Motor dies

[hotrod316]

Spud,
we took the dragster out today for some shake down runs. we changed lots of things based on your great calculator thanks, it helped alot! But  after a semi hard burn out the motor quit  reprimed it, fired right back up did a great pass but at the end of the track it died again.

we have two vents, one in the  front and one in the back, on the top
7 gal tank with the pickup on the bottom, 1 inch tube, about 8 inch long, with the bottom scalloped
we think the fuel might be sloshing around in the tank uncovering the back of the pick up tube the scalloped part.
our plan before the next test was to put a trap door in side the tank
   
we would like your thoughts !

is there is something stupid we are missing or over looking
 
YES the tank was full of fuel !! 

we made 3 passes on this motor last year before the cam went south and it did the same thing
so we still have the same issues or some thing still wrong
thanks for your time
steve m
 ps is it vacation time yet ?

[Paul New]

Is there baffles in the tank?

[Paul New]

Did you get on the brakes hard after the burnout

[BK]

If tank is long and narrow try extending the pickup into the tank about a third of the way. You should be able to do it without cutting tank up.

[hotrod316]

no baffles in the tank, the pick up is about 8 inches into the tank, will ask the driver about the brakes
thanks
steve

[dreracecar]

First test is to remove tank and fill with water with the outlet covered, remove cover and watch flow, should be a constant streem and not surge, if it surges the there is a vent problem.
 Had a similar problem that was pump related, screwed up the endplay an wore the pump cover so bad that it lost pressure at low rpm and coming down after the burnout was not enough fuel to keep it running.
 After the burnout, does the rpm rise before it dies or does it just quit???

[hotrod316]

we thought one of the problems was the vent,
only had one vent in the back with a  roll over, (last year)
we added one more vent to the tank in the front and removed the roller valve.
both vents are # 6

talked to the driver
not to hard on the brakes after the burn out, but harder on them than the other  2 pass. 3 pass when it died.

drive said, he started to back up and it just died, it may have started to lean out  but not sure.
on the big in it just died after lifting. does not know what the motor did.

other question
once the motor losses prime, does the pump have have to come to a rest before it will prime again ?  to lose the air pocket  it cannot self prime ?

will check the pump,  we had .007 cam end play between the pump and the cam but that was with the old cam.   

sorry this is a bbc injected on non drinkable - safely alc.

with all your help we will find it
thanks steve

[dreracecar]

We lost end play when we replaced cam,  was a fresh pump and had to turn with wrench, pulled the pump and spun the drive like a top.. that would be my first step based on what happened before

[dreracecar]

Didn't mention size of pump

[hotrod316]

-1 hillborn

[dreracecar]

How big is that in gpm?
How high is the idle?
What dia fuel line and how long? thanks no

[GlennLever]

We had the same problem, do the burn out and then brake to back up, the engine would die.

Also have the problem at the top end, make it through the finish line , brake to make the turn of the track and the engine dies again.

We solved the burn out problem by adding a baffle with a flapper that closes when the fuel wants to run forward (Roo Man built the tank).

The top end was no solved by the baffle as that negative g fource last longer.

I added a small tank in the return line and a primer pump that takes fuel from this tank and dumps it into the distribution block.

If the engine starts to stumble I give it a shot  from the primer pump and can make it around the corner. I can also start the engine if needed by myself this way if needed.
 

[hotrod316]

thanks Glenn sound just like our problem
what pump did you use?

Bruce 6 gmp
75 inches long tube with 12 inch of #12 hoses
1 inch od
.822 id

we are going to put a baffle with a doors
Does the baffle go all the way to the top of the tank?

we are trying to come after you Glenn and the rest of the pro comp gang 

[hotrod316]

sorry  idles about 1500

[Paul New]

we are going to put a baffle with a doors
Does the baffle go all the way to the top of the tank?

Yes