Rear main seal question??

[Anonymous]

If I have a bad rear main seal will it leak all the time at all RPM's or just once in awhile at certain rpm's???

I've had a oil leak since I put this engine together this spring and I thought it was the rear main seal...problem is it will not leak at idle...I'm only getting a oil leak going down the road at speed...

Just noticed last night that the gasket on my dipstick is shot....the oil leak (spray) is on the same side of the engine...

Also, it's not the head gasket, valve cover gasket, pcv sytem, front cover & seal, or oil pan gasket All those check out fine

Thanks,

Doug

 

[rickwrench]

I had a "high pressure only" leak at the oil pressure sender.
I've also blown oil out the dipstick at high rpm when the pcv valve was partly clogged.
Rick(wrench)

 

[Mike]

Did you use sealant on your flywheel bolts. The crank flange bolts go straight through to the crankcase.

Mike

 

[Anonymous]

I had a "high pressure only" leak at the oil pressure sender.
I've also blown oil out the dipstick at high rpm when the pcv valve was partly clogged.
Rick(wrench)

Oil sender is dry, but I'm replacing the dipstick tomorrow!

Did you use sealant on your flywheel bolts. The crank flange bolts go straight through to the crankcase.

No....didnt know anything about sealing the flex plate to crank bolts...

Hmmm....

Thanks,

Doug

 

[wsa111]

Doug, install the rear main seal with the ends at 10:00 o'clock on one side & 4:00 o'clock on the other side. Then put a small daub of sealer which you need to purchase at a toyota or lexus dealership. Its called FIPG. Put a small daub at the butting surfaces of the neoprene rear main oil seal. Before you put the rear main bearing cap in place place a very small bead of this sealer at the outer edge or lip where the rear main bearing cap contacts the block.
Using this procedure i have never had a rear main oil seal leak or even seep. This applies to fords & chevrolets, big block or small block with the 2 piece rear main seals. :idea: william

 

[jamerson84]

Whats a good sealent to use on the flywheel bolts? Or would locktight work?

 

[addo]

The Ford unmachined flywheels I have (original engine enamel overspray on them), show something that looks like Permatex No.3. It may be more a "locking" compound of some type, though.

Regards, Adam.

 

[MustangSix]

Doug, have you looked at the crankcase ventilation system?

Is the PCV working? Is there adequate ventilation to the atmosphere or air cleaner?

 

[Anonymous]

Doug, install the rear main seal with the ends at 10:00 o'clock on one side & 4:00 o'clock on the other side. Then put a small daub of sealer which you need to purchase at a toyota or lexus dealership. Its called FIPG.

I didnt offset them quite that much and IIRC, I used a dab of black Permatex where the ends came together.

Doug, have you looked at the crankcase ventilation system?

Is the PCV working? Is there adequate ventilation to the atmosphere or air cleaner?

Appears to be working OK. Plenty of suction at the end of the PCV valve, and on the other end of the valve cover is the connection to the back of the aircleaner which is connected by a 3/4" prebent hose, so there should be plenty of ventilation going on....

I'ts just enough that I have a drip pan on the floor and I probably couldnt pass tech at our local track

I was just under the assumption that a rear amin seal would leak at idle too....which this doesnt seem to want to....

Thanks!!

Doug

 

[wsa111]

Doug, jack brought up a good check on your pcv vent system.Check to see if you have the proper valve for your engine?. Do you still have the pcv valve located in the front part of the log?? I'm just taking a wild shot at the location of the pcv valve. With the valve mounted in the front of the log you are leaning out the front cylinders,which would normally run lean without the induction of fresh air. You might give thought of moving the vacuum source to the pcv port on the back side of the throttle plate on your holley???After you do this, you might be able to go from a .033 accerator discharge nozzle back to the .028 vinicity. Remember you have a 50cc accerator pump providing the possibility of too much pump shot to cover up a lean condition with the pcv located at the front of the log. Remember these 500 cfm carbs are used on 350 chevys which require a huge pump shot to prevent hesition? Just a possibility. Excessive crankcase pressure can produce all sorts of oil leaks. worth checking. : :idea: william

 

[Anonymous]

Doug, jack brought up a good check on your pcv vent system.Check to see if you have the proper valve for your engine?. Do you still have the pcv valve located in the front part of the log?? I'm just taking a wild shot at the location of the pcv valve. With the valve mounted in the front of the log you are leaning out the front cylinders,which would normally run lean without the induction of fresh air. You might give thought of moving the vacuum source to the pcv port on the back side of the throttle plate on your holley???After you do this, you might be able to go from a .033 accerator discharge nozzle back to the .028 vinicity. Remember you have a 50cc accerator pump providing the possibility of too much pump shot to cover up a lean condition with the pcv located at the front of the log. Remember these 500 cfm carbs are used on 350 chevys which require a huge pump shot to prevent hesition? Just a possibility. Excessive crankcase pressure can produce all sorts of oil leaks. worth checking. : :idea: william

Heres how I have it run,

I can switch it to the carb tomorrow...never gave it much of a thought...

Thanks,

Doug

 

[MustangSix]

Doug, are you running a vented cap or to the air cleaner in the rear? Either is fine, but a closed cap would allow pressure buildup at high engine loads. No vacuum at load, so any combustion gasses in the crankcase have to go somewhere.

Usually the dipstick gets blown out, the rear main leaks, and the front seal leaks when that happens.

 

[Anonymous]

Doug, are you running a vented cap or to the air cleaner in the rear? Either is fine, but a closed cap would allow pressure buildup at high engine loads. No vacuum at load, so any combustion gasses in the crankcase have to go somewhere.

Usually the dipstick gets blown out, the rear main leaks, and the front seal leaks when that happens.

Jack & Bill,

It has a vented cap in the rear that has a line that runs up to the air cleaner.

I picked up a prebent vacuum hose from CarQuest yesterday and rerun the line as shown to the back of the Holley,

I guess I will try running a smaller center squirter now....The throttle response doesnt seem to be as crisp now with the current pcv setup but it does seem to idle a bit different now...

The front 2 cylinders always ran a bit leaner than the other cylinders according to the plugs. I assumed that it was just the way it flowed with the log head. Never thought about the pcv leaning out the front 2 cylinders.

I'll clean the plugs and check them again and see if they are still running leaner than the rest. Also, I'll wipe off the motor real good and check for oil leaks again!

Thanks for the help!!

Doug

 

[BIGREDRASA]

You might want to hook a vacuum gauge teed into the PCV line, and run it into the cockpit. You may not be pulling enough vacuum at WOT to adequately scavange crankcase gases. This is probably why race engines run extra large vented breathers.

 

[I66coupe]

The new neoprene seals require that you remove the little spike that used to hold the old rope style seal in place. Did you remove it? If not, it may be creating a poor seal at that location that gets overwhelmed by high rpm oil pressure.

 

[Anonymous]

I have a vacuum gauge for it...I oughta actually hook it up and see what it does one of these days!

Its a 78 motor so it doesnt have one of the little spikes like the older ones did...I did check just in case when I rebuilt it though!!

Its easier to pull the motor to install my new stall convertor, so while I have it out I'll pull the pan and see whats going on with it!!

Thanks for all the ideas!!

Doug