350 TBI seized, rebuild advice needed...

[chevy666]

Hello,

I own a -89 K2500 with a 5,7 350 TBI.
The issue is that it has seized in form of the piston rings in cylinder 2 seized agains the wall, so the cylinder wouldnt move, I have picked apart the engine only to find this issue and gladly no damage against the cylinderwall was found.
Why this happend i have thought of two issues, either bad oil level or pump, this day when it seized it was approx -35 celsius so the oil might have been to thick....
So im thinking that i will hone the cylinderwalls, but can anybody suggest a rebuild kit with pistons similar to OEM? I´m hoping to change the pistons and rings without a rebalance due to the cost of that here in sweden...this is a low budget rebuild for a daily driver...

Any suggestions or advice? Am i stupid to even think of not rebalancing the assembly?

Thank you in advance and looking forward your reply!

Best regards
Sam

[Schurkey]

Originally Posted by chevy666

it has seized in form of the piston rings in cylinder 2 seized agains the wall, so the cylinder wouldnt move, I have picked apart the engine only to find this issue and gladly no damage against the cylinderwall was found.
Why this happend i have thought of two issues, either bad oil level or pump, this day when it seized it was approx -35 celsius so the oil might have been to thick....
So im thinking that i will hone the cylinderwalls, but can anybody suggest a rebuild kit with pistons similar to OEM?

How bad is the formerly-seized piston? How bad are the rest of them? High mileage? Lots of bearing and camshaft/lifter wear?

Originally Posted by chevy666

I´m hoping to change the pistons and rings without a rebalance due to the cost of that here in sweden...this is a low budget rebuild for a daily driver...

Any suggestions or advice? Am i stupid to even think of not rebalancing the assembly?

Thank you in advance and looking forward your reply!

Best regards
Sam

I'd be looking at Sealed Power hypereutectic pistons. That's probably what GM used to build the engine to begin with. GM built the 350/5.7L TBI engines with (at least) two different compression ratios, a dish piston for approx 9.2:1 compression (trucks) and flat-top pistons for approx 9.6:1 compression ('91, '92, '93 B and D body cars)

For what it's worth, I put the flat-top B/D body crate engine into my '88 K1500 using the existing throttle body, computer, and all original sensors; the truck runs flawlessly with the extra compression.

I'm sure that rebalancing is not a particular issue; and you could confirm that by weighing the original pistons, and then weighing the new pistons. The OEM balance is pretty loose-tolerance to begin with--just about any aftermarket balance shop will get things MUCH closer than GM, Ford, or Chrysler cared about doing. You'd be better off to balance the engine...but I understand why you would like to avoid that.

[chevy666]

Originally Posted by Schurkey

How bad is the formerly-seized piston? How bad are the rest of them? High mileage? Lots of bearing and camshaft/lifter wear?



I'd be looking at Sealed Power hypereutectic pistons. That's probably what GM used to build the engine to begin with. GM built the 350/5.7L TBI engines with (at least) two different compression ratios, a dish piston for approx 9.2:1 compression (trucks) and flat-top pistons for approx 9.6:1 compression ('91, '92, '93 B and D body cars)

For what it's worth, I put the flat-top B/D body crate engine into my '88 K1500 using the existing throttle body, computer, and all original sensors; the truck runs flawlessly with the extra compression.

I'm sure that rebalancing is not a particular issue; and you could confirm that by weighing the original pistons, and then weighing the new pistons. The OEM balance is pretty loose-tolerance to begin with--just about any aftermarket balance shop will get things MUCH closer than GM, Ford, or Chrysler cared about doing. You'd be better off to balance the engine...but I understand why you would like to avoid that.

Hello Schurkey!

Thank you for the reply!

One piston is missing a piece, approx 0,5inch X 0,5inch, don´t know if this append during disambly or during drift. The seized piston on the other hand is not damaged or so, just the rings had stuck.
But im thinking if it´s possible to just change that pistons and rings on the rest of them, do a quick hone of the cylinders at home and weight match the piston that is being changed, have found a Badger piston that seem to work, in other word they say it´s a direct exchange to OEM.
I know this is a "redneck" build due to no rebalancing and changing one piston.....

Do you know if the harmonic balancer is neutral on these engines?

Is there anywhere i can find info regading these engines, on how they where built and so on...

Thanks again for the reply!

Best regards
Sam

[Schurkey]

Originally Posted by chevy666

One piston is missing a piece, approx 0,5inch X 0,5inch, don´t know if this append during disambly or during drift. The seized piston on the other hand is not damaged or so, just the rings had stuck.

I'd be very suspicious of cracks and ring-land damage on the seized piston.

Originally Posted by chevy666

But im thinking if it´s possible to just change that pistons and rings on the rest of them, do a quick hone of the cylinders at home and weight match the piston that is being changed, have found a Badger piston that seem to work, in other word they say it´s a direct exchange to OEM.
I know this is a "redneck" build due to no rebalancing and changing one piston...

That can work. As said, I'd want at least two pistons.

Originally Posted by chevy666

Do you know if the harmonic balancer is neutral on these engines?

Should be. Flywheel is not, though.

Originally Posted by chevy666

Is there anywhere i can find info regading these engines, on how they where built and so on...

The only thing I'm aware of is the replacement crate engine description. This may not have been how the ORIGINAL engine was built, but it should be functionally equivalent.
P/N 12568758
Description
For 1987-1995 Chevy/Gmc trucks with 350 vin code "K" engine up to 7200 GVRW

1986 AND UP 2 BOLT MAIN 1 PIECE CRANKSHAFT SEAL BLOCK( NO MECHANICAL FUEL PUMP PROVISION)
NODULAR IRON CRANKSHAFT
POWDERED METAL CONNECTING RODS
DISHED HYPEREUTECTIC PISTONS
9.25:1 COMPRESSION RATIO
HIGH VOLUME OIL PUMP
MORSE LINK TYPE TIMING CHAIN

CAMSHAFT SPECS AS FOLLOWS:
FLAT TAPPET HYDRAULIC CAMSHAFT
INTAKE LIFT-.382" * EXHAUST LIFT.402" *
INTAKE DURATION @.050-165.9 * EXHAUST DURATION @.050-174.8
LOBE CENTER SEPERATION -111.9
CAMSHAFT MECHANICAL SPECS:
INTAKE VALVE OPENS @ -30.2 BTDC * INTAKE VALVE CLOSES @ 16.1ATDC * INTAKE LOBE CENTERLINE - 111.8
EXHAUST VALVE OPENS @ 18.1BBDC * EXHAUST VALVE CLOSES @ -23.3 ATDC * EXHAUST LOBE CENTERLINE - 111.8
CYLINDER HEAD SPECS:
CASTING NUMBER 14102193
SWIRL PORT INTAKE PORT DESIGN
64cc COMBUSTION CHAMBER
1.94" INTAKE 1.50" EXHAUST VALVE
VALVE SPRING PART NUMBER IS 3911068 (SAME SPRING USED WITH THE OLD 300H.P 350 CRATE)
INSTALLED HEIGHT 1.70" PRESSURE @ INSTALLED HEIGHT IS 80 LBS * PRESSURE WITH VALVE OPEN IS 267 LBS.
THESE SPRINGS ARE GOOD FOR .550" LIFT BUT CLEARENCE BETWEEN GUIDE AND RETAINER MUST BE DOUBLE CHECKED BEFORE ATTEMPTING.
7 BOLT EXHAUST FLANGE
CENTERBOLT VALVE COVER FLANGE
1987-1995 INTAKE MANIFOLD BOLT PATTERN WITH CENTER INTAKE BOLTS CANTED @ 72 ANGLE
THIS CYLINDER HEAD IS NOT A PERFORMANCE ORIENTED CYLINDER HEAD. IT IS CLASSIFIED AS A HIGH SWIRL HEAD THAT WAS INTENDED FOR GOOD BOTTOM END TORQUE AND FUEL ECONOMY. THE INTAKE RUNNER IS RESTRICTIVE BECCAUSE IT HAS A RAMP CAST INTO THE BOTTOM OF THE BOWL TO PROMOTE HIGH SWIRL.

ENGINE ALSO INCLUDES

4 QUART OIL PAN (5W/ FILTER)

TIMING COVER

8" BALANCER

VALVE COVERS