Moaning-Howling= Tailpipe fire
 

Help
I'm running a Ram 750p in a Trim F-86,bypassed.I was at a meet in Montana over the weekend,elevation 5000' and temp around 100 degrees out.On start-up i would get a moaning -howling noise in the intake and the noise would go away after the rpm's came up.On one flight i started my take off roll,the noise started as i began to advance the throttle,then 4' of flames shot out the tail pipe.What do you think could be going on ?

Thanks Charlie