectly before this. I thought maybe my fuel gauge might be inaccurate (but doubted that since this entire car just went through a 7-year frame-off resto). I stopped in gas station but it only took about 8 gallons, so that wasn’t the problem. After that, the stumble got markedly worse. Car would kick, stutter, jerk and backfire. I nursed it back hone and the first thing I checked was timing. The distributor was not loose and the initial timing looked like it was at about 8 degrees. But the timing was very erratic as I could never get engine to smooth out using the throttle. I checked the rotor and it wasn’t cracked or loose. I also put the timing light lead on each wire as the car idled (roughly) just to make sure that there wasn’t a miss. Each wire would trigger the light. I thought I might try swapping on a different carb, just to rule that out as a possible issue. When I went to pull the fuel inlet line, no fuel leaked out of the carb. I seem to remember every time I pulled a carb in the past, some fuel would always dribble out. Any suggestions would be appreciated. https://uploads.tapatalk-cdn.com/202...e2a174f2dc.jpg Sent from my iPhone using Tapatalk |
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Ok. I’ll give that a try. I tried running it with no filter, but then had same problem. Then I swapped on a carb I know works well, and again same problem. So I know the issue is not the carb or filter.
I also noticed that asi rev the engine and you feel it miss, the timing light strobe gets intermittent. It flashed faster as i rev, but then you’ll see the blinking misses a beat or so. Could that still happen even if it’s a fuel problem? What about the points? Again, they are brand new but I know that is no guarantee on the quality (sadly). Sent from my iPhone using Tapatalk |
You did not talk about what you have for an ignition system. Stock GM points and coil, aftermarket electronic like Petronix? Points triggering an ignition box like MSD or the dozens of others? You didn't really specify. In general, a quality timing light will flash each time the #1 plug fires and not miss any cycles. That's assuming good clean hook-ups, good timing light and good plug wires.
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Stock distributor, stock coil and points. Everything new/rebuilt. Using an Innova digital timing light.
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Fuel delivery is at least part of the issue.
The way that we check the fuel system is to get a small funnel and fill the quadrajet with gasoline through the bowl vent. The fuel line needs to be hooked up to do this.
Pour in several ounces, even to the point that it overflows a little. Start the engine. It should run without missing for ten or fifteen seconds if there are no other problems (like ignition issues). If it is flooded a little, it may sputter, then clear out and run smoothly and then, basically, run out of gas. If it runs clean for a moment or two before it dies, check your fuel pressure and fuel delivery volume. My guess is that either your fuel pump crapped out or there is a leak in the fuel line somewhere between the pump and the fuel tank allowing it to suck air rather than gasoline. Either will cause the symptoms you describe. It could also be the sock inside the tank over your pickup line. The ethanol and other additives in the fuel basically destroy them and they collapse. Good luck! |
bad condenser ....
are you using delco remy points n condenser ?? |
I bet that in your distributor the wire that runs under the breaker plate has totally dry rotted insulation with a lot of it missing off the wire, and when the plate move as you give the motor throttle the power to the points gets shorted out!
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Thanks Joe. I’ll try that this morning. The fuel pick up in the tank is new. Well, it’s probably 3-4 years old, but it was replaced with the tank when Steve Barr was doing the restoration, so I’m assuming that should be ok. Sent from my iPhone using Tapatalk |
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I’m not sure. I think so. I sent the distributor out to be completely restored (may have sent it to Pete Serio) and it came back ready to drop in. How do I check if condenser is bad? Sent from my iPhone using Tapatalk |
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Thanks Steve. I popped off the cap to check the rotor, but maybe I should also pop off the rotor to check the breaker plate. I’ll take a photo and post it. Sent from my iPhone using Tapatalk |
To test the condenser fully which is a capacitor you need a meter that can test for ESR ( effective series resistance) because a cap should have very very low resistance to it.
In place of that tester if you have a ohm meter hook it up to the lead and the body of the condenser. When you do this the meter will flash a resistance reading and then go to infinity, or reading open. If you get any reading once the condenser charges up of even 10,000 ohms then it’s bad. |
I pulled the rotor and everything appears in order. No wires have any worn insulation.
https://uploads.tapatalk-cdn.com/202...be8cfec254.jpg https://uploads.tapatalk-cdn.com/202...300191d8ed.jpg Sent from my iPhone using Tapatalk |
If your timing light is going intermittent and then that’s when you drop cylinders, then you 100% have a ignition issue and not a fuel supply issue.
With this being said just to be sure you should test that timing light on another car! How do the connections on the coil look in regards to the plus and minus wires and there crimped on terminals? |
Ok. I also have another issue that is fuel related. There is all kinds of junk in the fuel inlet in the body. After I put the correct carb back on, I noticed it was leaking a little bit. I went to tighten it and it seemed that the big 1” fitting was loose. I removed the fitting altogether ant there was all this ‘grit’ in the inlet and on the little bronze filter. Almost seems like the threads were ground up. I wiped my finger in the inlet and pulled out even more of it. I don’t think this was what caused the rough idle because when I swapped carbs last night, it still ran rough.
I think the fuel inlet needs a helicoil repair. You can see some of the grit in this photo: https://uploads.tapatalk-cdn.com/202...7f64f2dee0.jpg Here it is after I wiped the inlet threads with my finger: https://uploads.tapatalk-cdn.com/202...0767a5f40f.jpg https://uploads.tapatalk-cdn.com/202...e118901a1f.jpg I’m assuming I should no try to do anything until this gets repaired. Do I have to send this out to someone like Cliff Ruffles? Sent from my iPhone using Tapatalk |
Ouch.
Yes, that needs to be repaired before you try to run that carb any more. Otherwise the grit will work its way thru everything in the carb....
Sorry to see that happen, but these are fifty-year-old parts. :rolleyes: We've had three qjets do this and EVERY ONE was a Carter-manufactured quadrajet. One of them even stripped out the needle and seat threads. I presume lesser quality metal was used when they were made. When you get it fixed, I'd suggest losing the bronze filter and installed a good paper one instead. My 2 cents. |
Ok, thanks. I still have my other Q-jet that I can use to at least track down this rough idle. I’ll use a paper filter next time.
I found a site (quadrajetparts.com) that offers the service of re-machining the threads. I’m going to call them tomorrow. Sent from my iPhone using Tapatalk |
I don't use the in carb filter. One, no reason to remove those fittings and two, those filters can plug up easily. I use a robbmc big body filter. It sounds like it was starving for gas if carb needle was blocked with debris. The timing light behavior makes me think fouled plug or bad wire.
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Thanks chip. I get that the grit may have blocked the carb that was in the car, but I swapped on another carb and I still have the rough engine. I will pull each plug later.
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But it would still seem to be even flashing, what I hear being described is uneven flashing accompanied by misfire. Quote:
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https://uploads.tapatalk-cdn.com/202...300191d8ed.jpg That's not the distributor condenser. That one is for the voltage regulator. There'll be another one on the + side of the coil. It isn't that one, either. The one in the distributor is electrically connected to the - side of the coil, but it's housed in the distributor. Quote:
Using some sort of fuel additive? Mixture overly-rich? Fuel curve wrong? Choke stuck on? Idle mixture screws not adjusted properly? Quote:
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OP mentioned that he had swapped the carb out in a diagnosis attempt. Maybe the pic is during that swap.
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Have you tried a different coil ?
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Could be the point contacts are burnt. The over the counter points that are sold these days burn easily, especially when the ballast resistor sends to much voltage to them. The OEM sets in the past were much better, but too much voltage would kill them fairly quickly to. Usually points start missing at the higher rpms, and as the problem gets worse it starts to run rough at lower rpms to.
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So a bad coil could also cause the problems am having as well? |
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I don’t know of any high quality point available new other than a couple decade old NOS points on eBay.
We don’t run much with points anymore though, and have converted nearly everything to some type of electronic. Have ran at least one MSD box from points and did ok. If I am stuck with a points distributer we generally use a pertronix and keep a old set of points in the glove box in case it fails. Have used pertronix in antique tractors to 12 second 455s. The pertronix seem like they are can erratic if voltage is too high, and just like anything else electronic they need a good ground. I don’t miss wondering what rpm the points are going to act up though. |
Those plugs are pretty dark. I'd change them and the wires unless the wires are new. What heads, compression and plug heat range?
Edit: I see 670 heads. Those plugs are fouled. My 670s never blackened plugs like that with R45S. The Autolite 303s (fairly cold range) would get some color on a nitrous load, but not like that. I'd take a hard look at the ballast wire or ballast resistor setup and the coil selected. Some coils have an internal resistor and some are designed to be used with an external ballast resistor or resistor wire, and some coils are very low resistance for use with electronic CD ignition. I'd make sure it is all designed to work together. Gap the plugs to .035 to .040". Points inductive ignition has a lower peak plug voltage and longer duration than CD. In english, run a smaller gap with points. Once the ignition is sorted, go back to fuel. Verify the carb's calibration hasn't wandered off in the grass and fouled the plugs. It should run better once you change the plugs. I'm thinking the plugs fouled out, and changing carbs can't fix that after the fact. |
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The weights and springs are not your problem, if they're faulty, it's on the guy who restored your distributor. I don't think there's anything wrong with them, as long as they provide a decent advance curve. Don't REPLACE the points, TEST the resistance through them. A simple ohmmeter would work. The points have to be CLOSED to test resistance, and the ignition should be off. And verify the dwell, THEN verify the ignition timing. (Not the other way around.) Quote:
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An ohmmeter and a spark-tester is all that's needed; as this ignition system uses a ballast resistor in the primary circuit, you'd want a spark tester that is not calibrated for HEI ignitions. Check resistance between the two screw terminals, and between either of the screw terminals and the metal case. Check resistance of the coil-wire terminal and either one of the screw terminals, and between the coil wire terminal and the metal case. Example: (Ignore the crap about "exclusively for small engines", it's not. They're lying.) https://www.amazon.com/Stens-750-018...764548&sr=8-30 |
High quality points CAN be bought , if needed or wanted)
By specifying you want MARINE application I know Blue Streak has them. Try a Napa store. Marine electronics are made to a much higher reliability standard. |
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I don’t know how accurate this old Sears Engine Analyzer is, or even if I hooked it up right, but I attached the green alligator clip to the negative (-) side of the coil and the positive/negative clamps to the battery. I set the Range Selector and Function Selector to ‘Points’. When I switched on the ignition it showed the needle in the ‘Bad’ range for points:
https://uploads.tapatalk-cdn.com/202...7f1272eeda.jpg Sent from my iPhone using Tapatalk |
Here’s another possibility that I just recalled I had happen to a car of mine ages ago, and the car had symptoms just like yours.
I had a spare car at the time that I was starting to restore and it sat outside during a full Summer. When I started it up after those many months it did so just fine, but could not get out of its own way even on a level driveway due to ignition break down. After going thru a 2 day long troubleshooting session I found the root cause of the problem. I Mouse or Mice had partially eaten tru the wire feeding the coil that I had extended into the passenger area and had wired to a kill switch. The bottom line was that the 5 straind’s of wire that where left unchewed could not pass the current needed to run the motor much above a idle! This took a long while for me to find out since the wire was passing 12 volts as needed, but only some 30% of the current needed! Your issue may not be a chewed thru wire, but any crimp on wire connector not done tight enough can make for the same low current feed issue. |
If that analysis of the points on that meter is correct then that very high resistance could very well be the root cause of your issue!
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I would not expect the ignition to be turned on to get a reading on points resistance--but it COULD be wired that way. Looking at the meter face, the "Points" scale seems to be shared with the "Low Volts" scale, indicating that they're using voltage to measure points conductivity rather than resistance. If the points have high resistance, they provide a poor ground for the primary current/voltage, and the voltage is what the machine reads. The points would have to be closed. |
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I took the rotor off again, Is there a better way to check the points? |
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Here are the instructions:
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Just out of curiosity, have you pulled the valve covers to see if perhaps there is a broken valve spring? I had that happen once and it still ran, just had a miss.
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I haven’t, but will do that tomorrow. Thanks! Sent from my iPhone using Tapatalk |
Assuming your analyzer is working, your points have closed up. Dwell should be 30 degrees. Your points either vibrated loose or are burned and bridged momentarily, forming a pointed tip which results in a less than optimal point gap. Your spark intensity drops and you foul your plugs when this occurs.
Pick up a cheap ignition file at the auto parts store and run it between the points contacts to smooth them. Reinstall your rotor and cap and re-adjust your dwell. You can do it with the engine running or pull the coil high tension lead and have someone just crank the motor over while you adjust the dwell with an allen key inserted through the window on the distributor cap into the adjusting barrel on the points. That will get you running fine until you can buy a new set of points. If you don't know how to do this with the dwell meter, then leave the cap off, bump the ignition until the rubbing block of the points is on a high point of the distributor cam. You can insert the rotor and rotate the distributor cam slightly by hand to a high point. Then adjust the point gap with the adjusting barrel screw until you have a 0.016" gap between the points contacts. A bad, shorted-to-ground condensor will give a no spark, no-start condition or if failing, it will be reactive to heat and intermittently kill the motor. Following a cool-down the engine will fire again and run until it shorts again as it is heated up by the motor and current flow. It will fail in completely in short order after this starts. Also not sure where your condensor is mounted, on the outside of the distributor housing maybe? They are typically affixed to the points breaker plate like this set. The canister coming off the back of the points is the condensor. https://i.ebayimg.com/images/g/ws0AA...JE/s-l1600.jpg |
Here are what the points look like. Should there be a hole through the fixed base or should that be solid?
https://uploads.tapatalk-cdn.com/202...7ed8b4d6f9.jpg Here you can see through the base to the paper towel https://uploads.tapatalk-cdn.com/202...6d088c5d8e.jpg Sent from my iPhone using Tapatalk |
They're toast......
You've found at least part of your problem.
And, yes, the hole is there on some manufacturer's points to ventilate them and keep the points cooler. |
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He'd have to turn the selector knob to "Dwell" to measure dwell. (Which would be a good idea once it's reassembled, and after that, verify initial timing.) Quote:
GM service procedure was to NOT remove the cone of metal transferred from one contact to the other. The point set was usable until the cone of transferred metal was taller/wider/bigger than the point gap--and then the point set should be replaced. The metal transfer is still contact area that shouldn't be removed. Look, folks--I haven't held a set of points in my hand in thirty years. I use "Points" distributors as oil pump primers, after I yank them out of the engine and replace 'em with HEI. So my eyes are not calibrated to see problems with points--but--those points don't "look" bad to me. Maybe they are bad, maybe I'm senile, but I remember used points looking much worse than that. The only reason I question them is that crappy-looking point sets came out of cars with 12,000 miles sometimes more; and these came out after 250 miles. Quote:
HOWEVER, the previous system was to install the points, with the condenser mounted separately on the breaker plate--NOT on the "outside of the distributor housing", using a single screw and hold-down bracket. The condenser lead was tucked under the points spring just like the coil lead. Once somebody installed a "Uni-Set", the car got Uni-Sets from then onward, because the condenser hold-down bracket and the machine screw were long gone. The "mechanic" wasn't about to waste time removing the old condenser from the bracket, and then re-attaching the empty bracket to the breaker plate with the screw. All that went into the garbage can. I'm reasonably sure the condenser of this distributor is behind the mainshaft, invisible in the photo--but he should check to be certain. https://www.summitracing.com/parts/a...make/chevrolet https://static.summitracing.com/glob...acc-8101_w.jpg Quote:
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From the latest pictures, the points are fine.
Filing excessive metal deposited between the points is a temporary measure when the gap is closed up to the point that plugs are fouling and the vehicle becomes undrivable. GM did not condone it in the long run but it will get one to and from the parts store to get a new set of points if excessive electrode transfer (cone) has occurred. These cars are not driven like they were in the '60's so points don't fail from high mileage. There is usually a resistance issue that causes a failure or just faulty materials. |
Just as everyone said, the condenser was tucked away from view. All of the screws holding the points and condenser were tight and the condenser wire was also tight. There is no abrasion on any of the wires. A friend of mine gave me a new set of points, but if the ones I already have are still good, I’ll just put them back in for now.
I did get a new set of plugs (R45S) and set the gap to .035. I haven’t restarted it since I put the plugs in because I’m not sure that could be the root cause? As I said in my original post, car was running fine and then I felt this little stumble and everything went downhill from there. I didn’t over-rev it or anything like that. I was just cruising at about 50 mph when it first stumbled. I did have someone crank the car with the fuel going into a container and it seemed to fill that pretty quick, so I think the fuel pump is probably ok. I’d never done that before and the fuel came out in spurts as opposed to an even flow, but I’m assuming that’s by design of the eccentric. Sent from my iPhone using Tapatalk |
I used to pull 400 grit paper through the points when they were closed 2 times each side got rid of high points from arc transfer
I would do this rather than a file to keep surfaces perpendicular I usually did this just once in the points life then replaced them the next time I felt like they were long in the tooth usually early fall time I replaced them and early spring time dress them But I just run HEI's. since about 1983 ish. |
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on the front of the camshaft. 2) As the "Excentric" rotates it compresses a spring in the fuel pump housing. 3) The spring is compressed with the "Excentric" is in one position and is at installed height in the other position. 4) When the engine is cranking/running at idle speed, the there are "pulsations" in the supply to the carburetor. So you are absolutely correct that that pulsing at low speeds is caused by the "Excentric" operating at slow speeds and is apparent. THE "Excentric" IS ALWAYS PULSATING, THE TIME SPAN BETWEEN PULSES JUST SHORTER WITH INCREASED RPM. Some applications have a small return to bleed off trapped air/pressure. Mostly on A/C built vehicles. Tom V. |
Go on e-Bay and get a set of Accel 8104 32 ounce points. Get the 110128 points and condenser kit. Look for the vintage accel points that are from the seventies. There the best.
Those points you have are, well, just get the points I suggested. If you can't find them I have a set I can sell you.. Set the dwell to 30. Make sure you have the vacuum advance plugged and keep it plugged through the troubleshooting process.. If you have a return line from the pump to the tank the gas line will always be empty when removed.. If you don't have one I would get one. Just tee the line going to the carb and run a 1/4" line back to the tank and install a piece of 1/4" tubing next to the other connections in the access plate.. But it's not the issue your having.. The return line keeps the fuel cooler and mixed up, we especially need this with todays moisture attracting Ethanol. I really think its the points.. Also when its idling, Check the voltage at the coil + positive. It should be around 9-10 volts. When started it should jump up a volt or two then settle back down under 10... What ever you do keep the distributor you have, its a very good unit. Frankly, you all ready have one of the best ignitions going.. If you want a more powerful ignition connect a Vertex Z-6 CD box to it.. But for now, I would put the NOS Accel 32 ounce points and condenser in and keep on trying.. Don't start throwing money at it. no matter how tempting, take your time with it and enjoy the detictive work.. It's not like you need the car to go to work or anything.. |
So I tried putting in the new points. That didn’t work. I followed instructions to set the gap at .019 when the rubbing block was on the peak of the cam. Engine wouldn’t start. Figuring I didn’t set the gap right, I put the old points back in. Still no start. [emoji53]
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