Some basic questions

[steve ravet]

jkooser at impsat.com wrote:
> 
> 
> > I have read that you won't like how a carb gas tank works in an EFI
> > vehicle.  Carb tanks don't need baffling since the bowl takes care of
> > buffering fuel.  EFI tanks do since there's no equivalent of
> > a bowl.  So
> > you might consider getting a fuel tank from a later model EFI
> > suburban.
> > I know there were some years of your body style that were EFI.  It'll
> > also have a return line fitting, etc.  No problem then with a factory
> > style in tank pump either.
> >
> 
> Any idea of what year Subs had EFI?  Or a reference for fuel tank
> interchangeability between models?  If the van tank fits, I'll be set.

Do some browsing around the gmecm page, especially the links page.  Lots
and lots of good reading can be had.  Also, there is a link to the gmecm
archive from the main gmecm WWW page.  Do some browsing in there, I
guarrantee you'll come up with interesting information.  Ludis has an
ECM crossreference page that shows C/K trucks used the 1227747 from
'87-'90 or so.  www.cruzers.com/~ludis, click on C3 ECM crossreference. 
I don't know when the bodystyle you have changed to the next, but I
would bet that a tank from EFI sub w/ your bodystyle would bolt right
in, have the baffling, and the proper sender w/fuel pump attached.

> 
> > I know the answer to this is no.  747 won't do the electronic
> > transmission.  All it understands is TCC lockup, if you start with an
> > auto bin versus a manual.  You'll need a later ECM, I think '92 or
> > later, to do an electronic transmission.  But I wouldn't worry about
> > that at first, get your 747 conversion working.  The ECM and
> > trans have
> > to go together -- a P4 that can control the trans wouldn't be
> > happy with
> > your THM400.
> >
> 
> Okay, that's what I suspected as well from reading the ECM listings.  What
> about differences in the connectors between the '747 and a later model that
> can do the transmission?  Are there any - i.e. am I going to have to totally
> redo my wiring harness when I get ready to swap?  P4, what's that?

The original GM ECMs were called C3, "computer command control" or
something like that.  They have a lot of features in common like slow
ALDL data rate, removable EPROM, etc.  P4 came along in '86 or so and
has a faster processer, faster ALDL connection, MEMCAL instead of bare
PROM, etc.  But C3s were still used, especially in V8 TBI applications,
until the early 90s.  Anything that controls an automatic would be P4 or
later (also called PCM, powertrain control module, versus ECM, engine
control module).  So a P4 from a 92 or later pickup wouldn't work
without the 60E/80E trans.  The C3 won't care if the TCC isn't hooked
up.  If you can build a 700R4 with the durability you need (you can,
just need to find the right rebuilder) then you might like it a lot
better than the THM 400.  Better mileage, lower ratio in 1st, lock up
converter keeps temps down, etc.  

The connector pinout will be different will be different between C3 and
P4.  But trucks were MAP based TBI up until the Vortec in '96, so
although the pinout is different my guess (without seeing pinouts for
the P4 ECM) is that most of the needed signals/sensors for the engine
would already be in place from your C3 conversion, you'll just have to
cut off the 747 connector and rewire a P4 style connector, adding the
transmission stuff.

You might consider a powertrain swap (junkyard motor/trans/ECM/PCM) that
all came together as one piece.  That's what I did for my S-10 V8
conversion and it was much simpler that way.

--steve

> 
> Thanks,
> 
> Jake Kooser
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-- 
Steve Ravet
steve.ravet at arm.com
ARM,Inc.
www.arm.com
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