Cooked 3.9 EFI

[ChrisJC]

It's still worth getting the block pressure tested if you can. They should be tested hot ideally.

When I did mine, I made up some blanking plates to cover all the ports, then dropped the block in a tub of hot water:



Then hooked the water jacket up to an air-compressor and looked for bubbles....

Chris.

[POAH]

Si,

Your second question re increasing capacity, the 4.6 engine rotating assembly does not fit the earlier 3.9 blocks because of larger main bearing size, you can buy a 4.8 stroker kit or even larger capacities are available but are more expensive, see link to V8 Tuner at bottom of main index page.

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Kevin.

mine is a 95 block it would seem is it possible to convert that to a 4.6 since its a later version

It will still have the smaller main bearing size so it's the same amount of work and cost to convert to 4.6.

You might pick up the crank rods and piston from a 4.6 with a cracked block and have the crank main bearings machined down to the 3.9 size which may be economic.

Kevin

I don't want to do it I'm just having a legal problem with the dealer I bought the car off. he sold it to me as a crate 4.6L but I've since found out its a 3.9L block and the letter from his lawyers says its been stroked with 4.6 crank, rods and pistons.

[CastleMGBV8]

It's fairly uncommon to mod a 3.9 by the method I suggested, it was just something that could be done.

The only way to find out what you have is to have the sump off and check the balance weights which if it's a 4.6 crank should be marked as such.

The pistons may also be marked on the tops 4.6 HC or LC for compression ratio.

Kevin.