1990 350 motor

[bigbluesuburban]

I have a 3" lift, run a true 33" tire with 4.10's and no mods to the motor with just over 100K in an '89 Burb. I get a consistent 19mpg in the city and on long trips I have gotten 23mpg. I use my GPS to check distance and speed for my calcs. I run 40psi in the tires and use Regular Fuel. My truck is no rocket off the line, but it does ok... faster is always better... but I am satisfied with what I have.

I am planning these upgrades...

Throttle body spacer
MSD Ignition including Billet Distributor
Edelbrock intake
Headers
Mild Cam
4.56's

I have a K&N and I have advanced the timing a little, right up to the 'ping' point. I also wax it regularly so the air flow over the body creates less drag.

I love this truck and this motor for daily driving and most pulling. But if I make it a full time tow rig it will get a BB or a Cummins.

 

[4xcrazy]

I I get a consistent 19mpg in the city and on long trips I have gotten 23mpg.
.

UUUUM,,,,,ooook

 

[bigbluesuburban]

UUUUM..... What?

Edit/Add: Prior to getting the GPS... I thought I was getting like 22 and 26!!! I knew that wasn't happening so I got the GPS and took 2 months of mileage and fuel. I suppose driving habits may have something to do with it. But I know what I get for mileage.

As soon as I get lead footed, lower my tire pressure or start towing, my mileage drops to 14mpg instantly.

 

[4xcrazy]

dude, even when my truck was stock,,,,'89 Suburban, TBI 350/700r4 10 bolts with 3.42 gears and 31" tires,,, it STILL woudn't get but around 15-17 MPG...and i thought that was pretty damn good for a truck of this size.

When you lift them, add different gears and tires, it gets worse, NOT better.

4" lift, 4.10 gears 35" tires, same motor and trans and i get about 12, on the highway now....less the faster i go

seriously think you have some measurements alittle off.

 

[76zimmer]

My 95 Burb will get 15-16 at 70mph....3.42's and OD 31" tires. If I try to do 75 it goes down to 14, 80 its down to 13.
What a pig

 

[1990k5fan]

Got the hi-flo cat installed today. Made my motor run like new again.
:].
Also made my flowmaster sound a lot better too.

 

[bigbluesuburban]

dude, even when my truck was stock,,,,'89 Suburban, TBI 350/700r4 10 bolts with 3.42 gears and 31" tires,,, it STILL woudn't get but around 15-17 MPG...and i thought that was pretty damn good for a truck of this size.

When you lift them, add different gears and tires, it gets worse, NOT better.

4" lift, 4.10 gears 35" tires, same motor and trans and i get about 12, on the highway now....less the faster i go

seriously think you have some measurements alittle off.

And ya know what... everything you said is true. And it still doesn't change what I am getting. Just don't know what to tell ya.

 

[txfiremank5]

Got the hi-flo cat installed today. Made my motor run like new again.

Sweet Glad it helped. That's about how I felt on my old K5 when I got mine changed out. I was amazed at the improvement it made on mine.

 

[4X4HIGH]

Got the hi-flo cat installed today. Made my motor run like new again.
:].
Also made my flowmaster sound a lot better too.

Glad it cured your problem. Sounds like you owe me lunch now.

 

[rjfguitar]

Got the hi-flo cat installed today. Made my motor run like new again.
:].
Also made my flowmaster sound a lot better too.

Sounds like you had kind of a potato up the tailpipe thing going on with the old converter then....

 

[1990k5fan]

Glad it cured your problem. Sounds like you owe me lunch now.

Haha fo sho. . The guy there was really cool. Art or something. Only thing sucked was that I was stranded in the shop for like 2 hours :P.

I'm going back in a few months to get a dual exhaust setup from them.

 

[4X4HIGH]

Haha fo sho. . The guy there was really cool. Art or something. Only thing sucked was that I was stranded in the shop for like 2 hours :P.

I'm going back in a few months to get a dual exhaust setup from them.

Art, is he a black dude? If so he just recently bought into the shop and he is a pretty cool dude. He used to have a shop in Hayward called GM Classics IIRC.

Just a thing to keep in mind, if you need to pass California emissions with your rig and you get a dual exhaust it will no longer pass emissions testing. Blazers in 1990 never came with a dual exhaust in California and even if you installed a CAT on the other side it still will fail testing. If you don't believe me call your local referee and ask them. I know this first hand.

You would be better off running a single 3" exhaust over a dual exhaust any day for more torque. You should look at my exhaust before you go making any decisions about having it done.

 

[1990k5fan]

Art, is he a black dude? If so he just recently bought into the shop and he is a pretty cool dude. He used to have a shop in Hayward called GM Classics IIRC.

Just a thing to keep in mind, if you need to pass California emissions with your rig and you get a dual exhaust it will no longer pass emissions testing. Blazers in 1990 never came with a dual exhaust in California and even if you installed a CAT on the other side it still will fail testing. If you don't believe me call your local referee and ask them. I know this first hand.

You would be better off running a single 3" exhaust over a dual exhaust any day for more torque. You should look at my exhaust before you go making any decisions about having it done.

What exactly is your exhaust? Right now I just have a basic flowmaster setup. Goes from the two manifolds to the 1 pipe. I want to have it go from 1 muffler to 2 mufflers for more sound.

Also, would getting a pair of C.A.R.B. Legal Headers help my motor alot over the stock manifolds?

 

[rjfguitar]

What exactly is your exhaust? Right now I just have a basic flowmaster setup. Goes from the two manifolds to the 1 pipe. I want to have it go from 1 muffler to 2 mufflers for more sound.

Also, would getting a pair of C.A.R.B. Legal Headers help my motor alot over the stock manifolds?

Scott is completely correct. dual exhaust with dual cats is illegal on our K5's of this vintage. I originally thought it was really stupid, you'd think two cats would make the exhaust even cleaner. I think I later heard once that splitting the exhaust up in half only lets half the heat flow through the Cat, making it not work as well. The hotter the cat gets, the better it does.

You [could] leave your y-pipe (thats the pipe you mentioned that comes down from the manifolds and joins into a single pipe) and have it go through your new cat and then "Y" back out into two mufflers. This still though would be a hokie dual setup and you would be better off with a single 3" system, close to what you already have.


I wouldn't mess with headers. You aren't going to really see much for a SOP feeling out of a set and they won't do much for sound as good headers loose that "tiny" header sound because quality headers are built out of thicker guage steel. Headers don't do much on a stock motor, but they do work well with a built engine.

 

[4xcrazy]

I think I later heard once that splitting the exhaust up in half only lets half the heat flow through the Cat, making it not work as well. The hotter the cat gets, the better it does.

DING DING,

and i believe this is a main problem as to why i cannot get my "81 C-20 to pass emissions either (the sniff test) P.O. had duals installed with two cats, i can literally reach up under the truck while it is running, and touch those cats, similar to a muffler,hot, but NOT VERY HOT.

want a dual look, install the y-pipe, run it through a single cat, single muffler and dual out the muffler out the back or the truck..just my opinion

 

[1990k5fan]

So what should be my next motor upgrades?
Intake?
Have the fuel injectors cleaned.
I'm going to get new spark plug wires too because mine are original.
What else?

 

[4xcrazy]

So what should be my next motor upgrades?
Intake?
Have the fuel injectors cleaned.
I'm going to get new spark plug wires too because mine are original.
What else?

I think you should go all out, and just spend the money on that right foot replacement, there is this carbon fiber unit, looks really cool, and is super light weight. Will help with your fuel mileage, and let your motor last longer.

 

[1990k5fan]

I think you should go all out, and just spend the money on that right foot replacement, there is this carbon fiber unit, looks really cool, and is super light weight. Will help with your fuel mileage, and let your motor last longer.

Haha. I'm just trying to get ready for blazerfest in Hollister. :P But really, what should my next engine upgrades or maintence be? I'm planning on getting the injectors cleaned in the next week or so and I'm looking for a guide to try and clean them myself.

 

[rjfguitar]

Haha. I'm just trying to get ready for blazerfest in Hollister. :P But really, what should my next engine upgrades or maintence be? I'm planning on getting the injectors cleaned in the next week or so and I'm looking for a guide to try and clean them myself.

Plugs, wires, cap, rotor are important. I'd consider an aluminum intake as it should help you gain a few ponies along with shedding some weight up front.

 

[4X4HIGH]

Plugs, wires, cap, rotor are important. I'd consider an aluminum intake as it should help you gain a few ponies along with shedding some weight up front.

ALL TBI manifolds are aluminum.