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Topic Review (Newest First)
02-17-2013 01:56 PM
ssmonty You said you put RTV on intake. Was that while the intake was still installed? Just smearing it on the front where it mates with the block won't keep it fron getting blown out from excess pressure.
After its been cleaned, and warmed up good, hood up, chock the wheels, have a friend get in and hold the brake hard while pressing the throttle till just before it starts to rotate the wheels or move, and watch for blowby/oil.
Might pull the pcv valve and watch for excess blowby. If there is allot its probably going to blow out any gaskets(front of intake, front of oil pan, timing cover seal, valve covers, ect...) no matter what you do except re-ring/overhaul. JMO
02-16-2013 03:34 PM
BigEsGarage I agree with the Many suggestions to the oil dye, that stuff is awesome!
If you think or wondering if it's blow by; plug all the vents on the engine.
Install a fuel pressure gauge on the dipstick tube, which I would keep low, like, 2~4 psi and feed it, through PVC grommet, compressed air
whilst the engine runs at a high idle. Make it 2700 for whatever reason.
Then you'll be able to replicate a high blow-by situation at cruse speed and find that damn leak. If that's what it is.
Best of luck.
02-16-2013 01:38 PM
cobalt327 Thin front pan seal where a thick seal should be? Has the lip that secures the front pan seal become detached from the rest of the timing cover? (The channel where the seal resides is only spot welded to the cover.)

If it was me I would clean the engine compartment spotless, then go out and run it however you need to to make it leak. Then park over a large piece of cardboard and let it drip. In many cases, right above the furthest FORWARD spots are going to be where the leak is.
02-15-2013 01:32 PM
lmsport Are you sure the head gasket is sealing? If the heads have been angle milled, or sometimes after conventional flat milling, the head will not be flat at the top of the deck where the gasket has to seal the crankcase.

It would be the flat surface of the head that mates to the surface of the lower left in this image where the deck transitions into the china wall.

A feeler gauge might work to check that.
02-15-2013 12:30 PM
oldskool66 i replaced my fuel pump. all ready i used rtv on the intake. and ive replaced every seal on this motor except the head gasket. i really appreciate all the help this is super frustrating.
02-15-2013 07:28 AM
Coram Stiner
help with weird oil leak

I know this may sound a little off the wall but thier are 2 things that I have run into with my sbc 1. wrong rear seal 2. there is a spot on top of intake manifold for egr valve back by distributer. It is recessed into manifold with 2 bolt holes these dont go thru casting (not suposed too) 1 of mine opened up some how and at higher rpm would throw oil out. you can only see it if you stand on drivers side hood open and rev up motor with throttle linkage. I hope this helps. PS. there are 2 different rear main seals
02-15-2013 07:26 AM
lmsport I have had fuel pumps leak oil from the vent hole on the top side of the diaphragm when used in oval track racing.
02-15-2013 06:32 AM
Originally Posted by oldskool66 View Post
i guess ill do a leak down test this weekend... im really thinking ill just build a new motor. it is a 307 thats punched .060 over so its may be time to just do a new one..
Replacing the entire engine because of an oil leak is absurd.
What you can do is get it on the dyno and have someone else drive while you watch for where the oil comes from, while wearing eye protection of course.
Or pull the hood off and rig up a camera and take it for a drive.
Id also recommed getting some dye, it might help you identify they general location that's causing the problem.
02-14-2013 09:34 PM
oldskool66 i guess ill do a leak down test this weekend... im really thinking ill just build a new motor. it is a 307 thats punched .060 over so its may be time to just do a new one..
02-14-2013 06:57 PM
Originally Posted by bob wilcox View Post
there is supposed to be a conical shaped washer, an oil slinger, on the crank. the flared side of it goes toward the crank, the rear. If it is not in there or is in there backward you will have an oil leak. From what you said, the only other things I can think of that after market timing cover might have a defect causing it--check the end play in your crank--too much and it will eat the seal--a little more and it will wipe your main webs in the block. I don't know what else to tell you, good luck!
Bob, Ive never seen an oil slinger in a small block, am I missing something?
02-14-2013 06:50 PM
T-bucket23 Where is your PCV connected. When under heavy load the pcv will not be doing much due to a lack of vacuum. This could cause crank case pressure to build and blow out oil. When you loose pcv vacuum is you have a weak seal combined with excessive increased crank case pressure it could blow out. You need to figure out where it is coming out to start with. My guess is the front of the intake. Did you use RTV on the intake ends or the gaskets. The gaskets don't seal. At higher rpm you will also have a lot of oil flowing in the lifter valley which could contribute to intake leaks.
02-14-2013 06:15 PM
Originally Posted by oldskool66 View Post
it only leaks oil when there is load on the motor i can run it at 6k all day no leaks get on it on the free way and it blows oil at 2500... i replaced every gasket and seal including intake manifold timing cover valve cover gasket.
Apparently my simple answer isn't the problem, I hate that when it happens, then I've got to think.

When you say run the engine all day at 6000 and it doesn't leak with no load, expain how you're getting 6Krrrs and no load. I think I can guess but I'd rather hear your explanation.

If you're just revving the engine with no load on it there isn't a need for much throttle to get it up to 6000 RPM so the pressures in the cylinders are actually pretty low thus not a lot of forces to cause blowby. However, when the engine is truly working by moving a 2 ton car, the cylinder pressures get to be quite high even at a modest 2500 RPM this will make a lot of blowby.

If this is a blowby issue from a broken ring for example, as the cylinder pressures rise a lot of compression pressure will get into the crankcase and it will blow oil out the weakest place. Usually this comes out the breathers and often out the crankshaft seals or where the pan mates with the timing cover. Older heads with the cast gasket rail of the rocker cover are another common leak point as are the corners of the intake manifold. The pan rail can be another troublesome spot as often too much tightening of the pan bolts dimples the pan's stamped rail crushing the gasket, this can also happen to the rocker covers, and the timing cover if they are sheetmetal.

I'd think the locations of leakage would be visable; but if not, I'd clean the engine and take it out just enough to promote the leakage but short of soaking everything in oil so you can see where it comes from. I'd also recommend a leak down test in addition to a compression test. Low compression or fast leakdown can identify any ring problems. If the engine ever kissed serious detonation even for a few moments this can damage the ring lands grabbing the rings often busting them but not holing the piston. So the rings will fail to hold compression at some level from mild to wild but the piston won't have a hole right into the pan.

One might even consider the front of the crank got assembled without the oil slinger that fits between the crank's timing gear and the front seal. If the slinger isn't there; as crankcase pressure builds it will pump oil up the crank and past the seal like it wasn't even there. And yes wear on the seal surface of the damper can leak and leak a lot even though the seal itself is good. There are thin repair sleeves that slide down inside the damper to restore the sealing surface if this is a problem.

02-14-2013 05:56 PM
64nailhead When I said have someone else run the heck out of it, I meant with hood off and uou in the passenger seat.

In terms of the dye, you add the dye to the crankcase, go run the car 50 yards hard, and check it, then 100 yards and recheck it, etc. The dye is a guarantee to find the source of the leak(s) if you have a system for checking it starting with a short interval to longer intervals. Have done it many times and it has always worked. Give it a try and you'll see what I mean.
02-14-2013 05:44 PM
oldskool66 it only leaks oil when there is load on the motor i can run it at 6k all day no leaks get on it on the free way and it blows oil at 2500... i replaced every gasket and seal including intake manifold timing cover valve cover gasket.
02-14-2013 04:10 PM
64nailhead Buy some leak detection dye and grab a black light. It should do te trick.

X2 on it coming from or getting into the front of engine accessories by the way it is all over.

My last resort would be to remove the hood and have someone else run the heck out of it while you're watching. That should at leeast give you an area to look closer.

The black light and dye system works great. You can grab the dye from Napa or most any truck dealership.

Good luck - nice looking motor.
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