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View Full Version : 383 rear main seal leaking?


BILL STRASSBERG
11-10-2004, 05:46 PM
I have replaced seal twice now, the second time i installed a new seal retainer and seal kit from Chrysler. Slowed it down but still is leaking? I have made sure that 1st seal was installed correctly which it was, also using sealer to assist, 2nd seal i did not remove crank but did have engine out, made sure once again that seal was installed correctly, using sealer, using seal install tool as to not tear seal when going into block, also i made sure crank had a smooth surface. I can drive car about 40 miles come home and oil has leaked out covering tranny pan and mount, may dripp a little on floor while sitting after driving, also if i drive it nice no hard runs it does not leak at all or if i wipe up oil before i put into garage it wont dripp anything. Seems to be only when hard running, any suggestion would be a great help as it sucks to RR engine RR seal and find out it still leaks. Thanks to anyone with suggestions.

MoparMarcIdaho
11-10-2004, 06:13 PM
How is your thrust bearing wear surface on the crank?Had one once that still moved some with new inserts causing a similar situation. :shrug:

waldo67
11-10-2004, 11:23 PM
think about it if you dont run the bag of it it dosent leak sounds like to me the crank area is getting pressurized under a hard load and pushing the oil out did you go through the engine if so id check the ring end gaps to make sure their not all lined up letting the crank area pressurize the and pushing the oil out or put in some push in breathers and see if it helps relieve the pressur or if its not a fresh engine could be alot of blow by doing it

robboski
11-11-2004, 08:52 AM
another possibillity would be wear on the cranks seal surface. if you are running a h v oil pump or h p oil pump and this surface is worn the pressure can push past the seal especially during higher than normal rpm's when the pressure is usually increased.

BILL STRASSBERG
11-11-2004, 03:16 PM
The oil pressure in this engine is 75 psi, Im using 20w-40w valvoline race oil, engine has about 100 miles on it. I assembled it myself, I did align rings, and rings end gap was good. I do wonder about high oil pressure, I do have engine breather hooked up with pcv valve, and inlet filter on other valve cover, Im using Mopar performance alum valve covers with baffles on all four holes two fill holes and two breather holes. Engine does not smoke, or seem to burn oil. Maybe I should lower the oil pressure? Or should I think of a better way to scavenge engine pressure?

MoparMarcIdaho
11-11-2004, 03:21 PM
How much crank end play do you have?When the crank lives in front of a 4 sp,pushing the clutch can wear the thrust bearing wear surface sometimes.

JoeGrapes
11-12-2004, 06:30 AM
I'm sure I know what your problem is. I have had the same leak in both 383 and 440. The factory seal was a rope seal. But the replacement is a two piece rubber one. On the crank where the seal runs are little serations. Fine little lines that have to be polished off before you can use the new seal. Unless of coarse the crank was ground. I've tried every thing. Even milling .01 off the retainer. But it always drips. Not enough to see an oil loss but just enough to be embarrasing. I didn't learn this untill after I built the motors and I'm not about to pull the crank out so for now I just live with it. And keep a rag with me, lol

BILL STRASSBERG
11-12-2004, 10:34 AM
Hey, now that sounds like a good idea. I do have those serations like you say. I did wonder what those were and if I should do something with them but I was told by others to leave them alone. Im like you so far I removed the engine once but for now I have a rag with me.

JoeGrapes
11-12-2004, 06:36 PM
Hey Bill. One thing, 75 psi is kinda high. Mine runs right where Mopar said it should be at 55 psi. If you lowered the psi it might leak a little less. But anyway I came up with a band aid way to solve mine. I figured since I couldn't stop the leak then catch it. I have a 4 speed so I took the insection cover off and with some 1/4" felt I got from work I made a gasket for inbetween the cover and the bell housing. I cut little pieces of tubing with a ID the size of the mounting screws and after punching out holes in the felt for the screw I put the spacers in so that when the screws are tight they won't crush the felt. The drips just get absorbed into the felt and every ounce in a while I take it off, clean the felt, and put it back on. It sounds wierd but it works and it's a whole lot easier than pulling the crank out again.

GaryS
11-12-2004, 06:52 PM
My experience with big blocks is that they tend to leak around the back side of the seal. I now apply a thin layer of sealer between the seal and the retainer and have not had a problem since.

I wouldn't do anything to the machine marks on the crank. I've been told those are cut in a pattern to help direct oil back into the engine.

23T
11-12-2004, 08:27 PM
Try to get the psi down to 55-60 and drive it like your ex is after you for hup-teen $$$$ in back support

BILL STRASSBERG
11-15-2004, 12:45 PM
Yeh I did talk to someone about marks in crank sounds like they think they should be there too, but I also was surprised about the rope seal theory. I did not think these had come with rope seals, but maybe they did. Good idea on felt for leak control, and lowering oil pressure might be an avenue to venture. Again thank for all ideas something to think about before I take that dam thing back out again.

DavidA
11-15-2004, 03:15 PM
Bill

I am having the same problem with my 383. It was recently rebuilt and the Oil pressure is around 55psi once the motor is warmed up. I installed a brand new High volume pump (Fedral Mogul) and new everything else.

I am putting some miles on the motor before I decide whether to replace the seal. It is interesting that there has been quite a few people on this board who have also had a exactly the same problem with the Mopar big block. Obviously these rear seals are not easy to install with no leaks. To me the whole set up of the rear retainer and seal looks a little crappy...some kind of after thought ??

Anyway I talked to a local engine re-builder who specializes in Mopar race engines and he always now installs the Indy style rear retainer and seal. He said he has good success with them. Much better than the stock one. They can be purchased from Mancini Racing and probably others. They are a little more expensive (approx $70) but if they work that is what I'll be using for my replacement.

The felt idea was very novel and I might try that as well. However it is only hiding the problem.

I hate that little drip after taking the car out for a run !!

Cheers and good luck.

MoparMarcIdaho
11-15-2004, 03:27 PM
The local postmaster has his dads 85 S-10 and it started puking out of the rear main recently and it was rope seal in 85 which surprised me.In order to replace it with a neoprene setup he purchased some special glue to bond the seal halves together.Ive always just used rtv hi-temp but this is special stuff for this application he said.The only b\rb engine I ever had leak was my very first one and I had put the seal in backwards.That was in 77.every one I have done since has been just fine and had the directional grooves in them also.An old used car lot trick is to dump some brake fluid in the oil-it will swell the seal and usually stops the leak.Do so at your own risk. :idea:

DavidA
11-15-2004, 03:42 PM
I assume those "Stop Oil Leak" products also do something similar but I am a little nervous to put anything into the oil after spending a lot of money and time on my new motor.

MoparMarcIdaho
11-15-2004, 03:58 PM
I agree-new pts shouldnt need anything

eckertt@epri.co
11-15-2004, 04:19 PM
Many years ago, I read about a case on a GTO where the rear main seal really pumped oil big time. After months of work, the GTO owner hasseling the problem contacted an expert at one of the car magazines. The expert knew that the crankshaft had knurling marks to pump any oil at the rear seal back into the engine, but that the Pontiac factory had made a batch of crankshafts WRONG (by mistake) with incorrect knurling. The bad knurling was actually pumping oil out of the engine.

I am not suggesting that mopar ever made such bad cranks, just offering food for thought.

Tim
72 Cuda
360/904

DavidA
11-15-2004, 05:01 PM
Well that would be one way they could ensure the sale of more rear seal kits !!

Just kidding of course.

GaryS
11-15-2004, 05:54 PM
Many years ago, I read about a case on a GTO where the rear main seal really pumped oil big time. After months of work, the GTO owner hasseling the problem contacted an expert at one of the car magazines. The expert knew that the crankshaft had knurling marks to pump any oil at the rear seal back into the engine, but that the Pontiac factory had made a batch of crankshafts WRONG (by mistake) with incorrect knurling. The bad knurling was actually pumping oil out of the engine.

I am not suggesting that mopar ever made such bad cranks, just offering food for thought.

Tim
72 Cuda
360/904

I recall such a situation with 318 cranks back in the late 60's. Apparenty reverse rotation marine cranks are knurled in the opposite direction, and a few hundred of them wound up on the auto production line. I have never heard of that situation with big blocks

zij576ca
11-15-2004, 07:05 PM
Here's a thought for you, Bill. If the oil seal retainer cap is not bolted (seated) flush against the block it will leak. This can happen if main studs are used rather than bolts. The studs are just long enough that when the retainer is bolted down it comes in contact with the ends of the studs on the #5 journal and does not seat properly, allowing oil to get past the seal. You didn't say if you are using main studs or bolts in your engine, but this might also happen if the bolts used have thicker heads than normal. If the Indy type retainer has reliefs for the bolts/studs then using this retainer may be your answer.

Rare TA
11-17-2004, 11:26 AM
When I put togather the 383 in my RR I put a beed of hi-temp RTV arpund the seal cap. Mine has no leaks or drips from the engine at all. I put 3500 miles on this moter this summer and it has 70 psi on the highway and idles at 35 psi. I see nothing wrong with having good oil psi. I have a friend who's car idles a 5psi and runs down the road at 30psi. Now that would make me look into the oil system. He says it's got oil psi so there's nothing to worry about. He has a point I guess. I do like the felt idea, good going!

Just my .02

383bird
08-21-2012, 09:54 PM
just rebuild my 383 40 over 525 lift cam 440 stock heads team g manifold 750barry grant double bumper.I am not a pro builder but i do my best for my ride .my oil pressure at idle is 15 thats super low where did i go wrong.need help please.

JVMopar
08-21-2012, 11:47 PM
What were your bearing clearences?

What weight oil are you running?

What kind of oil filter are you using?

15 psi isn't low at idle. What is the hot PSI at 3000 rpm?

cudabob496
08-22-2012, 06:40 AM
just rebuild my 383 40 over 525 lift cam 440 stock heads team g manifold 750barry grant double bumper.I am not a pro builder but i do my best for my ride .my oil pressure at idle is 15 thats super low where did i go wrong.need help please.

at idle mine is 40psig. Maybe you just need the high pressure spring for your oil pump.
Maybe you need a new oil pump?

John Kunkel
08-22-2012, 06:59 PM
Changing the spring in the relief valve won't help the idle pressure.

As stated, 15 psi isn't "low" as long as the pressure climbs with rpm...I like the old rule of thumb 10 psi for every 1000 rpm.

mopar29mod
08-22-2012, 08:42 PM
were all the galley plugs in? are all the lifters still in there bores? I have seen numerous B/RB motors bend a couple of left side pushrods and spit a lifter out of its bore

cudabob496
08-22-2012, 10:02 PM
lifter out of bore would give zero oil pressure. been there!

383bird
09-21-2012, 09:43 PM
thanks for the heads up very helpfull Thanks.

383bird
12-03-2012, 08:10 PM
Hello sorry for not replying for along time health reasons.About my low oil pressure Ispun a bearing so i changed all bearings and the connecting rod.But i did not change the cam shaft bearings.Is this apossible problem in my low pressure problem.Ichanged the oil 20 50 and oil pump high valume.Where did i go wrong.HELP PLEASE.

chirorod
12-03-2012, 08:52 PM
If you spun a bearing, something is seriously wrong. Did you make sure to align the oil holes in the bearings? Sounds like oil was not getting to that bearing. Add that to the low oil pressure and that means something is seriously wrong. I wouldn't even try to guess. I would tear the thing back down and check absolutely everything.

John Kunkel
12-04-2012, 05:27 PM
You spun a rod bearing and the crankshaft journal was good enough to run?

The camshaft turns at half the crankshaft speed so the cam bearings don't usually fail.

383bird
12-04-2012, 06:33 PM
Hey sorry idid not mention ichanged the crank off a 400block