RPM Drop Part II

[GuinnessGuy74]

I had previously posted that my Chevy 350 (merc) had experienced a bog down(drop of RPMs from ~3500 down to 2500-300)) after a few minutes of running. Afterwards, no increase can be seen with increase in throttle. I had recieved a couple responses saying to check fuel filter, clogged fuel vent, timing, etc..... The entire ignition system is brand new. I changed the filter/water seperator, and eliminated the gas tank altogether by puting the hose directly into a can of gas. SAME PROBLEM. Any other suggestions on what is causing this. I am pretty sure it is in the fuel delivery system, and I am going to rebuild the carburetor. But do these symptoms point to anything? I thought at first it might be starving for gas, but now I am thinking it is flooding. ANy other suggestions would be appreciated. Thanks in advance!<br /><br />Jim

 

[tommays]

Re: RPM Drop Part II

if your good at reading spark plugs they should look compleatly different if they are runing rich vs lean<br /><br />a rich plug is going to look black and wet from not being able to burn all the fuel <br /><br />a lean one is going to be towards white from the heat<br /><br />tommays

 

[navigator336]

Re: RPM Drop Part II

Tommays suggestion is a good one. It could well be too rich of a mixture once the engine gets warm. Make sure the choke is opening completely. Check to make sure the air emulsion tubes in the carb throat are clear (little vertical holes above the venturi's). These allow air to pre-mix with the gas and emulsify it prior to entering the venturi. It makes for a much more atomized mixture.

 

[WSUDERMAN]

Re: RPM Drop Part II

Just a couple of thoughts. (these may have been covered in part I but i missed that)...<br /><br />Fuel Pressure & Volume. You might want to install a pressure gauge and check it as your rpm's start to drop. You might have a pump that is working ok @ the lower rpms, but when the demand goes up it can not keep the pressure up at the higher rpms...<br /><br />If you want to check the plugs do it immediately following the problem. Don't idle back into harbor and then check because the time @ idle will change the plug reading.<br /><br />Wes

 

[GuinnessGuy74]

Re: RPM Drop Part II

Thanks for all the suggestions.....I will check the plugs when I go out in the morning. I would have, but didn't have a plug socket with me at the time. I also thought about the fuel pump, but figured if that was the case it would be a constant problem not a tempermental one at high RPM's. I am going to hook-up an electric fuel pump and see if that helps as well. Thanks again for all the help, and any other idea's please shoot em out to me!<br /><br />Jim