Rear Main Seal Conversion

Hey all. The engine is at the machinist. Going .020 over on the pistons and .010 on the rod and main bearings. Wondering if I should I install a rear main seal conversion kit or stick with the rope.

If I go with the conversion, who’s should I use, Terry’s, SNG Barratt’s or Martin Robey’s.

Please share your experiences.


Rear conversion is not guaranteed leak free…just search the forum to find many who are dissapointed after doing it…then its no going back becaus the crank has been machined…just ensure that the rope seal is fitted by someone who knows what they doing…and pay attention to the rear sump real which is often found to be the culprit some who thing they have a rear crank leak…Steve

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The rope seal is cheap, the conversion is expensive.

The conversion also puts your crankshaft at risk (a little) of being destroyed inadvertently by the machinist.

I have done both a few times. I have found they both leak a little drip.

Therefore I would stick with the original rope seal, just make sure the builder knows how to size it correctly when fitting it,

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I ordered the Barret and the Terry’s kit, examined both, and then returned the Barret “clam shell” design. The Terry’s kit uses a GM/Federal Mogul Nibral seal as installed in millions of GM engines. No leaks on my engine in ten years. (I don’t believe the Robey seal was available at the time, so can’t comment). Most, if not all leak issues that I’ve read about were associated with the improper/difficult installation of the radial spring for the clamshell design after the crankshaft is installed. BTW, the machine shop I used had a plasma device that they used to bring bearing/seal surfaces back to factory specification (I asked before they machined the seal surface}. So, the suggestion that the crank cannot be returned to original is not quite accurate…it just takes money.

I spoke with Bill Terry himself before he passed. He explained that he originally developed the conversion for his race engines, as he didn’t want his power plants leaking oil onto circuits. Here’s Bill’s video.

Rear crankshaft seal conversion for 3.4, 3.8 & 4.2 liter Jaguar engines - Bing video

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A properly installed rope seal will provide perfectly acceptable results.

The ultimate upgraded rear main thread - E-Type - Jag-lovers Forums

I tend to agree with John.

None of my 4 XK engined vehicles leak from the rear seal. All have the rope seal.

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Thanks everyone!