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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: kmcbride74 on June 06, 2011, 09:55:32 pm
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Background/context: Just put in my rebuilt 350, mild cam, headers, edelbrock carb, etc. I have the HEI distributor with the coil ontop. I put the engine at tdc. verified this via the mark on the harmonic balancer and *gently* put a screwdriver in the number one cylinder to verify. Put the distributor in ensuring that the key for the oil pump shaft lined up and that the rotor was pointing to the lead for the number one cylinder. After some tweaking of the positioning of the distributor, the engine runs, but it idles rough.
The Cam I have said start at 14 degrees btdc. I painted a white line on the tdc mark on the harmonic balancer which is chevy orange.
Connected my timing light to the battery and the number one cylinder plug wire. Started engine. Turned on light. It strobes. I can read writing on the belts, but I cannot see my tdc mark anywhere near the timing gauge on the timing cover.
Clearly it is not off by that much or it wouldnt even run! I've tried 2 different timing lights. Still cannot see the timing mark. What am I missing here guys???????
Thanks in advance!
Kurt
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Are you sure you're on #1 and not #2? Which bank are you on Driver or passenger? Double check the firing order. Did you cross 5 & 7?
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Are you sure you're on #1 and not #2? Which bank are you on Driver or passenger? Double check the firing order. Did you cross 5 & 7?
Driver's side, front-most cylinder, I wired it like this: http://www.classiccarauto.com/impala/how_to/images/distributor.png
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Double check you didn't cross any wires.
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You could have also ended up a tooth off on your dist., But do check your wiring first.
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Check the previously mentioned things first, but additionally, have you tried turning the distributor while watching for the mark with the timing light while it's running? It will run with your timing so advanced that you can't easily see the mark.
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Also make sure you number 1 piston is tdc compression. That is very important. it will run 180° off if you have it advance/retarded enough. So, when checking for tdc, put your finger on the sparj plug hole and when its on its compression stroke it will push air out of the hole. When you feel air, bring your piston all the way to the top. The mark on the balancer WILL line up on both the compression and the exhaust/intake stroke.
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This may help too. http://forum.73-87chevytrucks.com/smforum/index.php?topic=20821.msg169907#msg169907 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=20821.msg169907#msg169907)
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Okay, last night, I did the following. It will not fire at all now...
1) Put the engine at 14 degrees btdc
2) Pulled cap, rotor was just about 180 off from tdc
3) Pulled distributor, spun the rotor such that the metal contact on it was pointing to #1 contact on the cap
4) Reinstalled cap
5) Pulled all other wires, reconnected them to the proper contacts on cap
Weird.....
Question: In this picture, the metal contact should point to #1 lead on cap when #1 cylinder is in firing position, right?
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Question: In this picture, the metal contact should point to #1 lead on cap when #1 cylinder is in firing position, right?
you want the #1 to fire when #1 is TDC, correct.
The firing order should be 1-8-4-3-6-5-7-2.
left bank: 1-3-5-7 and right bank: 2-4-6-8.
what year is your vehicle? It's not TBI is it? do you have vacuum advance?
remember, the actual position of where the order starts on the cap is not important.--it doesnt have to look like the pic you provided. #1 can be towards the firewall if desired, but the order is important, wherever #1 starts on the distributor, the order must be followed. #1 can be anywhere on the cap, as long as it points to the #1 plug wire when #1 is TDC on fire stroke. In other words, when i drop a distributor in, i usually strip all plug wires off the cap. Get #1 piston at TDC, then place #1 plug wire on cap point where rotor points---so #1 will fire. Then place the rest of wires in order.
Pulled distributor, spun the rotor such that the metal contact on it was pointing to #1 contact on the cap
I wouldn't pull the distributor to match the rotor with the plug wire, i'd match the plug wire with the rotor. No need to pull the distributor.
I hope you broke in the cam correctly, even though it didn't idle correctly initially.
if it is tbi: http://forum.73-87chevytrucks.com/smforum/index.php?topic=9232.0
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Question: In this picture, the metal contact should point to #1 lead on cap when #1 cylinder is in firing position, right?
you want the #1 to fire when #1 is TDC, correct.
The firing order should be 1-8-4-3-6-5-7-2.
left bank: 1-3-5-7 and right bank: 2-4-6-8.
what year is your vehicle?
KURT: 1985
It's not TBI is it?
KURT: No, it is not TBI, straight carb
do you have vacuum advance?
KURT: Yes, on the distributor
remember, the actual position of where the order starts on the cap is not important.--it doesnt have to look like the pic you provided. #1 can be towards the firewall if desired, but the order is important, wherever #1 starts on the distributor, the order must be followed. #1 can be anywhere on the cap, as long as it points to the #1 plug wire when #1 is TDC on fire stroke. In other words, when i drop a distributor in, i usually strip all plug wires off the cap. Get #1 piston at TDC, then place #1 plug wire on cap point where rotor points---so #1 will fire. Then place the rest of wires in order.
KURT: This is exactly what I did.
Pulled distributor, spun the rotor such that the metal contact on it was pointing to #1 contact on the cap
I wouldn't pull the distributor to match the rotor with the plug wire, i'd match the plug wire with the rotor. No need to pull the distributor.
I hope you broke in the cam correctly, even though it didn't idle correctly initially.
if it is tbi: http://forum.73-87chevytrucks.com/smforum/index.php?topic=9232.0
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good, now, it has vacuum advance. did you unhook the vacuum advance and plug the vacuum with a golf tee or something when checking timing?
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good, now, it has vacuum advance. did you unhook the vacuum advance and plug the vacuum with a golf tee or something when checking timing?
when I had it running, yes. At this point, the engine will not even fire :(
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btw, additional data point, turned it over with timing light on #1, and it is getting spark, at least to number 1
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i'd suggest it is 180 off, meaning the #1 tdc may be tdc on exhaust stroke. I'd try this:
Pull your #1 wire off cap and put where #6 is. Then follow #1 with proper firing order.
if that doesnt work, and you are certain you are getting spark and certain #1 is at tdc when rotor point generally towards #1, I'd look at the fuel delivery and/or carb adjustment / vacuum leak.
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i'd suggest it is 180 off, meaning the #1 tdc may be tdc on exhaust stroke. I'd try this:
Pull your #1 wire off cap and put where #6 is. Then follow #1 with proper firing order.
if that doesnt work, and you are certain you are getting spark and certain #1 is at tdc when rotor point generally towards #1, I'd look at the fuel delivery and/or carb adjustment / vacuum leak.
Thanks for the replies. I just checked again, put engine at 8 degress btdc by bumping strater, pulled cap, the metal lead on the rotor is right at the lead on the cap with the #1 wire. Double checked firing order as well. Is it possible that the plug going from the distributor to the coil in the cap is backwards? It appears to plug in one way....
In terms of fuel, carb, vacuum, it ran yesterday before all of this. I saw some fuel squirt into the carb when I operated the linkage manually.
This dang thing should start! Is there any logical flaw in my procedure, debug steps or approach here?????
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that plug you refer to only goes one way, because there is a clip on it that snaps it in place.
did you try putting #1 plug wire where #6 is and rerouting the following wires? i still say, it could be 180 off, though you set the mark at 8 btdc, it still could be exhaust stroke. remember, for each fire stroke, the crank/balancer turns twice.
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Instead of guessing, start from scratch, and forget about the 14 degrees or whatever the cam specifies. Pull the #1 plug and the distributor. Have somebody bump the key with your thumb in the hole until it pushes your thumb off. Then the mark on the balancer should be close enough that you can turn it by hand or with a ratchet and 5/8" socket on the balancer and make the mark line up perfectly with zero on the tab. Then stab the distributor back in and make sure the rotor is pointed at #1. If the oil pump shaft doesn't line up use a long flat screwdriver to turn it until it does. I don't like cranking the engine to get the distributor to drop. Triple check your wires that you have the right firing order and then set the 14 degrees by turning the distributor when it's running.
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that plug you refer to only goes one way, because there is a clip on it that snaps it in place.
did you try putting #1 plug wire where #6 is and rerouting the following wires? i still say, it could be 180 off, though you set the mark at 8 btdc, it still could be exhaust stroke. remember, for each fire stroke, the crank/balancer turns twice.
I have not tried this yet. I can/will. So that I'm clear, you're saying the balancer could tell me tdc, when the number 1 piston is down not up? i.e. that every other 360 degrees, the #1 piston is up?
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the balancer marks will reflect the same way whether on exhaust stroke when #1 piston is up AND fire stroke when #1 is on top. Crank turns twice for every fire stroke. Piston comes up twice for every one fire stroke. Every other rise of piston is fire stroke. You could have rotor pointing to #1 at exhaust stroke. Put #1 plug wire on #6 and reroute the rest of wires and see what you got. It only takes 5 or 6 minutes to check out.
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Ever 180° The number 1 piston is UP.
The piston strokes are....
*********
TM U= Timing Mark/Piston UP
TM D= Timing Mark/Piston DOWN
********
> TDC Compression> Fire >TDC Exhaust > Intake \/
| TM U TM D TM U TM D |
/\________________REPEAT_________________<
So, pull your distributor out. Pull number 1 plug out. put your finger on the spark plug hole. Bump the engine over until you feel air come out, then bring the piston all the way to the top. that will be TDC compression. Put your distributor in the hole. Bump the key to line up the oil pump shaft(http://forum.73-87chevytrucks.com/smforum/index.php?topic=20821.msg169907#msg169907 (http://forum.73-87chevytrucks.com/smforum/index.php?topic=20821.msg169907#msg169907)). Then put your cap on and set your timing. That should solve EVERYTHING. If anyone else thinks otherwise, they will post it. I had the Exact same problem when I fist built my engine because my dad wasnt specific about TDC compression or TDC exhaust. Ran like CRAAAP.
Good luck. Let us know what happens.
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Just wondering if you got this figured out?
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Just wondering if you got this figured out?
My buddy was able to see the mark on the balancer. It's good now. The root cause of my poor running issue was valves too tight! Too many beers the night we adjusted them before the motor went in. ;)
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That doesn't sound too good. Hope you didn't run it long like that.
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On 454s, the finger over the plug hole trick doesn't work. It's too deeply recessed. I tried using a compression gauge, but that really wasn't helpful either. I finally stabbed the dizzy, started it, pulled the dizzy, flipped it 180 and started it again. The winning position was the one that ran the best. LOL