73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: txchainsawgogi on December 02, 2010, 09:29:30 pm
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So the autozone by my house carries "spectre" brand universal timing marker tabs that appear to bolt on. Would these work for a chevy 350? I haven't been able to set the timing yet since I'm missing the tab!
12/7/10 EDIT* due to my engine setup I can't possibly bolt on a new marker, there just isn't enough room. Are there any suggestions for atleast sorta setting my timing for good gas mileage. Right now my exhaust pipe is sooty and I can tell its obviously burning through a lot of fuel.
Currently I have my vaccuum advance blocked off, because if I attach it...the engine stumbles and shakes.
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Yessur. They'll work fine
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Only problem I found with mine is it covers up the width of the balancer, making it difficult to impossible to see the mark on the balancer if it's anywhere within the the scale on the pointer. I'm gonna mod mine a bit to make it easier to read.
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Hmm, I hope it works! If I'm not using the original tab, can I ever set it back to factory specs? Seems like if its not in the exact same spot(with the exact markings) as the GM one, it'll always be slightly off.
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Is there anything I can do to find tdc other than use a piston stop? I'm SUPER broke thanks to xmas(gotta buy the gf stuff instead of my project this month, terrible huh?) and can't go out and buy one.
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Jam Insert a screwdiver in the spark plug hole and turn it over till you feel it hit. Put rubber over the screwdriver, too. This really isn't the smartest way, so disregard if someone has a better plan ;)
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How do I turn it over? Use the starter or...?
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You can stick your thumb over the spark plug hole while someone "taps" the starter. When it blows your thumb away from the hole its near tdc on the compression stroke. You can use a straw or something plastic instead of a screwdriver as well. Once its close with the starter you can use a breaker bar on the dampener to fine tune it to tdc.
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Define "Taps" haha. I've never done this on a car before.
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Bump the key slightly with the coil unplugged to get the engine to turn. You don't need to find TDCC just TDC so just turn the engine over by hand with the #1 spark plug removed. If you have an assistant get a flashlight and look in the hole until you see the piston go all the way to the top. Once it's up you're at TDC.
When I build an engine I always verify my marks before the heads go on.
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I don't even understand how to get the timing marker on there...it seems too cramped.
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With all the accessories mounted it will be very cramped trying to get the marker tab mounted. But it mounts using two of the bolts on the timing cover. The one I use mounts at about the 2 O'clock position, right under the water pump. The power steering pump, if you have one in place, could be a real pain to work around while trying to get that thing mounted.
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Yeah there's no way someone with normal sized hands can fit a new timing marker in there. Are there any suggestions for atleast sorta setting my timing for good gas mileage? Right now my exhaust pipe is sooty and I can tell its obviously burning through a lot of fuel. Currently I have my vaccuum advance blocked off, because if I attach it...the engine stumbles and shakes.
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You may have to remove belt driven accessories to reach it. It can be done.
Is your vacuum advance hooked to ported or full manifold vacuum?
Turn the distributor CCW until it pings and then back it off til it doesn't. That will get you pretty close.
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I know it can be done, but I work all the time during the holidays... so any tear downs are gonna have to wait atleast a month.
How do I figure out if its ported or manifold? I don't know what that means!
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This can explain it a lot better than I can: http://www.hotrodders.com/forum/distributor-tuning-theory-part-1-a-59033.html?highlight=DISTRIBUTOR+TUNING+theory
A full manifold source will be pulling vacuum at idle, a ported source will not. Unplug the hose and if it whistles and sucks air and engine rpm changes, it's full vacuum. That vacuum to the distributor will advance your timing a few degrees. There is a debate about using full or ported for the vac advance. My motor prefers a ported source, so that's what I use.
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Seems to be pulling nonstop. Are there downsides to keeping the advance capped off? I've fiddled with it in the past and everytime I connected it, the engine ran like crap. I figured the new distributor would help but no.
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Ahh ok so it needs to be hooked up. But why does it make the engine run so poorly when I connect it?
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Define poorly? If you mean detonating, then you've prolly got too much initial advance.
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When I hook up the vacuum advance it makes the engine shake, and feels like its about to die. Driveable, but it feels off. It even sounds rough.
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when you were explaining how to turn the distributor CCW until it pings, was I supposed to do this with the vacuum advance hooked up? Or capped off?
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Something sounds amiss. Did you also cap off the vacuum port on the carb when you cap the vacuum advance on the distributor?
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when you were explaining how to turn the distributor CCW until it pings, was I supposed to do this with the vacuum advance hooked up? Or capped off?
If you are using manifold vacuum you would want to leave it hooked up when turning the distributor. If using ported vacuum it doesn't really matter because it won't be pulling in any advance at idle. You can get this to work, but I suggest that when you get the time, install the timing tab, verify TDC, and get a baseline on your timing to save yourself some trouble in the future.
Something sounds amiss. Did you also cap off the vacuum port on the carb when you cap the vacuum advance on the distributor?
Agreed. The vac advance on the distibutor only reacts to the vacuum applied from the carb. It needs to be capped coming from the carb, not at the dist.
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My vacuum advance line goes to the three pronged thing that screws into the thermostat housing. Should it? That's how it was when I got it :/
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Im pretty sure that three prong port on therm housing has something to do with vacum activating once engine gets to certain temp.
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Do you have any ports on the carb that are capped off and not being used? I'm not sure but I think there is only 1 port on most q-jets that are ported (no vacuum signal at idle). Find it and hook it to your dist. Some engines don't respond well to full manifold vacuum, and if that's what you were running it could be why it runs rough with it hooked up. You can change the hose routing and optimize it later but for right now I would just get a dedicated timed vacuum supply to the distributor from the carb if you can. Just make sure you don't bypass any vital systems. You may have to use a tee connector.
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Ill take pics of everything when I get home so I can explain it better.
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Get me a decent job in Austin, and I'd come help ya out ;)
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Haha id have to get me one first. There are actually a lot of places hiring right now.
Pics on the way!
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Ok here they are. Middle prong blocked off and distributor blocked off. Not sure if the tubes are how they should be...that's how they were when I got it.
(http://i51.tinypic.com/288wdco.jpg)
(http://i56.tinypic.com/9qia1x.jpg)
(http://i54.tinypic.com/vrv5ol.jpg)
(http://i54.tinypic.com/2w3b2x0.jpg)
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Your fuel line is completely hashed.
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I need to change it I know! Old owner decided it would be ok to remove the fuel filter, and bend the line while he was at it.
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First, that air cleaner should never be sold.
Is it just me or is that choke pulloff hooked up to the EGR vacuum port on the carb?
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Haha its the only filter I had in storage. The truck didn't come with the original :-X
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I've been looking for photos for proper routing and can't find anything. Help!
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http://forum.73-87chevytrucks.com/smforum/index.php?topic=18126.0
What's the year of your truck and what trans and what other emissions equipment again?
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Just a few notes-
1- those see thru caps are crap. I'd junk it.
2- You are trying to get a vehicle to run right with a SERIOUS restriction in the fuel supply. I'd fix that to
3- Then I'd find an emissions diagram online, and re run all the hoses I need to.
4- Then I'd time it.
Anything outside of that order and that list, is just asking for issues when trying to get an engine to run properly.
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1978 350 5.7, no emissions. Auto trans. Previous owner hacked all the emissions stuff out and seems they put hoses back willy nilly.
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I'd fix the fuel line first, too.
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I'm replacing it when I replace the rochester later this month. How should I have my hoses routed though? I see those charts but what if I have no emissions components hooked up?
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If it was mine the very first thing I would do is pull all of those clear lines and caps off and throw them away. Then I would replace the fuel line and remove the EGR valve if there was one and put a plate over it. Then I would run full manifold vacuum to the PCV, brake booster, and HVAC reserve cannister, and a timed vacuum to the distributor. Whatever vacuum you have for the choke pulloff, etc should be short little lines that go right from the carb to it. Any left over ports on the carb would be capped. That's what I run on mine, and it's simple and clean.
edit: and full manifold vacuum to your trans if you have a modulator, and your low vacuum switch if you have a lock up converter
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So do I need to use that three prong thing that screws into the thermostat housing? I'm mainly confused by all of this because I don't know the names of everything.
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It's a thermal vacuum switch, and if your not running any emissions control you don't need it.
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As it is right now, I don't see where you need that vacuum switch on the t-stat housing at all. Unless you have something that's vacuum operated and don't want it operating until the engine warms up. Certainly not needed if all the other emissions stuff is gone.
I too would get rid of the clear lines and use real vacuum line.
If the fuel line still flows, it's aint the end of the world, but should be replaced when you get a chance. Unless you experience the motor starving on the top end, it's probably flowing enough to keep the bowl on the carb full.
as for that air cleaner...if your truck ever burps enough fuel out of the carb to soak into that element, it can/will start a fire under the hood of your truck. That's why no-one likes them. they have caused many a fire where it could have been avoid by running a more conventional air cleaner.
Grim82 had a good post on where to locate all the vacuum lines you need for it to function.
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Yeah I don't care for the clear lines, but its all I had...same with the orange one. Its all getting replaced next paycheck.
So the vacuum advance should be hooked to the carb and not the t-stat switch? Viewing the emissions diagram is confusing since all mine is gone. Can someone with a similar set up post a photo? Id really appreciate it. I've already learned a lot about these lines :/
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So the vacuum advance should be hooked to the carb and not the t-stat switch?
That's what I would do.
Also on that foam air filter; they are notorious for falling apart and your carb sucks in all the little pieces.
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So do I hook it up to the port in front of the carb? And use a T to connect it to the port next to the choke housing? Because that seems like how its already set up using the 3 prong thermostat switch.
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Run a hose from the timed port on the carb to the dizzy (it will be higher up on the carb body than manifold ports, and have no vacuum at idle), and full manifold vacuum to everything else-should have a short hose to the choke pulloff, a bigger line from the back of the carb to the brake booster, a 3/8" hose to the PCV, a small line for your trans, and one for your HVAC canister on the firewall. Then cap all the extra ports. If you have to use a tee for manifold that's fine.