So im going to start digging a little further into this 76 american spec 5.3 v12. I havent found any specs to reference to for either good compression test results or acceptable cylinder leakdown test percentages. Anyone have the reference numbers or numbers from their own tests to compare to?

 

Comp pressure reading of "about" 140psi would be deemed GOOD, with approx 10% variation across one bank.

I have yet to see a PreHE V12 with compression issues. These things are robust in teh true sense of the word.

Many years of standing is the glitch, but 1 here that sat for 12 years came to life with some ATF down the bores, and some patience to manually turn it over, clockwise ONLY. This took about 3 weeks, and then fuel added, and away it went.

Leak down, never bothered. The more you delve into the PreHE the more you will understand just how good these engines really are.

 

03impala9ci,

I recently purchased a 76 pre-HE V12 to install in my 72 XJ6. I just came across this thread and wanted to ask how your ownership experience has been.
Any issues with the engine?

Thanks,
Jeff H.