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What can be done to free up air flow in the TPI plenums?
Can I install the L69 dual snorkle intake on my LG4 engine?
What tools make an easy job of changing the spark plugs?
Do any performance chips allow me to moderate the amount of
power?
How hot does my thermostat run?
When do the primary and secondary fans kick in?
Can the fans be rigged to come on while the engine is not
running?
Why can't I seem to get a proper timing
reading?
How can I bypass the speed limiter?
What is the
difference between TPI, SFI, MPFI, TBI, and CPI injection?
What is needed to convert my engine to TPI fuel injection?
What fuel pressure setting will give me the best
performance?
Why is my car getting harder to start day by
day?
Should I use self-aligning or non-self-aligning
rockers?
Which cars came with a stock dual exhaust
system?
Does my car have an engine oil cooler?
Is there anything I can do to improve my 4 cylinder
engine?
Is there anything I can do to improve my 6
cylinder engine?
Does it pay to swap my 4 or 6 cylinder
engine for an 8 cylinder?
What can be
done to free up air flow in the TPI plenums?
The stock plenum has about 52mm openings, but there
are some serious blockages about 1/4" inside. This brings the open area down
considerably. There are 2 cast 'walls' just inside that need to be knocked out
before any "opening" is done. These apparently shroud
the EGR holes.
Start by removing the plenum and then carefully grind
out the walls. This should result in a noticeable
performance increase by
itself. Then you can go even further by putting on a 58 mm throttle body, but
this will require boring out of the plenum air inlets. This is a large amount
of metal to take off and requires a lot of time and patients. It is doable
though with a carbide bit and an air grinder. You will need to radius blend the
openings (you can't just bore them, there isn't enough metal all around). The
result is much better flow.
If you're not familiar with using the tools
mentioned, then you're better off having it done professionally. TPIS will do
it for $85, but you'll have to send them the plenum.
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Can I install the L69
dual snorkle intake on my LG4 engine?
Yes. If you can't find one in a junk yard, the part
numbers are as follows:
Part No. Description
-------------------------
25043641 Air cleaner
14070917 Left scoop
14070918 Right scoop
14073299 Left hose
14083990 Right hose
11513801 Screws
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What tools make an
easy job of changing the spark plugs?
For your ratchet: a 3/8" drive socket, a 3"
extension, a 3/8" U-joint, and the plug socket. As for the real tough plugs,
use a 'swivel' ratchet with a spark plug socket with a hex end. Then you can
get an open end wrench around it and pop it loose.
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Do any performance
chips allow me to moderate the amount of power?
There isn't a chip which allows you to modify the
actual "program", but JET (Jones Electronic Technology) offers a 6-chip setup:
Economy, Towing, Stage1, Stage2, Valet and Security. Each chip is designed for
a different type of application. That way, you can pop in the valet chip to cut
the power (and prevent possible valet joy rides) or use a stage chip to work in
conjunction with other performance modifications for even more power.
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How hot does my
thermostat run?
Stock thermostats on 3rd generation cars are 195
degrees. If you want to go colder, you must change the PROM.
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When do the primary
and secondary fans kick in?
According to the 1990 service manual, the primary fan
is controlled by the ECM and will come on when the coolant temperature reaches
190 degrees F. The secondary fan has its own temperature sensor in the bottom
of the engine block (passenger side) and will turn on when both of these
conditions exist:
The Auxiliary Coolant Fan is controlled by the A/C
Pressure switch and the auxiliary coolant fan switch. It is not controlled by
the ECM. It should have black and black/pink wires going to it, and the coolant
fan will have black and black/red wires going to it.
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Can the fans be
rigged to come on while the engine is not running?
Yes. There is a temperature sensor on the block
(passenger side under the third spark plug) with one wire going to it. Take the
wire off and splice another wire off of it. Route that spliced wire into the
car and up behind the dash. Then just hook it up to a switch. Run another wire
from the other contact on the switch to a ground, and then when you switch it
on, both fans will come on high.
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Why can't I seem to get
a proper timing reading?
The computer is programmed to automatically advance
the timing. You need to disconnect the brown/black striped wire next to the
heater box/fan housing and then you can get a real reading. Otherwise it will
seem like it's advanced a great deal.
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How can I bypass the
speed limiter?
Try the following steps:
-
Install a Zemco Performance Timer and instead of
using the speed sensor supplied, tap into the electronic output from the normal
sensor in the tranny (there shouldn't be a problem driving two sets of
electronics in parallel).
-
Then fit an ON/OFF switch into the speed sensor
wires that goes into the ECM.
-
Wire the torque converter so it's not controlled
by the ECM, but rather by on ON/OFF circuit switch. This results in non-lockup
when the shifter is manually put into 1,2 or 3. Selecting OD will get normal
up-shifts without lockup until 4th when lockup comes in. The while in OD, if
the tranny downshifts due to speed/throttle settings, the TCC stays locked
unless drop it out using the switch (except for 1st gear which doesn't allow
pressure to the TCC anyway due to the hydraulics).
The Zemco unit can be easily recalibrated if you
change tire size or rear gear ratios. When you want to push the car past the
speed limiter in the ECM, just switch OFF the speed sensor input to the ECM and
use the Zemco unit to show your speed. All that happens with the ECM is the
normal speedo stops working and you lose cruise control. After about a minute
the ECM realizes that the pulses are missing from the sensor and gives you a
service engine light. This does not affect the normal operation of the engine
and the light goes out again after a few seconds when the sensor is switched
back on.
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What is the
difference between TPI, SFI, MPFI, TBI, and CPI injection?
TPI (Tuned Port Injection) is a "batch" fire system
(from the factory) which means that each bank of injectors will fire all at the
same time. SFI (Sequential Fuel Injection) is sequential in that only the
injector that needs to fire does so. Both TPI and SFI have injectors located in
every runner of the intake manifold. MPFI (Muti-Port Fuel Injection) has one
injector per cylinder for more power and precise amounts of air and fuel
delivered directly to each cylinder via fuel rails. However, there are more
parts to wear or break. TBI (Throttle Body Injection) has two injectors placed
over the throttle body (carb bowl type unit) indirectly injecting through the
intake manifold. This result in less power and imprecise amounts of air and
fuel delivered to the cylinders, but there are less parts to wear or break. CPI
(Central Point Injection) is a hybrid of MPFI and TBI in that there are two
injectors placed over throttle body sending more precise amount of air and fuel
to the cylinders through a direct injection via a plastic tube and poppit valve
at each cylinder. There are less parts to wear or break this way.
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What is needed to
convert my engine to TPI fuel injection?
You'll need to find the following:
-
TPI intake
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TPI plenum and runners
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Throttle body
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MAF sensor, intake hose, filter case
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Injectors (19 lb/hr for 305, 22 lb/hr for a 350)
-
Oxygen sensor (if
yours don't already have one)
-
Knock sensor (if
yours don't already have one)
-
Intake air temp sensor (goes in plenum underside)
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EGR solenoid
-
Coolant temperature sensor
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Cold start injector sensor
-
Electronic Control Module
(ECM or computer)
-
Re-route EGR and charcoal
canister ported vacuum
as per TPI setup
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A/C bracket to TPI intake (upside-down U-shaped
bracket)
The best (cheapest) way, is to find the parts through
junkyards.
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What fuel pressure
setting will give me the best performance?
The stock setting is 42
PSI. Much track testing has
showed that any type of increase will greatly benefit both horse power and
torque. Here's some dyno testing on a stock 350 motor which substantiates those
claims:
42 PSI (stock) 46 PSI 50 PSI
RPM Torq HP Torq/diff HP/diff Torq/diff HP/diff
------------------------------------------------------------------------
2250 237.7 101.8 254.9/17.2 109.2/ 7.4 275.0/37.3 117.8/16.0
2500 241.7 115.1 262.1/20.4 124.8/ 9.7 283.3/41.6 134.9/19.8
2750 241.5 126.5 275.2/33.7 144.1/17.6 297.0/55.5 155.5/29.0
3000 237.1 135.4 278.2/41.1 158.9/23.5 305.5/68.4 174.5/39.1
3250 233.8 144.7 278.9/45.1 172.6/27.9 311.3/77.5 192.6/47.9
3500 241.0 160.6 278.2/37.2 185.4/24.8 309.5/68.5 206.3/45.7
3750 246.6 176.1 283.4/36.8 202.4/26.8 303.3/56.7 216.6/40.5
4000 250.4 190.7 278.3/27.9 212.0/21.3 298.0/47.6 227.0/36.3
4250 251.6 203.6 272.5/20.9 220.5/16.9 289.1/37.5 233.9/30.3
4500 253.5 217.2 257.3/ 4.2 220.5/ 3.3 277.0/23.5 237.3/20.1
4750 245.0 221.6 242.1/-2.9 219.0/-2.6 266.4/21.4 240.9/19.3
5000 227.6 216.7 225.0/-1.4 214.2/-2.5 237.8/10.2 226.4/ 9.7
It shows that by increasing the fuel pressure to 50
PSI, results in maximum torque increase of 58 ft-lbs (along with a much flatter
torque curve) and a maximum horse power increase of 19 HP over stock. 46 PSI
also provides a noticeable increase which should work well for day-to-day street
driving. An adjustable fuel pressure regulator (See General Information FAQ -
Engine Section) is required to increase the fuel pressure.
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Why is my car getting
harder to start day by day?
Before you go spending big bucks on a new starter or
fuel pump. Check the The fuel pump relay. It could be dying and you might be
able to save a large sum of money.
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Should I use
self-aligning or non-self-aligning rockers?
You have to use a self-aligning type otherwise you
will have to pull the heads to tap them since the studs are pressed in.
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Which cars came with
a stock dual exhaust system?
Starting in 1989, cars with the G92 option got the
dual cat system, but the post-cat exhaust is tied into a single 3" pipe and fed
through a single muffler with dual outlets. GM rated the dual cat version at 10
more HP than the single cat versions. Putting a good aftermarket system w/
mandrel bent pipes and a free flowing muffler will still give you better power
though on a car with dual cats.
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Does my car have an
engine oil cooler?
All cars with the 350 ci (L98), 1LE, or B4C option
got an oil cooler.
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Is there anything I
can do to improve my 4 cylinder engine?
Yes, especially the Iron Duke 2.5L which came in the
first 3rd gen cars:
-
Holley T.B.I. unit (20% larger unit)
-
Edelbrock Performer T.B.I. manifold
-
Hooker Super Competition Headers
-
Holley open element air cleaner
-
K&N filter air cleaner
-
NOS nitrous kit (single fogger, 40 or 70 HP)
-
Turbo Muffler
-
B&M shift improver kit for 200C tranny
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Is there anything I
can do to improve my 6 cylinder engine?
Yes, just about anything you can do with the 8
cylinder, can be done with the 6. Parts my be a little harder to find, but ads
in the back of any Chevy magazine is best place to start. The most basic things
are upgrading the intake and exhaust. A K&N air filter as well as freer
flowing intake tubing can do allot. On the later models, you might want to try
drilling holes in the water shields under the air filters (about five 1/4 inch
holes). This will allow much more air into the motor. As for the exhaust,
Edelbrock and Dynomax make some excellent free flowing systems for the V6s. And
Products for Performance makes a freer flowing replacement catalytic
converter.
For the spark, try the Crane HI-2000 ignition
discharge unit and the Crane PS91 coil. Also use 8mm helicoil plug wires from
MSD and Bosch platinum spark plugs.
You can even swap the cam. Competition Cams makes the
CompuCam 2000 which is "computer friendly". Try something with .432 intake and
exhaust lifts. In combination with that, use Competition Cams 1.6 roller
rockers. All this allows for better breathing, so you might want to have the
intake manifold ported. Also port and polish the heads.
Finally, you can go with forged pistons, chrome moly
rings, Federal Mogul bearings, a remanufactured crank. This will be plenty
strong to handle a nice nitrous set up from NOS.
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Does it pay to swap
my 4 or 6 cylinder engine for an 8 cylinder?
First of all, you have to decide if you are going to
keep the computer system. It's a bigger hassle if you do. Your best bet is to
go to a junkyard or find someone who is parting out a V8 Camaro/Firebird, and
pull as many parts as possible off the same car. You will need brackets (i.e.
alternator, AC, smog pump, and power steering pump - save the bolts too), AC
hoses, and Pulleys. You will also need new rubber motor mounts (about $20 at
local parts store) and the engine side brackets that these mounts bolt to. Make
sure you get the engine side motor mount brackets from a Camaro or Firebird as
they are a little shallower and are needed to get the engine to sit low enough
in the bay. The holes for the motor mounts are already in your
cross member. You
will also need to get the engine fan and fan shroud (junkyard or new - your
choice). You will need to buy a starter, water pump, and probably a power
steering pump (get these from a junkyard as they're almost always still good).
You'll need a V8 HEI distributor. An ACCEL rebuilt HEI works great and costs
less than $150.00. And of course plugs and wires. Assuming an automatic tranny,
you will need a new tranny since the bell housing
bolt pattern is different on
the V8 car from the 4 and 6 cylinders. A Turbo 350 will bolt right in with
B&M's $75.00 conversion kit. It just lets you hook up the torque arm, but
you'll lose overdrive. Take a Polaroid camera to the junkyard, and you should
be able to figure all this stuff out. Finally, you will probably have to change
the front coil springs. I know this sounds like a ton of work (especially since
it doesn't even include what you have to buy to assemble the engine), but this
swap is really a piece of cake - everything drops in like it was supposed to be
there. At the very least, assemble all the components you'll need (build the
motor on an engine stand over a few months with all accessories and brackets),
and have someone drop it in for you. A shop would charge you an arm and a leg
if they had to scrounge all this stuff up themselves.
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