When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
my 350 was completely gone thru in late 2016 - .030 over, all new major internals w/Howards street performance cam, Pertronix Flamethrower III ignition and a 800 QJet built to the motor from Everyday Performance. New fuel tank went in at that time as well.
Flat-top pistons with 9.5:1 compression overall.
Had been running beautifully until a week or so ago, when erratic/rough idle set in, stalling and overly-rich fuel conditions occurred - thinking classic failing coil issues, replaced that and changed plugs (which were now horribly carbon-fouled). New set of AC Delco R46SZ gapped .060 are installed now
No change in the condition except now the car won't even stay running when I take my foot off the gas. I did notice one of the dist cap hold-downs were turned out (loose cap) while changing coil so checked inside and all looked ok - re-secured the cap as well.
so the car starts and re-starts ok and no miss in the engine when I run the rpms up in park/neutral but when placing in gear once engine warms up, either runs rough again or stalls immediately out.
New Carter fuel pump was installed at time of engine rebuild, I haven't yet checked the carb fuel filter - motor has approx. 5k miles on it since rebuild. No obvious vacuum leaks.
I run 92-93 ethanol-blend pump gas, but about 2 weeks ago about 10 gallons of octane 90 non-ethanol went in during a road trip. I've since driven the car about 150 miles and refueled with the 93 pump blend though. Wondering if any problem caused by this mix?
any thoughts on what to try next - is it possible the carb has developed an incidental issue? I'd presume if it were a Pertronix module issue, the car would simply shut down entirely (had that happen on a prior car).
open to ideas on what to check next and hoping this doesn't become a parts chase
Last edited by 70sgeek; June 9th, 2018 at 09:31 AM.
I've had the pertronix module run poorly right outta the box...after futzing around, had it replaced and was GTG. I've also had them fail dead w no spark, I stopped using them ~15 yrs ago for those reasons
I gapped at .060 essentially per suggestions recommended within several GM-related blog sites for this plug - this is a plug referenced for later-70's HEI-equipped GM cars so I thought I'd go with that as a start. My prior plugs were gapped at .045, which will be my next adjustment.
D7110700 is the Pertronix p/n
Last edited by 70sgeek; June 9th, 2018 at 09:10 AM.
.060 was originally suggested by GM with first gen HEI. They retracted that suggestion due to coil failures. Either way yours is not an HEI. I'd also run your stock plugs. Looking at all the wiring diagrams for Pertronix, the module needs to be hooked to a switched 12v source. If your using a stock coil then you need to connect your resistance wire to the coil+ terminal and the black wire of the module to the negative. If your using their Flamethrower II coil the coil+ terminal needs to be connected to a switched 12v source.
I believe the Ignitor II and III use the same wiring diagram:
erratic/rough idle set in, stalling and overly-rich fuel conditions occurred - thinking classic failing coil issues,
I'm curious why you went straight to ignition. My first reaction from your description is either a saturated float or debris in the needle and seat in the carb causing an over-rich condition. That would also explain why it runs when you hold the throttle but not at idle.
When I first installed the Pertronix distributor I also added an MSD 8202 blaster 2 coil. No issues all this time until recently as described. I contemplated that a coil failure might be causing the problems because they all seemed potentially consistent with a weakening coil AND I only recently read that MSD recommended their oil-filled coils to be installed straight up v. laying on side (as mine is, in the bracket bolted to block). the new Accel 8140 coil was a cheap option ($25 at my local Advance), as were the plugs ($2 each), so I went that route first. I'm not running a ballast resistor. So I just now cleaned and re-gapped the plugs to .045 and I'm going to check my idle screw settings on the carb before I fire up again. Will also check the fuel filter - I did spray carb cleaner into the front barrels but apparently no real help.
Earlier with the plugs gapped at .060 I only had the car running under 10 minutes total (no drive time) and they came out carbon fouled.
Last edited by 70sgeek; June 9th, 2018 at 10:47 AM.
When I first installed the Pertronix distributor I also added an MSD 8202 blaster 2 coil. No issues all this time until recently as described. I contemplated that a coil failure might be causing the problems because they all seemed potentially consistent with a weakening coil AND I only recently read that MSD recommended their oil-filled coils to be installed straight up v. laying on side (as mine is, in the bracket bolted to block). the new Accel 8140 coil was a cheap option ($25 at my local Advance), as were the plugs ($2 each), so I went that route first. I'm not running a ballast resistor. So I just now cleaned and re-gapped the plugs to .045 and I'm going to check my idle screw settings on the carb before I fire up again. Will also check the fuel filter
Earlier with the plugs gapped at .060 I only had the car running under 10 minutes total (no drive time) and they came out carbon fouled.
Carbon fouled plugs are probably NOT an ignition problem. Idle screws will not fix a float problem. I struggle to understand how the fuel filter can cause an over-rich condition. I can understand a plugged filter causing a lean condition.
I agree, but trying to hit the simplest areas first - guess I'm hoping maybe pulling the filter will allow any loose junk to come out if that's an issue. I can install and tune carbs fairly well from the outside, but not much experience digging into them - I do have another QJ I can swap in that was on the car before with no issues, but it wasn't built specifically to this motor like Ken's was.
Last edited by 70sgeek; June 9th, 2018 at 10:54 AM.
I agree, but trying to hit the simplest areas first -
Changing the brake shoes is simple too, and will have about as much effect as changing the fuel filter...
If you're going to waste time and money on parts changing as a substitute for real troubleshooting, at least start with the most likely causes, not the simplest.
Low voltage spark can cause fouled plugs also as well as extended idling. I know you would not be using a ballast resister, but are you using the stock resistance wire? Is the coil you bought meant for this application resistance wise? If the ignition checks ok, then you may be running pig rich, look at the suggestion that Joe threw out there.
Definitely not into wasting $$ on unnecessary parts - this site's advice is always well regarded - I just wish I had more carb experience to diagnose it better.
Pertronix specs say to use their coil with .32 primary ohms but other info I've read including past Pertronix tech comments say the Accel/MSD coils are ok. Accel is 1.4 primary ohms per their specs.
Again, the MSD was on the car for over a year with no issues until recently so that's part of the reason I believed it could have gone bad only now, for whatever reason (to possibly include the position mount issue)
I believe the stock resistance wire is retained, I'm using a stock engine harness (new M&H wiring) setup with the only change having been to an updated alternator with internal VR - the Pertronix dist is a simple 2-wire hook up unit in and of itself.
Last edited by 70sgeek; June 9th, 2018 at 11:09 AM.
You are not supposed to use the resistance wire. It will create a low voltage situation causing the Pertronix III to overheat over time. Run a 12ga wire from the IGN terminal in the fuse block to the coil+ terminal and remove and stow the resistance wire.
One wire is from the solenoid, it should be yellow, its the resistance bypass wire. The other should go to the connector on the firewall and it turns on with the ignition switch. If its really stiff then its a resistance wire. If you ordered a stock harness for points with the exception of the internal VR alternator, it will be a resistance wire.
the yellow and black are same thin gauge, so is this a case where should I disconnect the yellow and run a separate heavier gauge wire from the solenoid right to the coil connection?
Last edited by 70sgeek; June 9th, 2018 at 12:09 PM.
No, I would run a wire from the fuse box ign term (12v switched with the ign key). Or if you'd like, a temporary 12ga jumper from the battery positive terminal to coil+. Note to stop the engine you need to turn off the key and remove the jumper.
so I would disconnect the yellow from coil/solenoid and instead, run a new wire from solenoid to fuse box IGN as a permanent re-direct of power to the solenoid?
Ok, many thanks for staying with me on this - I'll work on it some more over the weekend and post results on whether that makes any difference
I still haven't quite figured out how all was well for over a year before these conditions occurred but ignition is easier for me to isolate first than internal carb issues, so I'll have at it some more.
For the carb, hook up a vacuum gauge, make sure the needle is steady. Then adjust your air/fuel mixture screws for the highest vacuum. Also make sure your timing is correct after you get the power wire installed. Let me know if it gets corrected.
Ok, so I believe I have ruled out carb issues from the mix, as I swapped another known good Qjet that I had onto the motor this morning and no matter what incremental adjustments I made, same problem - car would start but not stay running at idle even after full warm up. Park idle was roughly 900 rpm, drive idle 700 - cam is not radical, just a Howards street performer and NEVER had this issue before now.
Leaned the swap carb out a bit in comparison to the one Ken built and not running as rich as it was before the swap. but that's about the only change.
Everything was essentially stock-wired under the hood, only change I previously made was to install an internal VR alternator, for which I got the wiring adapter from M&H.
In update to the coil issues, with motor running, I was reading 1.5v on the (+) side with stock wiring setup - I just this afternoon rewired the yellow wire from starter directly to IGN on the fuse box and coil now shows approx. 12.8v on the (+) side. The (-) side reads about 1 volt lower than that - I don't know if these readings are what they should be but maybe they are correct given it's a Pertronix electronic ignition setup) - Not sure why (+) read so low with stock wiring hookup - that's concerning to me.
Still having some running issues but possibly that might be from the fouling of plugs which occurred before - still using the swap carb to sort everything else out, before I put the Everyday Performance carb back on.
I seem to have plenty of fuel delivery and it's clean, so I'm not thinking fuel pump - that was new (Carter) at time of motor build too.
No changes to engine timing, no issue with that that I know of. Distributor was also new at time of engine build so not sure what to look for next....
Once I put another set of fresh plugs in I'll recheck the idle which is still unstable and causing the motor to stall in gear, especially if turn the a/c on to check for idle drop (it's a new Vintage Air system - all electronic, so no vacuum pull, but still draws power down on the motor). That may just be an idle solenoid adjustment in the end.
Still looking for any other experienced suggestions on what to check - really want to sort this issue out since I don't know what happened to cause it and I still don't know if I'm heading in right direction to sort it out. I've not driven it out of the garage yet, as when last attempted, it wouldn't stay running in the road .
Last edited by 70sgeek; June 10th, 2018 at 01:25 PM.
SO the wire runs from the ign terminal to the coil+ now, no others on there? 12.8v on the coil+ terminal running is perfect. Did you adjust the carb for highest vacuum? What is your timing now?
Positive coil now has distributor red, engine harness black and radio capacitor. Neg side has tach and distributor black. Haven't rechecked timing or vacuum yet. Figured I would change plugs again first to see if it'l run better
Running a little less rough but still unstable - Won't stay running long enough to set the carb or drive. The new plugs I put in yesterday carbon fouled almost immediately before the changes I did today so hoping another clean set will get the car running well again now that the coil has full power to it.
still don't know why it only had 1.5v at (+) before I changed the wiring from stock setup.. Feel like I'm missing a bigger picture there.
Ok so after my 2nd plug change (AC Delco R46SZ at .040 gap this time) and a retune of the swap carb idle screws, the engine park idle is better and the plugs are burning clean, but it still won't stay running. After warming to full operating temp in park or neutral (180 or so, which is what it's always been), it'll eventually stall itself out, or immediately stall itself out when I drop it into gear.
can't even keep it in gear long enough to check vacuum or timing. My plan is put the good carb back on tomorrow when engine is cold, then attempt to get it running again well enough for timing and vacuum checks.
Battery voltage is good all around and exhaust burning clean, I tried varying the idle screw settings a bit more rich just to see if any difference in running conditions, but I stopped messing with them after each was 3 turns out. Still no obvious vacuum leaks and the car fires right back up each time it stalls out.
Park idle is about 900 rpm right now, no idea what drive idle is because it won't run in gear.
I'm out of ideas at this point but for fuel pump or Pertronix distributor module (which I thought these either work or completely die, no gradual failure symptoms)...
Last edited by 70sgeek; June 11th, 2018 at 04:56 PM.
I know it would seem like a leak but I can't find one anywhere.
I've been all over the motor checking for them - carb ports, brake booster, PCV, etc. Since I'm running the Vintage Air a/c, no under-hood vacuum can in use. carb properly bolted down to manifold as well. Carb currently on the car is a '76 Olds 800 Qjet w/electric choke conversion - it was rebuilt a few years back with all ethanol-friendly parts as well and is a known good carb.
I really don't believe it's fuel related and if there isn't a vacuum leak somewhere I haven't found, I'm down to the Pertronix as possibly my last easy wild card.
I don't know why I previously only had 1.5v at the coil (+) with engine running (and if it had been that way the whole time with my stock engine harness, how the car ran as well as it did until now) but now there's 12v at the coil when running and still not running any better (except for running cleaner now).
Last edited by 70sgeek; June 11th, 2018 at 05:43 PM.
You can try spraying some starter fluid where the intake meets the heads and around the intake manifold to see if the idle improves. Try loosening the distributor and increase timing to see if idle improves.
I'm going to swap my Everyday Performance carb back onto the motor and attempt to check timing / vacuum tonight. Will report back as soon as I have any new results.
June 9th, 2018, 08:22 AM
