Landracing Forum
Tech Information => Technical Discussion => Topic started by: mstrdinan on October 06, 2010, 01:58:23 PM
-
We suspect a problem with the msd
cant rev over 65 - 7000 on the salt
hits 8000 on chassis dyno
put in 8000 then 8300 chip
does it make sense to send it back to msd ?
fuel etc all seems ok any Ideas?
305 chev msd 6al blaster trigger wires
holley 750
in a roadster thanks
-
I had the same trouble with my MSD. It would only rev to 7650 on the salt but to 8500 on dyno. Luckily 7650 is 274mph and that is my record in C/GL. LOL
-
I have nothing but good experience dealing with MSD repair tech ... great service ... most often no charge ... I sent a distributor that was in an engine fire for repair and it looks like all I got back from the original was the housings as the rest was melted. Charged me less then a new rotor and cap which they included.
-
Like I said the aero of your roadster, your gear ratio and the power of your engine (or lack of) in conjunction with the great white dyno,is acting like a built in rev limiter. We've all experienced it!!!
-
Change your gear ratio to a shorter gear and see what happens. I se it all the time that folks think just because it will pull 8,000 rpms on a chassis dyno they think it will do it on the salt. They forget that on the salt you have to push a whole lotta air that you don't find on a chassis dyno!!!
I bet your MSD ignition is fine!!
But if you are not sure answer this... Will it pull 8,000 rpms in first gear? if so then you are geared too tall.
-
Like I said the aero of your roadster, your gear ratio and the power of your engine (or lack of) in conjunction with the great white dyno,is acting like a built in rev limiter. We've all experienced it!!!
That's why I now have a dent in the firewall under my gas pedal :mrgreen:
-
Change your gear ratio to a shorter gear and see what happens. I se it all the time that folks think just because it will pull 8,000 rpms on a chassis dyno they think it will do it on the salt. They forget that on the salt you have to push a whole lotta air that you don't find on a chassis dyno!!!
I bet your MSD ignition is fine!!
But if you are not sure answer this... Will it pull 8,000 rpms in first gear? if so then you are geared too tall.
sorry, neglected to give all the info...
2 speed powerglide.....and.......
alternator not charging
we
were running on 12 volts poss prob ???
-
I started reading the first post and working my way down, the first thing that popped in to my head was "Good strong power". Those things suck up a lot of juice, especially at higher rpm's. Like anything, the harder you make it work, the more power it needs.
Also don't over look the need for a GOOD ground. Bad grounds can run you around the block. Because we drive in a salty/corrossive atmosphere it makes things rust in between the connections.
Good luck, RICK
-
I think its your gear ratio. I have a power glide in the Saltosaurus and I can tell you from personal experience that a 2 speed compounds the problem of trying to pull to much gear. First it hurts your run up speed (acceleration) and when you make your gear change your going fast enough that your already coming up against the air wall . The little 305 in. engine is making so little power after the shift that it won't recover as the air resistance mounts. A roadster is probably the worst offender in this regard. I just bought a Liberty 4 speed and expect to see some good gains as a result of a much improved 1/4 mile time. Either way, 2 speed 4 speed or direct drive your final gear ratio must reflect what your car is capable of running (from an aero and power stand point) not what YOU want it to go.
-
Change your gear ratio to a shorter gear and see what happens. I se it all the time that folks think just because it will pull 8,000 rpms on a chassis dyno they think it will do it on the salt. They forget that on the salt you have to push a whole lotta air that you don't find on a chassis dyno!!!
I bet your MSD ignition is fine!!
But if you are not sure answer this... Will it pull 8,000 rpms in first gear? if so then you are geared too tall.
sorry, neglected to give all the info...
2 speed powerglide.....and.......
alternator not charging
we
were running on 12 volts poss prob ???
i know running my msd at the drags that if you don't have more than 12 volts , an msd box works like crap. they seem to like 14-16 volts.
-
Keep volts to MSD high.
Keep the MSD cool.
Mount the MSD so it is isolated from vibrations.
Go overkill on the grounds.
~JH
-
JHN said it , keep voltage up, make sure grounds a perfect or better.
Rex
-
OMG;
I think you guys solved my problems. Does the tach output get fuzzy with this low voltage problem? I'm Running two optima's with one dedicated to the MSD 6, no alternator, at 5600 the last two years in a row, i've hammered my valves. My machinist says i'm floating the valves, I tell him that I haven't been able to get to the RPM to float the valves. The gear thing is also a problem of mine.
Thanks Steve,
-
maybe you better hook up two #27 size batteries together to just run the MSD...
you best have a battery volt meter wired in directly...
and another seperate battery system just for powering anything else.
have a 5000watt generator powering up a giant charger
hooked up to a seperate extra pair of batteries in the pits..change out the batteries for the fresh ones every pass.
the high heat and salt conditions really take a toll on batteries...
-
I have an inverter on the truck that charges the optima's in between runs. Ten minutes to fully charge the pump battery, 7 minute to fully charge the ignition battery. I'm thinking, put in a 16 volt for the ignition, and put an inverter off of the 12 volt to charge the 16. Replace the MSD6 with a Jakobs, 3 batteries altogether, keep the same optima on the pumps.
Steve
-
I have found that Optima batteries do not like high amperage recharging- it is very likely that your "topping off" between runs is finding false peaks. We lead-acid batteries don't care so much, but the acid-impregnated felt used in the Optimas care quite a bit about the amps/mins ratio. Also, be careful charging and discharging an Optima too quickly- their construction leads to very poor heat dissipation. Ten amps is OK, fourty is not.
I would check input voltage to the 6AL next time you have the engine spun up on the dyno- I have had spark fall apart when voltage drops below 11, and in a high-demand situation even closer to 12. As mentioned above, the MSD guys are very easy-going and easy to work with if there is any problem with the 6AL- they really have the customer service thing figured out.
Good luck!
-
I used to run a stock car with an MSD and no charging system. Start the race at 13.6 volts and run 30 laps be at about 12 volts at the end of the race,no problems. It's your gear ratio trans. combination. I'd bet money. :-)
-
If you are worried about running out of volts why not use a 16 volt battery, the MSD unit will tolerate it.
http://www.turbostart.com/
-
Thanks for the info on the optimas, the times in between runs is at ten amps. I liked the fact that last winter, I left them in the car with disconnect off, once a month I would check the charge, and they stayed at 12 volts all winter no heat and about 3 weeks of below zero weather (shop is not heated unless I'm working in it). I don't understand the electronic ignition, my car went faster stock with the dual point distributer.
Steve
-
I used to run a stock car with an MSD and no charging system. Start the race at 13.6 volts and run 30 laps be at about 12 volts at the end of the race,no problems. It's your gear ratio trans. combination. I'd bet money.
Thanks for info
Looking at my timing slip speeds there was definatly a problem either with my digital tack, or the output of the MSD.
At 142 I should have been at 5300 RPM and the tach said 4300. At 148 the tach said 5300, that is when I bent the valves. During one of the 142 runs I put it in 5th, realized then my rear 2:78 gears were way to high. Going to have my sh-t together next year I'm to old for this once a year learn the hard way stuff.
Steve
-
It was a reference to the original poster, my bad.
-
Sorry racergeo, I'm the one stepping on the original poster. I was so wound up over realizing that my problems could be solved with the posts on his problem that I lost my etiquette. As you can see I don't know how to shadow correctly a quote. Know about as much about forum ethics as I do about electronic ignitions.
DW told me at the flats that this web site could benefit my build and he was definitely right on that one. :-)
Steve
-
On recommmendation from a specialist in ignition systems, we run a six volt battery in series with our 12 volt battery- a total of 18 volts.... the MSD seems to keep working just fine.... extra ballast and easier to charge a 12 and a 6 volt battery with chargers I already own....
Pulling your gear ratio is a separate issue..... but it feels like all kinds of things are not working correctly as you watch the tach- climbing seemingly far too slowly..... so like how in the hell can we ge like 1200 horsepower over a 4000 rpm power band from our off the shelves at Summit Racing 355 CID Chevys anyway?