I might not be whoopin on anybody at the HAMB drags if I can't resolve this. Usually in second gear around 4000 rpm the engine will just nose over for a split second and then pick right back up. This might happen 2 or 3 times before I shift around 5500. The thing that ticks me off is that back in April I had it all dialed in and running GOOD. Watching the fuel pressure guage at the log shows pressure. I've tried adjusting it up and down just for. I have put some bigger jets in but that has no effect. My ignition system consists of a pertronix ignighter, and MSD boost timing retard box, a Mallory Hyfire 6al ignition box, and a pertronix coil. I replaced the Hyfire box and later byp***ed it. No difference. Tried it without the boost timing retard, no difference. Tried a different Pertronix ignighter, no difference. Tried an Accel super coil, no difference. Replaced wiring and switch that provide power, no difference. Replaced main ignition switch, no difference. HELP!!! What have I missed? I have not tried going back to points. This is so discouraging since I know what she's like when things are working. I should note it seems to be worse when hot but I might be imagining things.
Sounds like what mine does at high rpm, surges. Found the stock dizzy just can't advance enough to keep up. Your electronic setup shouldn't do this though. Is the initial timing set exactly as it was when it ran good before?
Umm, if it's worse when hot I would check your grounds (all of them). Even if they look clean, it's worth cleaning them anyway. I don't expect that setup uses a ballast resistor, but if it does try a different one. If it's not electrical, how stable is the timing? Could it have a stretched timing chain or sloppy gears (cam or distributor). I had a distributor with an electronic pickup do that to me when the distributor shaft bushings got sloppy. Are you sure the carbs themselves might not have some schmutz rattling around in them causing momentary fuel starvation (or maybe some water)?
Yep. The only thing I changed on the distributor is the pertronix. I have tinkered with the timing one way or the other. Still drops out.
I've had the afb's open several times. Clean as a whistle. The distributor is tight, but I might setup a different one tonight and try it. Right, there's no ballast resister. Not sure on the timing chain. It's possible it has some stretch but I've not heard of beahavior like this from a chain. I'll check grounds.
I want to say fuel volume problem; some cars nose-over if the carb bowls get drained at the top end of the track. Except you say it was fine before. Maybe Ne** is right; something clogging fuel that wasn't before? Edit: Nevermind. Now that you say AFB's (plural). Doubtful you can drain dual carbs dry. Plus you checked for gunk.
Sometimes water can "dissolve" into fuel (called "entrainment") but you would likely see it. If your fuel is clean appearing and you suspect contamination by water take a sample and stick it in your freezer (carefully) if there is any water present, it will settle out. I had this problem on a production based racer that was my daily as well. The filler tube had cracked where I couldn't see it. It didn't leak fuel (even at the gas station) but anytime you drove in the rain the right rear tire was pumping loads of water into the tank. Could it be something blocking the pickup in the cell / tank intermittently? Yeah the timing chain thing would be rare and it's kinda remote, but you had already checked the obvious.
My opinion ..its not ignition related. does it Pop? or back fire when it comes back in? if not i would figure fuel related. If your engine was running at 4grand and you shut down the fire (ignition) and started it back up while spinning it would definetly bark! I vote fuel starvation issue
check to see if one of your plug wires is bad.. I had a similar situation on the street.. (my 40 ford) it would ONLY carry on at full throttle above 80mph.. drove it that way for a good while until the arcing ruined the distributors pickup module (hei) after replacing the dizzy by the side of the road.. (i had a spare distributor with me) the next evening I noticed the arcing on one of the plug wires. replaced the plug wire and all is good.. keep in mind.. this would arcing would only happen at high speed.. similar to what your experiencing (high engine speed) could one of your plug wires (or boots?) been burnt? sawzall
Plug wires physically look good but I was thinking of throwing a different set of plugs in tonight. What was your plug wire arcing to? A ground or another wire? There is no pop or bark when it kicks back in. Good point though. The reason I don't think it's starvation is that I've still got fuel pressure at the log.
Sounds like not enough fuel volume, check filter being to small not letting fuel in carb fast enough at RPMs
You can have pressure but very little volume...and if it catches up on one or the other carbs on the return, you could be running out of fuel and never know it! I also ran into a goofy one the other day-brand new fuel pump-less than 2 weeks old, loads of pressure, no volume... The very end of the fuel pump arm was bent-which made it pump some fuel, but not enough for high r.p.m.
Makes sense. I have a new (two month old) mechanical Carter and an old used Holley blue pump for racing. I just ordered a Procomp black pump to replace the tired Holley. Should be here the first of next week. I have noticed that going down the interstate when it's 95+ it'll loose fuel pressure with just the mechanical pump. Flipping the Holley on picks up the slack. I think I'll slit some rubber hose to put over and insulate my 3/8 steel line to keep it cooler.
Something similar happened when I switched over to a Pertronix set up on my caddy...turns out there was a little slop in the dizzy and it was 'walking' at high revs and I was creating too large a gap between the ring and sensor, thus no spark! I shimmed the dizzy and no problems since...not sure if this is your problem but worth a look?
I think the fuel volume guys got it right. Even 3/8" line will not be enough with a big inch motor winding through the low gears at those rps. you may have to increase the entire line from pickup to inlet to 1/2" Old drag race trick, was a manual pressure pump, to sink the floats, at the starting line, for a long pull through the gears, quickly. Sparky
Hey Kerry, I've been through somthing similar & it was the damndest thing. It's a little long winded for me to type so gimmie a ring & I'll tell you what I learned. Or PM me your # & I'll call you on my dime. D.W. 512.944.0311
My 462" used to drain 2 600 Carters after the 1/8 mile mark with a mechanical pump. There are no decent mech pumps for a Poncho.. If you install the Holley elec pump, totally byp*** teh mechanical and see what that does. Also, DW can you give me a little hint just in case I run into the same thing? I haven't done a full throttle p*** on my new set up yet. The first full throttle first, second, third attempt will be at the Drags. Hope everything works OK.... Good luck, Kerry. Holler if you need me. -Abone.
After installing the new motor, the coupe would "fall off" under certain throttle conditions. Namely, leaving the car wound up near a shift point & leaving it there a while before shifting. Such as 3rd gear, approx 40-50% throttle, 4-5 grand. It would seem to misfire or drop cyls. It was felt as well as heard in the exhaust note. I went through the entire fuel system, tank to carbs. Thought it was a fuel pressure issue due to a glycerin filled gage reading falsely when hot. Sight gl***es on the carbs told me I wasn't starving for fuel. Went through three different fuel pumps and a new filter to no end. Finally learned I was chasing my tail on the fuel thing because of the gage. Got in to the ignition system. Went through everything from ignition box to the spark plugs including rev limit chips, boost retard, plug wires, ignition switch, primary source for the ignition switch, even the magnetic pickup. After exhausting every single component of the fuel and ignition system I learned that I had created my own problem. In an effort to get all of my ignition advance in by 2500 rpms, I had installed both light duty silver springs on the mechanical advance mechanism in my msd dist. With the engine load just so and the planets in the heavens aligned right, my ignition timing would fluxuate or dance around causing me to drop cylinders. By reinstalling the heavier springs the problem went away but left me unable to achieve my desired ignition timing curve. So I took the advance mechanism out and locked the dist. running 34 degrees at all times. Problem solved. Not sure what sort of advance mechanism Kerry is running or what kind of ignition curve he's after but his issues sound strikingly similar to what I went through. As long winded as this sounds, there's even more details to my story. Give me a ring if you want to and I'll bore the ***s off you with the rest of it. D.W.
OK. I spent some time today and the miss is gone. I replaced the fuel filter with a new larger one. I took the distributor out to change the light spring. In the procces I found the vacuum advance was bad. Checking timing showed it jumping all over at rpm. This dist did have some play I didn't like. I pulled the converted 413 tach drive dist off the shelf, took the points off, and put my spare Pertronix in. On this dist both mech adv springs are light. So I have her pulling all the way through the rpm range but I doubt I'll be hitting any 11's without some tuning. Time will tell. I want to try and get back to the tuneup I had in April that worked so well. Thanks ALL for the advice and suggestions. See ya at the DRAGS!
As you know, you are 'sposed to only change one thing at a time to diagnose a problem, but what teh hell, it is fixed. What is so diffrent from April till now? Plus, you are scareing me.. My little car hasn't had a full throttle blast with teh new set up. I have no idea what she will do at teh Drags. I have visions of her in the pits in Joplin with lots of guys standing around going...well...have you tried the....??? Hopefully EVERYONE hits on all 8 and makes lots of power with out hurting any parts, Amen. See you in a few days, -Abone.
Glad to hear it is better. Good luck at the drags. While we are praying, I hope all that attend go home at the end, and with all original body parts (human) attached and functioning as well or better than when they showed up, participants and spectators alike.
It's been a busy weekend and I had limited hot rod time so I just threw all the changes in at once. Yeah, I know better but was in a hurry. Jetting saw a big change. I set both carbs way fat to see if it would help. Timing is going to stay pretty close to what I have now.
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