Engine Mechanical problem
1996 Chevy Tahoe V8 Four Wheel Drive Automatic 190000 miles
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I have a 1996 chevy tahoe (5.7) vortec engine .. I WOULD LIKE to know if i could use a engine out of a 1995 chevy pick-up truck(1500) which has a(5.7) liter engine(not a vortec) the only diffrences i see are my alternator and ac areon oppisite sides , but if i use the brackets off my vortec engine will the bracket holes line up on the other engine so i could use my original alternator on ac compressor, also would i have to change the intake manifold

the reason i felt i needed to change the engine is because,.when i start the truck it has a knocking sound that strart about (30sec)after the engine strarts running if i press on the gas pedal and raise the r.p.m,s the noise kind of dies down ,also if i put the truck in drive the noise is not as loud as it is in park . i.ve checkedthe oil ,not water is in it ,l.ve changed th oil too.also i,ve checked the spark plugs.the look fine..the check engine, service engine lwarning lights are not on ,it has around (40psi) oil pressure,..so i really cant find anything wrong ..

ok, well ill give you a few things that can cause a knocking sound like you described and are relatively easy to check, and probably save you the trouble of the new engine.

I would eliminate the valves clicking because sounds like you got sufficent oil.

A torque convertor that is loose on the flex plate or a cracked flex plate will cause a knockiing sound like that, usually mistaken for a main bearing going. its normally most noticable in idle when speed is low and no engine load.

next thign to do is ground out one cylinder at a time and see if the noise stops. do this by putting a piece of vaccum hose in the spark plug wire and on the spark plug then grounding it out with a grounded test light, if noise stops when one cylinder is disabled it could be a piston pin that knocks, it also usually gives off a double knock sound.

i would eliminate timing chain noise as if the vehicles chain is worn that badly your vehicle will be running poorly. with main and rod bearing noise it depends on speed and engien load the noise it will make so i dont think that would be the problem.

If you have a heat riser remove the vaccum line from it and remove the drive belt, does noise stop when this is done?

so ,when i ground the spark plug and wire with a test light and the engine noise stops what is causing the problem? and if it,s a piston pin who will i know? also i put a wrench on the belt tensioner(which is so weak i could have held it down by hand) and let slack in the belt and the noise is still the ..does this mean any thing...PS I ONLY GET PAID ONCE A MONTH(1st-3rd) I,LL BE SURE TO SEND YOU A DONATION YOU HAVE BEEN A REAL HELP IN TIME OF NEED AND I WANT TO SAY THANK YOU!!!

are you saying the noise stops when you ground out a cylinder? which one?

take the drivebelt completely off and see if the noise still continues, a defective belt can cause a knocking type noise and is often mistaken as something much more serious.\

and i would like to thank you ahead of time for the donation, it is very helpful!

get back to me.

if it stops on a particuallar cylinder you can suspect a worn rod bearing on that cylinder or piston slap on that cylinder.

if it dont stop on any cylinders yoiu can suspect everything else i listed.

id like to ask some more questions bout the sound

is it a clicking noise like clicking a pen?
a clanking noise such as tapping on metal?
clunking like shutting a door
clatter, like marbles rolling around
knock, such as knockign on a door
or rattle type noise.

i,am sorry!! my question was (if) the noise did stop what was causing the problem? also if it didn,t stop what was causeing the problem? the noise i hear is that of a metal clanking sound..just a regular clank,clank,clank as in it something metal with a hammer

as i said above if the knocking stops then either you have a case of piston slap or rod bearing on that cylinder, even a hole in the piston!

when grounding out the cylinder where shoul i ground the clip end of the test light on,..and what do i touch with the probe end of the test light the spark plug wire or the spark plug itself

hook the groudn on a good engine ground on the block, touch the probe on the vaccum line you put on the spark plug tip and into the spark plug wire.

to ground it out simply touch th eprobe part of the test light on the vaccum line.