[Diy_efi] Engine ECM combination

[Shannen Durphey]

1)  Put need number 5 with druther number 2 and you've got an issue.  The
xfire intake has way more plenum volume, so you need to change PE and/or AE
data.  Without the change, step on the throttle and "pop" just like a badly
tuned carb.  Plus the runners in the xfire are longer, yet smaller, so the
VE tables ends up being different.

2) most blocks cast after 1987 and installed in light duty trucks or cars
have the casting for roller lifters.  But many are not machined for roller
lifters.  For what you want, a 3/4 or one ton truck made after 1993-ish
should do.  

3) I don't know the new head casting nos.  The heads used on tbi engines
made from 86 on, and on carby angines in 86 and 87 have the wrong bolt
pattern for the xfire.  If you don't mind adapting, the tbi heads are good
for torque.  A nice combination might involve the xfire and a set of
aluminum heads from a tpi Vette.  Otherwise, all pre '86 heads will bolt up
to the roller block and the xfire intake.  My xfire intake is currently on
a set of 83 vintage 305 heads.

4) 7747 plus custom image.  You might get some great starter images from
people who have installed a 7747 onna xfire.  You might want to make
changes for durability as the van is likely to spend more time under load. 
I'd go with less agressive timing, possibly even copying spark data from a
van or 3/4 ton truck based calibration.

5) xfire throttle cable enters from the front of the engine instead of the
rear.  I'd look at a detent cable from an xfire equipped Vette or F car. 
The van throttle cables are usually a mile long, so you should be ok with
that.

6) fuel pump:  Best bet is to get a gm designed tank to install.  It can be
much easier in the long run.  
Shannen

Mike Turner/ENGR/HQ/KEMET/US wrote:
> 
> I am helping a friend do an engine swap. Vehicle is 1988 2500 series Chevy
> van with a very tired carburated 350, automatic transmission, and air
> conditioning. The van is mostly used as as tow vehicle for his trailered
> autocross Corvette. My friend has a short list of givens and druthers.
> 
> Givens:
> 1) Replacement engine should be stock 4bolt main 350 SB.
> 2) Exhaust to be dual all the way to rear.
> 3) Engine management and emissions stuff to be stock parts.
> 4) O2 sensors working closed loop.
> 5) No tweaking of fuel/air/accel maps. Burning chips is not a problem.
> 
> Druthers:
> 1) New engine should be stock roller cam with iron heads.
> 2) Old style TBI (Crossfire) fuel injection used because of torque curve.
> He wants high torque in the low to mid range rpm. He already has one of
> these intakes. He also has an 88 Camaro TPI intake but prefers the XF.
> 3) ECM should be pre-OBDII.
> 4) Get engine, ECM, and transmission as assembly from the junk (recycle)
> yard. Yeah. Right.
> 5) New transmission should probably be a 700R4.
> 6) Ignition should be the small distributor cap HEI.
> 
> Questions:
> 1) My research leads me to believe only the 880 block is roller 4 bolt main
> and the 898 or 906 head is appropriate. Correct?
> 2) Given the use of crossfire TBI injection and iron heads on a roller
> block, does this combination require modifying the intake to match bolt
> holes on the heads?
> 3) Given the use of stock 350 engine and heads, crossfire TBI injection,
> and an automatic transmission, any suggestions as to ECM and prom image?
> 4) Are there any issues such as linkages to using the XF intake with
> automatic transmission that might be a problem?
> 5) The fuel pump issues are being worked on. We are leaning toward pulling
> the fuel tank and retrofitting an electric fuel pump and return line. A
> fall back plan involves a small forward mounted tank with electric pump
> located there. Suggestions or comments?
> 
> TIA.
> 
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