I have a '97 Blazer 4x4 LT and I am torn between replacing the 242K mile-ridden 4.3 with a new one and just beefing it up a bit or with a v8. What are the pros and cons of both?

 

How are you going to use the Blazer? Heavy towing, drag racing, extreme off roading? If none of these, I suggest replacing the 4.3 with a GM reman. 4.3L. I think some research into the amount of work to put a V8 into a 4WD Blazer with help you decide against that project.

 

Pros: Power. Cons: More work. Fuel economy suffers a bit, but not bad. Putting the engine in is only part of it. The differentials aren't up to the torque of a V8.

 

Isn't installing a V8 in the 4WD harder to do than the 2WD version? I have read that it is. I want to admit when I first got interested in buying a Blazer with the 4.3L V6, I daydreamed about a V8 swap. But when I got it and drove it, the power was surprising. I am now happy with the stock V6, since I only tow (occasionally) a light one axle trailer. RE: the fuel mileage. I am not sure you would lose much MPG with the Chevy V8. I have a friend with a 1996 GMC Yukon(stock) and he gets 19 mpg hwy, where my 2003 4.3L is only getting about 17 mpg combination hwy/city. That, of course, depends on keeping your right foot off the loud pedal.

 

A 4wd V8 conversion uses a few different parts than the 2wd, but I wouldn't say it's harder.
In some conditions, I'm sure the V8 would get better mileage than the V6, but we all love the skinny pedal.
A 50 hp nitrous kit would bring you up to the same power as the V8. Just sayin...