The Original 355 took a hit.

[Bruce Plecan]

From: "Dave Zug" <dzug at delanet.com>
> We can rebuilt it... we have the technology..
> Better, Stronger, Faster.

At this stage, it's just seeing how far it will go.
Also, bare in mind the lil guys used the FBod for parts chasing.

> The standard abrasives doc (on street level head portintg) is a nice
> document, if you have not seen it... I can't imagine you have not, but on
> the topic of DIY, its directed to others.
> http://www.sa-motorsports.com/diyport.htm

It's almost funny that people make money off of pocket porting.
GM has the shape about right, and if you just clean up the production part
of things usually have a decent head.  generally the short side radius is
poor just from coring, and little errors in initially locating the
machining.  Taking the sholder of off the valve guide is another quick gain.
The trick is really knowing when to stop.
you can do too many  good things and wind up with a lousier then stock head.

Gotta repeat after just knocking the edges of off the chambers is a real
winner.

> I'm lookin for "donor" (don't read: donated) parts for the budget 400 TPI
> project, if anything fell off that aint goin back on .. like those heads
;-)

These are the first gen D port AL vette ones.
For the money would be hard to beat, thou some of the new iron ones sound
like fun.

Was loooking thru some other heads at a friends shop.  The Edelbrock RPMs
seemed to have things well in hand for someone not wanting to get gritty
with grinding.

> PS (Thanks, I'll stop thrashing my car in 20 degrees now - you may have
just
> saved me $4k)

Just back the timing up a few degrees.
I peeked at some gm S/C MAT tables and they danced the timing around 10
degrees from cold to hot vs Airflow.

I think, I'm going to use something like

50-70dF as being the 0 correction area,
Then 70-90 add 2
100+ a total of 3
30-50dF  2 less
single digit to 30s 4 less
there I said it <g>
Bruce

    So far, both the GN and SBC seem to like this, though, haven't had any
traction for testing in the lower temps., thou the plugs bare this out.
    Also, entertaining using the cross fire with two small two barrel TBIs.
It already took the 90#/hr injectors to feed her, so the with this can run
(4) 55 #/Hr injectors, though would mean an injector driver board.
    thou I have a dual butterfly 2"er sitting on the kitchen table


>
>
> ----- Original Message -----
> From: Bruce Plecan <nacelp at bright.net>
> To: <gmecm at diy-efi.org>
> Sent: Saturday, January 27, 2001 3:40 PM
> Subject: The Original 355 took a hit.
>
>
> >
> >
> >
> > The 355 that I wrote about in tuning tips, and used for lots of 747
info.,
> > finally had it's first internal problem.   Well over 100 1/4m passes,
and
> > too many 600' passes to even guess at.   Now at about 70K miles, it's
> blown
> > a headgasket.  Happened on a really cold night, and the stations are
known
> > for adding lots of alky during the cold season, so I'd be easily talked
> into
> > it being not a real tuning problem, per se.   It microscopicly (?) blew
> the
> > fire band over maybe .020" near a water passage hole (rear side of #7).
> My
> > best guess is that there was a tank or two of heavily alkied fuel, and
was
> > just enough trace detonation that it silently lifted the head.   We've
had
> > enough single digit temps., that I just should have taken an addition 2
> > degrees of timing due to the weather <sigh>.....
> >   Just to summarize, this was a Comp Cammed, 9.5:1 AL vett headed SBC.
> >   At this stage the hone pattern is fully intact,  the pistons still
have
> > there crisp corners at the perimeters, no incidation of any valve
burning,
> > no large amounts of Carbon,  in general the wear is typical of a 10K old
> > stock engine.
> >
> > While apart, for the gasket change, going to clean the chambers (smooth
> > them, to avoid any machining edges), do a little pocket porting, and
> freshen
> > the valve job..
> > As much as a success this engine has been, just can't help to entertain
> the
> > idea of surfacing the heads, and tweaking it up a little more in HP.
> > While not a screamer HP wise, it's spent alot more time at WOT then most
> any
> > other street motor that I can imagine.
> >
> > Course, there are some ecm options, for things to do <g>.
> >
> > Course being the President of CSH, I'm also a customer.
> > Bruce
> >
> >
>
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