Rear Main Seal 351W

[ralt962 11]

I have a leaking rear seal.  Not sure the cause but its fairly new two piece.  Is it possible to replace the rear seal with the trans (FMX) installed?  Drop the pan and pull the rear bearing cap off.  

What is in there is not a rope seal.  

Thanks for the help.  Have not tried this one before.

 

[Ridge Runner 1,112]

Not lubing the seal when it was replaced could cause this ,if it wasnt well lubed it could have burned after running . Aligning the ends of the seal with the surface of the block can also cause a leak ,the seal should be rotated atleast a 1/4 inch . Replacing the seal with the trany in place would be a tough trick .

[1969_Mach1 333]

Yes you change a 2-piece rear main seal by simply dropping the pan and rear main cap.  I've done it.  It was common practice back in the day when 2-piece rear main seals were common.  You have probably already realized the easiest way to remove the oil pan is to remove that tubular crossmember, and remove the steering center link and push it out of the way.  You can leave the tie rods connected at both ends and the steering spindles.  The center link will still move out of the way.

Be careful installing the upper half.  The block can cut it's being installed.  I would buy two rear main seals in case you damage one.  Lube everything and offset the ends like Ridge Runner mentioned.  Basically you don't want the seal ends flush with the block surface the cap seats against.  If you can, coat the back sides of the seals with something like Permatex Aviation Form-A-Gasket liquid sealant.  Make certain on the cap side, the hole for the pin that locked the original rope seal in place has silicone sealant plugging it.  If the pin is still there, remove it then plug the hole.  Put a very thin film, almost not noticeable, of something like that Permatex Aviation Form-A-Gasket liquid sealant on the cap surfaces that seat to the block.  If not, it's possible oil can slowly creep through that joint.  I also put a small film of the same sealant on the ends of the rear main seal halves.  I don't know if that is needed.

[barnett468 418]

2 piece seals often leak irregardless of how meticulously they are installed, especially if the seal lip rides on the oil grooves in the crank.

 

 

[Alan_Mac 48]

You can install the rear main seal successfully without taking the FMX out.  I used felpro fluorelastomer 2 piece seals with no leaking on my 351w.  Apparently Felpro no longer makes it.  I would not use a rubber main seal.  I would use this  https://www.summitracing.com/parts/cgt-c5689/overview/make/ford 

Like previously mentioned offset the edges by 1/4" . put a dab of suitable RTV  on the ends of the cap side seal.  No need for RTV anywhere else on the seals.  Make sure you install them in the correct orientation.     

[1969_Mach1 333]

10 hours ago, barnett468 said:

2 piece seals often leak irregardless of how meticulously they are installed, especially if the seal lip rides on the oil grooves in the crank.

 

 

That is true.  I have seen that and wondered if the oil grooves in the crank were contributing to a small leak.  I think the oil grooves were intended to work in conjunction with the rope type seals.

[RPM 1,190]

To you fellas who have successfully performed this bit of magic, with which tools do you grab hold of the seal end protruding, or push the seal thru? All the kings horses couldn't accomplish this task at my place. 

[Alan_Mac 48]

21 minutes ago, RPM said:

To you fellas who have successfully performed this bit of magic, with which tools do you grab hold of the seal end protruding, or push the seal thru? All the kings horses couldn't accomplish this task at my place. 

I replace a few of them successfully.  I am not sure what I used to push it far enough to grab it with either a needle nose or vice grip pliers. 

[Ridge Runner 1,112]

The pladtic seal can be tapped out with a blunt end punch ,be careful not to hit the crank . Once it is out a bit you can usually grab it with a pair of heavy pointed nose pliers .

If for some reason you used a rope seal...good luck ,a old compacted one may come out but a fresh one ,have fun

[barnett468 418]

6 hours ago, 1969_Mach1 said:

I think the oil grooves were intended to work in conjunction with the rope type seals.

yes they are. the mopars have a similar problem with the aftermarket 2 piece seal lips running on the oil grooves in the crank.

for those that don't know, there are no oil grooves in a 5.0 crank that uses a 1 piece seal.

[barnett468 418]

4 hours ago, RPM said:

To you fellas who have successfully performed this bit of magic, with which tools do you grab hold of the seal end protruding, or push the seal thru? All the kings horses couldn't accomplish this task at my place. 

yes, as was mentioned, it can be tapped around with a punch enough so there is around 1 inch of it exposed. or you can push on one end with the punch while prying the other end towards the crank. i then use small needle nose (real) vice grips to grab it with, then i push the seal towards the crank a little right where the main cap meets the crank (because this sometimes makes it easier to spin out) then i rotate the seal out while continuing to push it in towards the crank. the way those seals are designed, i'm actually surprised when they do actually seal, but the same thing goes for the rope seal.

[ralt962 11]

Thanks everyone for the great suggestions.  Looks like my next task.  I used a one piece oil pan gasket from Felpro.  I comes with those plastic screw in studs that hold the gasket in place.  Saved a lot of wrestling last time I did a pan gasket.  

But this will be a new one.  Looks like a tight space up there with the flywheel right there.  This is why these cars are such fun!

[ralt962 11]

One new Viton rear seal and a new one piece gasket later.  Started, ran for about 10 minutes.  I shut it off thinking I've got this one.  Then a small drip started followed by more.

Anyone every get a oil pan that was not a good fit?  I still have the original which I'm thinking of reconditioning.  I'm running out of ideas.  Next would be pull the motor so I can ensure i get the pan back in place.  

By the way the little plastic studs that hold the gasket, don't fit the gasket.  The studs are too large to fit through the holes in the gasket or the pan.  Not useful.  Not sure Felpro checked this out.

[barnett468 418]

so you determined it is now the oil pan that is leaking?

 

i have always used the regular style gaskets and never have a leak from the pan but it can be a bit of an an art to get them to seal. . i use permatex ultra gray in the corners and on the end seals and the bottom side of the cork gasket.

[1969_Mach1 333]

I've installed the Fel-Pro one piece gaskets using those plastic studs/guide pins many times with the motor still in the car.  The plastic pins work fine.  They are designed so both the gasket and the oil pan will kind of "snap" over the pins, hold the gasket in place, then also the oil pan in place.

Aftermarket oil pans typically do not fit very well.  Also, if the timing cover in the front is not centered very well, the entire oil pan will be off a little.  I had that happen after installing a new timing cover.  Early small blocks do not have locator dowels for the timing cover.

Even with the one piece gaskets you still need a bead of silicone sealer at the front time cover and the rear main bearing cap.

On my 351W motor, I have had better luck with the rubber rear main seals instead of the viton type.

Do you have unusually high oil pressure going on?  You do have good engine vacuum and the PCV and breather are setup correctly?  Low engine vacuum and/or improper PCV and breather system will only aid in oil leaks. 

[ralt962 11]

Not positive its the pan.  But the 2 piece main seal I just installed seemed to fit snugly.  Put a bit of sealer on the ends.  Used the brown Forma gasket #2 to seal the corners and the pan gasket.  Its odd that it took about 5-10 min. of running before it started to leak.  And the engine was off when the leak started.  Makes me think the pan in the seal area just doesnt fit tight.  

I was thinking crank case pressure.   I do have the PVC set up to the air filter.  Not a lot of vacuum but would still be negative pressure.  

1969 Mach 1, did you have leaks with the viton?  Felpro doesnt make it any more it comes from a different vendor.  The main seal I pulled out came out easily.  I could see that one leaking.  

Barnett468 do you put any sealant on the pan rails or just in the front and back seals?

thanks for the help.  Perplexing. 

[barnett468 418]

its a bit complicated to explain but i put gaska cinch on the block and top side of the cork gasket but i stop around 1/2" short of the end of the gasket and end of the pan rail. i then CAREFULLY install the cork gaskets a small section at a time if im doing it in the car and make sure all the screw holes line up. then i squeeze a small amount of silicone into the 4 recessed corners the ends of the rubber seals fit into then put a small bead on the curved area of the timing cover and rear of the block where the seals seal to then a small amount on the ends of the pan rails on the block that i did not put gaska cinch on. i then put silicone on the entire sealing surface of the pan then install the end seals then install the pan then install 1 screw on each side of the pan near the center to hold the pan in place while install the rest of the screws. other people do it differently but i have been ding it this way for around 40 years and it works for me but the pan and block must be 100% clean so i use q tips to clean the recesses where the end seals go in the block.

 

[barnett468 418]

27 minutes ago, ralt962 said:

...the 2 piece main seal I just installed seemed to fit snugly. 

unfortunately in my experience, that means absolutely nothing.

[1969_Mach1 333]

Mine always had a very small leak in that area.  Not enough to drip but very slowly build get a oil film on the bottom of the bell housing.  It got worse with a viton rear main seal.  But I think in my case the crank is an original 1969 piece and has those diagonal hatch lines where the original rope rubbed against the crank.  I've always believed it's those hatch lines causing the very small leak on mine.

What kind of oil are you using?  Since I switched to Lucas Hot Rod and Classic Car oil, 10W-40, l I haven't seen any oil film accumulate on the bottom of the bell housing.

Even with the Fel-Pro one piece Perma-Dry Plus oil pan gasket, I use silicone on both sides of it at the front and rear end seals.  I don't like to but aftermarket pans simply do not fit well enough.  The side rails I leave dry.  Works fine for me like that.

[ralt962 11]

Thanks guys.  I have 10-30 Valvoline in there now.  

The odd part of this is that it started to drip after I shut it off.  It may have taken my warm up time to move oil to that area.  Not sure, but dripping after its off means that oil has gotten past the main seal or the pan gasket.  I cant tell which.  I need to go back under and run it again.  

Next time I will duplicate what you've done.  I do have the original crank that is cross hatched.  But this is more than weeping out, its a drip.

[1969_Mach1 333]

I'm not certain if it's the oil pan or the rear main seal.  What side of the engine block plate does it run down, the engine side or the trans side?

Are you using conventional Valvoline 10W-30 or the Valvoline Racing oil?  If you have a flat tappet cam a conventional oil isn't a very good choice.  One of Valvoline's racing oils would be better if you want to stay with Valvoline.  Plus, for some reason, if your car has an oil leak, it will be worse with Valvoline conventional 10W-30 than other oils.  I don't know why, just something I've noticed over the years.  If you want to use a conventional oil, I've had better luck with Castrol GTX.  Is the motor old or new?  Just wondering why a 10W-30 instead of a 10W-40?

[barnett468 418]

Just for general info for those that don't know, when referring to automotive oil, the word "conventional" technically means non synthetic, and there are some very good non synthetic oils that are good for flat tappet cams. The most important thing to look for in any oil that is going to be used in an engine with a flat tappet cam is zinc, or zddp, or zddb in levels of around 1250 - 1400 ppm. The zinc/zddp/zddb content of an oil can often be found on the mfg's msds (material safety data sheet)or technical data sheet which can often be found on line or emailed to you by the mfg if you request it.

I also only usually only agree with 1969_Mach1 when he agrees with me, but in this rare instance, I agree with him in that, if you are using valvoline non racing oil, there are better oils out there that are better for flat tappet cams and valvoline racing oil is one of them.

 

 

 

[ralt962 11]

1 hour ago, barnett468 said:

Just for general info for those that don't know, when referring to automotive oil, the word "conventional" technically means non synthetic, and there are some very good non synthetic oils that are good for flat tappet cams. The most important thing to look for in any oil that is going to be used in an engine with a flat tappet cam is zinc, or zddp, or zddb in levels of around 1250 - 1400 ppm. The zinc/zddp/zddb content of an oil can often be found on the mfg's msds (material safety data sheet)or technical data sheet which can often be found on line or emailed to you by the mfg if you request it.

I also only usually only agree with 1969_Mach1 when he agrees with me, but in this rare instance, I agree with him in that, if you are using valvoline non racing oil, there are better oils out there that are better for flat tappet cams and valvoline racing oil is one of them.

 

 

 

I'm using non blend oil.  It was fresh when I put the pan back on.   Its not racing oil.  Its a new build and thought it would not need the 10-40 oil viscosity (after break in).  But agree something better with the flat tappet will be next.  Given I"m not going anywhere with the leak and I have and winter setting in I'll likely drain this out anyway.  Will go with the 40 weight and try GTX.  I've had luck with that in the past also.  Used Valvoline racing in all my race cars in the past.  Built a number of engines during those days and never had issues like these.  But then race car parts were much more expensive.

I broke the engine in with zinc comp cams additive and Rotella (although the diesel oils dont seem to have as much zinc as they used to).

The oil drips down the front cover of the trans cover plate vs coming down the oil pan.  There is very little clearance between the trans cover and the oil pan.  

Appreciate your help.  Its been a long time since I rebuilt a real motor.  Disappointed in the quality of the "new" parts I've bought for this.  Chased those issues all summer long.

[barnett468 418]

1 hour ago, ralt962 said:

I'm using non blend oil.  It was fresh when I put the pan back on.   Its not racing oil.  Its a new build and thought it would not need the 10-40 oil viscosity (after break in).  But agree something better with the flat tappet will be next.  Given I"m not going anywhere with the leak and I have and winter setting in I'll likely drain this out anyway.  Will go with the 40 weight and try GTX.  I've had luck with that in the past also.  Used Valvoline racing in all my race cars in the past.  Built a number of engines during those days and never had issues like these.  But then race car parts were much more expensive.

I broke the engine in with zinc comp cams additive and Rotella (although the diesel oils dont seem to have as much zinc as they used to).

The oil drips down the front cover of the trans cover plate vs coming down the oil pan.  There is very little clearance between the trans cover and the oil pan.  

Appreciate your help.  Its been a long time since I rebuilt a real motor.  Disappointed in the quality of the "new" parts I've bought for this.  Chased those issues all summer long.

the comp cams additive with regular oil is no where as good as joe gibbs break in oil or a similar break in oil. i personally would not run that engine any longer with the oil you have in it if you have a flat tappet cam, and if you do have a flat tappet cam, you may have already damaged it some. the diesel oil typically has much more detergents in it then auto oil and they try to wash the zddp off the cam and other parts during break in when it is needed the most. also, hopefully you didn't use comp cams lifters because they are crap.

 

 

 

 

[ralt962 11]

Thanks,  my break in oil has been gone.   I'm just on straight 10-30, but will jump up to 10-40 after I redo the pan seal again.  

I dont believe I have Comp Cams tappets.   But what have you seen with those?  Have you had one wear quickly?