91 k1500 4.3 to 5.7 motor swap?


Jeff7076
05-02-2004, 05:36 PM
Can anyone help me with this project? I would like to know what I need to swap my 4.3 to a 5.7. The 4.3 has TBI with a 700R4 trans? The smog pump has been removed prior to my ownership. The big question is will I have to worry about the Transmission and the TBI if I get a small block with no intake? Can I use the existing TBI unit? I know I will have to change the fly wheel, motor mounts and Prom.
Any advice is greatly appreciated.

Thanks Jeff

live_&_breath_cars
05-02-2004, 07:54 PM
before u get yourself into anything i would just like u to think about a few things first.
is the 5.7 rebult or new, cus if it isn't then do that first.
next, is the engine dune up?? if it isn't then all ur doing is adding 30 hp with extra weight of the engine.

i don't want to discurage u but i want u to know that it is alot of work.
trust me i know.

i have a 93 1500 that had a 4.3 with a five speed manuel,
i did the engine swap in my garage by myself.
after i was done i had small electrical problems and some others,
to make a long story short, i'm putting the 4.3 bake in.
if i spent the money on performance parts for my 4.3 i would have been much more ahead of ware i am now.

i have way more info on it, if u want to know e-mail me at svt_cobrajet85@hotmail.com,

broughy84
05-02-2004, 10:01 PM
Your trans will have no problem bolting up....I have a 700r4 behind my 350. You will need to have a different intake because the 350 is two cylinders longer, but the TBI will bolt to the 350 intake. Just a word of advice though, my truck has a 350 in it and yes they do have a lot of power and torque, BUT, the 700r4's are not a real strong trans to be behind a V-8. I have put two in my truck. If you really want to do this I would look into having the trans done too. A 700r4 w/v6 does not have as many clutches in it as a 700r4 w/v8 does. Just a word to the wise.

Matthew Brough

chevytrucks92
05-02-2004, 11:00 PM
before u get yourself into anything i would just like u to think about a few things first.
is the 5.7 rebult or new, cus if it isn't then do that first.
next, is the engine dune up?? if it isn't then all ur doing is adding 30 hp with extra weight of the engine.

i don't want to discurage u but i want u to know that it is alot of work.
trust me i know.

i have a 93 1500 that had a 4.3 with a five speed manuel,
i did the engine swap in my garage by myself.
after i was done i had small electrical problems and some others,
to make a long story short, i'm putting the 4.3 bake in.
if i spent the money on performance parts for my 4.3 i would have been much more ahead of ware i am now.

i have way more info on it, if u want to know e-mail me at svt_cobrajet85@hotmail.com,

I agree that it is alot of work, and money, and time BUT there is no comparison from the TBI 4.3 to TBI 350. Not even close! The gas mileage is not even that much better. Friend of mine has one, just like my truck, only its a 4.3 and 5-spd and it has no power and gets about 21 mpg, and mine is 5.7 with 4-spd auto and it gets 19 mpg.

live_&_breath_cars
05-04-2004, 10:38 AM
don't get me wrong, i think that the swap is a good one, but unless ur willing to spend the money, the swap isn't gona be what u expect.

how much power do u think the 91' 5.7 for a chevy has?? and,
how much power do u think the 91' 4.3 for a chevy has??


u can do what u want, but i would recommend doing some research on the type of engine u put in, unless u are rebuilding it with performance parts.

live_&_breath_cars
05-04-2004, 10:42 AM
Can anyone help me with this project? I would like to know what I need to swap my 4.3 to a 5.7. The 4.3 has TBI with a 700R4 trans? The smog pump has been removed prior to my ownership. The big question is will I have to worry about the Transmission and the TBI if I get a small block with no intake? Can I use the existing TBI unit? I know I will have to change the fly wheel, motor mounts and Prom.
Any advice is greatly appreciated.

Thanks Jeff


forgot to mention u can't use the TBI off of the 4.3 because the fuel injectors have a different spec from one engine to the next.

live_&_breath_cars
05-04-2004, 11:41 AM
don't get me wrong, i think that the swap is a good one, but unless ur willing to spend the money, the swap isn't gona be what u expect.

how much power do u think the 91' 5.7 for a chevy has?? and,
how much power do u think the 91' 4.3 for a chevy has??


u can do what u want, but i would recommend doing some research on the type of engine u put in, unless u are rebuilding it with performance parts.
-----------------------------------------------

ok, i found that the 91' 4.3 is rated at 155 hp/230lbs
and that the 91' 5.7 is rated at 190hp/300lbs

that's only 35 hp and 70lbs.

if ur gona go stock, whats the point??

chevytrucks92
05-04-2004, 04:33 PM
35 hp and 70 lbs-tq is big gains. And like I said, there is no comparison to a TBI 4.3 to TBI 350 as far as performance.

And there is bunches of hp ratings for those engines. I've seen as high as 160 for the 4.3 and 210 for the 5.7. Either way, you could def. feel a difference in 35 hp and especially 70 lbs-tq.

broughy84
05-05-2004, 12:23 AM
My bosses truck is a 1992 Chevy Cheyenne, 4.3L 700r4. Mine is a 1988 Chevy Silverado 5.7L 700r4. I can't believe the difference in pickup, towing power, and response. There is no comparison to a SBC 350, none. I have seen some powerful, 4.3L (i just refer to them as Astro engines, afterall that's really all they are good in) engines but none and I mean none can match a SBC 350.

chevytrucks92
05-05-2004, 12:32 AM
My bosses truck is a 1992 Chevy Cheyenne, 4.3L 700r4. Mine is a 1988 Chevy Silverado 5.7L 700r4. I can't believe the difference in pickup, towing power, and response. There is no comparison to a SBC 350, none. I have seen some powerful, 4.3L (i just refer to them as Astro engines, afterall that's really all they are good in) engines but none and I mean none can match a SBC 350.

exactly.

BobM46128
05-05-2004, 01:08 PM
I have seen some powerful, 4.3L (i just refer to them as Astro engines, afterall that's really all they are good in) engines but none and I mean none can match a SBC 350.

Hey an Astro really needs a 350! :biggrin:

broughy84
05-05-2004, 01:53 PM
my father in law put one in his astro after he blew the 4.3. :) He also has a 1981 chevy 1/2ton 4x4 4 speed with a 1970 454 high performance engine in it!!!!

quaddriver
05-05-2004, 10:40 PM
to do the swap:

need radiator, fan shroud, exhaust system front to back, prom (ecm isthe same), the complete engine, exh manifolds

trust me, the bone stock 350 will rip the doors off a built 4.3 truck. I should know, I have/ have had both. (88 4.3, 88 305 converted to 350)

of note, jasper makes a 350 late model (correct heads) that makes 260hp, with the tbi setup and the stock 3" exhaust it only makes a tad over 230, but if you are going to do any work, you want the v8.

Vortec350S10
05-06-2004, 12:22 AM
I have done this swap in my '89 S10 and I have to say that actually hooking up everything isn't that hard. I had a lot of other problems in my S10- but they aren't made to fit a small block like a fullsize is.
One thing I have to point out is that I don't think the ECM's are the same. I know in S10s the 4.3 ECM ends in xxxx1062- is the model #. The 350 ECM ends in 1147 or something-I don't have one in front of me. I tried putting my 350 prom in my 4.3 ECM-it doesn't work. Maybe the ECM's in 4.3 full sizes are differnent from S10's, I could be wrong.

The nice thing about the swap is minor tweaks are all that is needed to hook up all engine accessories, hoses and wiring harness.

Also I don't know why you will need to change radiators- you should be fine. Mine cooled fine with a 4.3 radiator- which is much narrower with than one in a fullsize.
Just a few thoughts...

Jeff7076
05-06-2004, 12:29 AM
Thanks to all of you for your help. Keep the good info comming. Seems every animal is different.

Thanks Again
Jeff

Add your comment to this topic!