Race car mystery-Help us solve PLEASE

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Fish-so far we have limited it to the end of the run , on the back side of the track-steve
 
To me it sounds like a timing issue, Are you running a locked distributor? I had a Mopar Performance Race distributor in the car and I set it at 34 degress timing at 2000 rpms
 
Also if it back fires through the headers the accelerator pump is too tight and push extra fuel into the carb
 
To lose a full second is a LOT. I would think it would have to be down on power through out the run to lose that much ET. For example: On my car, if I lift at the 1/8 mile marker and coast the last half of the track it still runs 11.4x (this is on a run where it was going to run 10.7x all out). I'm leaning towards bad valve springs. Have you pulled your dipstick on the trans and smelled the fluid? Make sure it doesn't smell burnt, or look too dark.

Good luck at Monster Mopar. I'm not attending this year, even though I have had great success at those races in the past....actually, now that I think about it, I have always won more $$$$ than I spent in entry fees at those races (crap, now I kinda want to go)...oh well, that leaves more money for you guys to win :D.
 
How did the driver know "something happened"? Did the car drop it's nose? Did he see a gage or hear something? Did he not notice until he got the time slip? Were the incrementals on before the 600' mark?
If the leakdown was good, the physical parts are good, then you have either fuel or spark. My experience is like Lenny - once a convertor breaks the stall speed goes through the roof or it slips in high gear and sounds like a supercharger. Inspect the MSD - especially the advance system(s). Wet flow the fuel system to make sure it's maintaining pressure. That is a lot so something went away. Direction from the driver would help discern what it was.
 
Cudafever said:
My vote would be valves spring gone weak.

here is a couple other thoughts. bad axle bearing or maybe in the ring and pinion area.

A rear drum brake adj up to much.

has the car become harder to push lately?

When you look at your ET slip, were does the ET start to fall behind?
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Steve -Cudafever might be onto something here, jack the car up and see if the front tires spin free. You did change the brake set up, try to push the car in straight line and see how easy it rolls. Do have the front end tied down to tight or if the toe or caster is off it will slow the car down.

Check you slip as Cuda said against your old slip when the car went fast
60' times-330' 660' and 1/8 mile and compare them
 
I'm going with a couple valve springs are weak, Sounds like it runs too good.... Just my 2 cents..
 
You hurt a piston or a valve some where pull the heads and physically look . Happened to me car ran great sounded great but hurt a piston . Loosing that much time and power its serious . Just my opinion
 
I would jack it up and check all the wheels to see if they turn free. We had a brake caliper cost .3. Good luck
 
hotrodhoodlum said:
You hurt a piston or a valve some where pull the heads and physically look . Happened to me car ran great sounded great but hurt a piston . Loosing that much time and power its serious . Just my opinion
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I can't see that making it past a leak down test.
Did you do a leak down test on yours?

I only ask as he did, and it was good.


EDIT:
Sorry that sounded a bit snooty.:protest: Was just asking if something like that had past a leak down test.:D
 
WE GOT IT -THIS is going to sound weird but the whole issue was the alternator and voltage.we went to the 3rd round today and lost by .001 so we cant complain.at the hotel right now so I'll go into detail when we get home.were running 6.50 1/8 mile, car is launching great , its fricken 98 degrees and 70% humidity down here. Good turn out today on the race and show side.talk to u guys later-THANKS FOR ALL THE HELP -Steve&zach
 
Yes leakdown test was fine . We pulled heads and did a old fashion rod and piston check took a wooded hammer head put each pistion at tdc push down to see how much up and downplay we had . Set a dial indicator on zero at each pistion to see clearence found wound up being a bad bearing right before it would go where a rod bearing will only knock under a load if it fires car ran great but would not go over 6000 rpm st any shift

Cudafever said:
I can't see that making it past a leak down test.
Did you do a leak down test on yours?

I only ask as he did, and it was good.


EDIT:
Sorry that sounded a bit snooty.:protest: Was just asking if something like that had past a leak down test.:D
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Well got to thru the third round today but had a .006 red light in the fourth, so all in all zach did a great job, I'm hoping kegan can post a video he has several of zachs launches.-steve
 
Ok I'll do my best to explain,The thing that had everyone scratching there heads was when we went out for a run the batt's were at 80-100 percent charged,Zach would make a run and we would put the charger on and the batt's were at 30 % ???? so we started to inspect things between rounds and the issues kept happening.We found a burned out diode in the alternator,so we removed the alt. all together and the problem went away,We think what was happening was since the diode was burnt out the alternator was working in reverse and massively stealing power from the batt's so voltage got low and the ignition box was starving for power and hence we had no high rpm spark and broke up,the issues was completely removed once we took the alt. off,he was once again going thru the traps at 7600 and pulling hard on the back side of the track,We ran a couple 10.5's in 98 degree heat and 85% humidity so in clean air we should be right back down to our 10.3's we ran originally.so lesson learned and i hope if you guy's ever have something like this happen you will remember this thread--Steve
 
that shorted diode would cause the alternator to be really hard to turn at high rpms, It turned into an electric brake.
 
I wish I had known you were there I would have stopped by and introduced myself. Glad you figured out the problem. This weekend was my best ever going three rounds both days, no red lights or silly mistakes. Maybe going to Wisconsin on the weekend of the 12th to race with some friends. near lake winnebago?
 
Hey where were you parked in the pits??????? Did you have the car in your sig.??? Steve
 
mikedevore said:
I just fought a simular problem.
My Barracuda went from 6.40 @ 106 MPH to a 6.90 @ 99 MPH.
Thought it was the convertor, sent it in, tighten it up.
Same numbers. sent the convertor back, loosened it up.
Same numbers.

The problem was when the heads were ported, the porter had broken thru the casting on a intake runner at the push rod pinch. It had been brazed up & blended.
ran a leak down, worst cylinder was 2.5 percent.
removed the rockers & installed a plate to vacuum check the intake & heads.
I was suspecting a failed intake gasket.
I could blow into the hose that was hooked up & see it leaking out when I sprayed wd40 on it.

I have since put epoxy on it & going to run it this weekend to see if that fixed the problem.

That lost numbers seem like alot for valve springs.
Check the basics, leakdown to eleminate the short block.

I also had a friend with a 340 that no matter what you did, it would only run 11.20's every time.
I installed my carb (750 holley) same as his & changed the dist., same as his.
The car responded with a 11.56 pass.
These kind of problems will eat you up.
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Back to the drawing board for me.
Unloaded the Barracuda this weekend, ran 7.27!
It looked like it left in 2nd gear. It was a turd.
Sounds like a Pro Stocker idling.
My Son said he knew it was going to be a pig in the burnout.

I do have an alternator on this car as well.
It maintains 14 volts at all times.
That is something to check as well.

The one constant is the engine surges thru all gears, it never misses or pop's.
It seems like it is trying to run, but something is holding it back.
I can even hear it on the GoPro, fuel pressure is steady @ 7PSI.
My buddies are pointing their finger at the valve springs, since I found one with an inner spring broken.
I'm also going to check the carb & fuel filter, I'm running Alcohol.

At least we had taken "Ole" Reliable with us & the Son won the first race & got down to 8 in the second race.

Since I have been throwing my money into the Barracuda, we have let the Demon go.
It has 4 bald race tires on it, My Son did a hell of a job driving.
He went 7 rounds, his dial in never changed (7.22). his 60 ft. was anywhere from 1.51 to 1.65 all day.
He used the NOS in 2nd & 3rd gear to make up the difference on every pass.
The final was fantastic, he left the line & the car headed for the tree, I just shook my head.
He had the light & ran dead on!
Used a full bottle of NOS that first race.
His average reaction was .019.
He got beat in the second race, he had a .005 RT to his opponet's .015, he went 1 above & the other guy ran dead on. He said he didn't get on the button quick enough.
Not a bad day for driving by the seat of his pants.

Just ordered a full set of Hoosier's for the Demon this morning.
 
Mike--LOL--we have a lot in common except Zach says the wheels aren't off the ground far enough !!!!! Geez the car hangs the wheels 2 1/2 to three feet off the ground !!!!! I'm trying to pound in his head that going up isn't going forward !!!!!!! I wish I could post some video's but I have no idea how to do it--Steve
 
Did u see our valiant? ???? I think u were just three cars down from us-steve
 
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