What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

Need help figuring out exact specs. on '90 Jimmy 1500

Well modifying the existing engine for more power is a can f worms you may not want to open. The TBI computer is not the easiest platform to mess with. It can tolerate small changes, but even a mild cam can make your life a misery trying to get the tune right. The tune on the TBI motors is done with PROM chips rather than being able to tune with a laptop.

At 150K miles I doubt that 350 is in bad enough shape to need a rebuild. If it is in need a good option is a new TBI crate from GM. They're dirt cheap, and will play nice with the TBI computer.

Or, if you feel a little more adventurous you could undertake what is becoming a common swap. A 5.3 LS engine and 4L60e. 120 hp more than the TBI 350, and not expensive at all. It's not uncommon to be able to complete the whole swap with a low mile pull out engine for well under $3000...or roughly the same as the cost of a good rebuild on the 350.
 
I ran the vin for you.
VIN: 1GKEV18K0LF502709 RPO Code Description
1SC PACKAGE-OPTION 03
1SZ PACKAGE OPTION-
75A ACCENT STRIPE,RED
82D TRIM COMBINATION,CLOTH,MEDIUM DARK GRAY
82I INTERIOR TRIM,MEDIUM DARK GRAY 83K
83L EXTERIOR COLOR,SECONDARY
96U EXTERIOR COLOR,PRIMARYPRIMARY COLOR- EXTERIOR,DK. SMOKE GRAY MET.
A31 WINDOW,ELECTRIC OPERATED,SIDE
AD5 WINDOW SIDE,REAR SLIDING
AJ1 GLASS,DEEP TINT(REAR SIDE WINDOWS AND REAR DOOR WINDOW)
AM7 SEAT,REAR FOLDING AQ9 SEAT,FRONT BUCKET,DRIVER,PASSENGER,RECLINING
AU3 LOCK,SIDE DOOR,ELECTRIC
AXP VIN IDENT POSITION, MULTI- PURPOSE VEHICLE
B30 CARPET,FLOOR AND WHEELHOUSE
B32 COVERING,FLOOR MATS,FRONT AUXILIARY
B33 COVERING,FLOOR MATS,REAR AUXILIARY
B85 ORNAMENTATION,EXTERIOR,BELT REVEAL MOLDING
B96 ORNAMENTATION,EXTERIOR,WHEEL OPENING MOLDING(BRIGHT)
BB5 ORNAMENTATION,INTERIOR,HEADLINER
BC3 ORNAMENTATION,INTERIOR,INSTRUMENT PANEL(DELUXE)
BY1 ORNAMENTATION,EXTERIOR,BODY EMBLEM
C5M GVW RATING(6100 LBS)
C60 AIR CONDITIONER,FRONT,MANUAL CONTROLS CMD
D45 MIRROR,OUTSIDE,BELOW EYELINE(STAINLESS STEEL)(9.5 X 6)
F60 SPRING,HEAVY DUTY,FRONT
G80 AXLE,REAR,POSITRACTION,LIMITED SLIP
GU6 AXLE,REAR,3.42 RATIO
JB5 BRAKE SYSTEM,VACUUM POWER DISC,DRUM
K34 CRUISE CONTROL,AUTOMATIC,ELECTRONIC
K60 GENERATOR,100 AMPERE
KC4 COOLING SYSTEM,ENGINE OIL
L05 ENGINE,5.7L,8 CYLINDER,TBI
MD8 TRANSMISSION,AUTOMATIC 4-SPEED(THM700R4/4L60)
MX0 TRANSMISSION,AUTOMATIC,OVERDRIVE(MERCHANDISING OPTION)
N33 STEERING COLUMN,TILT TYPE
N90 WHEEL,15X7(CAST ALUMINUM)
NA5 EMISSION SYSTEM,FEDERAL REQUIREMENTS
NK3 STEERING WHEEL,SPORT,SOFT RIM,SIMULATED LEATHER
NY1 SHIELD,FUEL TANK
NY7 SHIELD,TRANSFER CASE
P17 COVER,SPARE WHEEL AND TIRE(FULL SIZE SPARE)
R6N CONTROL SALES ITEM NO. 14 Code Description
SLM SALES PROCESSING-STOCK ORDERS
TFE SALES INCENTIVE COMMITMENT PLUS
TR9 LAMP GROUP,COURTESY
TT4 HEADLAMPS,TUNGSTEN QUARTZ HALOGEN
U73 ANTENNA,FIXED UN9 RADIO SUPPRESSION EQUIPMENT
UP8 RADIO,PROVISIONS FOR STEREO INSTRUMENTATION
UX1 RADIO,AM/FM STEREO,WEATHER,CASSETTE,EQUALIZER,ETR,INCLUDES CLOCK
UY7 TRAILER WIRING,7 WIRE,2 LEAD FRONT HARNESS,5 LEAD REAR HARNESS
V02 RADIATOR,HEAVY DUTY,INCLUDES HEAVY DUTY TRANSMISSION OIL COOLER
V22 GRILLE,RADIATOR(CHROME)
V73 VEHICLE STATEMENT - US/CANADA
VE5 STRIP,FRONT AND REAR BUMPER IMPACT(BLACK)
VG3 STRIP,FRONT BUMPER IMPACT
VG5 STRIP,REAR BUMPER IMPACT
VR4 TRAILER HITCH(WEIGHT DISTRIBUTING PLATFORM)
X6Z HUB,LOCKING AUTOMATIC XUZ
YD3 AXLE FRONT (BASE EQUIP) FOR SCHEDULING GVW PLATE
YD6 SPRING,REAR(BASE EQUIPMENT)
YE9 SILVERADO/SIERRA CLASSIC/SLE PACKAGE
YG3 MOLDING,BODY SIDE AND WHEEL OPENING(BRIGHT)
YUZ TIRE REAR 31X10.50R15LT/B WOL R/PE ST TL OOR (9591094)
Z75 SHOCKS,FRONT QUAD
Z82 TRAILERING PACKAGE(SPECIAL)(REESE TYPE HITCH)
Z88 GMC TRUCK
ZQ2 DRIVER CONVENIENCE PACKAGE
ZQ3 DRIVER CONVENIENCE PACKAGE II(MERCHANDISING OPTION) ZUZ
ZW9 BASE BODY OR CHASSIS ZY4 COLOR COMBINATION,DELUXE(TWO-TONE)

Getting back to the engine question. If the engine isn't a 2 bolt it's not the end of the world. You won't be building the engine to a high enough level to require the need of a 4bolt main block. Keep this in mind only the middle three main bearings are 4 bolt, but the front and rear are still 2 bolts.
 
tRusty and ZooMad, I guess first I should say that since there's so much to do to get this thing anywhere near "tough" that I'm going to keep it as original LOOKING as I can. Right now it's all numbers matching. Please remember that I'm trying to deal with a 35 years of technology advancement. I was using the casting number and the part number interchangeably. I'm not used to that making much if any difference. There's a world of difference in the way things were made and what the equipment did. The radio was the highest tech piece in our cars That has alot to do with me asking questions that sometimes seem like I'm splitting hairs. I guess that you're going to have to explain things like I'm a complete noobe, I guess that I really am. That being said:

I know that a 2 bolt block is ok. I would just prefer a 4 bolt. In my research it has been said that a nodular iron crank is ok up to 4 to 600 H.P. depending where you get your info. Iron cranks must have really come a long way. You would have preferred to not even have one in your lawn mower then. Billet was the only way to go, if you wanted it to last or if you were really going to use it for what it was designed.

The power that this engine had went down pretty quick for a 350. I've got and have had several to compare it to. I never did a compression check or really any type of trouble shooting to see why and that's my fault. Between the weak engine, heavy tires, tall gears (3.42) and having to run it in drive not overdrive and my foot had alot to do with the 6 mpg.

I thought that as long as I stay reasonable with the build, that I could use alot of the stuff for heavier duty trucks or whatever from the same era to offset the higher performance stuff like the cam as long as I don't get stupid.

I'm thinking things like shorty headers and a real dual exhaust system (X pipe?), maybe a little head work (smoothing and port matching, maybe a valve job and springs, depending on what I can gain, probably some other stuff), a little bigger injectors like they would use on a engine for a custom van. A little more bottom end torque to help getting the heavier van moving. Definately a high volume/pressure oil pump. I'm thinking as long as I don't push it too far that I can do this type of stuff without having computer problems. What do you think?

Oh, and while I'm thinking about it, Thanks for running my VIN and getting me the options list, ZooMad.

I guess that I'm asking if I'm headed the right direction to keep the original look and get better performance without it tearing itself to pieces?

It's supposed to have a 9.25 compression ratio, maybe up that slightly,thin head gasket or a clean up cut on the block and heads. Rocker arms, stuff like this keeps coming to mind and I'm thinking that most wouldn't affect the computer. If you see things that will be a real problem, please point them out and if you know a way to accomplish basically same thing.

Sorry that I went so far but, better that I get some idea of what's involved now than later, Thank You again, Paul
 
2 things. First, the weight of the tire is not what's throwing your gearing off. Your gearing is off because the tires are of a larger diameter. Heavy tires do take more energy to accelerate, so starting and stopping will be minorly affected. But the size is what's kicking it out of O/D.

Second, it sounds like if your engine was running properly you would have the better performance that you're looking for. Mods may not be required, figure out what's broken before you get too far down the rabbit trail...
 
Good points,I had to go look at the tires to be sure of the size. They are 33-12.50R15LT and they have deeper tread than what was std. when I bought them. An old friend owns a tire store and gets my tires for me. Now the standard tread depth isn't as deep as it was a few years back. It's about 1/8" shallower, if I remember and that was just before it was parked. At one time it had 35-12.50 MT's on it. I only did that once, you could tell that the truck was straining to pull them, especially in traffic. My wife worked downtown, so it was in alot of traffic. My buddy tried to warn me, but I didn't listen. I had to run lower air pressure to keep from eating the centers out of them. That must have been around '96 or so.

There may be something wrong with the engine but, it never has seemed to have the power, torque I guess that it should have had, even new. I had bought a '89 Z-71 the year before the Jimmy was given to her and it couldn't come close to it. They both had the same engine, gears, etc. My P/U was a step side so it had a fiberglass bed at least on the outside.

Any idea what may have been off when it came from the factory? I do want to run a compression test. The problem of the oil return holes getting clogged, was there a set of heads that were worse about that than others? If she drove it alot where it didn't get up to temp, I could understand, but that wasn't the case.

I guess that I'm going to try to start it after I get the top and rain gutters done. I've asked before and don't remember the answer. I want to disconnect the whole fuel system from the throttle body. Can I gravity feed the injection enough to try to just crank it and let it idle for a minute? I'm planning on pulling the fuel pump fuse too. If there's anything else that you can think of , let me know. I just thought about it, I haven't even tried to turn it over by hand yet. I hope that it's not seized. I know that I can spray oil into the plug holes but I'd just rather that it's not necessary.

I ought be out side working on it, but I'm lazy and it's too cold to paint so I don't want to sand. At least that's my excuse today.

Paul
 
Switching from 31" to 35" tires is like adding a 0.88 overdrive to every gear. It wouldn't be so bad if you started with factory 3/4 ton towing gears (4.10 or so), but with 3.42 and overdrive it's a recipe for misery. You had no gearing to spare, the factory had already set it up perfectly for smaller tires.

This is the first thing I would adjust if I were wanting more power. You'll never have enough power at 900RPM, it just isn't spinning fast enough.
 
And I'll repeat what others have already said. You CANNOT gravity feed a TBI system the way you can a carb. It requires pressure to operate. And if you want it to run smoothly, it requires steady pressure.
 
I knew that I had asked the question re: gravity feed, I just couldn't remember what I was told. My memory is hit and miss. I'll remember next time. I can use starter fluid (ether) just to hear if it will fire can't I?(I don't remember if I've asked this before or not)

I only put 35's on it that one time. That was about 3 sets ago. It's got 33's on it now. So, I guess that I've got about a .44 overdrive. Until recently, because of my beliefs that towing packages still had lower gears like they used to, I really thought that I had more gear. I should have checked. I really thought that it had at least something around 3.70's and maybe even up to 3.90's. I'm not going to throw these away if they are ok, I'll try to sell them. They were put on less than 1K before it was parked. There aren't any dry rot cracks in them now, that might change after I drive it. Where it's parked the sun can't get on the tires and I'm hoping that helped.

I guess that I'll siphon the tank, then drop it so that I can really clean it out and check for rust.

Thanks
 
Not 0.44, take 31 divided by 33 to get 0.94 ratio. A 6 percent change may not sound like much, but it is enough to make a medium difference. For reference, switching from 3rd to 4th with your 700R4 takes your engine speed from 1 down to 0.7. So the .88 drop you briefly tried is like shifting each gear ratio by almost half of a gear (1st is like 1.5th, 2nd is like 2.5th, etc). Being half a gear behind would make most 1/2 ton trucks sluggish. 33s shouldn't be terrible, but you are at least moving in that same direction.

If you want power with your larger tires, you will want lower gears like you said. 3.73 and 4.10 are both really common GM ratios if you decide to redo axles. Or you can decrease the tire size. Or you can live with the current situation.
 
Yes, you can start & run the truck on ether. Don't be surprised if it throws an error code for low fuel pressure or something similar. And the ECM will probably start playing with control variables to try to stabilize the variable burning that will result from tampering with the fuel supply. So it might throw a few codes. But it will be fine.
 
-26 C here this morning, I'm not painting or sanding anything either. :D
 
If the ratio's had been like I thought they were, I'd be fine, but you know what they say about hind sight. As far as the starter fluid, all I want is to hear it fire, not even run. Before I get much farther, I'd like to have a little reassurance, that's all. Won't the computer reset the codes if I leave the battery disconnected for an hour or so?

If I can get the engine to run like I think it should with 150K miles I don't think that the tires (aren't they 1 size larger than stock?) would be a real problem now that it won't be in traffic very often. When it was parked, gas was $3 or more per gallon.

Have you heard of any problems of the oil drains in the heads having problems with clogging? The mechanic said that he had to scrape the sludge out of the heads and like I said it's never had a tendency to run hot, excessive short runs so it doesn't get up to temp and we used good oil.

I'm going to try to turn the motor a little by hand in the next couple of days just to see what I've got.

Thanks, Paul
 
scpaul said:
If the ratio's had been like I thought they were, I'd be fine, but you know what they say about hind sight. As far as the starter fluid, all I want is to hear it fire, not even run. Before I get much farther, I'd like to have a little reassurance, that's all. Won't the computer reset the codes if I leave the battery disconnected for an hour or so?

If I can get the engine to run like I think it should with 150K miles I don't think that the tires (aren't they 1 size larger than stock?) would be a real problem now that it won't be in traffic very often. When it was parked, gas was $3 or more per gallon.

Have you heard of any problems of the oil drains in the heads having problems with clogging? The mechanic said that he had to scrape the sludge out of the heads and like I said it's never had a tendency to run hot, excessive short runs so it doesn't get up to temp and we used good oil.

I'm going to try to turn the motor a little by hand in the next couple of days just to see what I've got.

Thanks, Paul
Click to expand...

You can clear the codes via the ALDL (On Board Diagnostics) connector. But I think you should use them to your advantage. If something is wrong, you want whatever info is available. Often the ECM can tell you what's wrong a bunch faster than you could otherwise diagnose the problem. I'd pull whatever codes are there before you try cranking it. And pull codes whenever the Check Engine light comes on. It's trying to tell you something, and that knowledge can be really handy.

I haven't personally had a problem with clogged oil drains on any of the heads I've worked on. But that doesn't mean yours will be like mine.
 
I'll look it up and write the procedure down before I do it. Refresh my memory on this one, do you have to short 2 pins in a connector or turn the key in a certain sequence, it's been along time, any other tips?

I guess that I should read them before I corrupt them by bumping it over with starter fluid.
 
I'd bet campy is on to something with the doggy power being due to the larger tires and less than optimal gearing.

I'll second what Trusty has noted too. 150k miles the engine probably isn't worn that bad. It's a good idea to try to get it running before blowing it apart for a full blown rebuild. If it's sat for any length I'd bet the pump and rubber in the tank is junk. Mine was. The rubber just turned to goo.
 
It's been sitting about 8(?) years I guess. It seems like it had 1/2 tank or more gas in it. I guess that I've got to find a place to dispose of about 15 gal. of old gas. I doubt if it would even be good enough to wash parts. I agree now that I've thought about it. It never seemed as strong as my other small blocks, maybe a buddies 307 2 bbl. I don't know of any 307's that had 4 bbls from the factory. They were reliable but gutless, at least the ones I was around.
 
I ran 35's with 3.42's under my 1990 Blazer. Pretty much the same thing you have. My TBI 350 was at least as worn as yours. My Blazer has 287,000 miles on it. It was never the fastest rig I've ever had, but it did OK. I just never used overdrive and it was tolerable. I ran into a 5.3/4L60E combo I couldn't turn down and replaced the 350. I have yet to drive it with the new set-up, not quite done the swap.

Oh yeah, With the TBI 350 I was averaging 12 mpg with 75% highway driving.
 
You must log in or register to reply here.

Latest Posts

Top Bottom