we can can work out the cause through testing
you can,t guess you need to deal in verified facts,
please post very clear pictures of your spark plugs,
whats your fuel pressure at the carb inlet port read? and check your vacuum at idle and again at 3000rpm with a vacuum gauge, then verify your ignition timing curve, check your float levels are set correctly.
a 600-750 cfm carb can be rather easily tuned on a typical chevy 350-400 it just takes experience and facts to work from, if you don,t know how to do something or what I'm talking about, ASK QUESTIONS,WE ALL START OUT with LESS THAN IDEAL EXPERIENCE
we can certainly find the cause and correct it but you need to deal in verified facts, its a simple step by step process of check, test eliminate the potential cause and re-test, Id suggest you get a timing light and b, verity TDC as a starting point then borrow, buy or find someone to help you tune that has access to one, (a fuel/air ratio scanner) and take a compression test and verify your ignition advance curve,the fact is that due to manufacturing tolerances a dot-to-dot install will frequently be a few degrees off! now most guys might never notice, but it can and frequently does effect the engines power band so getting it correct helps and eliminates one potential source of problems (be damn sure you verify the cams degreed in correctly and the ignition firing orders correct and all the distributor wires go to the correct cylinder,s spark plugs and distributor cap locations)
GENERALLY your fuel/air ratio should be in these ranges
Idle- up too about 2500 rpm try for 14.7:1-15:1 f/a ratio
from about 2500 rpm- too about 4500 rpm try to smoothly and predictably transition the fuel/air ratio mix richer to about 13.5:1
from about 4500 rpm- too about 6500 rpm and higher ,try to smoothly and predictably transition the fuel/air ratio mix richer to about 12.5:1this is only a starting point on the tune but it generally gets you in the ball park and tends to reduce the chances of the engine reaching detonation conditions.
the ignition advance curve needs to be checked, the chart below is a very good starting point to work from, and USE OF A RICHER FUEL/AIR MIX, WILL AT TIMES BE REQUIRED IN THE OFF IDLE TO 3500 rpm range
if your experiencing detonation issues that are cured by swapping to higher octane rated fuel, and you would prefer to use the lower octane , less expensive fuel, you should adjust your cars ignition advance combination , so that its advance curve has either less initial timing, or delaying the mechanical advance vs. rpm with some stiffer springs, or a combination of both might reduce the pinging under load at 2500-3500 rpm where its most commonly seen,. Does this detonation or pinging, only occur at WOT? If not, limiting the vacuum advance with a stop, or using an adjustable vacuum advance unit and raising the amount of vacuum required vs. the amount of vacuum advance might be warranted also and installing a lower temp rated t-stat and adjusting the engine fuel/air ratio a bit richer may also help..
the guys have a point, best power and in many cases durability, is generally found at nearer 12.7:1 f/a ratio, I don,t ever remember your engine getting near that lean while we discussed getting it tuned up?
without testing you simply guessing
GET A FUEL PRESSURE GAUGE AND MEASURE DON,T GUESS
how can you possibly set up your fuel system unless you know the pressure and flow rates required and what currently exist's
as always it helps to have a shop manual for your year and model car, then I'd suggest, you get out your multi meter and verify the alternator is putting out about 14 volts while the engine runs,pull the trouble codes with a code reader, then check the electrical grounds and fuses as a first step, in isolating the problems source
reading these links will be helpful
yes I know it will take some time and effort to isolate and test
but its the only 100% sure route to finding and fixing your problem,
don,t get over whelmed,
simply break the problem down to testing each basic sub system,
test each related sensor and electrical component and electrical sensor and connection.
some reading on the threads posted below, a bit of logic and deductive reasoning, and a multi meter and a shop manual will go a long way toward finding and fixing the problem.
Measured Value
Engine Coolant Temperature Sensor. 185 Ohms @ 210F, 3400 Ohms @ 68F, 7,500 Ohms @ 39 F.
Engine Oil Temperature Sensor. 185 Ohms @ 210 F, 3400 Ohms @ 68 F, 7,500 Ohms @39 F.
Oil Pressure Sender/Switch. 1 Ohms @ 0 PSI, 43 Ohms @ 30 PSI, 86 Ohms @ 60 PSI.
Fuel Quantity Sender. 0 Ohms @ Empty, 45 Ohms @ 1/2 Full, 90 Ohms @ Full.
MAT (Manifold Absolute Temperature Sensor). 185 Ohms @ 210 F, 3400 Ohms @ 70 F, 15,000 Ohms @ 40 F.
Outside Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
In Car Temp Temperature Sensor. 4400 Ohms @ 60 F, 2200 Ohms @ 85 F.
MAF (Mass Air Flow) Sensor. .4 Volts @ idle, 5 Volts @ Full Throttle.
Oxygen (O2) Sensor. .1 Volt Lean Mixture, .9 Volt Rich Mixture.
TPS (Throttle Position Sensor). .54 Volts Idle, ~ 5 Volts Full Throttle.
Sensor Locations
Sensor
Location
Engine Coolant Temperature Sensor. Front of engine, below Throttle Body.
Engine Oil Temperature Sensor. Left rear of engine, just above the oil filter.
Oil Pressure Sender/Switch. Top, left hand rear of engine.
Fuel Quantity Sender. Top of fuel tank, beneath filler pipe escutcheon panel.
MAT (Manifold Absolute Temperature Sensor). Underside of manifold air plenum at rear.
Outside Temperature Sensor. Right side of engine, top right corner of radiator.
In Car Temp Temperature Sensor. Coupe: above left seat near interior courtesy light, Convertible: center of cargo compartment lid.
MAF (Mass Air Flow) Sensor. Front of engine ahead of throttle body.
Oxygen (O2) Sensor. Left side of engine, in exhaust pipe.
TPS (Throttle Position Sensor). Right side of throttle body at the front.
sensor locations
- Mass Air Flow (MAF), mounts in intake ducting between air filter and throttle body.
- Throttle Position Sensor (TPS), mounts on right side of throttle body.
- Idle Air Control valve (IAC), mounts in small manifold on bottom of throttle body.
- MAF power relay, in relay center on firewall beside master cylinder.
- MAF burn off relay, in relay center on firewall beside master cylinder.
- Manifold Air Temperature sensor (MAT), mounts in bottom of plenum near the back
- Coolant Temperature Sensor (CTS), mounts on front right of intake manifold base, below IAC valve
- Cold start switch, front right of intake manifold base, below CTS
- Exhaust Gas Recirculation valve(EGR), on top of intake manifold base, centered under plenum
- EGR solenoid, on top of intake manifold, rear, between distributor and valve cover.
- EGR diagnostic switch, on base of EGR valve.
- Electronic Spark Control (ESC)knock sensor, bottom right of engine block, in front of starter just above oil pan rail, in the coolant drain boss.
- ESC module, in relay center on firewall beside master cylinder
- Electronic Spark Timing (EST) module, on distributor.
- Oxygen (O2) sensor, in left exhaust manifold.
- Air Injection Reactor (AIR) convertor divert solenoid and port solenoid, both together at front of right valve cover.
- Oil pressure switch, on Y fitting with oil pressure gauge sender mounted in the oil pressure boss on the top left rear of the engine block behind intake manifold base. (applies power to fuel pump if fuel pump relay or relay circuit fails).
- Fuel pump relay, in relay center on firewall beside master cylinder.
- Fuel vaper canister (charcoal can) solenoid, on top of charcoal can in front left corner of engine bay.
- Air Conditioner (AC) pressure switch, in boss on AC high pressure side aluminum tube beside right strut tower.
- vehicle speed sensor, back of speedometer.
- Cooling fan relay, on core support beside battery.
this is the most consistently accurate I.R temp gun I've used for testing[/img]
http://www.testequipmentdepot.com/extech/thermometers-and-humidity-meters/infrared-thermometers/high-temperature-infrared-thermometer-58to1832f-50to1-laser-pointer-42545.htm?utm_source=bing&utm_medium=cpc&utm_campaign=NEXT - Bing Shopping - Extech&utm_term=1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN
you always need a base line to start from, on a corvette.
a logical step by step approach and keeping accurate notes helps.
youll NEED a multi meter, a shop manual
and a timing light and fuel pressure gauge at a minimum,
set and verify your ignition timing, pull trouble codes,set your tps and iac,, then check for vacuum leaks on the lines and intake,then get out your multi meter and verify all the sensors, chances are good a logical step by step approach will lead you to the problem, youll be amazed at what youll learn reading links. use of a shop manual and multi meter can be very helpful
http://garage.grumpysperformance.com/index.php?threads/testing-an-alternator.3222/#post-46703
http://garage.grumpysperformance.com/index.php?threads/is-my-alternator-shot.7808/#post-26803
http://garage.grumpysperformance.co...4-started-running-like-crap.10970/#post-48278
http://garage.grumpysperformance.com/index.php?threads/cs-144-troubleshooting.12494/
http://garage.grumpysperformance.co...lay-switch-locations-and-info.728/#post-43477
http://garage.grumpysperformance.co...ood-alternator-putting-out-low-voltage.12221/
http://garage.grumpysperformance.com/index.php?threads/battery-or-alternator.10003/#post-43220
http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-69239
http://garage.grumpysperformance.com/index.php?threads/electrical-puzzler.13038/#post-67835
http://garage.grumpysperformance.co...questions-can-be-found-here.12892/#post-66934
http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772
http://garage.grumpysperformance.com/index.php?threads/multi-meters.3110/#post-59136
RELATED INFO
A couple days of
reading the linked and sub-linked info
could save you a great deal of wasted time and money
and money spent on wrong or un-necessary parts
read the links and sub links below
a day or so spent doing reading and research,
(reading links and threads)
will frequently save you thousands of dollars and weeks of wasted work.
if you want a fast dependable car you will need to either do the research required to know exactly how and why things should work, or pay someone else to do the work that has taken that time and effort.
http://garage.grumpysperformance.com/index.php?threads/setting-up-your-fuel-system.211/
http://garage.grumpysperformance.com/index.php?threads/fuel-pressure-regulators.635/
http://garage.grumpysperformance.com/index.php?threads/how-big-a-fuel-pump-do-you-need.1939/
http://garage.grumpysperformance.co...ss-fuel-pressure-regulators.12776/#post-65998
http://garage.grumpysperformance.com/index.php?threads/drop-back-to-basics.12943/#post-67323
http://garage.grumpysperformance.co...hink-logically-don-t-assume.12484/#post-62772
http://garage.grumpysperformance.co...-test-seems-to-be-a-forgotten-art-form.11838/
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/
having a few basic meters,gauges etc.
IT sure helps too have basic tools, when isolating issues
MULTI METER
INFRARED TEMP GUN
TIMING LIGHT
COMPRESSION GAUGE
PRESSURE/VACUUM GAUGE
read the links and sub links
http://garage.grumpysperformance.com/index.php?threads/verifying-your-real-advance-curve.4683/
http://garage.grumpysperformance.com/index.php?threads/carb-tuning-info-and-links.109/
http://garage.grumpysperformance.com/index.php?threads/holley-carb-power-valves.1639/
http://garage.grumpysperformance.co...oven-facts-if-your-in-doubt.13051/#post-69824
http://garage.grumpysperformance.co...u-need-to-know-setting-float-levels-etc.1115/
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