blew my vortec 5.7. can i use my zz3 short block???

gmbrasco · March 5, 2007

as the title say's, my 97 gmc 1500 4x4 sounds pretty bad. i believe i have a floating valve on number 6 . truck feels like its got a miss, my idle races up and down, i ran the scanner on it and its telling us it a miss. i gave it a full tune up i even changed the injectors to the new updated one's, we did all this then determined the valve.( compression was good under cranking but lost it when running). the truck got 170k i have a slight bearing sound on morning start up and depending on what side of the bed she woke up on she will knock loudly under half acceleration at hwy speeds. she still has good power, no smoke out the rear yet, i do lose about a quart a month. i did read that the later models knock alot also, im not sure if it something to really be concerned about, the knock is worse on some days then others. i drive about 100 miles a day with it for the past month with no issues other then the rough idle at lights and the rattling under acceleration. i have a 74 c10 2wd with a zz3 in it with about 1000 miles on a fresh rebuild, she's rotten away on me so im concidering pulling the zz and putting a set of vortec heads on it and putting it into the 97.

my mechanice said the heads should bolt up but wasnt sure about everything else, he mentioned the crank sensor and the pieace that goes on the crank, i forgot what he called it, and all the other sensors locations. all this blabber comes down to this.

can i use my zz in the 97, if so what mods are needed if any, and would it be easier and cheaper to look for a rebuilt L31.

any help will be greatly appreciated.

gmbrasco · March 6, 2007

any help out there, please.

redvett · March 6, 2007

Cheaper and much easier to rebuild your L31 since the heads and block are different along with the crank & tone wheel.

gmbrasco · March 9, 2007

Cheaper and much easier to rebuild your L31 since the heads and block are different along with the crank & tone wheel.

thanks for the info, does anyone know what a typical rebuild should run, chevy has a new l31 for about 2000.

Westlotorn · March 29, 2007

as the title say's, my 97 gmc 1500 4x4 sounds pretty bad. i believe i have a floating valve on number 6 . truck feels like its got a miss, my idle races up and down, i ran the scanner on it and its telling us it a miss. i gave it a full tune up i even changed the injectors to the new updated one's, we did all this then determined the valve.( compression was good under cranking but lost it when running). the truck got 170k i have a slight bearing sound on morning start up and depending on what side of the bed she woke up on she will knock loudly under half acceleration at hwy speeds. she still has good power, no smoke out the rear yet, i do lose about a quart a month. i did read that the later models knock alot also, im not sure if it something to really be concerned about, the knock is worse on some days then others. i drive about 100 miles a day with it for the past month with no issues other then the rough idle at lights and the rattling under acceleration. i have a 74 c10 2wd with a zz3 in it with about 1000 miles on a fresh rebuild, she's rotten away on me so im concidering pulling the zz and putting a set of vortec heads on it and putting it into the 97.
my mechanice said the heads should bolt up but wasnt sure about everything else, he mentioned the crank sensor and the pieace that goes on the crank, i forgot what he called it, and all the other sensors locations. all this blabber comes down to this.

can i use my zz in the 97, if so what mods are needed if any, and would it be easier and cheaper to look for a rebuilt L31.

any help will be greatly appreciated.

Westlotorn · March 29, 2007

You may have taken action already, I don't check this site often. A stock Vortec 350 full rebuild is available for 1500 or so in the market. Make sure it is a full rebuild and not some patch kit. Should include, Bored, New Pistons Rings, Crank Turned, New Cam and Lifters, Timing, Gaskets, Bearings, Cam Bearings and Decked or line bored if necessary.

If you rebuild yours you will need to clean your Oil Pan, Timing Cover, and Intake completely before assembling to the new parts. Must be done or dirt and contamination from the old will go into the new and cause early engine failure.

Also a new engine runs hotter and will need better cooling, make sure the radiator is cleaned out and flush the system. Use a new Water pump, Fan Clutch, Belt and hoses, Spark Plugs and Wires. Distributor cap and Rotor.

There are many ways a perfect new engine can fail after a rebuild, the above list helps avoid some of these early failures. If you don't know what your doing let a good mechanic do it.

Installation is usually a 8 to 13 hour job at $ 100.00 per hour at most shops.

Use a reputable rebuilder with modern equipment, a good shop can give you better than OE performance for less than the GM Target engine cost. Use quality parts.

Your Truck probably has an oil cooler in the Radiator, the cooler and the oil lines must be raplaced. The knocking you hear in your engine is parts wearing out quickly, they deposit metal into the Oil system and it gathers in the Oil Cooler. When oil gets hot this metal will migrate to the engine bearings first and then the rest of the engine. Many times this causes catastrofic failure in the new replacement engine. It costs money to change this stuff, probably an additional $ 300.00 to $ 500.00 if you do it yourself.

Once installed there are very specific start up procedures to break in a new camshaft.

As soon as it starts you must maintain a minimum of 1500 RPM for the first 20 minutes to break in the cam. 1500 RPM to 2500 max is fine for break in. IF you skip this the cam will go flat 50% of the time. Don't gamble do it right. Oil pressure and Radiator temp must be monitored the entire break in time. You might need to run fans or cool the radiator with water from a garden hose to keep the engine cool through the break in.

For about $ 500.00 more you can increase your 350 to a 383, they really pull stronger than any 350 ever did. Keep the compression and camshaft very close to stock or you will have computer problems on the 350 or the 383 engine in a Vortec.

Good Luck

as the title say's, my 97 gmc 1500 4x4 sounds pretty bad. i believe i have a floating valve on number 6 . truck feels like its got a miss, my idle races up and down, i ran the scanner on it and its telling us it a miss. i gave it a full tune up i even changed the injectors to the new updated one's, we did all this then determined the valve.( compression was good under cranking but lost it when running). the truck got 170k i have a slight bearing sound on morning start up and depending on what side of the bed she woke up on she will knock loudly under half acceleration at hwy speeds. she still has good power, no smoke out the rear yet, i do lose about a quart a month. i did read that the later models knock alot also, im not sure if it something to really be concerned about, the knock is worse on some days then others. i drive about 100 miles a day with it for the past month with no issues other then the rough idle at lights and the rattling under acceleration. i have a 74 c10 2wd with a zz3 in it with about 1000 miles on a fresh rebuild, she's rotten away on me so im concidering pulling the zz and putting a set of vortec heads on it and putting it into the 97.
my mechanice said the heads should bolt up but wasnt sure about everything else, he mentioned the crank sensor and the pieace that goes on the crank, i forgot what he called it, and all the other sensors locations. all this blabber comes down to this.

can i use my zz in the 97, if so what mods are needed if any, and would it be easier and cheaper to look for a rebuilt L31.

any help will be greatly appreciated.