True,
We need to know some history about the engine and how it performed up to now. Also, what about some specs, carb size, cam lift & duration, type of fuel delivery (mechanical or electric?). A cam that is too lumpy and incorrectly matched with an oversized carb could allow more time for fuel to load up the cylinders at a rate that the ignition cannot efficiently combust and exhaust.
When did the problem first occur and how long have you run the engine since? If the cylinders became loaded with fuel, the fuel may have washed down the cylinder walls. You said it's coming out of the sidepipes. Are you getting
oil out of the sidepipes? When I had my problem. there was actually wet
oil at the sidepipes. Fuel had washed out the cylinder walls and even removed the crosshatch honing from the cylinder walls.
You said that the
oil is very thin. This would occur with gas in the oil. You should also be able to smell the fuel in the oil. What about the oil itself, are there any metal particles in the oil? You may want to pull the oil filter and cut it open to inspect for any metal particles. Be careful when you cut it open so you don't confuse the filings from cutting it open with any metal already in the filter.
You said that the engine had been running poorly and possibly not firing on all eight. Are you sure that the valve timing is correct? Ignition timing could also be a cause of problems. If a cylinder is not firing when it should, the fuel mixture in that cylinder has to go somewhere, but usually if the ignition timing is off, the mixture will ignite either on intake or exhaust stroke causing a backfire either through the carb or through the exhaust. Cold time the ignition. Disconnect the secondary coil wire, pull #1 plug and with your finger in the plug hole bump crank the engine until you feel pressure at the plug hole. then hand crank the engine bringing #1 to TDC. Then follow the firing order making sure of the firing order sequence.
Unless the problem is obvious such as a carb that is improperly adjusted allowing raw fuel to leak down into the engine, or it's a blown diaphragm on the fuel pump, I would begin by doing a compression test of all cylinders. What you should look for is consistency in the reading from cylinder to cylinder +/- 15 psi. Depending what heads and cam you're running you should see compression readings somwhere in the 175-180 psi. Perform the test dry first and then squirt some oil into each cylinder and try the test again. If there is a vast increase in the readings with the oil test, that would indicate rings. If the readings are low and using the oil doesn't increase the readings, that would indicate worn valve guides or valve timing is out.
If the readings are good wet & dry, you may be okay as far as internal troubles. If the readings are generally low or if one or more is considerably lower than the others, you have an internal problem. If you have two adjacent cylinders with low readings and the others are fine, that would indicate a blown head gasket.
Once you've completed the compression test, if you haven't discovered the cause, my next step would be to drop the pan and pull a main cap and also a rod cap and inspect the bearings. Also examine the crank journals, they should be smooth with no scoring.
The bearings are copper with a coating of babbit. The babbit is a dull grey color and if the bearings are okay, that's what they should like. If they have washed out, the dull grey finish will be worn off and you will see the copper core of the bearings. In my case the babbit wore off and the crank journals were scored.
I pulled my block and when I had the cylinders dial bore gauged, they were on average .036" over in the centers of the cylinders. My block was supposedly .030'd over, but the excessive wear indicated it had already been .030'd over and the builder probably just honed the heck out of the cylinders to try and true them up.
I ended up getting another block and I built it up myself and no problems since.
By the way, to rule out the carb I changed my Road Demon 725 for a Holley 600 and to rule out the pump, I changed the mechanical fuel pump from an Edelbrock to a stock pump.
I don't say any of the above to discourage you but rather to make you aware of what the worst case scenario could be. Take your time and be methodical about how you proceed to diagnose the problem and hopefully your situation won't be as bad as mine was.
Keep in mind that the two most common ways for fuel to get into the oil is either past the rings or through a blown fuel pump diaphragm.
I will try to find pics of my worn bearings and post them here.
Good luck and I'd be more than glad to help in any way I can.
Tony
Help...Fuel in my oil !!!
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