PDA

View Full Version : popping at speed?



Moody Blu'
07-25-2002, 02:41 PM
at certain throttle positions I can hear my motor making a popping sound.....

is this from being to lean or to rich?

to much advance or to much retard???????

when it does pop it slows down and then goes again...

anyone have a clue?

now that I have my water problem solved its time to work on this......

its not that bad, but it is surely annoying....
I dont like to hear popping sounds.....

im running a 75ocfm carb on a 351w

I have a jetting kit too...

Jamesbon
07-25-2002, 02:53 PM
Whew! It could be a hundred different things. I would get the facts first. Try a timing lite and check your initial advance, then total advance. Should be fully advanced around 3k rpm's. Do you have points? Maybe read the plugs as well...

Moody Blu'
07-25-2002, 03:14 PM
its a msd maganetic pick up distributor.

I think I have like 4 degrees of intial advance.

my total advance is 30 degrees.
Oh here may be a slight sympton that coems along with it....

after a nice ride when I come off plane for a no wake zone the engine rpms go down and go up with the throttle in the same position..

after a couple mintues it stops doing this though..

I think its something with the timing..

im not sure, I need one of you guys to come out with me and check it.... :)

BigGrizzly
07-25-2002, 03:27 PM
Two things. First sounds like the needles on a Carter or Eldbroch dropping there is a kit to dampen this effect for off road and Marine. Second yout timming is retarded bring up tp 34 degrees than work up from this point. I have found in my engines the best safe timming is from 34->37 deg at FULL advance.

Randy

Jamesbon
07-25-2002, 04:07 PM
Yeah, what Randy said. You'll be surprised how much more power 4 degrees of advance will make.

Does the MSD disty. have springs and weights inside? If so, make sure they're clean and "swinging" the way they should be.

Moody Blu'
07-25-2002, 04:14 PM
wow thanks for rememebering my carb randy, I should have said I was running the edelbrock sorry wink

ok heres another sympton that I forogot to mention.

but I thought this sympton was from to much advance.....

If I gas it abruptly sometimes it makes a loud PAP sound like its backfiring(idle to a little under half throttle). Or is that just from the large carb not bruning all the fuel???

this symptom doesnt always happen, but I was lead to believe it was from to much advance. Am I wrong on this?

randy chime in again?

Moody Blu'
07-25-2002, 08:31 PM
see that line running into my intake? well thats from the fuel overflow that is mandatory on marine fuel pumps....

someone helped me out and said this is causing a vaccum problem with my fuel pump and is not allowing the fuel pump to operate properly...

does this seem like the problem???

http://www.offshoreonly.com/forum/attachment.php?s=&postid=332428

MOP
07-25-2002, 09:20 PM
Moody that line from the fuel pump is an over flow safty that sends the fuel to the carb intake not the manifold if the pump goes bad. It is suppose to be made of a plastic like stuff that will colapse in case of fire and seal off. Mine is 1/4 tubing from a nipple on the pump to a 1/4 nipple at the top of the carb just below the breather. Yes the setup you have will screw something up.

Moody Blu'
07-25-2002, 10:00 PM
yeah thats the conclusion wec ame to.
I was told that it was ok to run it there, BUNCH OF ASSES......

PaulO
07-26-2002, 10:53 AM
That hose is to there in case the diaphram inside the mechanical fuel pump ruptures. On an automotive pump, the leakin fuel would accumulate in the crankcase and dilute the oil. With the tube in place, the fuel will dump into the carb and hopefully be burned. The idea is to avoid the fire hazard in a closed bilge when your crankcse begins to fill with gasoline.

As far as your popping sound, once you have elimnated the items above and if it is through the carb that it is popping, it may be either a sticky intake valve or a cross-firing cylinder due to leaky ignition wires or carbon tracking on your distributor cap or rotor. Replace and properly seperate your ignition wires with the proper replacement wires and carefully inspect the cap and rotor. If this does not do it, I would isolate the cylinder that is causing the popping by running the engine just long enough to make a determination with each plug wire dsconnected one by one. If it is 2 cylinders or more doing it, it is probably spark crossin over. If you get it down to one cylinder and eliminate the electrical portion, time to check for a sticky valve. There is no easy way to do that.

BigGrizzly
07-26-2002, 12:00 PM
Actually the fuel pump vent tube is on the top of the Diaphram and keeps fuel from going into the bilge. on a auto pump it goes to the atmospheer. I have seen the pump leak and fuel is in the line and gives a rich condition at mid and high rpms. I still going with the needles dropping or the timing

Randy

Moody Blu'
07-26-2002, 12:56 PM
I have brand new ford motor sport 9mm racing wires I do not think I am getting crossfiring..

the carbn tracking could be a possibility...
I will clean the cap..... I know the rotor is perfect, I inspected it....

I will clean the dist cap and put that overflow line into my spark arrestor...

once that is done, I wil play with the timing....

griz, my boat does this in smooth water so I dont think its the needles dropping...

I do think your right about my timing...shouldnt the motor rev out more when the timing is set correctly rather then being to far retarded or to far advanced?
griz, you dont think that overflow line from my fuel pump isnt causing problems?

Thanks for all the help so far guys!

MOP
07-26-2002, 05:12 PM
Moody I will not be at Art's I have a Major party to go to one that for biz and political reasons I can not afford to miss. Hope to catch with you over the summer.

Donzified
07-27-2002, 07:51 AM
Have you checked for water in your gas?

abbe
07-30-2002, 01:46 AM
broque runs a fuel filter/water seperator wink

Moody Blu'
07-31-2002, 11:54 AM
I will be testing my new 14 1/2 x 24p prop this weekend..

I will also move the overflow hose and ALSO install a new water filter seperator.....

after that ill look at timing...