[Diy_efi] vortec engine piston noise?

[Shannen Durphey]

mike katz wrote:
> 
> --- Shannen Durphey <shannen at grolen.com> wrote:
> > "Slap" occurs at idle also.
> 
> Only in no offset race motors.....

When you find a definition of piston slap that isn't just "piston
noise" then we can rule out piston noises at idle from everything that
is "slap."

> Sorry again, Shannen. Gm has lots of TSB's for motor
> noise due to loose clearances. Just about every 454
> truck motor made had this problem. Every marine motor
> did.

Got a list of tsb's right here.  Covers 1980 to 1999.
Care to mention a number?  Pretty tough to find any bulletins for 454
engine noises that are piston related from 1984 to 1994.
'Course in 95, with the  gen 5 engine, noise got real bad.  I'll check
and see if they ever fessed up on that one.  I did a few swaps for
customer satisfaction because of those.  Even bought the engines back
for core charge ($450) to use under carbys.

Lesse, some random samplings...
1991...  nope.  But here's the stainless steel exhaust gaskets
released in 95...  good idea there.
here's the "cold engine knock" that was referred to earlier in the
thread, and the "check valve oil filter" that was supposed to fix it. 
Here's a rocker bolt failure (funny they never mention intake bolt
failures or 1989-90 designfront accessory bracket failures).  Here's a
chart to help with engine overheat diagnosis (they don't mention that
the c/k design just does not allow as much air to move through the
engine compartment as the older R/V designs, and that they will be
plagued with heat related troubles in these trucks until the new
design in 96.)

1987... only engine noise bulletin for 454 is exhaust leaks

1984, 85, 86... no noises (pickups didn't make noise in those years; )
)

94?  Same story.

95, 96?  same.

Checked 91 350, too. 

The only thing that I heard of that happened was that a bulletin was
written for IDCS but never released through the system for the gen 6
big blocks.  "We know about it, but we don't have a fix yet."

 
> Sorry Shannen. For a car motor,no problem. For a truck
> motor that can see continuous full throttle loading
> with most of the work done in the head, serious
> problems can occur.

Serious problems can always occur.  That's kinda vague, dontcha
think?  Pickups aren't special.  Spend time comparing parts, part
numbers in GM land.  Only when approaching 10,000lb gvw do differences
begin to show up.  C-50, 60 series engines are built for reliability
under load much more than "little" c/k engines.  Forged cranks, small
valves, wide seats, thick heads, sodium filled stems, heavy rotating
assemblies all part of the package.  Won't find anything like that in
a garden variety pickup powerplant.

Continuous full throttle loading takes on new meaning when living in
and driving through mountain states.  BTDT, built motors that lasted
well enough.  Technology has been here for average guy to do 1 hp per
ci with plenty of reliability for 15 years.  Technology to do it at
the cost gm wants to spend is slow in coming.  Technology to support
OBDII emissions and decent power has been even slower.  General claim
that "300 hp is a delicate balance" is misleading at best.  It's a
cost versus performance issue more than anything else.

BTW, pickups aren't "Trucks."  Only city folk think that way.  lol... 
Not picking on ya, just seems like so many people think their pickup
is something it's not.

If extended full throttle loading and extreme heat in the heads were
part of the anticipated use for the Vortech 350 we'd see all the
"goodies."  Sodium filled valves, cooling oil spray on backside of the
piston, extra wide exhaust seats for maximum heat transfer, thick deck
surfaces to withstand large amounts of thermal cycling, silica-bronze
guides...  Look at the engine and you'll see those aren't part of it. 
And if there were enough problems with full throttle use (or any use)
causing engine damage and warranty claims, there would be changes made
to production engines that included the installing the "goodies." 
Lack of warranty claims show the demand isn't there.  Investigation
shows the design isn't there.  300 hp and above acceptable reliability
is do-able without any stretches of technology.  It's a money issue.

I will agree that there is a delicate balance, but it involves power,
reliability, and cost.  


> 
> C'mon dude. Dont' try and compare a low CR motor to a
> high CR motor. Peak pressures contribute a lot to
> piston slap. Hot exhaust manifolds don't count.

Oops-  We were generalizing, no?  CR isn't really so high on the
votech engines.  We're talking about a 9.4 c/r versus something in the
neighborhood of 8.0 for the 366...  Neither one is what I'd consider
all that high.  Or all that low.   Guarantee if I rebuild a 366 with a
set of 9.0:1 pistons it doesn't make noise like the new GM engines. 
There's plenty of room to run a longer skirt in that block.  That's
part of the reason the engine exists.  Too bad it's a piece of junk in
its own right.

And it was much more than exhaust manifolds on the phone co trucks. 
Thought they was gonna make GMC do a major buyback! : )  Engine oil
baking so bad in lifter valley that it took an air scaler to knock it
out!  We were installing big oil coolers, putting huge 110V fans in
front of radiators, running with hoods open...  it was a helluva
battle.  Cam timing + carburetion was finally blamed, and we did end
up replacing a few cams.  But some of the guys were just turning up
the jets and dumping a ton of fuel and getting fair results with
that.  Gotta consider that the engines were running an auxilliary 220v
alternator and turining at something like 2500 rpm for hours at a time
while the truck was stationary.  They should been buying diesels for
the job, but the boys in the spec dept. saw an opportunity to save $$.

> > The short skirt
> > hypereutectic slugs gm used made a ton of noise.
> 
> That's normal dude. I own a 93 ZZ3 motor, and it is
> all valvetrain noise. A bunch of weenies complained
> about the noise on a HP off road crate engine (give me
> a break). Go talk to Keith Black about piston noise.
> He will set you straight. Once again, loose is fast.

Yeah, I know it's normal.  Normal for that design.  And it's not all
valvetrain noise.  Dude, I've worked on those motors.  One tech I used
to work with has lifters, cams, cranks, pistons from those engines. 
Everything was replaced under warranty for noise complaints.  The only
one I ever saw (heard?) really quiet down was fitted with a new bore
and aftermarket pistons.

I don't own a ZZ engine, I like to build my own power.  "Loose is
fast" has been around for a long time.  But loose and quiet don't
belong together in a factory truck.  Besides, Chevy rarely builds
things for fast, they build 'em for reliable.  It's a whole different
world when you start thinking of things from the dealer side of
things.

.
> 
> If it can work for them, it will work for you. Just
> hand them a copy of the TSB. That becomes a legal
> issue.

So far I've never seen a printed copy.  There's a network of
"unpublic" tsb's that are not for general release.  They get reviewed
by lawyers then made available to dealerships.  If this sounds like
something from a movie, I can't argue with you.  But ask around about
the IDCS (or maybe IDCN) and see what turns up.  Stuff like piston
noise often doesn't make it to IDCS.   It gets squashed by lawyers
first.

> My suggestion
> would be that the everyday joe stop buying a truck as
> his family wagon if noise is going to be a problem.
LOL!!!!  Too true.  I wish we had more say in what GM builds.  There
might be a few more fun rides out there.

Downside is that Everyday Joe's wife will stop buying noisy GM
trucks.  My point is that if GM is going to build these trucks, they
should do it right.  They have been in business for enough years, they
know what people want and what they don't want.  They know what makes
an engine last and what doesn't.  If they can't make a 300 hp engine
and make it quiet, then they shouldn't put it into a vehicle that
they're designing to be a big, quiet car.  But the thing is, other
companies are doing it and not having problems.  

Shannen

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