Maybe someone has already suggested this and I missed it but why not just install a set of points to eliminate the Pertronix and narrow down the problem to either spark or fuel?? Many years ago, in fleet work, we used a similar set up to eliminate points but then it was called "Perlux". We found the conversion broke down as frequently as the factory points. I specifically remember the Perlux melting if the driver left the key on. These finding were in a very large fleet. Problem sounds kinda like fuel to me...no backfiring? Good luck Rhett! Tom Mooney
Great feedback from everyone and thanks! WildcatGS - I'd try points but I no longer have a distributor with a points plate (or a resistor wire) . Gonna take some work, but I know I'll get to the bottom of this. Doc and Tom - I know the term, and firsthand. Nothing would windmill like my Corvair 140.... would rev quick as you could shift, but at 5500 rpm it would... falling on it's face isnt a strong enough description. Thank god it wasnt an interference motor. Tom - I like the 12 volt temp jumper - While I have your carb I'll try it too although I'm not leaning toward Q-Jet bowl capacity issues. I did discover that I had a 5/16th line from the filter to the carb.. that might be part of it. All the rest is 3/8. Thanks to Doc for making me put the car in the air and actually check! Buickrat - I was thinking the same thing, it's such small guage wire to begin with.. it really feels like fusable link. Is there any wire at all in there? I've got a good solder gun, and heat shrink tubing and a good heat gun, so if it comes to that I'll do it.. last resort as I'll have to pull the distributor to do it clean. CameoInvicta - Didnt pick up what you were describing earlier, read it too fast - Got it now. If the jumper wire works, thats what I'll do. I'll keep messing with it tomorrow.
Another thing I have in stock are "Nail" distributors. I could set one up for points & do a little re-curve to try. All that would be needed is a ballast resistor we could run inline with the 12 volt supply wire, which I also have in stock. Let me know.
It has been my experience that nailheads dont ''float the valves'' like the old flatheads would....[Tom, you can splain that term to the younger ones:Brow::laugh:] The engine would reach max rpm's and then just kind of level off ,,but not make any more power.... ''windmilling''...... The factories, back in the day,, would call valve ''float'' ,,,,, ''valve toss''..... and i might add,,, you oughta see a strobe light video of it.... the pushrods look like spaghetti , the rocker arms are going every which way,,, and the lifters make sparks like the 4th of July..... made us all wonder how a engine survived it at all..... Rhett, I had another thought,,,, Your problem may be ''all of the above'' or a ''combination '' problem..... the restricted gas line , AND the ign system may the the problem...... not just one or the other.....fix both for sure......
Doc - I'm thinking you're right. Right out of the gate I'm gonna do the line and run the 12v jumper and see where I stand, then when I get the coil specs back from Pertronix I'm probably gonna wind up replacing that coil too. Maybe one of the three will actually fix it!
What are you running for a fuel pump????? And,,,, is there a fitting anywhere in the system that does not have a 3/8's inside dia.....???? and ,,, if that sock is not out of the tank,,, take it out and depend on a good inline filter entirely... a big one.....and,,,,, If I was there ,,,, he he,,,, that car would make a run, with a good holley on it,,,, if i had to put it on by myself...... it is too good a car to not have..... BTW, I'll bet that the people that watches the car run really likes it.... like they did my car..... when i would come back down the return road in front of the bleachers , the people would stand up and clap, whistle, ect.... folks like something besides a chebby....Hey,,, I am your no 1 fan......
Heard back from Pertronix, they say the spec on a Flamethrower III is .028-0.40 ohms. Mine's at 1.7, so I'm gonna start there and use the relay idea to make sure I'm getting full voltage to the coil. I did find that the GF-94 filter outlet and the fuel inlet on my 66 Q-Jet both are spec'd for a 5/16 fuel line, the 3/8 line just wont seal with a corbin clamp, and you'd have to really scrunch it down with a hose clamp to seal it. But if the the carb inlet is still 5/16, what do you gain except ugly hose clamps? The tank is almost empty, so I'll get in there maybe tonight and check the sock out.... BTW Doc, I'm running a AC mechanical pump with 4-5 lbs. One thing I did discover is that the fuel is getting hot. Still considering the phenolic spacer idea, and also found the filter was resting low in the bracket against the water bridge. Raised that and insulated the line where it comes by the heater hose. You're right about the car being a crowd favorite... always lots of commentary from the track announcer. Last time his comment was "that car is too nice to race" - I guess you cant see the bondo from the tower! And for whatever reason, people are really suprised to see it's still a nailhead when I open the hood - everyone thinks I'd have swapped a BBB or SBC or something. It's kinda instant cred with the old timers, I really dig the reaction it gets. And more than a few have picked up on the Q-Jet conversion.
Wellllll,,,,, You need about 5 psi right at the carb entrance...... at speed.... what is the pressure when it noses over.... ???? Gotta rig up so you can tell.... but be very carefull, dont want a fire..... keep the pressure gage outside the car.... dont want to get burnt all over,,, I did that once and trust me, you dont want to do that,,, in fact you dont want to do 2 things in life,,,, get burned real bad and die,,, in that order.....:Smarty: What would work best is for you to drive,,, and someone else watch the gage and tach and record the ''nose over'' event... at what ever rpm and pressure.... another thing I thought about,,,, wonder what it would do if you put the heat back under the carb???? It may be that the fuel does not have enough time to flash into a vapor at high rpm but does at lower speeds.... the symptoms that you described are very close to what my engine did when I blocked the heat out.... and that was back when I could buy real gas not the cat pee we get now.... Just an idea.... you have tried everything else.... Even with the heat in my intake,, the temp only reaches 127 deg at full warm up....idling ,,,, dont know what it falls to when i open the carb wide open and all that cool air rushes in ..... just an idea....:grin::Brow:
Hey Doc! Had to walk away from this thing for a week or so just to get my enthusiasm back up...was a little frustrated. I'm gonna start on electrical, here's why: I took the AFB set up off, and put everything back together with the old Flamethrower coil and Q-Jet so I could track the oriignal problem. Took it for a ride and it's not doing it anymore...Aaarrgghh! But what it does do now is die when you nail the throttle open from a start, a probelem I thought I'd solved some time ago with a good accell pump..it was doing it when I put the AFB on (with the AFB it would stumble more but still rev) and I thought it was because the carb had sit for a year. I tried my race Q-Jet and it's doing the same thing. I bang the throttle open and goes out like a candle - poof. Both carbs have good shot, it's only on the primaries and there's plenty of fuel. Do it from a roll and lessen the load, no problems - great throttle response and it takes right off. For whatever reason, it feels electrical - like there's no spark at idle -(it idles rougher than normal too, and rich although Cliff Ruggles thinks I set it up rich to begin with) I've been chasing carb demons for a year, I think I was headed in the wrong direction all along. Since the tank is totally empty today, I'll check the sock first. Tom T...you had offered up the GM part # for the sock and I didnt have anythign to write on while we were on the phone.... if you see this could you drop it into a reply? It does have good manifold heat (I'll get a measurement at the carb pad)- the carb gets hot enough that you cant hold it from the bottom for any length of time when swapping. Parts came in - I'll replace the coil next, although I'm not sure it's as bad as i thought. It measured 1.7 ohms, but after I ordered a new coil I measured the baseline resistance on my 3 dollar harbor frieght ohmeter - 1.3! So it's JUST out of spec. It could still go bad when hot, but the probelm has now shifted to either cold or hot. Could a coil that has slightly high primary resistance do what I'm describing? Then run the coil voltage through the 4 pin relay. I cant see 11.8V at idle vs. normal 13 V being the issue, and I dont like adding complexity to the system but I have to try it. Then the guy I race with is really bugging me to get rid of the module with the formerly pinched wire. I see the logic, but before I spend 120.00 I'm gonna take your advice and check fuel pressure at full boogie. What's frustrating is as bad as I describe these things, the car actually really runs well, it ran a 15.2 @ 88 the other day.... but it's definatlely not running as well as it can, the 60 ft's tell that tale... Normal drivabilty is great, and you'd have to have seen the car run well before you'd know the idle is rough now. I'm really chasing 10ths here....back and forth to work the car is flawless..
Rhett,,,, tighten up the secondary spring on the carbs to make the secondaries open later... and see what that does.....i have had to do this with every carb that I have used on nailheads.... including my beloved holleys..... Did that put the heat back in the intake when you reinstalled the qjet???? if not,,, do it and see what happens.....a big shot of fuel into a cold intake just makes it take longer for the engine to clear it out so the fuel will vaporize.... guys block the heat risers under the carb and then when the engine bogs, they increase the fuel pump shot to richen it up and that increases the flooding because the fuel still has not vaporized.....What works best on a nailhead is a warm manifold/carb that can pull cold air from the outside as the rpm's come up..... If I had any doubts as to the ign. system I would change that too.... And write all the changes down... make them one at a time,,, make them one at a time,,,, make them one at a time,,,,, Did i say make them one at a time????:laugh::laugh: and write them and the result down?????:laugh::laugh: It is easy to lower the et seconds, it is the 10ths and 100ths that is hard to get...... and Rhett,,, pard,,, sometimes we have to ''unlearn'' some things... what works on your buddys car, may not work good at all on your car... because of the other variables involved..... what you do is try stuff, log it,, and then experience the result of the change.... good luck......
Thanks.. I always had heat to the manifold, just blocked at the carb pad. I think I'm OK there. First change - Fuel sock. No scale on the sock or inside the tank, but could not see through the sock at light. Hit it with some brakeclean, now can see light. Fuel seems clear with no setiment. Next change - relay 12v to coil - just rechecked, input voltage at the wire was fluctuating between 12v and 10.8. 11.8 I might be able to live with, but not 10.8. Have to go buy heavier guage wire next. I really should tear into the harness and figure out where they did the splice but I'm lazy. No voltage fluctuation anywhere else and it's a fairly new Wells regulator.
I once had a corroded distributor terminal for the coil wire. Car ran okay, just down on power. Since you're using a mech fuel pump, a pinhole leak in the line anywhere before the pump would allow air in and aerate the gas. I have a Carter elec pump on my blue car. Never had any problems with fuel delivery using 5/16" line/fittings and a '66 Q-jet. Hope you find the problem.
12 volt jumper to coil seems to make big difference.. definately clears the off idle bog....on the right track I think.
Glad to hear the 12V jumper worked! Rather than replacing the whole module to fix the pinched wire, couldn't you just cut the wire before the pinched portion, and splice in a new portion of wire?
It doesnt seem to be the module wire, but the 12v wire to the coil that had low voltage. ---------- Post added at 04:44 PM ---------- Previous post was at 03:53 PM ---------- Well, I fixed something anyway - the relay and full 12v to the coil has restored alot of low end power and throttle response, havent had a chance to test a WOT shift yet...however, it will go up in smoke from a 15 mph roll. I like that. Funny how the low voltage only killed throttle response from a dead stop, but not on a roll. Go figure.
completely logical... has to do with the amount of pressure in the cyls.... the higher the pressure , the more resistance to the spark plug firing.... at a dead stop the pressure is more because of the engine working against moving all the weight of the vehicle.. at a roll there is less resistance , because the weight is already moving....:Brow:
Ok, I follow you on that. Could that same low voltage be responsible for the thing nosing over at 4500 rpm? I think it is, but I dont understand why....
as the rpm's go up the pressure goes up and that makes the plugs/wires/rotor/dist cap the electrical fire always searches for the path of least resistance and will fail to fire or fire weak... plus the electrical system [coil] has less time to saturate at high rpm.... modern ign systems are not as bad as the old points system about this, but at 5500 rpm there is a lot of pulses going thru the system.... and the coil is usuallythe thing that breaks down first....
Thanks Doc - saw you called yesterday, I'll give you a shout this afternoon. My wife's got me taking out the air conditioners this morning... so much for Summer.
