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Tech Question
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 pieces
and rebuilt it as a fairly stock motor. It has always suffered a leak from
the 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 to
spend some $ and wake this motor up. The oil leak situation (plus the solid
cam) prompted me to use a professional engine builder and the guy I chose
has 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 the
engine and dynoed it to the tune of 612 hp, 630 ft/lb. Good numbers, but
that was not my main concern. The rear did not leak on the dyno. As soon as
I bolted the motor in the car and started it, guess what? Oil all over the
floor. Twice this has happened. The second time, he used a rope seal and ran
the engine on the dyno several times to check the rear was not leaking. This
guy is very conscientious and does his best to avoid unhappy customers. So
imagine 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 of
the motor. Oil seeping out of the timing chain cover at the top, some fuming
out of rocker cover breathers.
- Leak-down testing shows 14-18% on all but one cyl - the #4 has about
22%.
- Compression test gives perfect results - 170 on all 8 cylinders.
Rick, this oil leaks out 5 drops at a time. Have you seen anything like this before? Any ideas you have would be appreciated. Peter
Peter, I'd measure the blowby CFM (volume) and/or pressure. The leakdown sounds 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:
Q.:
OK, I am desperate for your help! I have a large oil leak in a 383 that I can't seem to fix. The 383 is from a '68 truck according to the letters/numbers on the oil pan rail. It's in the '66 Charger 4 speed I picked up 11 years ago. The engine was rebuilt before I got the car, doesn't smoke at all, is quiet, and has good oil pressure. It loses 1-2 quarts every 200-300 miles! It's getting on the clutch/flywheel.
I changed the clutch and put in a FelPro rear seal setup when I got the car 11 years ago. No improvement at all! I tried the Mancini retainer setup a few years ago and again, no change at all. I had a shop do the clutch again and the rear seal a few months ago and again, no change at all. Still leaks as much as always.
No leaks from the valve covers, valley pan, oil pan, or anywhere on the engine. It only leaks when it is running. It's still getting on the clutch/flywheel so I assume it's still the rear main seal unless there is some place on the back of the engine that I'm missing that could piss oil out at this rate? Is there some problem with the B/RB engines that can cause this severe of an oil leak? Aside from yanking the engine and rebuilding it again do you have any suggestions?
A.:
We'll begin by looking at the rear main seal. There's a few tricks to making it leak-free. Some builders like to install the seal slightly cocked, so one side sticks up above the block 1/8" or so. The theory is that the parting line of the seal isn't lined up with the block-seal retainer line. I don't bother with this, I just use a small daub of silicone on the seat mating edges.
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, then quickly slid into place. I don't use 'em at all, instead, I just run a heavy bead 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 very thin coat of RTV where the face of aluminum retainer meets the block is a good idea, too.
Then there's the very real possibility that the problem isn't the seal at all. It could just as easily be seeping past the oil gallery plugs, the cam welch plug, or leaking down the rear of the block from a loose or failed oil pressure sender. There could also be a crack back there somewhere, near the cam 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 rear main bearings that have grooves to avoid spraying high-pressure oil directly against the sealing lips.
I have also seen porous castings in cylinder blocks. The factory fix was grinding away some of the affected area, cleaning with hydrochloric acid, then soldering up the leaky area with a big electric soldering iron (at least 300 watts) and special solder (30-20-50% tin/zinc/lead). Frankly, since this soldering works only on non-pressurized areas, I think RTV silicone (with, also, extreme cleaning) or several coats of Glyptal paint, would do as well with a lot less hassle involved.
Rick
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