Mopar Action On-line – Tech Questions
Peter Black, Geelong, Australia, 1967 Dodge Coronet 440 500
Hi Rick, long-time reader & subscriber, big fan.
I’ve had this 440 engine for about 15 years now. Bought it in 1000 piecesand rebuilt it as a fairly stock motor. It has always suffered a leak fromthe rear main area. Seems every time I’ve tried to fix it, it has got worse.I’ve tried the Indy billet retainer – no improvement. 2006 – decided tospend some $ and wake this motor up. The oil leak situation (plus the solidcam) prompted me to use a professional engine builder and the guy I chosehas an engine dyno and a great rep. He would need to have some patience,because this oil leak has been a real challenge for us. He has rebuilt theengine and dynoed it to the tune of 612 hp, 630 ft/lb. Good numbers, butthat was not my main concern. The rear did not leak on the dyno. As soon asI bolted the motor in the car and started it, guess what? Oil all over thefloor. Twice this has happened. The second time, he used a rope seal and ranthe engine on the dyno several times to check the rear was not leaking. Thisguy is very conscientious and does his best to avoid unhappy customers. Soimagine his dismay when I rang him after Xmas and told him the oily news.
Some other clues:
– It would appear that there is some crankcase pressure forcing oil out ofthe motor. Oil seeping out of the timing chain cover at the top, some fumingout of rocker cover breathers.
– Leak-down testing shows 14-18% on all but one cyl – the #4 has about22%.
– Compression test gives perfect results – 170 on all 8 cylinders.
Rick, this oil leaks out 5 drops at a time. Have you seen anything likethis before? Any ideas you have would be appreciated. Peter
Peter, I’d measure the blowby CFM (volume) and/or pressure. The leakdownsounds VERY bad for a fresh engine. Normally, a home-rebuild is maybe 5%,pro / honed with deck plate, under 2%. Be sure there’s lots of ventilation,but if there’s so much blowby…?? My guess: The rings never seated. It,frankly, simply sounds like a junk engine! But see this earlier Q&A:
OK, I am desperate for your help! I have a large oil leak in a 383 that Ican’t seem to fix. The 383 is from a ’68 truck according to theletters/numbers on the oil pan rail. It’s in the ’66 Charger 4 speed Ipicked up 11 years ago. The engine was rebuilt before I got the car, doesn’tsmoke at all, is quiet, and has good oil pressure. It loses 1-2 quarts every200-300 miles! It’s getting on the clutch/flywheel.
I changed the clutch and put in a FelPro rear seal setup when I got the car11 years ago. No improvement at all! I tried the Mancini retainer setup afew years ago and again, no change at all. I had a shop do the clutch againand the rear seal a few months ago and again, no change at all. Still leaksas much as always.
No leaks from the valve covers, valley pan, oil pan, or anywhere on theengine. It only leaks when it is running. It’s still getting on theclutch/flywheel so I assume it’s still the rear main seal unless there issome place on the back of the engine that I’m missing that could piss oilout at this rate? Is there some problem with the B/RB engines that can causethis severe of an oil leak? Aside from yanking the engine and rebuilding itagain do you have any suggestions?
We’ll begin by looking at the rear main seal. There’s a few tricks to makingit leak-free. Some builders like to install the seal slightly cocked, so oneside sticks up above the block 1/8″ or so. The theory is that the partingline of the seal isn’t lined up with the block-seal retainer line. I don’tbother with this, I just use a small daub of silicone on the seat matingedges.
The factory side seals are pretty hard to install so they are leak-free.They must be soaked in diesel fuel, etc., until they begin to swell, thenquickly slid into place. I don’t use ’em at all, instead, I just run a heavybead of RTV silicone sealer on the outside (rear.) See photos on page **.Also, you must be sure that the retainer isn’t cracked, and applying a verythin coat of RTV where the face of aluminum retainer meets the block is agood idea, too.
Then there’s the very real possibility that the problem isn’t the seal atall. It could just as easily be seeping past the oil gallery plugs, the camwelch plug, or leaking down the rear of the block from a loose or failed oilpressure sender. There could also be a crack back there somewhere, near thecam or on the China wall would be the prime suspect areas.
If you finally prove that it is the rear main seal, there are special rearmain bearings that have grooves to avoid spraying high-pressure oil directlyagainst the sealing lips.
I have also seen porous castings in cylinder blocks. The factory fix wasgrinding away some of the affected area, cleaning with hydrochloric acid,then soldering up the leaky area with a big electric soldering iron (atleast 300 watts) and special solder (30-20-50% tin/zinc/lead). Frankly,since this soldering works only on non-pressurized areas, I think RTVsilicone (with, also, extreme cleaning) or several coats of Glyptal paint,would do as well with a lot less hassle involved.