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Old 06-20-2004, 09:53 PM
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bad timing problem..

well i got my new motor all together and in the truck... now i cant figure out y i cant get the timing rite.. i hook up my timing lite.. my vacum gage and plug vacum advance.. after breaking it in for half hour i drop the idle to do the timing.. when i dropped the distributer in the harmonic balancer was at 0* and i never turned the distributer.. n e ways.. it fires.. i play with the distributer and noticed the best vacum and highest idle was at around 24* then i try to back it down to 12* and it just idles so low and wants to die.. i would leave the timing at 24* but when i sit there and stomp on the throttle i can hear the more chattering.. detonation i assume? then when i try to advance the timing more to see if its not enough advance. concidering the harmonic balencr doesn't mean n e thing rite now.. so i turn the distributer till it hits the manifold.. and its at around 18 vacum and think it was still going up.. should i pull the distributer and try relocating it so i can get a bit more advance? o ya and i thought i would mention that my temperature gage is stuck at 130 till i start the motor then it reachs 230 so i shut her down! i no for sure i need a new gage.. but i think it is getting pretty hot.. and isnt that a sign of bad timing?? thanx for any help
bye the way the motors a 350 sbc bored 60 over.. camel hump heads.. mild blazer cam..(not sure of specs) edelbrock manifold, carb headers.. roller rockers.. if ya need n e more info let me no.. this is all in my 1979 chevy pick up..

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Old 06-20-2004, 10:59 PM
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set the timing at 12 degree`s before top dead center with the vacuum advance disconnected and plugged, then connect the vacuum advance to a manifold source or constant vacuum. if it still doesn`t idle look elsewhere.
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Old 06-21-2004, 08:28 PM
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well it idles like that.. but barly.. sounds like it wants to die.. and my temp is gettin hot still..
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Old 06-22-2004, 06:47 PM
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ok i played with it some more today.. i had my vacum guage hooked up, my timing light and my advance plugged.. well i tried as u suggested doublevision.. and my results.. > it was to much retard i guess.. it didn't idle very good at all.. and when i pulled the throttle wide open quikly bye hand it shot a flame/backfire at me! but my vacum guage was reading normal.. so i said forget the guage im doing it bye sound and the timing lite cuz everytime i got it sounding good the guage would say late timing... so i advanced it till it chatterd. i guess that would be detonation or pinging? just sounds like a bunch of loose lifters or soemthin.. but anyways i turned it down till i had no more of that.. then i went till it started back fireing again.. so i put it rite in between.. but the weird thing is.. its sitting at around 19* with advanced plugged.. then i plugged advance back in.. idle is better now! i got a edelbrock performer carburator on there so i made sure my choke was working fine and i changed the jet springs back to stock.. set the air screws.. now it idles fine.. but! it idles at 1000rpm! when i try to turn it down a bit to around 600 it doesnt wana idle.. i rev it up.. it'll sit at 1000 rpm then after 10 seconds it'll drop down to 600 rpm again.. then slowly drop lower and lower till it dies.... this is messed up.. my old motor did this rite before she blew! well the old motor pulled the rocker studs outa the heads and valves hit on every piston.. maybe could it just be loose rockers? or wut would make it idle so shi*y??
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Old 06-22-2004, 06:56 PM
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Set it at 12o advance. Raise your idle speed at the carb. Then, set the mixture.

Did you tighten the valves too much? That is another possiblity.
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Old 06-22-2004, 07:44 PM
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im gona check the valves rite now.. and my points... if that would have n e thing to do with it?
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Old 06-22-2004, 08:14 PM
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I cant tell you much about your timing requirements,but if you want to get the distributor to not hit the manifold,rotate it all the way to the retarded direction,then move all your spark plug wires one position advanced,and you will then have about another 40 degrees of timing you can get before the canister hits.You dont need to remove the distributor at all.Good luck.
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Old 06-22-2004, 08:43 PM
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Trav, You had the procedure correct the first time. Don't rev it with the vacuum advance disconnected. The reason it backfired through the carb is the advance was disconnected.

Do the same thing again same as the first post. Set initial timing ti 12 degrees. Reconnect your vacuum advance, set idle speed and go from there.

The vacuum gauge was showing "late timing" because of low vacuum. This is not in reference to ignition timing. It is in reference to camshaft timing. A late closing intake valve, like a rumpity cam causes, indirectly causes low manifold vacuum. That's what the vacuum gauge was showing.

Now the most likely cause of the erratic idle is a busted vacuum advance canister or it's not adjusted correctly. If it's adjustable. This is assuming you have no other vacuum leaks.

Connect the vacuum gauge and the timing light. Hold them side by side and have a buddy rev the engine and release the throttle slowly. Watch the timing decrease as the revs drop. Take note of the vacuum reading when the timing jumps back up, or stops decreasing. If the timing falls low and jumps up then it is not set correctly.

When you rev the engine the timing should drop and then come back up in sync with the vacuum reading. This is what it's supposed to do. If it isn't then you have problems with the vacuum advance canister on the distributor. Either not working or it is not adjusted properly.

If you do not have an adjustable vacuum advance you need to purchase one. It's good to have if you have a fairly rumpity camshaft. They're cheap and easy to install.

I hope this helps

Larry
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Old 06-22-2004, 10:16 PM
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hey man thanx for the reply.. yes i do have a adjustable vacum advance.. and i turned it all the way in and 1 turn out.. inside the canister, n e ways.. i found my timing problem rough running problem.. 2 of my wires were burnt off the headers! so i replaced then with some other wires i had lying around and dam she fired up no problem.. set it at 12o like u guys said.. reconnected the advance and also reset my idle and air screws.. well all done there and it was idleing fine.. so i decided to take it around the block.. has no power wut so ever.. im thinkin thats timing.. but even tho its at 12o like u guys said... n e ways.. then i got back home after the 5 minute drive and teh thing didn't wana idle.. and it seemed like it was flooding itself then it died.. rite at the bottom of my driveway thank god.. so i checked everything out and nothin melted or broke.. good oil level temperature is good.. so i jumped in and turned it over again and after holding the throttle wide open it eventauly started.. didn't wana idle but ran barly enough to make it back up the driveway.. o ya and i did notice a oil leak already!!rite on the crank/harmonic balencer..so that really sux alot!! i guess the new seal didn't seal tight enough.. n e ways i guess im gona take another look at it tomorrow.. it seems liek the timings off because of the way it had no power.. i remember this happending to my old 350.. but i could be wrong... i might just try going for a ride and turning the distributer a bit everytime till it feels good then check with the lite.. im not sure wut else it could be at this point.. vacum leak maybe? leak me no wut u think and wut else to check.. thanx again
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Old 06-22-2004, 10:28 PM
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Your timing is set. No need to monkey with it further.

Try the float level in the carb first. Make sure the needle isn't sticking open. If it does or the float level is too high it'll run too rich or flood when it sticks.

Sounds like you might have both happening.

Larry
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Old 06-22-2004, 11:13 PM
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I notice you said points in a earlier post, I hope you don`t mean your using a points distributor, the best place for points is the trash.
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Old 06-23-2004, 06:45 PM
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hahah ok should i try for eletronic then? well my problem is that i wana get this thing running good but cheap as possible because this truck is for sale.. and i no wut i put into it i won't get back!
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Old 06-23-2004, 09:41 PM
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ok i fired it up again today.. after turning over for a while she finaly started.... turned the idle up again to keep it running was gona check my timing again but i think the last time the timing lite felll off the truck it broke.. cuz it didn't work.. so i set it at roughly the same place it was at when it was 12o n e ways.. got it idleing fine again.. revs fine.. then i decided to hold the gas at steady 2000rpm... didn't heat up at all... so i held it for around 5 minutes.. maybe more.. then when i let off the gas it dies.. doesnt even try to idle.. my old motor did this to!! im starting to think its time for a new distributer.. wut else could it be? fuel pumps new.. carbs not even a year old.. plugs are new.. im stuck on this one.. almost time to bring it to the shop.. even tho my guess is as good as theres...

hey sorry guys forgot to mention something.. i think the reason for no power is cuz my clutch might be slipping.. even tho its brand new i think i might of over adjusted it.. how do u check free play? my clutch grabs at the very top of the pedal.. there as to be some play before it grabs rite? and also when i put the clutch in and hold it.. for say 10 seconds it starts making a almost chattering nose.. not good.. not to mention my rpms drop 200 rpm.. if that means n e thing?

Last edited by Trav; 06-23-2004 at 09:41 PM.
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Old 06-23-2004, 10:42 PM
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Fuel might be percolating after five minutes of idling. That'll cause it to shut off rather abruptly.

The release bearing might be used up. That would put a bit of drag on the engine with the clutch disengaged.

Larry
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Old 06-23-2004, 11:18 PM
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Shut down

[color=lightblue]Doc here

OK, If I understand it correctly, It only dies on abrupt shut down? But is OK if you slowly back it down?

If So Adjust the Vacuum or mechanical (which ever applies to you) Dashpot on the throttle return.

If the Clutch is "Chattering" on pedal, I'd be thinkin' Throw out bearing real soon....

Free Play if I remember right, (been a while) is about 3/4 to 1 inch free pedal movement, Could be wrong on this but at least it should be close.

Doc

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