Is it possible to "BLOW OUT THE REAR SEAL"? (1988 LS7). When setting the mechanical advance on my MSD I saw that I had not used all of the parts I got. So I put the O rings on the dist shaft. Shortly thereafter I have a major oil leak. After all efforts failed to locate the oil leak I reread the instructions on the MSD and learned that the O rings will increase oil pressure, should not normally be used and some mods to the block in the area of the dist are required. I am using the orig factory elec oil pressure gauge which stays pegged at 60 psi above 2000 rpm so I did not notice any significent increase in oil pressure. To end this long story I have long ago removed the O rings and I still have an oil leak. Any oil leak is a bad oil leak and I am worried about my clutch. TIA
Have A Great Chevelle Day
MikEC

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Mike,
There is no actual oil "pressure" at the rear main seal area so I doubt that your using the o-rings with the MSD dist caused a problem there. As far as I know, there should not be a problem using the o-rings. They are included on most MSD distributors, including the street replacement ones. They might increase oil pressure a bit because they seal up the oil transfer area around the distributor better, but it should not be a problem. If it is indeed the rear main seal leaking it is probably just coincidence. Does the motor have much blow-by ? This will cause the rear seal to leak if the rest of the crankcase breathing system / pcv system is not working properly. Did you change anything else at the same time as the dist ? E-mail me some more details and I will try to help.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

There is a possibility of a leaking rear camshaft plug. if the pressure was increased whick the orings do it is possible it is leaking out of the cam plug at the rear of the block.

Interesting information Bill.
What, if any , would the disadvantages be of running these o-rings?
Curiousity is peaked here abit.

Sean

Sean,
The distributor body actually acts as a "seal" for the oil galley. This is why you cannot use just a straight blade as an oil pump primer tool. You must have an old distributor body or a primer that simulates one. It is a pretty snug fit in the block but does allow some oil to leak around it. Using the o-rings seals off this leakage. I would say it is of no advantage at all on a street motor, but on a race engine where you want every thing perfect, it may help. The one thing you have to do when using the o-rings is machine a groove in the distributor body to allow some oil down to the cam gear. The MSD distributors have this feature built in but stock ones do not.


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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I'm like everyone else, what you did should not have caused a problem. Can you tell us what else you might have done to maybe have caused your problem?

Check the front of your tranny where that shaft sticks out(if its a muncie) I chased a wat I thought to be a rear main leak till I pulled the tranny and found out it was coming from this shaft, if it is let me know I have discovered a fix without sending the case out to be rebored, Good Luck L89SEDAN

Thanks everyone. It seems like no matter how careful you are you seem to leave out some vital info. This is a new engine started the first time on Jul 5. About a week later I pulled the HEI dist and installed the MSD and 6AL. Another week goes by and I pull the MSD to work the timing curve. This is when I put the O rings on. No oil leaks prior to this. Now, major oil leak. Underside of car, passenger side, and collectors. New Tilton starter starts to give trouble (starter is on remote solenoid). I removed the chrome dist hold down because it looked like it may be touching the GM highrise intake and replaced it with the orig hold down. Still leaking so I pulled the dist and removed the O rings. Leak has stopped and eventually the starter begins to work like it is supposed to. While I had the car on the lift the other day I noticed oil on the frame near the clutch fork and oil leaking around the starter. This suggest that I still have an oil leak but may be that the oil I see is leftover and cannot escape out of the Lakewood scattershield, although I have shimmed a washer between the scattershield and it's front plate. This LS7 is in a 78 Elky and everything to do with this installation is new. I changed oil after breakin and changed it again at about 150 miles. Since the last oil change (after O ring removal) I have put approx 800 miles and had to add 1.5 qts (Mobile 1).

It makes perfect sense that there is no oil pressure at the rear seal, so that would not be the source under these circumstances. Would the cam shaft plug leak under high pressure and then quit when the pressure is reduced? That's scary!! I have not installed a PCV and there is little blow by that I can tell. After a few good romps the valve cover breather caps will drip a little. I will replumb the power brakes to the intake and put a PCV in to the carb this weekend. The tranny is a BW and leaks a little around the shifter fork shafts but not enough to make a mess. TIA. Mike

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Mike,
Do you have access to a "black" light ? If so GM sells some die that you can put in the oil to find leaks. It glows bright green/yellow under ultra-violet light. It is pretty cheap (about $4.00) and the dealers in our area have it in stock. We have been fooled a couple of times by what we though were rear main leaks but the die will show you exactly where it is coming from.

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Bill Koustenis
Advanced Automotive Machine
Waldorf Md

the whole purpose of a PCV is keep the pressure from forcing oil out your rear main. without one you can potentialy blow out the rear seal. there is no advantage in not running one. they also promote ring seal.
something else that could be the culprit is synthetic oil, you didnt say if thats what you had, because it doesnt build up gunk it doesnt seal around the gaskets. if there is a place it could leak synthetic will find it!
good luck!