Hi everyone,
Is there a way to replace the rear main seal in a 1968 GT 390 engine without removing the engine from the vehicle. I have an automatic transmission and power steering if that matters. I see there are YouTube video’s out there but I could not find a 390 motor example with the motor still in the car. It seems very possible but I thought I would ask here. The engine was rebuilt but I think it sat too long before it was started and running again.
Sure. Follow the directions in the shop manual.
Page 8-111 in the '68 shop manual. Shockingly, the older two-piece seals are friendlier for in-car replacement than the later 302 one piece seal that you tap in from behind.
Order a Mahle seal kit, the side seals are soft, the nails are correct, and the seal is high quality.
The Felpro version was recently changed, the seal itself is good, but the side seals are hard and nails don’t fit well and are sharp. I toss them now from engine kits and order Mahles
Thanks for all the input especially on the better seal. I almost ordered the Fel-Pro 2 piece seal BS-30138 yesterday.
I did not have the Shop Manual with me when I asked the question but I will get the Manual back next week. I’m glad I still have the break-in oil in engine.
You’ll likely crack up when you see what Ford said. It includes “lowering the crankshaft but not more than 1/32 inch,” to closely paraphrase.
Sounds like a good outcome. Gives you a chance to inspect the break in oil, too.
Be sure to either oil or grease the seal where it contacts the crankshaft as it says in the text.
If the seal has been replaced with a rubber seal, you should be able to follow the shop manual.
However, if it still have the original rope seal (like my '68 did), it is likely to be rock hard and the top half will not budge.
If the rear main seal has been replaced with a neoprene seal, you should be able to follow the shop manual as recommended by Royce.
However, if it still has the original rope seal (like my '68 did), it is likely to be rock hard and the top half will not budge.
I used the recommended KW upper rear main seal removal kit - it had a punch and a Chinese-style finger cuff but was unable to remove it.
I am sure the engine rebuilder used the 2 piece rubber style seal. I just let the engine sit too long after the rebuild.
Of course, I didn’t know or plan for my Cougar to be held hostage in the Restoration Shop owner’s divorce. That held up the process a good 6 months or more. I finally had the local county sheriff go with me and my title to verify it was my car. The owner’s wife could not refuse the sheriff when he told her it was my car.
Just glad I am almost done! There a few little quirks to figure out like the fuel gauge doesn’t read more than 1/2 a tank when full. I used the original float so it might be leaking.
So as we all said before,the shop manual will get you in and back out in an expeditious manner, but let me throw you some tips to make it not leak
Before anything, make sure it isn’t the valve covers or rear china wall. Both often leak, intake gaskets if not trimmed can cut the valve cover gaskets, and some guys have a hard time sealing the China wall.
For the seal installation though
1 - After cleaning, install the cap without the side seals, seal needs to be the right orientation, and add a little oil on the seal surface and on the bearing, just a little, nowhere else
2 - With Felpros, which as I said, I don’t use anymore, you do a light interference fit (after the cap is on) with the groove it goes in. I use 80 grit on a flat block mounted in the vise sanding on the NAIL side (crank side) to make them fit. The Mahle versions need no sanding, are soft, and so far have fit nice. Put them to the side, but know which groove you test fit them in
3 - Squeeze a significant amount on RTV into that same groove, again cap is on and torqued, fill like you are trying to fill it up about 1/2 way. I like to use Black Ultra Permatex for heavy oil control, it’s readily available and marked that way on the package
4 - Push the side seal in with your fingers. You will see RTV push out of both sides of the cap. You won’t be able to clean up the flywheel side easily, but after you have it seated, wipe out the inside of the block with a screwdriver wrapped with a rag. When you see how the RTV travels, you can see clearly how this step helps the side seal do it’s job
5 - Drive the nails in behind the seal carefully, with Felpro, they are sharp and can cut and jam the side seals, another reason not to use them, Mahle nails are blunt and easy to do. Keep going until the nail hits bottom using a punch that fits in the hole well. It’s actually OK to compress the side seal a little, it will marshmallow a bit and seal tighter.
6 - Wipe up the RTV in the block a second time
7 - Put a small pea sized dollop of RTV on the top of the side seal, which is now about 1/8 inch below pan/block surface and a couple of dollops at the timing cover/block seams. I usually do the pan dry, but I use 3M Yellow to glue it to the block (on the stand) or to the pan and let it dry so it doesn’t try to push out
8 - Last, there is a notch at the rear of the FE pan, it matches a drain on the rear main cap that allows oil to drain back and not pressurize the seal. With aftermarket pans and/or windage trays, make sure that isn’t blocked by the pan, tray, or gasket. I generally have to grind windage trays, even stock Ford ones. Pans and gaskets are typically OK nowadays. Then put the pan on and finish up the job
Hope this helps