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Re: 1994 BMW 740iL (archive)

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Posted by David F on April 06, 2001 at 09:18:56:

In Reply to: 1994 BMW 740iL posted by Hanif on April 06, 2001 at 03:54:16:

The nickelsil (sp?) blocks are the reason people replace engines instead of re-building. The cylinder walls on the nickelsil blocks are damaged from the sulfur in the gasoline. I suppose you could install cast iron cylinder liners on a nickelsil block when rebuilding (new pistons would be required). Otherwise, you would need to purchase an alusil block and new pistons/rings.

To be wordy and expand further, you could bore the nickelsil block and intall oversized pistons and get maybe another 100k out of the engine, but to me this would be throwing good money after bad. Also, using the original pistons in a new block is NOT suggested as the piston and blocks wear together to a slightly oval condition (more wear on load side of piston). If the original pistons are used in a new block, you will wear the block quickly and have compression/oil control problems.

With all this said, I probably would look for a used alusil engine from a salvage yard. I would crank the engine on the stand to check compression, pull the valve covers to inspect the cam lobes, etc. I have seen a complete V8 engine in the warhouse of the salvage yard I use here in Austin, so they are available and fairly common (question of course is whether or not the block is alusil or not).

I just came back from the dealer and purchased a 1994 740iL with about 128000 km mileage clocked. But the V8 still sounds and idles perfect. Well, from what I can see anyway.

I read some posts about some people changing their engines instead of doing an overhaul after a couple of hundred thousand kilometres.

Any idea why changing the engine is better than repairing it? I thought the V8's are pretty durable except for the short block leakage problem which can be solved by changing to the Alusil short blocks.

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