FrontEngineDragsters.Org Forum
Technical => Spud Miller's Cave => Topic started by: tdietz on May 11, 2015, 04:49:50 AM
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Ok guys, 175" WB FED, 410 SBC timing around 36 degrees, MSD Pro-Billet Dist, MSD Blaster 2 coil, MSD 6 ignition box, MSD starter saver, and MSD 2 step rev control. Engine is fuel injected on Alcohol (down nozzles), Kinsler 450 mechanical pump.
The car on launch runs flat and breaks up. Our first pass of the day our 60' times were 1.415ish and our normal 60' times are roughly 1.16ish. It is flat then all of a sudden will pick up and our MPH on top end is normal 166MPH.
We tried leaning the barrel valve, then we tried richening the barrel valve, nothing made a difference. And by the end of the day the engine would clean out until I hit high gear (powerglide) and then it would break up again.
I'm pretty certain this is ignition, but where or what part of the ignition should I be looking at? Our tach is the digital shift light with the tach built in, and it seems very erratic as well....
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Dump the ignition system and put a Magneto in it.
It takes a lot of battery to run a MSD ign and unless you have an alt on the car, the battery cant keep up with it.
Mags do take HP to turn(very little) verses a standard ign system, but it also takes HP to turn an alt and push the extra weight of a battery, so its a wash, but the Mag gets the nod for its simplicity and reliability.
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That's all great and I understand you are probably correct. BUT, I didn't have issue last year and I don't have 600-800 for a Mag. I'm sorta stuck at this point with what I got. I can't afford to just dump all of it and go to a MAG.
For the previous 2 years we've had no issues. It developed late last year and we attributed it to weather. But, now I'm almost certain it is ignition related.
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Can you bypass the two step? take it out of the equation, borrow a coil if you do not have a spare.
If neither of those helps, I think the box itself may be suspect.
Assuming you have looked inside the distributor? No tracking in the cap or anything noticeable?
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Tim,
In in lieu of temporarily replacing ignition components individually to aid troubleshooting, sometimes tightening the plugs' gaps is suffice to flag a weak ignition system. Another thought is checking rotor phasing.
No argument that magneto has its advantages, but there are tons of drag cars running CDI ignition systems, w/o alternator.
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I can take the 2-step out of the equation. I also thought the same thing about checking the rotor phasing. I'll see what I can come up with. Really want this thing right before Memorial Day.....
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I have a couple of idea's for you to try . First is Battery voltage you need at least 12 volts at the box at all times durring a run . I have seen a battery with a bad cell that would start the car but not hold 12 volts . Next would be rotor phasing . Next thing I would check are the pickup wires . If they are backwards the car will run like you explained . Do you charge your battery between rounds ? If you don't you should . Another thing to check are your grounds also very important . I use a separate ground for my box to the chassis and I also ground the motor to the chassis .Plug gaps .025 or so I am not a big fan of large gaps . Double check that starter saver to make sure it is not staying activated . Hope this helps . Bill
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Bill we are getting 12 volts at least while it's running. I've checked this before. We charge the battery after every run. I'm going to check rotor phasing later this week and pick-up wires. I'm almost positive the wires are right but will make sure. I was thinking of eliminating the starter saver just to get that out of the system all together. We run a high torque starter and I feel it would start the same without it.
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Borrow a mag for the weekend
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Remove any RPM chips from the system they do go bad.... I was stuck at 186 mph for a long time removed the chip and went 205
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I re read your original post and you said that your tack is erratic . If you could borrow an MSD tester from someone it would help you a lot . You would be able to test your chips and see if your coil is working . A clogged fuel vent could also cause a similar problem . I had a problem one time with a nitrous bottle a spider decided to climb into the end of the bottle ! the little sucker made it all the way up to my nitrous solenoid and clogged it right up it wasn't very good for the spider either !
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Did you try the basics? New cap, rotor, plugs and wires. Especially the cap and rotor.
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Try a fresh battery. The mag is the best fix.
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All thanks for giving me some stuff to check. Going to begin looking through everything tonight. Hopefully it's something really noticeable that we just missed at the track! (but it never is! LOL)
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Sorry being late to the party...Mondays are brutal for me this time of year.
Lots of great ideas to try here! It does sound like ignition and you should find improvement pretty easily by trying some of them.
Let us know how it goes...
Spud
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Now I do not know here but it seems to me if it was a bad chip it hurt it more on top RPM. Do you know anyone who can loan you another ignition box to try? I know last year I had all kinds of problems car would run 5.09 one pass the next one 5.49 missing, popping and banging. Changed every thing out and kept testing the ignition box and it tested good. Finally changed it anyway and it ran like a top. Honestly I do not know what would make the ignition worse at low RPM and run good at higher RPM?
Rotor phasing may be an exception. Just do not know. Hope you find it quickly.
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All, thanks again. I did change out the ignition box, new cap and rotor went over all my grounds, and checked all my connections. I did find a loose wire from my distributor to my box, but that wire I would think would either give me spark or no spark at all. We will be racing this weekend. I'll keep everyone up on if it worked or not.
Thanks again!
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Good Luck with it and let us know how it works. :)
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Call this a wild idea, but we had a customer car doing exactly this same thing.
Chased it a good bit, found the converter fins were standing up and killing the middle of the run, K
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Thanks everyone for the help. We ended up changing to the Digital 6AL box, and put a new cap and rotor in it. And cleaned the problem right up. No more issues....Thanks again for the help!
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Thanks for the follow up, glad to know you got it handled.