Cylinder block rear main seal retainer groove

While rebuilding my ford 640 I replaced the rear main rope seal with a 2 piece neoprene seal. Instant leak. I tried different brands of seals but with the same results. The problem was that seal groove in the block was deeper than the seal. The block groove is 2mm deeper than the cap groove which was not detrimental to the rope seals. This allows oil to leak around the neoprene seal and block.

After some research I found that this was a common problem with the Ford Y-Block autos engines (312, 272 & 292 Ford engines) I spoke with 2 famous Y-Block engine builders (Ted Eaton and Don Hyde) and they told me it would be best to use the 2 piece neoprene seals and stay clear of the rope seals even if I went with the best rope seal (Best Gaskets). They had no solution to my problem as they machined their blocks to accept a dodge 318 seal which would not work with the tractor application. They both recalled a shim kit that was once available but could not recall anything further.

Can anyone comment on the seal grove shims? I am thinking I could manufacture a shim (metal, fiber) to take up the additional space in the block and then seal the shim and rear main seal to the block and cap with oil resistant RTV. Has anyone tried this or have any other suggestions?

I had not heard of that problem, but if you have the means to make a shim, that would be the only way I can see to make the neoprene seal work.

Or just go back with the rope seal. Rope seals work if they are properly installed. That's the problem, so few people know how or are not patient/willing to go through the pains taking process to get it trimmed right.

Anyone thinking of replying should consider looking at all of the history to this problem in order to see what has been going on. It appears that pburchett has a one off 134 block. There are about six pages in the archives.

Hey Showcrop! Why are you trying to get people to to not respond to my post? I truly need help with this one problem.

I am sorry that "you" do not understand and have the misconception that my crank has the oil slinger broken off and think that I have installed the seal in the wrong groove. As I have stated before "if you can show me a 640 crank with the oil slinger I will buy it!"

If you will look at the photo I attached you will see I am installing the seal in the groove with the RED arrow. If this is the incorrect position I will eat my words and buy you dinner.

If you will notice the yellow arrow you will see the bevel in the crank that acts as an oil slinger and helps return oil to the oil groove in the block and back to the oil pan.


I hate to be RUDE but you are providing nothing but inaccurate criticism and if you "Showcrop" have nothing helpful to say... say nothing at all.

I'm with Steve on this. It is all in the working the rope seal in the groove and getting it trimmed correctly. If done right will last just as long as any other seal will.