Engine is apart -- What would you do?

[zeeboost]

Hi all. As some of you may have read, when I first bought my hybrid the cam had a couple of rounded off lobes, and the engine has had some excessive blow-by, along with a couple of other problems. So, now that the engine is apart, I'm replacing the headgasket, trying to locate and remove any kind of metal shavings, and I'm going to be changing cams. The cam that I was thinking about was the Competition 270H (maybe 280H). My specs are:

 

*sbc 350 -- block came from GM factory from a 78 pickup (I forgot which model)

*Holly Systemax II Alum. Heads -- Intake flows 220, exhaust 178, 2.02/1.600 and 64 cc chambers

*Pistons are still stock dished pistons

*Drive line is a t56 with an aluminum flywheel and a 3.9 rear

*Victor jr. intake

*Edelbrock 600 carb

*MSD ignition

*Currently has a Lunati 300 cam, but I think it's too big for my setup

*True dual exhaust with headers and flows

 

If you need any other information, please let me know.

 

I'm looking to get between 350-370 rwhp -- I don't want too much because that's when things start breaking, and I gotta save some money for classes and books

 

So, I guess the questions are:

 

1) What kind of cam would you choose with this setup? This is pretty much going to be a daily driver, so I need something streetable - it just needs to pack a punch. Like I said, I think the Comp. 270H is a good candidate, but I'm not as experienced as many of you are with this, so prove me wrong if I am.

 

2) What would be causing the blow-by? With the engine apart, what can I check to make sure the engine is sound?

 

3) Is there anything else that I can buy for this engine that won't hurt reliability and still help out with performance? Is there anything else that you would buy for the engine if this was your engine? (and you wanted the same streetable setup, of course; not a 7 second monster)

 

I did search the archives, but everybody has a different setup, so I wasn't sure which one to go with. I also searched for one of grumpy's 500-point checklists, but it was unsuccessful. Thank you all in advance with any help. This forum kicks @ss!

[zeeboost]

Was this a stupid question? Should I re-search the archives?

[Guest woodyhooten]

I think you'll probably be able to find exactly what you want in the archive as this is a fairly common discussion. I seem to remember seeing a few of grumpy's checklists regarding this topic around here. Keep looking and good luck!

[Brad-ManQ45]

Read this thread:

 

http://www.hybridz.org/phpBB2/viewtopic.php?t=29983

 

I don't think it's any coicidence that the Cam Maker you picked is not on his list...

[grumpyvette]

HERE TWO CHECK LISTS

heres a few things that should always be checked on an engine build

 

heads

are the pushrods perfectly strait?

do the pushrods flow oil?

rocker studs/guides torqued correctly?

do the head bolts have washers under the bolt heads? are they the correct length for the cylinder heads in use?

have the heads been pocket ported?

combustion chambers unshrouded?

intake ports gasket matched"

are the valve guides cut to the correct length?

are the heads pocket ported?

is the retainer to valve guide clearance correct?

are the valve guide oil seals installed?

is there valve spring seats installed?

inner damper springs installed?

spring bind height checked? (to exceed max valve lift by .050 min.)

oil return holes cleaned of casting flash?

were steam holes in heads necessary?

were the spark plug threads of a installed spark plug extending into the combustion chamber?

rocker slot to rocker stud clearances ?

retainer to valve guide clearances?

spring bind height checked for the correct spring pressure?

valve lash/preload ?

are the valve springs the correct tension,height?dia.

keeper the correct angle? style? size?

valve seats the correct angles?

valves back cut?

valves the correct length, stemsthe correct diam.

strait?

rockers the correct ratio?

were the valve to valve guide clearances checked?

were the heads milled?

did the head gasket overlap the bore?

what are your valve train clearances?

is the rocker arm geometry correct!

chambers CC,ed

port work..(some steps optional)

 

(1) open throat to 85%-90% of valve size

(2)cut a 4 angle seat with 45 degree angle .065-.075 wide where the valve seats and about .100 at 60 degrees below and a .030 wide 30 degree cut above and a 20 degree cut above that rolled and blended into the combustion chamber

(3)blend the spark plug boss slightly and lay back the combustion chamber walls near the valves

(4)narrow but dont shorten the valve guide

(5) open and straiten and blend the upper two port corner edges along the port roof

(6) gasket match to/with intake and raise the port roof slightly

(7) back cut valves at 30 degrees

(8) polish valve face and round outer edges slightly

(9)polish combustion chamber surface and blend edges slightly

(10) remove and smooth away all casting flash , keep the floor of the port slightly rough but the roof and walls smoothed but not polished.

(11) use a head gasket to see the max you can open the combustion chamber walls

(12) blend but don,t grind away the short side radias

 

 

block

is the oil pump pick-up mounted 3/8"-1/2" from the oil pan floor/

is the windage screen mounted about 1/8" from the rotateing assembly/

is the pick-up brazed to the pump body?

has the oil pump relief piston in the oil pump been checked for free ,easy movement? clearance? spring tension?

is the oil pump pick-up tube inserted too far into the oil pump body,(binding the gears)

has the block been clearanced for the rotating assembly?

has the block been aline honed?

is the crank strait?

are the damper install keyway and threads ok?

counter weights clearanced?

MAGNAFLUXED?

OIL PASSAGES CLEANED?

GALLERY PLUGS INSTALLED CORRECTLY?

has the cam to rod bolt clearance been checked?

piston to valve clearances checked?

piston to bore clearances?

TRUST BEARING CLEARANCE?

what were the piston ring to slot clearances?

RING GAPS?

were the rings all checked individually for end gap in the cylinders they were used/installed in?

were the rings checked to make sure the correct side faced up, and the correct ring was in each groove?

what were the back clearance on the rings?

were the oil ring expanders carefully fitted for correct drag?

were the oil ring scraper ring rails checked for end gap?

total cam lift and remaining clearanceS?

WAS THE CAM DEGREED IN?

main bearing clearances?

what is the main bearing run-out clearance

piston to head clearance? (QUENCH?)

head gasket to coolent holes checked?

magnets installed?

rod bolt to block clearances?

what tq reading is necessay to spin the crank with no rods attached?

are the rod bolts and main caps torqued correctly? (rod bolts checked with a bolt stretch gauge?)

did you check the block for a strait main cap alignment?

what size journals and what were the bearings edge to filet clearance??

are the journals checked for finish and run-out/tapper?

did you use moly lube to assemble?

correct bearing crush?

did you pre-lube before start-up?

did the distributor gear fit the cam gear precisely?

was the distributor oil flow mod done?

was the correct style distributor gear used?

did you check the piston to piston pin bores for fit and clearance?

did the piston pins to snap ring clearance seem overly tight?

if they are pressed pins were they correctly matched and checked for free movement in the pistons?

was the engine ballanced?

cam button installed?, and lock plate installed?

were the rods resized? checked for parrallel bores/were the rods strait?

piston valve clearance notchs correctly located on the pistons? edges smoothed?

were the rods checked for length?

is there a few thousands clearance on the oil pump drive shaft AFTER the distributors bolted down?

did you install a steel collar on the oil pump drive shaft?

was the rod to piston pin side clearance checked? (at 4 places seperated bye 90 degree spots)

does the oil pump drive shaft mid section clear the block with the pump installed?

whats the starter to flywheel gear clearance?

is the pilot bearing to trans imput shaft clearance ok?

is the front motor mount bolt to fuel pump pushrod clearance ok? did the fuel pump pushrod move easily/

are you possitive the pistons were installed with the correct valve relief in the correct location?(eiieeiie) were the pistons installed with the correct side facing forward/

what torque values were used on all fasteners/ were they the correct length and type bolts?

were the bores honed with a torque plate in place?

was the cylinder finish correct for the type rings used?

was the oil pump itself checked for free spin and clearance AFTER THE PICK-UP WAS INSTALLED?

was the cam drive checked for free rotation and drag/

were the oil passage plugs drilled for extra oil flow?

were the lifter bores checked?

cam to timing cover clearance?

cam journal to cam bearing clearances?

was the cam journal run-out checked?

was the cam degreed in or just lined up useing factiory index marks?

has the rod and windage screen to oilpan clearnce been checked?

does the dipstick & tube clear the windage screen?

was the cam lobes/LSA/LIFT CHECKED?

is the deck square/level?

whats the cross hatch hone angle?

what grit hone was used?

are all the threads clean/clear?

brass freeze plugs installed?

block painted?

 

 

go through your standard check list, for carb cars,(some of the info works on all cars)

 

check that theres spark at all the plugs and the plugs are burning cleanly

 

check that your getting the correct voltage at the coil/ignition and plugs are not loose and gapped correctly,

 

check that the wires and coil are not arcing or shorting out

 

check that the throttle linkage opens fully

 

look for coolent on the plugs or coolent leaks under the car

 

look for loose vacume hoses, crimped lines, ETC,

 

check your oil level is correct

 

do a compression test if anything looks bad on the plugs or engines seems to not be running on all 8 cylinders

 

look for rocker arms that are not moveing correctly,bent push rods, loose rocker arm studs, broken valve retainers, or valve springs

 

check that your getting good oil pressure at idle(pressure switch can turn off ignition)

 

check that cam and ignition timeing is ok/not changed (timeing light,

 

loose timeing chain on cam drive, check that the distributor has not moved, check with a timing light)check that the rotors not loose under the distrib. cap and the distrib. cap itself is not loose or cracked

 

check that you have not wiped a cam lobe, broken a valve spring or valve spring damper.

 

look for loose rocker arm adjustment

 

look for vacuum leaks

 

look for loose electrical connections, fan belts or accesories that might be having a bearing or electrical failure putting excessive drag on the engine

 

look for low fuel pressure/clogged fuel filter, bad fuel, water in gas, rust in the gas or just low on fuel.

 

look for plugged up air filter/bad pvc/egr

 

check catalitic converters not plugged/restricting the exhaust flow

 

check for moisture in distributor cap.

 

check that the damper on the crank has not come loose and moved the timeing marks on the outer ring by having the elastic break loose between the rings on a stock style damper or that the key in the crank has not sheared allowing the damper to move possition

 

do a CYLINDER LEAK DOWN test

 

make sure the fuel pressure is correct and the fuel supply system is working at 6psi-8psi before the pressure regulator and about 5psi-6psi at the carb

 

http://www.centuryperformance.com/timing.htm

 

http://www.centuryperformance.com/vacuum.htm

 

http://www.boyleworks.com/ta400/psp/distcurve.html (pontiac but info the same for chevy)

 

http://www.73-87.com/garage/101s.htm

 

http://www.73-87.com/garage/hei.htm

 

[image]http://www.73-87.com/garage_photos/disremov/firingorder.jpg[/image]

[image]http://www.centuryperformance.com/images/tech/fuel2.gif[/image]

 

look for spark plug wires that are loose or not correctly connected

 

heres info later efi engines like my corvette can use

 

HERE TAKE IT STEP BY STEP

 

http://www.c4vettes.com/maf.htm

 

http://www.c4vettes.com/l98.htm

 

http://www.midniteworks.com/vettecodes/vettecodes.html

 

L-98 Engine Start Sequence

 

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.

 

Fuel Rail Pressurization:

 

When you first turn the key to the “on†position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.

 

Initial Crank Action:

 

If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.

 

Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).

 

The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.

 

ECM Reaction:

 

If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).

 

The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode†feature put in place to allow for a fuel pump relay failure).

 

The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)

 

Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catchâ€.

 

Engine "Catches":

 

When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).

 

The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.

 

If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.

 

ECM Mode:

 

The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.

 

Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time†or less “on timeâ€) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.

 

Note that prolonged idling can force the computer back into open loop mode.

 

Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.

 

Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.

 

Summary:

 

If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.

 

A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

 

 

Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).

 

A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).

 

Theory of Operation

 

As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.

 

Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.

 

It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.

 

MAF Operating Conditions

 

The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.

 

There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.

 

The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.

 

Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.

 

A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).

 

MAF Problems

 

Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.

 

Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.

 

A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.

 

AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.

 

The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.

 

MAF Mods

 

The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.

 

The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.

Welcome to C4 vette codes it is very ....repeat very

important that if you are not savvy of working on your

vette ...you would be better off - taking your car to a

dealership for repairs on your trouble codes.

However if you feel that you want to dive right in ..than you

have come to the right place.First locate your car's alcl

this component is located just below the instrument panel and

to the left of the center console. Remove the plastic cover

the first two slots to your right are the A & B slots for a drawing of

the alcl module's picture is added below.

The A slot is the diagnostic slot and the B slot is the ground

slot. insert the computer key into these slots (with the engine

off) this is very important...now only put the ignition key

to on ( not start !!!) the check engine light will display a

code 12 which is one flash followed by two flashes.

this code will be flashed three times ..followed by the

trouble code stored in your car's computer.

what ever the code is it will be flashed three times.

have a paper and pencil ready and write down the

code .

 

code 13 =1 flash followed by 3 flashes =>oxygen sensor

code 14 =1 flash followed by 4 flashes =>coolant sensor

code 15 =1 flash followed by 5 flashes =>coolant sensor

code 21 = 2 flashes followed by 1 flash =>throttle position sensor

code 22 = 2 flashes followed by 2 flashes=> throttle position sensor

code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor

code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor

code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor

code 32 =>egr system

code 33 =>map sensor

code 34 =>maf sensor

code 35 => idle air control

code 41 => cylinder select error

code 42 => electronic spark control

code 43 => electronic spark control

code 44 => lean exhaust

code 45 => rich exhaust

code 51 => PROM

code 52 => fuel calpak

code 53 => system over voltage

code 54 => fuel pump circuit

code 55 => ecm

code 62 => oil temp

please remember that if you have the computer key installed

in the alcl and you start the engine ( you will ruin the engine's computer

)

only put the ignition to on (not to start)

If you should get a check engine soon display.. you can use

the above procedure and codes to buy the right part

or at the very least to keep from getting taken for a ride

and be made to pay hight prices for some inexpensive

module that you could have installed yourself.

You never ask a barber if you need a haircut ..

so you have to be on guard they will see you comming

a mile away.

If your engine displays a trouble code ... your engine will

go into limp mode ..it will still run but very poorly.

you might be able to reset the computer if it will not start

( just to get home ) by disconnecting both battery cables

and re-installing them ...this is not recommended ..but if

you are stranded it might help unitl you get your car home

or to a repair shop..good luck

[zeeboost]

Sorry, I was hoping this post wouldn't be like one of those that I always see, "I HAVE A Z AND WANT 500 HP AND 30 MPG -- WHAT DO I NEED TO BUY, HOW MUCH WILL IT COST, AND HOW LONG WILL IT TAKE!!!"

 

I honestly did search the archives for a camshaft selection, but I couldn't find anything...guess I should've thrown the word "combo" in there. Thanks for the link, and thanks for the list grumpy. I guess the only question I have left is what kind of little things could I buy for it that won't hurt reliability, such as roller rockers. But I suppose I can search the archives for that one some more. Thanks again, and I apologize now for posting this up.

[Guest kc6wfs]

And be sure to double check the list.......

 

 

Thanks for the list Grump!!!

 

Dave

[Heavy Z]

9.5 comp or less I'd go with the comp XE268H - 224/230 @ .050 and 477/480 max lift or for 10:1 or higher the XE274H 230/236 and 487/490, both are at 110 ls. That 230/230 with .480 max lift you mentioned is also a good cam.

[love-my-V8-280Z]

OH MY GOD!

 

I wanted to someday rebuild a motor but you just scared the pants off me!