4.0 block or?

Velocewest

Velocewest

Well-known member
May 13, 2007
377
0
PDX Orygun
In stock RR terms, the 4.0 is no great improvement over a 3.9 in performance, but -- it has the stronger bottom end, and (please correct me if I'm wrong) the upgraded "not as likely to leak" heads, right?

I might be able to pick up a 4.0 for a reasonable price. What's the collective wisdom about the value of having the strong bottom end for an engine build? I'm tenuous, because at 143,000 miles, my 3.9 is tight, strong and clean. It makes me wonder why I would bother to change blocks when this one clearly has stood the test of time.

My preference would be to start the new engine before the current 3.9 craps, but that's not essential. Also, if I just grabbed a 4.2 and freshened it, I could use my nearly new PS pump, water pump, and the like. The 4.0 block uses different peripherals, does it not?

Thanks,
 
A

AKRover

Guest
Velocewest said:
In stock RR terms, the 4.0 is no great improvement over a 3.9 in performance, but -- it has the stronger bottom end, and (please correct me if I'm wrong) the upgraded "not as likely to leak" heads, right?

I might be able to pick up a 4.0 for a reasonable price. What's the collective wisdom about the value of having the strong bottom end for an engine build? I'm tenuous, because at 143,000 miles, my 3.9 is tight, strong and clean. It makes me wonder why I would bother to change blocks when this one clearly has stood the test of time.

My preference would be to start the new engine before the current 3.9 craps, but that's not essential. Also, if I just grabbed a 4.2 and freshened it, I could use my nearly new PS pump, water pump, and the like. The 4.0 block uses different peripherals, does it not?

Thanks,
Click to expand...
Wasn't the 4.2L only found in 95 LWB vehicles? If so that would make it a serpentine belt engine so I don't think you would be able to use your water pump and other stuff.
 
Velocewest

Velocewest

Well-known member
May 13, 2007
377
0
PDX Orygun
To be clear -- I'm definitely building an engine, at least a new bottom end. I'm setting up MegaSquirt on the current engine to get the bugs worked out, then I want a torque upgrade.
 
Velocewest

Velocewest

Well-known member
May 13, 2007
377
0
PDX Orygun
AKRover said:
Wasn't the 4.2L only found in 95 LWB vehicles? If so that would make it a serpentine belt engine so I don't think you would be able to use your water pump and other stuff.
Click to expand...
4.2 started in NAS in '93. Block is the same as the 3.9. I could build a 3.9 into 4.2 or use an existing 4.2 block. The peripherals are all interchangable from 3.9 to 4.2. I'm pretty sure the 4.0/4.6 block will not use the 3.9 PSP/WP.

Tony
 
P

Paul Grant

Well-known member
Sep 8, 2004
3,180
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CT
My case is a bit different but I took a 4.0L long block out of a Disco and put it in my 1985 Range Rover. I used the 3.5L engine cover and all the ancillaries fit with no problem.
 
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