Went up to the drags yesterday, and my nemisis problem came back to haunt me....I thought i had it fixed, but no! The car noses right over at about 4500 rpm and up at full throttle (or at least it did, more on that in a second) . It doesnt break up or misfire, just almost shuts off. I take my foot off the gas and get back in and it picks back up and goes. It generally does it hot, and intermittantly (but mostly) This problem started when I changed over to the Q-Jet, intake, etc... So at first I thought it wasnt shifting, and nosing over as it rev'ed past peak and floated valves.. It still kinda feels like that. I'd take my foot out, it would shift and I could get back in. It could be an issue with the SP switch and how it controls full throttle upshifts. But after talking to Tom T, if that was the issue it would short shift, or wouldnt upshift at PART throttle. And it would also do it in high gear when the revs climbed. So then I thought it was float level, as I put on a 66 Q-Jet with a notoriously small fuel reservior and bad float geometry. I messed with float level and my test runs (cold) on the street made me think I'd cured it. But I was able to do it yesterday with my other Q-Jet and my AFB, so carb is out. Maybe fuel delivery (pump gets hot, fuel sock gets intermittantly clogged?) So we looked around and started thinking about electrical - the car has a pertronix III (with rev limiter) and Ignitor II coil. Full 12 volts at coil (run from who knows where, I didnt do it). At first we were thinking heat soaked coil. We started to look around and found the black wire coil to module was pinched between the cap and distributor. Freed it, it wasnt cut but it is extremely flimsy wire- feels like fusable link as you handle it. Ran with the wire free and same deal. Grabbed a NAPA coil (no special voltage) and tried it. Now the condition has changed - feels more like on-off-on-off all the way down the track, not neccisarily at revs. So now I'm leaning toward electrical since the condition changed with the coil swap. I could have broken the module wire when I pinched it -is there any way to test for continuity other than poking it? It goes directly into the module the wire is so thin if I poke it I'm sure I'll screw it up worse. The module rev limiter was set at 5500 from the factory, I verified but never touched it when I installed a few years ago, and havent messed with it since. This issue has cost me two track days and is really getting aggrivating, especially since I the car is very healthy otherwise - great idle and 22 steady inches vacuum. Any ideas? I do have a second distributor with a pertronix I in it that I think I'll try next, but I'd like to do as much diagnosis on it as I can while in it's current condition and doing it fairly regularly. Thanks again to everyone...
try hooking up a fuel pressure gauge and run a temporary line into the car so you can have a passenger watch it and then do a run, wouldn't surprise me if your pump isn't keeping up at the higher RPM's. When I had my 69 dyno tuned, that was a problem they discovered and quickly shut it down to avoid possible damage.
I also have a Pertronix Ignitor III setup. It seems to be a little finicky when it doesn't get the proper voltage or have the correct coil. It needs a low resistance high voltage coil for optimal performance. Something like the Flame Thrower III coil from Pertronix, or even an MSD coil from your local auto parts store. I'd be willing to bet the "stock" type Napa coil just isn't cutting it. That's been my experience at least. I'd also double check the voltage at the coil with the engine running just to make sure your getting battery voltage. Otherwise I'd suspect a fuel delivery issue. When I was chasing a similar issue last year folks mentioned the "sock" in the tank, or possibly dry rotted rubber fuel lines sucking air. Like Chris suggested, getting a gauge to confirm adequate fuel pressure would be a good first step.
Pertronix on a 70 455, started great......................fell on its face at 4,400 rpm. Put in an old set of Accel points (wouldn't dare tell you how old!) and condenser and stock Delco coil. Now at 5,200 rpm shifts it still wants to keep going! Food for thought.
ok - so I'm gonna 1. Get the Q-jet intake back on the car 2. Field test the Pertronix coil and re-install 3. Confirm the original problem returns 4. Fuel pressure test w/ passenger - if low pressure: 5. Check sock (godd timing, tank's almost empty!) 6. Check lines for degeneration - swelling, cracking, etc...(they're new, but Tom doesn't trust new NAPA hose) 7. If problem persists: Install old distributor with Pertronix I unit (known good) Maybe I can get to all of this this weekend...maybe..??
I don't know who supplies NAPA hose, but I discovered a cracked CarQuest hose on on my Buchev pickup that was only three years old. My nose discovered the leak. I think that a lot of the fuel hose that is available is either crap, or it doesn't like 10% Ethanol.
And I thoiught thats what I bought - I'll double check the part # on the hose. In the meantime, can anyone tell me what the primary resistance spec for a Pertronix Flamethrower III should be? I've got 1.7 ohms.
i was thinking .32 not sure. the wire you pinched could be bad it happen to me. the outside was fine but when i cut it open it was apart
.32 is what they advertise (super low resistance) , but there probably is a range that tests within spec.. would high primary resistance do what I'm experiencing? The factory spec is 1.28 to 1.42, but thats for a Delco coil... I'll try the other unit, and see if it clears all this up. That wire is so thin, I'd love to check the resistance at the pinch but I think the other end just dissapears into the module. ---------- Post added at 02:45 PM ---------- Previous post was at 02:20 PM ---------- I also checked the voltage at the coil and found something funny - key on, I've got 13.0 volts, start the car and it drops to 11.8. I dont know if that makes a difference, as you're supposed to be able to run these through the resistance wire, but I wonder why it drops. It Looks like someone spliced the harness and cut out the resistor wire. The pink wire seems to be gone.
I would imagine at 1.7 ohms that is not within factory specs. Personally I'd replace the coil with a non Pertronix unit. I had one fail after only two seasons of cruising. And since you had one apparently fail as well, that doesn't fill me with a lot of confidence. For the Ignitor III, you cannot run it with the factory resistance wire. It needs battery voltage to operate properly. When I first installed mine I tried using the resistance wire. It ran, but you could tell it had a miss. I think 11.8V is borderline, since if it is suppose to see battery voltage, that should be around 14V. I'd run a new wire to the coil. I used a standard 4 pin relay with the factory resistance wire as the trigger, and ran a wire straight from the battery. Should be really easy to wire up without having to splice into the harness and try and figure out what the previous owner did.
I talked with someone at Pertronix when my coil died. They said that any low resistance performance coil should work. I asked about just picking up an MSD Blaster 2 from my local auto parts store and their representative said that should work no problem. That's what I was told anyway.
I could run power from an alternate source, but wouldnt you just want it to be "key on"? And I cant be too hard on Pertronix... This coil did get dropped once, and I understand thats death to a coil.... Andy's question is a good one: I put a try-on NAPA "whatever" coil in there, it runs fine but did change the issue from high revs to on-off-on-off under power...maybe thats due to low input voltage? At cruising speeds there is no issue, drove it home just fine.
Rhett,,, pard,,, take a two pronged approach.... make double sure the fuel supply is good and strong.... i always remove the sock that is in the tank on the sending unit... and then install a 3/8 fuel line from the sending unit to the inline filter, which is a big one like goes on a truck, big truck.... holley in fact.... :Brow::laugh: and,,,,, then,,,, if I remember right , the breakerless ign. does not use a resister wire..... it hooks up to straight 12 volts.... the factory set up from GM is designed so that you start on 12 volts but when the system comes off the start circuit , the voltage drops to about 9 to keep the stock coil from overheating.... I suggest that you get a 3/8 fuel line from the tank all the way to the carb,,,, and,,,, change the inbound voltage to a full 12 volts on your system..... a nailhead in good shape should pull 5500-5700 before it starts windmilling.....:Brow::Brow:
Using the relay method like I suggested above is only hot when the key is on or the engine is running. When the car is off the factory resistance wire is dead. Turn the key on, and the factory resistance wire will trigger the relay to close and take the incoming battery voltage and supply it to the coil.
Doc, haven't heard "Windmilling" in quite a few years. Bet not many know what it means. Care to elaborate for those who don't??? Something else to try Rhett to try & eleimante voltage supply. With car running run a jumper wire from the positive battery terminal to the "+" side of the ignition coil. If this cures or makes the problem better, now you have a direction to follow. Although many Pertonix set-ups seem to have the higher RPM problems, not so much low end. If not then I would concentrate on fuel supply issues. Again, as we discussed, the Holley with the larger fuel capacity float bowls may just eleiminate the problem entirely. We're not talking fuel pressure as much as fuel "Volume". But as the pressure starts to drop down to 3pds. or less @WOT then we know it's a supply problem.
I would try splicing that pinched section of wire to get it out of there. Continuity and current flow are two different things. Good continuity does not mean adequate current flow. Splice in a new piece with some quality heat shrink butt connectors.
