engine build 350 or 383?

[oregonhunter]

I am looking at an engine rebuild and have been trying to figure out what motor to build. I have a 76 K5 with a mild lift, 35's,stock gears and a TH350 with a NP 203.

My main use is to go hunting with my blazer. I don't go mud running, rock crawling, or dragging with my blazer. I am looking for a good strong motor with good low end torque for those unexpected times. Would I be smarter to build the 383, or stay with a 350?

Of course fuel millage ain't going to be good the bigger I go, but what would a mild 383 get me for fuel millage with the setup I have?

 

[4X4HIGH]

For your intended use i would say stick with a 350 with a Comp cams 4x4 grind cam.

 

[oregonhunter]

Thanks for the info. I was leaning towards the 350, just had to ask. New at doing all this, but having a ton of fun.

 

[4X4HIGH]

383's can be fun and make LOTS of power but also aren't cheap to build and useless to have unless you really plan to use the power they make.

 

[GNERGY]

I use my burban for street driving and to take me hunting, mostly in other states. I went with a 383, cost was the same to have it built for me. It had lots of low end torque and power. I had the guy that built it put in Edelbrock cam, manifold, carb and water pump. I'd do it again if I had to get another motor.
Tarey

 

[cuervo]

I use my burban for street driving and to take me hunting, mostly in other states. I went with a 383, cost was the same to have it built for me. It had lots of low end torque and power. I had the guy that built it put in Edelbrock cam, manifold, carb and water pump. I'd do it again if I had to get another motor.
Tarey

I do some towing with mine. I have a 21 foot mastercraft and with the weight of the two I'm almost tied to a 383 build but will keep my FI system. I'll use 454 injectors and get a new chip burned. I'm sure I wont like the gas cost but at least it's down to 3.65 a gallon now.

 

[4X4HIGH]

I do some towing with mine. I have a 21 foot mastercraft and with the weight of the two I'm almost tied to a 383 build but will keep my FI system. I'll use 454 injectors and get a new chip burned. I'm sure I wont like the gas cost but at least it's down to 3.65 a gallon now.

If you build a 383 your 350 TBI unit will not support the HP/TQ numbers even using the 454 injectors, you're going to need a 454 TBI unit with the 454 injectors. My hot 350 build would not even accept a 350 TBI unit to support my numbers.

 

[dyeager535]

Build your 350 for low end torque and you'll enjoy it.

Mine has plenty of low end power, no reason for a bigger motor. Sounds like you and I use ours for about the same purpose.

Don't forget exhuast and induction though. Get some real good heads on the motor, decent compression, good torquey cam, and good exhaust (headers, unquestionably) and you will make plenty of power for a pretty decent price. Don't throw it together, research, ask questions, then buy parts. Don't let someone talk you into race motor parts.

 

[pseudomike]

I second on the 4x4 grind cams. As for TBI thebest route is to have your TBI bored out, I went with www.rvmorsemachine.com. You shouldn't need 454 injectors until you start encroaching 275HP. A good fuel pump (AEP) and a tweak of the fuel pressure regulator will work fine until that point. As for heads, if you have a low RPM grind cam for good torque the stock L05 heads will work fine. It is true that these heads flow horrible, but it's not really until 4500RPMs..which with a low end cam,a wheeler, or a tow rig is not the range you are concerned with. I would recommend the 383 upgrade wayyyy before heads if you are looking for something in the torque spectrum. I have a friend who built a 383 with stock heads and Caprice police injectors and he's pulling about 285HP and 400ft/lb of torque...that more than a 454 TBI...and he gets 17mpg. It's not the HP that going to get that 5000lb beast moving down the road it's the torque and unless you are going to the dragstrip it's gonna be wasted $$$ and effort. If you start moving more into the street/strip grinds on the cam you will need to think about the heads, and yes you will definitely need bigger injectors. IMO thats wasted power in a truck...especially a 4x4 5000lb one.

Just my 2 cents.

 

[cuervo]

If you build a 383 your 350 TBI unit will not support the HP/TQ numbers even using the 454 injectors, you're going to need a 454 TBI unit with the 454 injectors. My hot 350 build would not even accept a 350 TBI unit to support my numbers.

Well, www.paceperfomace.com sells a complete 383, 310 hp, with a chip that runs just the 454 injectors and has a warrenty so I do think it can be done.

 

[4X4HIGH]

Well, www.paceperfomace.com sells a complete 383, 310 hp, with a chip that runs just the 454 injectors and has a warrenty so I do think it can be done.

Would you like to buy some beach front property in Arizona? I've got some i'll sell you.

I researched this enough on my own late last year when i was building my new engine. The 350 TBI unit only flows around 510cfm and that's only enough to support a stock 350. Yes people do very small mods such as adjustable fuel pressure regulator and TBI spacers and Injector pod spacersand the TBI well support those mods but not really much else. Injector sizing has nothing to do with CFM. If you add more fuel you must also add more air and the only way to do that is to bore out the 350 TBI unit or install an aftermarket unit or use a 454 TBI. The 454 TBI flows 670cfm and is well capable of supporting a 383.

 

[blazin_blazer]

i don't get why every1 exclaims 383 are so expensive, sure if topend parts are used, but if thats the case an = 350 would be $$$....i can build a compareable quality 383 for aprox as 350 build, maybe extra $500 over a comparably built 350

 

[pseudomike]

Yeah and I got the brigde in brooklyn to go with it. That maybe a 310HP engine...but not if you slap your stock 470cfm TBI on it.

You will definitely need more air (especially with more cubes), so a bigger TBI is in line. I had my stock TBI bored out to 52mm so thats about 670-700cfm (slightly larger than the stock 454 tbi). You will eventually peter out of fuel with stock injectors but that all depends on you head/cam selection. I have heard that you could safely make 350HP with a tight (fuel efficient torquey) duration cam and stock injectors. I have never seen it but on paper the math works out. The stock injectors are 55/lbs/hr, running at 18psi you could probably expect 65~ish lbs/hr of fuel out of them. GM tech performance recently published that they were able to pull 444hp out of a 355ci SB with a nice tight duration cam using no more than 168lbs of fuel/hr. That would be stock fuel pressure running 454 injectors 80lbs/hr. I'll let you do the math on that one.

 

[GNERGY]

Just get a 454 Throttle body to put on it from a bone yard, thats what I did. You can usually get them for around a 100 bucks or so. Don't waste the money boring a 350 one . Just tell your chip maker that you have a 454 tbi unit on there, thats all.
Tarey

 

[pseudomike]

Just make sure you got one with a TPS and IAC that are compatable with your 5.7 ECM

 

[4X4HIGH]

Just make sure you got one with a TPS and IAC that are compatable with your 5.7 ECM

They are all compatable it is just that the IAC has a different connector and depending on the year the TPS could be different as well but Turbo City offers an adapter harness(s) for this purpose.

 

[pseudomike]

If you can find a 454 TBI unit for $100 buy it up. Thats a rare piece in my part of the woods.

 

[nsxxtreme]

Where are all of your getting your chips burned?

I recently rebuilt my TBI 350 which came out of a 87 blazer.
I installed
Double roller timming chain
flat top pistons
crane cam
roller rockers

I've got 35" tires 4.56 gears and a new 700r4 tranny

I'm ready to sell the turd because it does not have enough power. I have a 4k lb boat that I want to be able to tow. There is a highway hill that I have to go up to make it home. I have to drop the thing into 2nd and floor the damn thing just to make it up at 50mph and even then it is struggling.

My Range Rover I can pull up the hill at 70 or more. I'm desperate, I would love to keep the truck but the power is unacceptible. Any suggestions? Keep in mind I have to pass smog test.

 

[4X4HIGH]

What cam are you running (specs). Most people get their chips done from Brian at TBIchips.com

 

[dyeager535]

As for heads, if you have a low RPM grind cam for good torque the stock L05 heads will work fine. It is true that these heads flow horrible, but it's not really until 4500RPMs..

While I will concede that I haven't seen L05 heads dynoed against Vortec heads, the 40+ HP gains seen against other stock heads vs. the Vortecs aren't all going to be at a high RPM. That higher velocity and better combustion will equate to better torque as well.

Head design isn't all about flow, but efficiency of design. Vortecs and later Chev heads work better all around because technology advanced. Heads are a microcosm of their own, when looking at an engine build as a complete package. All the components of a head design need to be factored into the decision when building an engine.

No way around the better combustion with fast burn chambers vs. older. It's called quench.

Quite simply, Vortecs were only used on trucks/vans. If they weren't better for a truck motor, they wouldn't have completely replaced the TBI heads, in the same vehicles.