Replace '86 350 with '94 4.3 in fullsize Jimmy

[hfranger]

I know this may sound pretty dumb, but it is all about dollars. I need to replace/rebuilt the 350 in my '86 Jimmy. I have access to a '94 Chev 1/2 ton pickup with a 4.3 in it. the rear end went out of the truck and then they blew the front getting it home. So it is a complete donor vehicle. I figure the newer V6 puts out about the same power as the carbed V8. I know the trucks history and the engine is in good shape with 84000 miles. Give it to me straight.

 

[4xcrazy]

same horsepower??? huh???? what ????


i am planning on swapping the 4.3 out of the parents 1/2 ton truck to replace it with a 350 due to its EXTREME lack of power.

they may be fine in the smaller pickups and Blazers, but i think they are too small for toting a big heavy truck around

 

[absolute]

I don't think its a bad idea...the numbers below show the power curves
the TBI will do better in gas milage especially if your using it for daily driving,
of course you could build either motor for huge horsepower and torque... but thats not what your looking for... in the end its about the greenback!

94 4.3L RPO code LB4 is rated at 160@4000rpm and 230lb-ft@2400 and should be TBI

A 86 5.7 RPO code LS9 is rated at 175@3800 and 275@1600 and is carbed

hope this helps for ya

 

[hfranger]

That's what I was thinking. it is not so much the dollars for the replace, as it is the mileage. this is a daily driver, so I need it to be more friendly at the pump.

 

[89GMCSuburban]

Worth a shot....You have to make some adapter plates for the motor mounts, I believe.

 

[beater_k20]

That's what I was thinking. it is not so much the dollars for the replace, as it is the mileage. this is a daily driver, so I need it to be more friendly at the pump.

then keep a V6 out from under the hood. the engine wasnt designed to carry a K series truck. milage on 4.3 equipped trucks are often slightly less than 305 or 350 powered trucks. my 93 C2500 with 5.7 gets 17 mpg, my uncle's 94 C1500 with 4.3 gets 15 at best. and i am the more agressive driver of the two of us.

 

[4X4HIGH]

If you're wanting to do this only temporarily until you can rebuild your engine and between now and then you don't have to pass an emissions test then i would say go for it but if you need to pass an emission test anytime soon forget about it because you cannot down size engines in the state of California.

 

[Inu-Hanyou1776]

If you're wanting to do this only temporarily until you can rebuild your engine and between now and then you don't have to pass an emissions test then i would say go for it but if you need to pass an emission test anytime soon forget about it because you cannot down size engines in the state of California.

Let me guess, even if they did allow engine downsizing, they'd fail him too just because he's put a much cleaner and efficient fuel injected engine in an earlier, originally-carb'd chassis too, right?

 

[4X4HIGH]

California law states that you may upgrade engine size but not downgrade it and the engine cannot be used from a HD vehicle into a light duty vehicle. You may install a newer engine into an older vehicle but you must use all of the emissions equipment from the newer engine as well.

 

[divorced]

then keep a V6 out from under the hood. the engine wasnt designed to carry a K series truck. milage on 4.3 equipped trucks are often slightly less than 305 or 350 powered trucks. my 93 C2500 with 5.7 gets 17 mpg, my uncle's 94 C1500 with 4.3 gets 15 at best. and i am the more agressive driver of the two of us.

My '95 C1500 with a 4.3/4L60E gets a little better than your uncle's truck - I get about 18.4 MPG. My girl's '96 K1500 with a 5.7 gets 17 MPG. The '96 weighs about 1,600 pounds more than the '95, so only 1.4 MPG less isn't really that bad. I agree with you, a 4.3 shouldn't be in a full size truck, and it doesn't get fantastically great milage as some people believe.

 

[beater_k20]

My '95 C1500 with a 4.3/4L60E gets a little better than your uncle's truck - I get about 18.4 MPG.

what gears? that could make a pretty big difference. my C2500 has 3.42s, and i believe the C1500 has 3.08s

 

[Inu-Hanyou1776]

Well, there's one bit of California law that actually does make sense! I wonder why you can't downsize engines? Seems strange to me.

Still, I bet the people at the CARB grumble and get all kinds of mad every time a SEMA company sends them a new hot-rod part that meets their stringent requirements, meaning they have to give it a number and meaning hot rodders can bolt that part onto their cars and still be emissions-legal. I bet stuff like that gets them mad, and that's a good thing.

 

[divorced]

what gears? that could make a pretty big difference. my C2500 has 3.42s, and i believe the C1500 has 3.08s

1995 C1500, 4.3/4L60E, 3.42 gears, 29" tires, weighs 4,100 pounds, 18.4 mpg
1996 K1500, 5.7/4L60E, 3.73 gears, 32" tires, weighs 5,700 pounds, 17 mpg

About 95% of my driving is highway miles. I wish my 4.3 would get better milage, but it isn't going to happen in a full size truck. I don't know why anyone would want a 4.3 - they have no power and really don't get any better milage (or sometimes less) than a V8...