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Serpentine 95 3.9l V8 Block


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Hi All,

Finally got around to starting to cleaning of the crud from my stripped engine that I removed a year ago. Still planning to fit a 4.6 at some point but measuring the cleaned bits to get a final idea on what would be required to get it running.

Any how, noticed an odd thing on the block. Aside from some excessive casting flash and other bits of heavy handed flash removal it looks as if they started drilling the block for cross bolting but then changed their mind! Some of the cast in bosses are machined flat and they started drilling one of them. Any one else seen this or is it on all pre-cross bolted serpentine blocks? The engine code is correct for a 3.9, but I would have thought the code marking would have been much later on in the manufacturing process as it's hardly durable!

Having heard stories of the block being graded with the best being directed to the Range Rovers I guess it is likely that they either mucked up and started to machine the block for a 4.6 but then realised it was a 3.9 or it was originally destined to be a 4.6 and they spotted a defect. if the latter I haven't spotted it yet.

What are the good indicators whether it is good or bad block? Slipped liners is an obvious one, but are we talking about mm here when they start to go or you can just about feel a step when you run your nail over it? The core plugs were corroded from the inside out and two of them (one of which is proving a pig to remove, centre broke out, ring still stuck) were slightly leaking. There is evidence of a lot of rust in the coolant channels which I presume has come from the back of the core plugs, pipe fittings and the radiator. Is this typical or just an indicator that the coolant had been replaced at some point with an insufficient mix of anti-freeze/corrosion inhibitor - or just left without a coolant change for too long leading to the corrosion inhibitor to loose efficiency?

Thanks for any tips!


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I'll look into pressure testing. Will need to fit new core plugs but that's not a major expense over building an engine up to fine out it's expired!

I'm aware of the interim engines having the boss in the casting but not drilled, what I found odd is that they'd started to drill for cross bolting but didn't finish. Most of the bosses have a nice machined flat surface and one of them has the beginnings of a cross bolt drilling. From what I've seen I'd be surprised if the engine had been out at any point in it's life.

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I can see what you mean - probably started as a back yard job and then thought better of it.  A good machine shop should be able to drill the block and bearing caps if you needed them.

If you are going to take it out to a 4.6 I assume you will be turning down the 4.6 crankshaft journals to fit in the 3.9 block.  A bit of grinding on the inside of the block might also be required to to get crank counter weight clearance.



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The brass thing is a simple drain tap..... so you can properly drain the block ...

As for the thing on the core plug I have no idea...... I bought this bottom end from a guy that has it built from a brand new block.... fully balanced. .. pistons weight matched.  Ross - end to end and overall etc... and balanced crank.... he had it in his cobra kit for 14k then went to a 4.6..... the other core plugs have temperature stickers and them and it's never been above about 95..... hopefully with the cam I chose and all the bits I'm using I'll have a super smooth motor.....

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