what is going on

[b0mbtrack]

4.3L LX merc with balancer shaft. 1997 hull.
Had strange popping and flames out of carb when i went to advance just past idle so i thought it could use a tune up.
started doing tune up when i saw rusty plugs and water in cylinders. Turns out to be bad manifolds. I still had those one piece ones that merc doesn't even make any more.
So i got the new manifold kit, sent the heads out to be inspected, got everything i needed and put it back together. Did an oil change before starting engine. started it up and......same exact popping noise with flames when i go to rev it up slowly past idle. It did run good at full throttle before i did this work but i haven't checked it out now. and i did finish the tune up with cap rotor plugs and wires.
To diagnose this popping i checked timing which is fine and i have a timing light that i can advance and the timing did advance. (I don't know if that tells me if the timing will advance without the light though). thought about bad valves but they were checked when the heads were sent out. i thought about bad lifters but with the rocker arm cover off and cranking engine i can see the valves going up and down without question.
i did see in the carburater what looked likes droplets all over the butterflies but i can't tell if it is fuel or water. i dont know if fuel collects like that on the butterflies.
the other thing i saw is that the oil is still milky after the oil change but i did put in a full 5 quarts and plan on doing another oil change but i don't think that will cause this popping. it sounds more electrical to me

 

[thrasher]

Re: what is going on

How old is the fuel? Any chance you have water mixed in with the fuel?

Gary

 

[b0mbtrack]

Re: what is going on

i did empty the fuel water seperator but didn't see any water in the jar. also the fuel is new.

 

[b0mbtrack]

Re: what is going on

is there anyway to test the distributor advance module, or bypass it so i can cancel that out as being the problem. or if that wasn't working would the timing not advance at all?

 

[Bondo]

Re: what is going on

or if that wasn't working would the timing not advance at all?

If it Wasn' Working,.........
It Wouldn't Run,....... At All........

Did you get all the Plug Wires in the Right places,..??..??

 

[b0mbtrack]

Re: what is going on

thanks, that saved me the money of going to buy a module just to see if it would work. I did double check the plug wires and they are in the right spots.
when i go to rev it up the engine also makes a noise like it is week in that rpm range, or like a sucking sound then it does the popping. i did get the carb rebuilt but that didn't fix it.

 

[lmannyr]

Re: what is going on

Just for kicks, check compression.

 

[freddyray21]

Re: what is going on

vacuum leak?

 

[Coors]

Re: what is going on

Droplets are water, as water has surface tension, gas don't.

 

[Coors]

Re: what is going on

Probably water in the carb bowl, leaning it out.

 

[b0mbtrack]

Re: what is going on

hey guys,
i think i figured it out unfortunately. took her for a test run, could only get about 3800 rpms, pulled each plug wire and it was hitting on all. got back to the dock, pulled the rocker cover off and milky white oil all over the place just like i had before i did all this work. So i pressurized the block stuck a stethocope in the head where the oil passages are and can hear it leaking air. Guess i got a bad block after all this, although i still would have needed these new manifolds and risers as those others were passed their time.

Now to pressurize the block i blocked off all the lines at the thermostat and at the raw water pump and pressurised to 15 psi. stuck the stethoscope at all connections and heard nothing, stuck it in the carb to check intake manifold and heard nothing, stuck it at all the places to drain the block and heard nothing, then heard it where i said before in the head passages.
Any ideas on if there is any other reason at all for the leak to be heard there other than a cracked block so i don't replace a block for the wrong reason?

 

[CharlieB]

Re: what is going on

You sent the heads out once already, they may NOT have pressure tested them.

You're going to pull the heads anyway, inspect the block surfaces under the intake parallel to the head deck not quite halfway down the wall towards the lifters for cracks.

Also very carefully inspect the heads within the intake ports, hopefully you'll see a distinct 'line' where the crack has exposed 'new' material to water and caused fresh rust.

The 4.3 as most all small block chevy's have a weakness for freeze damage, often taking the block before the heads.

But in overheat situations it is the heads that warp and crack while the block is most often OK.

Back to the original bill on the heads, where they surfaced because they needed it? Look at them very carefully in good light, bright sunlight replected into a port and between valve seats is better than any flashlight ever built to let you really SEE. Magnaflux and pressure test if you really want to be sure but I'd almost bet you will see your problem.

Good Luck.

 

[b0mbtrack]

Re: what is going on

when i sent the heads out they said both were cracked so i got already reconditioned ones. i dont know why they were cracked the engine never overheated. my theory on that was the heads were normal hot temperature but the cold sea water that was getting in the engine touched the hot head and cracked them. i will be gaking off the heads then again and double checking surfaces.

 

[lmannyr]

Re: what is going on

How did you torque the head down when you got th reconditioned set? Did you do it to spec, and in the correct pattern?

Sorry for the problems. Hopefully you'll get it all figured out and enjoy boating instead.

Luis

 

[Flukinicehole]

Re: what is going on

I just went through the same thing on my friends boat. He overheated his engine and had water in his oil. Did a compression test and didnt really see anything so I pull the head. Send it to the shop gasket looked good no signs of a blow out. They say his head is cracked so he gets another one and we put it back together. Start her up change the oil and filter 4 times and take it for a run. Oil in water again so I diagnose it as a cracked block. I dont know if his head was bad or not I know they can both crack but at the same time? I guess the cracked block could have caused the overheat which then could have cracked the head. I would have liked to see the crack though as I didnt see one, he said it was internal and failed the pressure test.

 

[b0mbtrack]

Re: what is going on

it makes me feel a little better knowing someone else has been through this hell.
i think what might have happened was the manifolds went bad some time ago during last summer (the reaon i think that was a cracked valve spring, when salt water hits them it takes about a year to crack) then the boat sat for the winter with water in some parts of the oil (for some reason none was in the crank case yet and it still doesn't seem to be getting down there) but the water in the rest of the oil might have froze and cracked some spots. anyway, thanks for the help guys.
as far as torqing the heads i followed #18 manual and did it in the pattern and in three steps i bielieve it was.

 

[MikDee]

Re: what is going on

Just a note here, an intake valve that's not seating properly for any reason, will cause a popping, or backfire through the carb, and a cracked valve seat (intake, or exhaust) may cause water ingestion.

 

[b0mbtrack]

Re: what is going on

ok, i finally got the block. It is a vesuvio engine, have used them before and haven't had any problems yet. My question is this. The original oil pan was some form of cast pan it wasn't just tin, and it was big. The pan that came with this block (not attached) is not cast and is smaller than the original. If i bought the block without the tin i would have put the original pan on this new block. Since i ordered the tin with it i now don't know which one to use, or if it even matters. I guess as long as it holds the right amount of oil and the dipstick read correctly it should all be the same.