Got my '65 383 done & broke in the cam today but it's leaking badly out the rear of the engine. I've never built a motor & I new to putting one together. I will be pulling it out tomorrow to try & see where the oil is coming from.

Lost about 2 quarts over running it for 20 min during break in. It had ran a while when I noticed it & I kept the rpm cycling 1800-2500 to but shut it off right around 10 minutes in to check/add oil. It was a quart low & I added 2 quarts to get it thru the cam break in period.

So it ran for 10 minutes at the high break in rpm, shut it off for 3 minutes to add oil & ran for another 10 minutes at the high break in rpm, shut it off 5 for minutes to add oil, ran a couple more minutes to set timing & idle speed.

It sounded good & idled nice after setting the timing. Hopefully shutting it off mid way thru was ok, I figure it's better than running it out of oil.

Any good info on installing the seal set-up or common mistakes?

[video:youtube]https://youtu.be/4HwZQzPHE7A[/video]

That's always a [censored] when the rear seal leaks like that. It's not too hard to fix though. You should consider just dropping the pan instead of lifting the motor back out, they come down pretty easy. You'll want to make sure that you have the seal in the right direction for starters. When putting it together you need to make sure that when you put the retainer up in place that it isn't distorting the seal in any way. You'll want to use some right stuff up both sides of the retainer and the block.

I recently had a leaking rear seal on my 505, it shouldn't have leaked but it did. What I did the second time around was install the seal so the ends of the seal were at 6 & 12 oclock positions. When the seal was in place it sat nice and firm around the crank. Then I slid the retainer up over the seal not to disturb it in any way. That's the position that I tightened it into place at. And sure enough, it was sitting closer to the rear main cap the second time around. Not a drop, bone dry by doing it this way.

If you do it this way, a very small dab of right stuff on the end of the seals where they are going to meet. Once the retainer is tight you can run some right stuff up each side of the retainer and the block. Also a little right stuff where the retainer meets the block.

This was the first time I installed a rear seal this way. I read another post here awhile back and a fellow has been installing them this way for a long time without ever a leak. Another guy tried this and it fixed his ongoing leaking seal problem too so I decided to give it a try. I'm glad that I did, I'll always do it this way going forward.

Good luck!

If you have main studs and an aftermarket windage tray that could be the problem. The studs hit the windage tray and prevent the pan from tightening down completely.

Could be the cam plug also.

I am running the stock bolts on the bottom end.

What keeps the cam from going back & knocking on that thin core plug directly behind the cam? Just curious if when initially starting the motor, I did have it 180 out & it backfired pretty good. With the hyd. lifters not being pumped much, there isn't much that would keep the cam from going back & possibly partially kicking that loose? Maybe overthinking it. I'll be pulling it tonight to see.

I was typing my big spiel when you mentioned this. Hope it's just that plug came out a little.

are you pulling the eng or just the pan? I would clean it up down there & have someone start it & you underneath & see if you can pin down the leak even if you cant visually pin it down exactly you might just pull the pan only.

Planning on pulling the engine. That's a good idae, I may just strap a GoPro under there with a bright LED light & fire it up & see if I can see where it's coming from. I can get it way up under there.

The cam gear won't let the cam go that far back.

That's good to hear.

I pull the motor last night & everything looks good around the back of the cam area.

There are no other ports to plug on the back of a '65 383 besides the 2 galley plugs, correct, nothing around the crank to plug off. The machine shop tore the block down & I rebuilt it. Looking around the crank area last night with a flashlight I didn't see any additional ports to plug.

I have pulled it apart. I came up with several things.

1st, I put the 1/2 of the seal in the block the correct direction. I put the seal 1/2 in the retainer block the opposite direction.

2nd, the seal surface is knurled, is that going to work with a rubber seal vs rope?

3rd, the rear main seal retainer block is .014 sunk into the surface of the block.

Most likely the only problem you have there is seal orientation. Too late to check if the retainer is an actual problem unless you want to pull the rods and crank but .014" don't seem unreasonable. The knurling should not have any effect if it's an OEM crank. The seal actually rides offset from the knurl.

One member I was helping just went through it with his 505 build. I think he ended up replacing the seal 3 or 4 times and finally it was good the last time - very minor leak.

The last couple of times did not do anything different. It just worked the last time.

There have been several good threads on this subject recently. I would recommend searching for them and then fully reading each of them.

I feel for you and good luck!

viton seal from 440 source and ditched the junk billet seal retainer

Is viton seal the best to use? I know viton o-rings in statik use work well but with a rotating crank shaft I don't know.

Install a new seal, both half and new side seals and then use some adhesive silicone (make sure it says adhesive sealer on the tube, not straight gasket maker ) to fill in the sides of the seal holder to the block completely and the same on the seal holder to the oil pan, rotate the crankshaft notch so you can smear the sealer in between the seal holder and oil pan Same thing on top of the seal to the block, push it in to seal that area also I've used this technique for many motors for many years with no leaks The next one will probably leak now, huh
Good luck on fixing it, you can do this
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