Anyone have any experience with the 5.7L V8? I'm just wondering what kind of an engine they are...both strengh wise, longevity and mileage? I'm assuming it has just as bad (if not worse) mileage then a 4.3?

 

Actually the 350 CI can have better MPG then a 4.3. The 4.3 is just a 5.7 with two cylinders cut off.

If you take two full size blazers (everything being equal except for the engine), the 5.7 should perform better and actually get better MPG.

 

assuming we're talking about a newer LT1 engine, I've actually heard pretty good things about the mileage. No worse than the 4.3. Strength wise they're bullet proof heard of alot of people running 100shots on DD's.
very good engine from what Ive always heard, unfortunately this is all based on hearsay I have no personal experience to relay

 

Thanks guys. I'm just curious...the specific engine I'm talking about is in a 97 burban. I've heard they can get better mileage then a 4.3, so I was just curious. I was looking online and the figures were in and around 12-16mpg.

 

If it is the lt1 version of the 350 then it will be really good.
Our high school drivers ed car was an old police intercepter (caprice classic), I believe like a 94/95.... It had the LT1 with SOOOOO many miles, and that thing would still burn out, turn it on to pass.... they sold it and some guy bought the motor and rebuilt for the track....

 

a 1997 5.7 is a good motor to drop into just about anything, depending on what it is out of it could be an lt1, or an ordinary (vortec) motor. the lt1 has issues with an optispark that is quite expensive to replace, but get good mpg, and has about 275 rwhp. The other problem with an lt1, aftermarket performance heads are expensive, due to the reverse cooling, but the camshafts are plentiful. The only difference with the camshafts is that the dowel that the timing gear uses to time the shaft is longer than the traditional 350. One other thing, the lt1 motors were only available in the Camaros and i believe the b-body car platforms. They never came in any of the pickup or suv models

 

The motor out of your suburban won't be an LT1, but it will make good power. The 350 chevy has been around for many many many years and has been used in very many applications. I would call it the most popular V8 engine in existence. The LT1 is a variation of the original 350 with revisions such as a front mount optical distributor and reverse flow cooling. An Fbody lt1 made about 275 horsepower in stock form. The corvette Lt1 made 300 horsepower. The corvette Lt4 which was basically a modified Lt1 made about 330 horsepower I believe, but i'm not 100% sure. I'm not sure on power numbers for your truck 350 either, but I would guess around 240. I know the older TBI 350s made 210 horsepower, and yours would be an improvement over that. Which when you look at it isn't really a great improvement over a 4.3. But they accept modifications better than a 4.3, and can run 300 crankshaft horsepower very easily. The aftermarket for a 350 is huge, while for the 4.3 it is very limited in comparison.

Fuel mileage will be similar to the 4.3...it mostly depends on how you drive it. I wouldn't make the change to get better fuel mileage because you may be disappointed. Your truck should get between 18-20 mpg driving it nicely with the 4.3. If you can't get close to that, theres other problems. I'm getting 16-17 mpg with the 4x4 driving through all the snow we've been having

 

Wow...an encyclopedia of comments lol. Thanks all.
I wouldn't mainly be making the switch (if I ever did) for mileage. I dream of having a full sized, so that would be the main reason. I'm a big fan of the burban's. I'm only getting 11mpg in my Blazer right now, but I found out my o2 sensor is bad. I have another one on order, so that should help my fuel economy woes. I didn't expect better MPG's as going to a bigger engine for better mpg's is sort of an oxymoron lol.

 

91chevywt is correct Alex, it won't be a LT1 in that 'Burb.

regarding fuel mileage, again, it all comes down to our own driving habits. but i can tell you for a fact that my '90 (gas) 'Burb got better fuel mileage than my '98 Blazer.

if i drove my Blazer like i did my 5.7 powered 'Burb, i sure as hell would be getting a lot worse mileage than the 13-14 MPG that i'm getting now. driving that 350 hard, i was getting 13-14 MPG. but if i drove like an old white guy (or any long hauls on the highway) i could get 20 MPG no problem.

i don't care what anyone says about these 4.3's, the newer ones aren't as good as the 1st gen ones-and i had quite a few of those.

not sure what the cost of diesel is out there Alex (it's currently around $0.96/L here), but you if you can find your Sierra or a 4th gen 'Burb with the 6.5 in it, it's worth the little bit extra to get it. i'm actually surprised @ how many 4th gen 'Burbs were bought with the diesel option, compared to my 3rd gen 'Burb.

just another avenue of thought for you to be looking/thinking about.

 

Thanks for the info Chris. I really don't expect a large mpg out of the 5.7 I was just researching to see how people who have owned one compare it to the 4.3. The results are right on par with what I was thinking.
I'm hopefully going soon to check out the burb. I highly doubt I'm going to trade. Mostly because its older, and I'm unsure of the current condition of it. I would only ever consider trading it if it was in mint condition. Anyway...still a BIG maybe, and lots of research to do on my end.