So here we go again with oil leaking from my 455 .I thought things were under control for a while but turns out i just stopped driving like a maniac! some of you may have read my blown oil seal thread last year.everything about this motor is great except everytime i get into it ,i get oil leaking out in the rear main seal area.the last time i found some oil pan bolts that weren't very tight and thought maybe that was the issue because things slowed down alot,but turns out things are get progressively worse.my rear endseal is bone dry as well as distributor seal and freeze plugs in the back of the block .this was the first time i noticed my oil dipstick tube was unseated.if i drive around under 2500 rpms i dont leak a drop .i need advice on tests i can perform to get to the bottom of this.my thoughts are faulty valve guide seals? broken or improperly seated rings?backstory on the motor is .030 over 455, 9.6:1 comp, iron big valve e-heads.motor doesn't smoke a bit at start up or driving ,reving etc.

 

Valve guide seals, no. Is the back of the intake manifold leaking oil? Do a leak down test. Confirm that PCV valve is working and that it is the correct valve
​​​See if the dipstick unseats again.
What breathers does it have, are they clean and clear?

Good luck!!!

 

back of the intake is completely dry ,pcv valve is working, the other valve cover has a push in style breather that is clean and clear.i dont have a leak down tester but i guess its time for one.

 

another question is blow-by the only thing that can cause excessive crankcase pressure?and as an added note the car sat in the garage since last october and no oil drops under it

 

If the crankcase is venting properly then yes leaking past the rings is about all that is left. If the dipstick blows out again that is not a good sign. It could be just a bad seal though, they leak worse under load.

If crank pressure is excessive, was this engine recently rebuilt? We're the rings properly seated on dino oil vs synthetic?

 

This motor was rebuilt about a year ago and was broke in on an engine run stand with comp cams break in oil . Installed in the car Last summer and driven a few hundred miles with no issues then this leaking started after a day of good hard running .ive ordered some leak down gauges

 

When the plugs are pulled keep them in order and try to read them, sometimes they give indications.

Can you feel pressure on the oil fill tube? If yes does the pressure increase at high rpm's?

​​​​​​The old school method for seating rings was to get the engine warm, while doing 20 mph go full throttle to 50 mph, then coast to 20 mph, full throttle to 50 mph...repeated ten times. Might be worth a try.

To current engine builders...are rings still seated this way? If not, how if at all?

Good luck!!!

 

if i have time ill pull the plugs tonight and post pics here .there is no pressure in the oil fill tube at idle so thats something i can check tonight as well

 

Hi,

I had a engine that ran, but kept blowing the dipstick out, ended up being a cracked piston.

If you have a similar problem the pressure will go to the least path of resistance

Pulling the plugs and maybe a compression test and see where that points you.

Good luck,

 

i tried a little test today .secured a surgical glove over the oil filler tube and when i rev the motor to say 4000rpms the glove starts to blow up like a balloon.i know most engines have some crank case pressure and its a crude test but i may try this same test on my other motors to get a comparison .waiting for my leak down gauge and that should tell the story.as far as the plugs go they seem to be awful rich this was not the case last year when i put the car away .i noticed my electric choke on the quadrajet was not opening fully when the motor was warmed up. so im sure that has alot to do with why it was running rich

 

If the glove filled, then you PCV is not working correctly.

 

Pcv valve is working I checked it a couple times . If I take the opposite side breather out of the valve cover it will suck tissue right up against the hole . Vacuum at the pcv port is 21 at idle and does drop to about 15 at 300 rpms . Don’t get me wrong the glove doesn’t blow right up it starts to .enough to know there is pressure there

 

Are the valve covers stock? I'm wondering about a defect in a baffle or vent. Were these valve covers on before the rebuild? Could probably do the glove test on the valve cover ports.

Are plugs 3 and 5 burning well and the rest are rich?

Did the car overheat before the rebuild? Was the rear end ratio changed? Was the radiator changed before or after the rebuild?

 

Aftermarket chrome valve covers with baffles been on from day one .it does appear that those two plugs are burning better than the rest.i bought the motor to rebuild no idea of its prior history ( it was hot tanked and magnafluxed)I did go from a 273 open rear to a 323 posi .radiator is new summit 4 core aluminum went in with the motor runs about 175 degrees all day

 

It will be interesting to see what the leakdown test shows, here's hoping it's good; but, then the question remains...

So the exact source of the leak isn't known correct? Just the general area. We used to find rear main leaks by running the car on a lift with the flywheel cover removed, rev the engine and hold a piece of cardboard by the converter. If it was the rear seal it would sling oil on the cardboard vs. drip.

Good luck!!!

 

At this point I don’t know the exact source of the leak but I’m leaning to a rear mail seal . The leak down test should at least confirm some things for me . Regardless the motor will have to come out to repair the seal and anything the leak down test reveals .

 

Do you a compression check, I’ll bet you have a broken oil ring, allowing oil into the compression chamber, and pressurizing the crankcase.

 

No. I've seen engines that pressurized the crankcase because the exhaust valve guides were wiped-out. At high RPM, there was enough exhaust system pressure to blow exhaust up the guide and into the valve-cover area.

More-or-less the same way. Get the trans in HIGH GEAR, because you want lots of load but not lots of RPM. Disable the automatic trans kickdown, if practical. Engine fully warmed-up, stab the gas pedal, back off and coast when the engine gets to ~4000 rpm. Repeat until it stops being fun. MPH is dependent on gearing.

A leakdown test would be better, but cranking compression testing can't hurt.

The downside of leakdown testing is the lack of uniformity among gauge sets. There's no "industry standard" or governmental regulation related to the orifice size in a leakdown tester for automotive engines. The closest we have is the FAA regulation on leakdown testing for aircraft engines, where engines with a 5" bore or smaller, use a .040 orifice having a 45 degree lead-in chamfer.

I used a Snap-On single-gauge leakdown tester for about twenty years. Some time ago, I bought an aircraft-calibrated leakdown tester from ATS on Amazon, but I don't see what I bought, listed any more.

 

Id like to hear opinions on the results of my compression test.
#1 173 dry 178 wet
#3 179 dry 182 wet
#5 176 dry 179 wet
#7 168 dry 175 wet
#2 173 dry 180 wet
#4 172 dry 177 wet
#6 175 dry 181 wet
#8 174 dry ? wet (spent 25 minutes getting compression hose started with ac box in the way and said f-it on the wet)
Theses numbers all seem great to me still waiting for my leak down tester should arrive today will post those results as well.

 

Pretty good #'s! Let's see what leakdown shows; probably will be good too. If there is pressure and the leakdown is good, the pressure is not getting vented.

Keep at it... you'll figure it out.

Good luck!!!

 

gauge came today and been busy doing the test i filled each cylinder with 70lbs or air and let it sit for 5 minutes each all on tdc
you can see cylinder 5 has the biggest discrepancy is this enough to say yes its a cracked ring? i can hear air seeping somewhere .not sure if this would warrant a tear down yet?
#1left gauge 70 right gauge 67
#3 left gauge 70 right gauge 67
#5 left gauge 70 right gauge 60
#7 left gauge 70 right gauge 67
#2 left gauge 70 right gauge 68
#4 left gauge 70 right guage 68
#6 left gauge 70 right guage 67
#8 left gauge 70 right gauge 68

 

I would try running the engine with no PCV, just a breather on each valve cover. Run it under load etc. and while revving the engine see if you have blow by coming from the crankcase. If you want to get real technical you could measure the pressure in the crankcase with the PCV hooked up using a minometer fixed to the return side of the PCV system.

 

From a percentage perspective #5 is high @ 14%. Is any air exiting the exhaust or carb? With a cheap endoscope on a cell phone you could look in the cylinder for wall scoring, if any is found it is time for a teardown. If no scoring is found, put a solvent in #5 overnight, seat the rings as mentioned earlier and rerun the test on #5.

I also like the idea of trying breathers on both valve covers as it would tell whether or not the leak is crankcase pressure related.

Good luck!

 

I just took test drive with breathers in both valve covers and no pcv hooked up and it leaks just as bad.Its hard to tell what direction to go as far as testing ,because now that the seals are compromised they'll probably always leak at high rpm until i replace them.i do have a bore scope i can look around a bit in there ,last time i did that couldn't really see and scoring in the cylinder walls . How would i reseat the rings in that cylinder?

 

no air that i can hear is coming out the carb or exhaust .i hooked compressed air to that cylinder and sounds like its going in the block

 

Your rear main leak really should have nothing to do with crankcase pressure. It could have all to do with creating a vac in the crankcase though caused by too much vac in the crankcase. VW/Audi do this all the time even with modern engines. If the seal is already compromised, yes, your going to need to change it. Step one, check crankcase pressure or vac, vac would mean PCV return clogged or too small or faulty. Possible wrong PCV valve. Pressure could be same, wrong valve, pressure getting by the rings. To find out exactly where the leak is you could get dye/black light kit for cheap. You may be chasing the crank pressure issue and it isn't even an issue. Oil pressure too high, incorrectly installed rear main or leak isn't even from the rear main.

 

my oil pressure is 40lbs at idle and about 65 cruising .the seal was installed by the machine shop(they do make mistakes) i had quite a lot of run time on this motor before this issue developed .wouldnt an improperly installed oil seal leak from day one? i took this pic from my bore scope and appears there are vertical scratches in the cylinder wall most likely where im getting blow by.Now, i agree this may or may not be the reason for the leaking.In any event looking at this pic the motor will come out sooner than later

 

wouldn't load try again

 

It would be great if the leak could be identified before pulling the engine. The picture didn't post of the scratches, how bad are they? Need boring or slight/honeable?

 

Pic is there. Can you scope another cylinder for comparison and post pic?

 

i should have done that sugar bear but ive had it for one day. its not the greatest picture. im curious if those lines would show up in another cylinder as well.Ill get back to it tomorrow

 

Why bother with "wet" testing when the dry seems better-than-expected?

I don't bother with "wet" testing because I've never seen it do what it's supposed to--seal worn rings. Maybe "wet" testing worked on inline 4 and 6 cylinders, where the oil stands a chance of wetting the rings 360 degrees around the bore. With a slanted-deck engine like a V-8 or "Slant 6", the oil is unlikely to get to the "high" side of the cylinder.

Most folks test at 100 psi; that way the leakage indication is the inverse of the percentage of leakage. Example: 100 psi inlet, 92 psi on right gauge = 100 - 92 = 8% leakage. Makes the math easier. This usually involves dialing up about 105 psi to begin with, because the pressure drops a bit once the leakdown tester is connected to the cylinder and functioning.

The aircraft procedure is to use 90 psi for testing. Nothing wrong with that, just makes finding the percentage of leakage a little tougher. I think my Snap-On single-gauge leakdown tester uses 60 psi input pressure, but the gauge is not calibrated in PSI, it's calibrated in leakdown percent.

The actual leakage numbers don't seem unreasonable, but I don't suppose you've got a "known-good" engine to test as a comparison.. The apparent scoring of the cylinder tells another story. Unless that scoring is an optical illusion from the viewing device, that engine is coming apart.

 

My reason for the wet test was I figured someone might ask about it, and it actually did make a slight difference I agree with the logic of how could oil coat all the way around a cylinder wall . 14 per cent leak down wouldn’t be that big of a deal except for the fact it’s so far off from all the rest .the plan tomorrow is to check a few more cylinders with the bore scope as well as put some compressed air in #5t and try to nail down where the air is going . I can’t hear worth a **** and the wind was howling today so couldn’t really figure that part out . Thanks to all for your input .

 

Those vertical marks don’t bother me nearly as much as what looks to be a very poor crosshatch. I think a teardown is imminent.

 

mark I don’t think that picture is telling the story . I remember getting this block back from the machine shop and it having nice crosshatch in all the cylinders . Regardless the motor is coming out when I have time and money to deal with it .does this crosshatch Remain in the cylinder wall well after break in ?

 

Likely correct. I've seen how a camera (especially with flash) can pick up or exaggerate details that are near-invisible to the eye. Problem is, you're not going to be able to verify without disassembly of the engine.

An engine can retain honing marks for tens of thousands of miles (potentially well over a hundred thousand miles)--but only if the air/fuel ratio is kept correct, (i.e., feedback fuel injection, no carb will meter this precisely) the oil is clean, the engine runs appropriately hot enough, and an overdrive trans helps by bringing the RPM down.

"Washing" the oil off the cylinder by over-fuelling; or running the engine so cold that the cylinder walls don't expand properly and the oil get contaminated with water, will not only allow the honing marks to be removed, you'll wind up with a ridge at the top of the cylinder. The ridge is the original diameter of the cylinder, the "step" below it is material worn-away by the top ring.

The Vortec 5.7L short-block I bought and rebuilt had only 0.0015 wear to the cylinders; and hone marks still on the walls except at the very top of the cylinders. I have to assume the engine had far more than 100,000 miles.

 

At it again and found something interesting i double checked with a hose to my ear to be sure the leak- by is in fact going into the block and not out the exhaust or intake valves.confirmed. got the engine up to good operating temp and seems to be much better when hot @70lbs of air right gauge showed 66.5 so about 5%leak down while hot so it appears the blow by gets better with heat.yesterday i feel the motor wasn't that warm by the time i did all the compression tests and leak downs but a cooler motor didnt seem to affect the other 7 cylinders.

 

That is good news. The camera might be distorting the actual condition of the cylinder wall, a comparison to other cylinders with the scope may be the best alternative before pulling apart the engine as it may be fine.

If they all look comparable and the dipstick stays in place, the leak as mentioned by others may be unrelated i.e., a bad seal or mating surface.

I'd also try seating the rings not on synthetic oil the old school way. It costs nothing and is fun to drive it that way!

Good luck!!!

 

i did check some other cylinders and got similar lines and distortion with the scope so im hopeful that cylinder isn't as bad as i first thought, at least not enough to start tearing the motor apart . i will have to address the leaks and in the mean time might as well try the old school break in .

 

What is the “old school break in”?