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Engine Won't idle

 
kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 01/23/10 03:59 PM

I just installed a 421 chevy sbc in my car.  It has all forged internals, a lunati cam with .480 lift and 230 at .050.  I also have vortec heads on it with the mods to accept that valve lift. 1.6 roller rockers, a rpm air gap intake, a new holley 750 double pumper and a dui hei distributor.  all the vacuum ports are pluged on the carb.  I am able to get the engine running at 2000 and up, it runs strong and the timing is all it with a total of 35 degrees at 3000.  but I can't get it to run below 2000. i have had the 6.5, a 4.5 and now a 3,5 power valve in the carb.  the engine pulls 23 inches of vacuum at 200, when i have the throttlee blades set where they shoulf be at idle it will fire a few cylinders then quit.  When  it fires those few cylinders the vacuum reading is at 10 inches. I have tried adjusting the timing as well with no luck.  I can't figure out wha the problem could be.  Any help would be appreciated greatly.

Thanks  

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gettnlarge01
Everything in my driveway’s a Chevy
Posts: 545
Joined: 01/10
Posted: 01/24/10 07:05 AM

are you using the plate between the carb and intake?  
luck is when skill and opportunity meet

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 01/24/10 07:31 AM

Yes I have a nitrous plate there which is also brand new  

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gettnlarge01
Everything in my driveway’s a Chevy
Posts: 545
Joined: 01/10
Posted: 01/24/10 12:51 PM

to run a holley carb on the performer rpm intake you need to run a flat plate to seal the passenger side backcorner or you will have a vacuum leak.  you can spray startting fluid around the carb base to see if that the problem  
luck is when skill and opportunity meet

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 01/25/10 09:30 AM

FIRST ... verify that the timing mark on the damper and the pointer are accurate... there are variations...12 o clock and 2 o clock versions..   dampers with the timing mark at 12 o clock are much more common...  mr gasket does make a bolt on timing pointer for the dampers with the 12 o clock marks... you will need to look straight down behind the water pump to use them.. but it sure makes setting your timing easier..  i cannot remember.. if there is 30 or 40 degrees of difference  between the two...

take the carb and nitrous plate back off... read the gasket impressions left by the clamping force... make sure there are not any gaps as described above...

do you have caps or plugs on the nitrous plate so it does not cause you vacuum leak... as it might not be hooked up yet???

power valves will not effect idle... except when they are leaking...

while you have the carb off.. turn it over.. make sure the choke is open.. hold it up to the light... look through the gaps around the throttle blades...  you should only see a tiny bit of light on the primary side..

while you have the choke open and the lever off fast idle..   the throttle blades should be just below the idle transition ports.. (they are the long slot in the base plate)  

what happens when you pull the idle mixture screws from the metering block.. and spray carb cleaner into the hole... does some of it come out the idle feed holes in the base plate.. and some out the transition slots..


try these... post what you find...  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 01/25/10 10:05 AM

I checked the timing again. When I put my finger in the number 1 spark plug hole and turn the engine over and once I first feel the air push out I stop.  The timing mark on the balancer is close to the 12 o clock position.  I then line it up with the 0 on the timing tab which is in the 2 o clock position.  and the rotor is pointing to where I have the number 1 spark plug wire on the distributor.  This is the second carb I have had on the engine and the holley is brand new. All vacuum ports are plugged and the everything is hooked up for the nitrous system to work except for the plugs to connect the wiring.  I was actually able to get the engine to idle at 500 rpm yesterday afternoon.  While it was running I sprayed carb cleaner where the intake ports were and around the base of the carb and nitrous plate.  There was no change in idle speed.  It sounded a bit off and I check the timing which was at 4 degrees after TDC which is odd to me.  When I tried to advance it the engine would cut off. I have the idle speed screw set per the instruction that came with the carb.  I just don't understand what is going on.  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 01/26/10 01:16 AM

ok... lets find TDC....  this is hard to do alone... pull your number one spark plug again. stick your finger over the hole and find the compression stroke.... find some solid copper house wire... 14 or 12 gauge... solid conductor.. a foot is too much..   bring the engine up to where the timing mark is at the 11 o clock position..   with this straight piece of soft copper wire pushed about 2 inches into the spark plug hole.. slowly with a breaker bar and a 5/8" 6 point deep socket on the crank bolt.. move the crank to the right... while feeling the copper wire touching the top of the piston... when it stops moving up... see where the mark on the balancer is pointing..

you can rock the crank back and forth.. while you hold the wire till you can find really close to top dead center... the piston will push it up .. and as it passes TDC.. it will start going back done..  

now... without turning the crank any more lets see if the damper lines up with 12 o clock or 2 o clock marks on the pointer...

post what you find..

just curious... who set the timing chain alignment?????







( i don't like people sticking anything into the spark plug hole...i have had several  accidents when this is done remotely..... bent valves, broken screw drivers, damaged piston tops, hands  stuck between the screw driver handle and something near by when the piston come up.....   copper wire will bend and deflect usually without damaging anything,  by people not really understanding the instructions over the phone.)  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 01/26/10 05:44 AM

The engine builder degreed the cam. You would think he did it correctly.  I will check with the copper wire and let you know what I find.  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 01/26/10 08:44 PM

this has nothing to do with cam timing.. it has to do with the marks that indicate when the crank at at top dead center so you can set the distributer timing..

let me describe...   i don't know what year they changed.. probably 1980 or so..  

the early timing marks were at 2 o clock....

the late timing marks were at 12 o clock...


there are a lot more late dampers.. than there are early dampers..  so there is a chance that you ended up with a late damper with an early timing mark..    you could even have it the other way... an early damper with a later timing pointer...


if you had the damper off..  you can tell the difference...  if the keyway in the damper is almost lined up with the timing mark on the outside.. it is an early damper...

if your keyway on the inside is an eighth of a turn to the right of the timing mark on the outside.. you have a later damper..

why....????

the woodruff keys in the crank are at at top dead center number one... since the number one cylinder is 45 degrees to the right of straight up... thats where the crank woodruff keys lineup in relation to the block with the crank at top dead center #1

right now... we are just worried about finding out where your actual top dead center marks are...


to see if you can get your car running properly...

i am posting all the theory.. so the many readers to come .. will learn ...  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 01/27/10 05:36 AM

I appreciate all the help.  I didn't get a chance to check it out last night but I will tonight.  

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gettnlarge01
Everything in my driveway’s a Chevy
Posts: 545
Joined: 01/10
Posted: 01/29/10 07:51 PM

+1  
luck is when skill and opportunity meet

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 02/02/10 07:34 AM

It has been crazy around here.  Went to Daytona for the 24 hour race this weekend, so no work on the car was done.  Hopefully I will in the next couple of days.  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 02/03/10 04:42 PM

I checked tonight.  I pulled all of the spark plugs out to rotate the engine over by hand.  I then plugged the #1 spark plug hole with a paper towell.  The paper towell then popped out when there was first compression in that cylinder.  The timing mark was at 11.  I then slid something in and held onto it as I rototaed the engine.  The piston slowly contacted it and as I rotated slowly I felt it start pushing down on my hand.  I was also watching the timing tab.  As the peice was being pushed into my hand the mark in the damper came closer to the timing tab.  Once the peice stopped pressing in my hand I stopped rotating and that was just after the mark was just passed the 0 on the timing tab.  I rotated the crank back and did it again to make sure.  The eninge is at TDC.  The rotor on the Distributor looks to be in about the 4 oclock position.  

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waynep7122
Everything in my driveway’s a Chevy
Posts: 556
Joined: 08/09
Posted: 02/04/10 02:27 PM

well the timing mark is right....

if the cap is still off..   pull the rotor and see where the timing mark on the balancer lines up somewhere between 0 and 25 before when the tips of the reluctor and the pick up coil line up...

i am taking  that the mechanical advance on the top of the HEI is free to snap back totally free when you twist it against the spring tension..


is there an adjustment knob on the timing light???

any chance of the wire cross firing.. .. you have a swapped firing order... as i recall...  the original firing order was 18436572..  is 6 still the 5th in the firing order...  hook your timing light to that one...   that should still light up the damper at the exact same time... ...

oh.. while you have the rotor off.. examine the pick up coil stacked parts.. Don't loosen it..  look for cracked magnets..

that will throw weird patterns.. might make it idle weird..  



i set the harmonic balancer  to what ever the base timing will be.. and turn the distributer body to line up the reluctor and pick up coil tips.. and lock it there... it is usually within a degree or two of being the exact timing i want... so i don't have to turn the distributer to get the engine started the first time...  makes me look like a magician when i can throw a distributer in.. then reach through the window and the engine starts on the first try..

i will be lurking around someplace...   post what you find..


by the way...    which carb????   have you verified that the carb is working right...  power valves don't effect idle..  idle circuits do..    are the throttle blades in the base plate properly centered..??? closing all the way...   can you take out the idle mixture screws.. blow some carb cleaner into them.. verify that the idle circuits are not clogged..  it should spray out the top.. and out the idle transition port and the idle feed port..

idle transition port is a slot above the throttle blade...     the idle feed port is a round hole.. usually just below where the closed primary throttle blade is at...

once in a while... while a carb is off..   the throttle blades can get shifted on their shafts.. when they get banged on a work bench or counter..    if they are off center... the car will have problems idling..

there is one other thing... is there a possibility that the base plate  to main body gasket got installed backwards..  with the idle feed holes in it on the wrong end...

i had a problem with a carb years ago.. seems that the sterile med flys they used to release around here liked the smell of carbs..  they climbed into 2 different ones on my bench.. they would sink and clog the main jets..  when the guy with the other carb came back.. complaining .. i told him .. he probably just has some bugs in the carb... when i took the top off.. and used tweezers to pull them out.. i thought he was going to fall over...  

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kempfer421
V-6 Camaros rule!
Posts: 38
Joined: 01/10
Posted: 02/04/10 03:32 PM

The carb on the engine is the brand new 750 holley, the 650 demon I rebuilt and had a part a few times to make sure I didn't put the gaskets on wrong.  I will check the rotor.  I can push it against the spring and it snaps back like it should.  I will also look at the reluctor and tip of the coil line up.  

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