Thread: White smoke from breather and oil drops formed

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Originally Posted by jerry clayton

To help try getting rings to seat you can lightly sprinkle BonAmi powder into the air horn on the carb while revving the motor --will help with the seating of the rings and valves-------

LOL, we used to use Borax back in the days! I guess that kinda dates us!!

Originally Posted by Jakemstar

Just tested the first cylinder. I got around 90 psi off the first stroke and then after another turn or 2 it topped off at about 155psi

The procedure for testing compression is as follows:
1. Warm the motor to operating temperature.
2. Remove all spark plugs to make the motor easier to turn over and save the starter motor.
3. Wire the carburetor primary throttle blades wide open so the motor can breathe.
4. Disable the ignition system so that you will not cause a fire.
5. Turn the crank through at least 5 compression cycles on each cylinder. This procedure will top out the readings. Make sure you have enough battery to accomplish this.

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Jerry has mentioned steam holes twice and you have not indicated whether or not you drilled the heads for steam holes. Any 400 block that will be operated on the street at less than ~3,000 rpm's will need steam holes between the block and the heads. Race motors that are wound up tight all the time will not need them because there is enough movement to the coolant that steam pockets will be washed away, causing no problems. Street motors that are operated at lower rpm's have insufficient coolant speed to wash the steam pockets away, so these steam hole points in the block build temperature until the block material grows at these points, causing the deck to be uneven and the motor spits out the gasket due to lack of clamping force. At least that's how it has been explained to me and that makes sense. Even if the gasket is not compromised, the hot spots can cause detonation in the motor.

I suspect the head gasket(s) have already been compromised if you did not drill steam holes in the heads and did not use head gaskets with steam holes in them.
Technical Articles at Greg's Engine & Machine
Here is the gasket normally used on these 400 builds....
http://www.summitracing.com/parts/fe...make/chevrolet
Speedway Motors sells a shim gasket, but I could not find it in their catalog. Maybe a call to them would turn it up. I'd like to know where you ended up for squish and what gaskets you used.

I would like to know the particulars of the motor too.
Part number of pistons used.
Piston deck height used.
Squish.
Measured cylinder head cc's. If you bought these heads used, one or more previous owners could have decked them and you have no idea about the volume of the chambers. They could have even angle milled them, causing oily vapors from the crankcase to be pulled into the cylinders from the underside gap between the intake manifold and the head ports. That could be one cause of the oily plugs.

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Ok let me try and catch up here....
i am not running a thermostat at the moment yet it stays at a constant temp between 170 to 185
edelbrock performer intake
i just replaced all the gaskets two days ago everything is felpro
There are no sleeves in the block
the block and both heads were given to the machine shop and the valve seats were redone and all checked out without any issues
the heads do have steam holes
the pcv is connected to the large outlet on the front of a edelbrock 650 thunder series carb
i do not have breathers on both valve covers, i just tried to switch the pcv and breather to see if it changed anything
the heads came off of the 305 sbc that was in the truck when i bought it.
their origional chamber size was 58 cc i believe but they have been decked. All i know about the pistons is that they are forged eagle dished pistons.
I know there are alot of issues with over boring sbc 400s and this block is 30 over. Crossing my fingers the walls are not cracked

All things point to at the very least a severe case of blow by the rings into crankcase and the oily fumes getting injested to the cylinders again which will cause black oily spark plugs
disconnect the pcv and see if plugs stay clean altho probably will still have blowby--------


Do you know what BonAmi is??????

On the previous page post #14, I gave you simple diagnostic procedures that will help determine what is wrong. Three cylinders on one bank are very low compression, this is sometimes due to valves being adjusted too tight, which can also cause excessive crankcase pressures.
If you follow all the test procedures outlined in post #14 you will know wether it is ring or valve related. If it is rings, there is a good possibility changing the oil to conventional with high zinc and using Jerry's BonAmie trick will seat them. BonAmie is a powder non-abrasive cleaner you can find at hardware stores.
Good luck..

are the fel pro head gaskets for an 400 block-4.155 bore and aluminum heads??????

36 sedan- i havent gotten around to using your procedures quite yet as ive been very busy with work lately but i will let you knos as soon as i do.


Jerry- they are 4.160 bore head gaskets that can be used on aluminum heads.


Later today i am going to get bon ami powder and then loosen the valves up and see if it works. If not then im going to try squirting oil in the cylinders and see where the pressure is. I will also clean the plugs and then try running it without the pcv and check to see if its still burning oil. Thank you all for your input.

JMHO, but I would do the testing first to see if it is the rings, before trying to re-seat rings that may not need it. It's better to be reasonably sure, rather than guess at a solution.

So how much oil do i need to put into the spark plug hole? And still crank it over 5 times?
Also how much powder if i reach that point?

I use an oil squirt can with a flexible tip and give it a couple squirts, probably equal to about a table spoon of engine oil and crank as usual, I crank it until the gauge stops climbing. Do one cylinder at a time (at least 5 compression strokes).
Jerry can tell how much bonamie, I haven't done that since the sixties.

Ok... and if it is NOT the rings the compression will not change correct?

That is correct.

Jerry- curious about the whole bonami thing. How much?

Ok so..... im pretty infuriated.... your oil test worked. Number 3 cylinder went from 105 psi to 120
number 5 went from 60 to 105 psi
number 7 went from 90 to 105

I didnt even go on to loosening the rocker arms to try and see if the tension was too tight. I adjusted them all the same anyways....

Ill replace the rings but i would like to figure out how those 3 pistons rings are messed up and not the other 5 sets? I just figure if theres anything i can fix while the motors out i need to figure it out. TIA