knocking noise 3400

[bjornmk1]

well eh..just bought me an 3400 engine
from a 97 transport with only 16miles on it.

it has a knocking sound according to
the guy that sold it to me.

it has been standing since 1997 at a GM dealer.
i bought it for like 600$.

already have the engine on the stand and removed the oilpan.
rod bearings and main bearings are ok.

only slight residue(greyish) on the pickup of the oilpump.
(i guess that's normal wear at break in).

took the valve covers off and looks okay there to.
although i was able to rotate some puhrods...but hey..
that's not so weird after 10 years of standing still right ?

maybe a bad lifter or a loud injector???

help please.

bjorn

[bszopi]

97 would lead me to think it would be piston slap, which isn't a big deal at all.

[bjornmk1]

that seems unlikly.
the engine only has 16 miles on it !!!

right ?

bjorn

[bszopi]

Piston slap was an issue from the factory, so it could easily be likely on an engine with only 16 miles on it.

[bjornmk1]

how come than ....
are the bores to big for the pistons or
are the pistons to small for the bore size ?

man this sucks..

[bjornmk1]

well..confirmed.
pulled the piston nr.5 out and it looks like it began to eat itself.
pretty deep grooves on the cam side of the piston and cylinderbore.

I guess a rebore will be in order here.
what pistons do you guys use for boost applications in this engine ?

bjorn

[bszopi]

Sucks that there is piston damage. But to explain GM's piston slap, it occurs when each component is at opposite extremes of the tolerances set by GM. Therefore yes... the piston is too small for the bore, (or vice versa) but everything is still within tolerance. The noise goes away once the engine has warmed up and the metals have expanded.

[pontiac3100]

so this does'nt cause any further damage??

[85_305]

Sucks that there is piston damage. But to explain GM's piston slap, it occurs when each component is at opposite extremes of the tolerances set by GM. Therefore yes... the piston is too small for the bore, (or vice versa) but everything is still within tolerance. The noise goes away once the engine has warmed up and the metals have expanded.

Ya this was EXTREMELY common in 3100's and the LSx series motors.

so this does'nt cause any further damage??

Nope, not at all. Piston slap motors have been ran deep into the 300k-mile range w/out problems. Some people dont like it because it's "too noisy"

[bjornmk1]

replace the worn piston ??

so I could possibly get away with a rebore and one new piston ?

bjorn

[85_305]

so I could possibly get away with a rebore and one new piston ?

bjorn

Not a good idea to bore/re-piston one ring one cylinder and not the others.

[bjornmk1]

so basicly i am fucked by GM.

I'm probably not the first one.

where can I get 3400 pistons(fed.mogul) cheap ?

B

[85_305]

so basicly i am fucked by GM.

I'm probably not the first one.

where can I get 3400 pistons(fed.mogul) cheap ?

B

How are you fucked by GM? Where did I say that Piston Slap causes damage to your fucking engine? If your motor is damaged it's not from GM screwing you over with its piston slap.

[bjornmk1]

pistonpin locked up

well..eh i moaned a bit to soon.
it seems the piston pin pretty much locked up.
so this was probably the cause of the piston scuffing the wall.

non the less I think new engines should not have piston slap.

looks like i am in need of a rebore and a new set of pistons.

[85_305]

well..eh i moaned a bit to soon.
it seems the piston pin pretty much locked up.
so this was probably the cause of the piston scuffing the wall.

non the less I think new engines should not have piston slap.

looks like i am in need of a rebore and a new set of pistons.

Dude there is nothing wrong with a motor with piston slap, except for those people whom are pompous asses and think they are driving a $100k Ferarri and should be no noise on the vehicle except out the exhaust.

But hey look on the bright side. You have a 16mile motor. I say a bore/stroke is in order, and heck why not just cam it, get some good heads, high comp rings etc? Hell it's already be apart right?
And shit, since it's only got 16miles on it, boost the bitch!