GAS IN OIL CRANKCASE

[man-of-war]

Hello Again,<br />I've just about run out of options on what's causing the gas to enter the crankcase. I replaced the carb, replaced the fuel filter/water separater, replaced the fuel pump, custom made fuel lines, new MSD 8.5MM plug wires, new distributor cover, new 14" air filter, new spark/ damp brown/black colour. The mechanic said that he ported the ebelbrock preformer 2 intake manifold because the ports on the head are round? So he made the ports on the ebelbrock round as well. I removed the carb and noticed that he also removed/shaved the divider in the ebelbrock intake. This divider separates the fuel/air from left to right. Could any of these be the problem of causing gas to enter the crankcase? Any other suggestions are welcome. The engine is a 1975 454 Chevy Big Block 7.4L V8. How can I check to tell if the intake manfold is cracked? I have a vaccuum gauge hooked up to the intake manifold. Is there anything I should be looking for on the gauge? Could this be a factor? Thank you

 

[lasvegaspatriot]

Re: GAS IN OIL CRANKCASE

man-o-war, ive got the same problem going on. and this is so aggravating isnt it? I myself am starting to think that my next step is the intake manifold. let me know if you figure it out and Ill do the same. we are probably looking at the same thing. thanks lasvegaspatriot

 

[tommays]

Re: GAS IN OIL CRANKCASE

new 14" air filter,<br /><br />would that be a K&N flame arrester ?<br /><br /><br />tommays

 

[greenbrg]

Re: GAS IN OIL CRANKCASE

I had the same problem and mine was fixed with replacing the fuel pump. You might have a crank in your block or in the manifod that leaks the fuel into the oil. Go to the junk yard and grab an intake manifod to see if it is the manifod that is leaking. 25 bucks at the yard vs. 150 from ebelbrock and then you know you have elimated that problem. Wish you luck.

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I removed the intake manifold an hour ago and it look's fine, no cracks any where .Befor i go any further disambling the engine i'll like to hear from the proes from this forum on what they would sudjest i do. THANKS

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I took the intake manifold in to the mechanic machine shop, hoping that he could find a crack. NO LUCK! It's fine but he did find some problems with the manifold (it was worped). There is a passage where the exhaust passes through the intake manifold just below where the carb sits and there is a block off plate on the outside. Just beside where the carb sits this block was leaking because, as it turns out, the thermostat was not installed properly. It was not seated in its groove so water was just bypassing the thermostat. That's why the engine was always running cold. I was told by the mechanic to disable the choke on the ebelbrock and strap the flaps open. I'm going to wait until the weekend and try it on the water instead of hooking it up to the hose. Everytime I hook this engine up to the hose the engine sweats / condensates then I get the water driplets in the oil which changes the colour of the oil. I'll keep you all posted on the outcome of my indeavers.

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I took the boat out today hoping that everything was well but I am still getting the gas in the oil. <br />I have dual batteries in the boat to crank the engine. If the battery selector is on 1 battery the engine will tumble but it will not start. If it is 2 batteries it will fire right up. Could this be a fault with the Thunderbolt IV? Maybe at idle it is not firing as it should??? <br />What temperature should the engine be running at? With the new thermostat in place it made no difference in temperature. The engine is still running cold. It is a thru hull water pickup; the water line running from the water pickup to the water pump is 1 1/2 inches. As it is right now it is running at 50 degrees at idle. When in drive, the needle lies right down. I adjusted the safety water shut-off valve to 1/2 way shut and got close to 180 degrees. Is it normal at 180 degrees to have steam coming out the exhaust at idle?<br />Thanks!

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

the float level in the new marine ebelbrock 1410 carb was off by 1/2''big. i cganged the oil and filter again and without starting the engine i did a smell test and could smell the gas in the new oil . i'll keep those that have a similar problem poasted on what steps i take to fix this problem .

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I think I solved the GAS IN CRANKCASE problem. It's the angle of the engine and how deep the boat sits in the water. My boat is a 1980 23ft Wellcraft which originally came with a V6 engine. The engine that is in this boat now is a 454bb, which I think dropped the backside 3 inches deeper in the water. This changed the angle of the engine. After the boat planes the engine runs and performs perfectly. The plugs are always clean. At idle, getting up to plane, launching, even travelling on trailer will cause gas to be dumped into the engine. My Holley and Ebelbrock are at the carb shop to have the floats adjusted to suit my application. I'll keep you up to date.

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I just did a complete check of that fuel pump looking for leaks. I hooked up my pressure pot to the fuel pump IN and ran some varsol through it at 5 psi. I pluged the OUT with my finger. There were no leaks. I also pumped the arm for a bit and nothing leaked through the vent hole. I removed all varsol and pumped air through the system and poured some soap water down where the arm and springs are. There were no bubbles... I got the carb back today and he adjusted the front float a little lower than the secondary - it will pour at a 45* anything lower than 45 will drip.......My question is I bought a pump to screw on a plastic bottle of gear lube for the lower unit. I used this pump to pump 2 shots of 20w-50 into each cylinder and left it overnight. This evening I tumbled the engine and only #6 spat oil out. The engine only has 5 hours on it. Are my rings gone? How much psi should I expect with new rings and pistions @ 5 hours old? Thanks

 

[Dunaruna]

Re: GAS IN OIL CRANKCASE

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

The engine was ran at 2500 TO 3200rpm for around 2 hours per day only weekends. the second day the michanic that rebuilt the engine took a test drive for an hour or so and he kept the speed at 3000 then blasted it up to 4200+ then right back down.he did this around 5 times for the hour that he spent on the boat.when i drive i stay at 3000rpm then drop down to 2500rpm .ill do the compression test tomorrow at what psi should i be reading on a new engine? i have gas geting into the crank case just lubeing the walls.last time my engine exploded this is my 3rd rebuild in two years 4000a pop .oil will pass the rings. thats goob to know....thanks

 

[rbezdon]

Re: GAS IN OIL CRANKCASE

I think it may depend on where in the cycle each cylinder is when you pump in the oil. If for example #6 was just entering the compression stroke when you tumble the engine it spits out the oil but if one of the other cylinders was just entering the exhaust cycle it may have spit the oil out the exhausr valve instead of the spark plug hole. I guess my point is just because the oil didnt come out the spark plug hole doesnt mean it didnt come out and I woiuld also think some would leak down past the rings even though they are OK.<br /><br />On the pressure I would think you shold be up around 150 +/- and they all should be nearly the same.<br /><br />Only two places gas touches the engine, the fuel pump and the carb. IF you can conclusively eliminate the pump, it has to be the carb and it basically has to be getting in when the engine is off. If the carb leaks into the engine when running you just get black smoke and rich running.

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

I used the MR43T AC Delco plugs with a .35 gap,i adjusted the air/fuel mixture 1/2 turn out from shut.made a restrictor for the fuel line OUT from the fuel pump.redused the fuel pressour from 7 psi to 5psi and started the engine had it runing for 20 min with with a couple of revs in between.shut the engine down and removed the plugs they were all dry but #1 plug was black with sut.what does that mean?

 

[Haut Medoc]

Re: GAS IN OIL CRANKCASE

It means that the cylinder is not firing correctly, you did a compression test, next is a leak down test. I suspect a bad lobe on cam, bad lifter, tuliped valve or weak valve spring. Is this the cylinder with the low compression? The compression #'s for an engine with 5 hours on it are not impressive at all. Sorry.......JK

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

jk,yes #1 cylinder is 135psi and the plug is black with sut. #6 is 130psi but clean with no gas, does this mean that thechanic did not change the rings? could you tell me how to go about doing a leakdown test?

 

[Haut Medoc]

Re: GAS IN OIL CRANKCASE

Look in the 'search' function under 'leakdown test' or 'cylinder leakdown test' and rummage around......Don S. posted a really good link on it. I think you have something amiss in the valves on that cylinder....Or a bad cam lobe...JK

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

LAST TIME THE ENGINE EXPLODED, THAT WAS THE PISTON THAT VAPORISED, AND THE CONECTING ROD WENT THROUGH THE BLOCK.ill look for the leek down test ...... thanks jk

 

[rbezdon]

Re: GAS IN OIL CRANKCASE

Man o, last time the mechanic rebuilt the block did he do any head work?? If the piuston detonated there may have been some pieces of it floating around in the cylinder(s) beating up the heads and valves. I had this happen to an old 307 Chevy, #6 piston got a hole in it the size of a quarter and #4 cylinder had a chunk of it in there smashed the tip completely off the spark plug and damaged the head.

 

[man-of-war]

Re: GAS IN OIL CRANKCASE

yes he did,he had to change #1 cylinder valvs, and #2 valvs .i rember because someone put the heads in the hot tank and melted my roller rockers.