73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: enaberif on February 16, 2009, 04:00:41 pm
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I recently discovered my vac advance on my dist wasn't hooked up so I hooked it up and now my truck won't properly idle and I'm going to assume my timing is now out too.
But my problem is that I can't see the timing marks and I need to know by these pics if its possible that I'll have to remove my power steering pump or the timing marker has been removed?
Thanks.
(http://img.photobucket.com/albums/v394/thevagabond/truck/IMG_6529636x424.jpg)
(http://img.photobucket.com/albums/v394/thevagabond/truck/IMG_6531636x424.jpg)
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If it's like mine you have to lean WAAAAAY over and look straight down between the water pump and timing cover. I hate setting the timing on mine.
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If it's like mine you have to lean WAAAAAY over and look straight down between the water pump and timing cover. I hate setting the timing on mine.
So .. just easier to remove the power steering pump then hahaha.
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It does look like it has been removed. Your idle should not be affected by hooking up your vacumn advance. You have to hook it up to a port above the baseplate which should have no vacumn at idle.
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It does look like it has been removed. Your idle should not be affected by hooking up your vacumn advance. You have to hook it up to a port above the baseplate which should have no vacumn at idle.
I actually found it... I'm not used to where I found it.
Its at the 12 position and yes when I hooked up the vac advance I had to redo my idle and timing.. it was that far out.
but the PO had played with it so much .. so who knows where and what it was doing.
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You don't have to hook your vacuum advance up to a ported vacuum source. You can run full vacuum and even may find better throttle response and stronger idle quality. Do you have a 305?
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You don't have to hook your vacuum advance up to a ported vacuum source. You can run full vacuum and even may find better throttle response and stronger idle quality. Do you have a 305?
Yah its a 305.
I'm running the vac advance off the carb right now but will be setting up a t on the manifold to run the distributor off there to see how that works too.
All I know at this point by hooking up the vac advance my fuel economy for city driving has gone way up.
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I run my vacuum advance on full manifold vacuum (as per Vile's recommendation) and the engine really seems to like it in terms of idle quality and off-idle responsiveness. You will likely have to make a small adjustment to your idle speed after switching.
BTW you should be able to find a full vacuum source on the carb if you want. The only difference between the two types on the carb is that one pulls vacuum from above the throttle blades (timed) and the other from below (full).
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Yes I did know you can hook up the advance to full vacumn. I was just relaying what Holley recommends in the instructions for the carb I just installed. It was a 670 Street Avenger. For some reason my motor doesn't like full vacumn on the advance. Might be because of the high lift roller cam, 11.5:1 compression and aluminum heads on a 383 but who knows. lol I actually had it hooked up to full vacumn before the carb swap and even after at first. Then I hooked it up to ported and it made all the difference in the world for me. Perhaps a milder motor doesn't need as much total advance as one like mine.
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Well I put a T onto my manifold port and now have both my vac advance and vac modulator for the transmission running off it.
My only concern is my truck only seems to have about 15hg of vacuum which seems to be a bit on the low side but still within spec.
Tho I pulled the distributor cover off and man the contacts points were burnt harsh.. so I scraped those off and the truck seems to idle a bit better. Next plugs and wires.
Seems this ole girl will be getting at tune up soon.
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Replace the cap and rotor, don't just scrape it. Try advancing the timing more, just make sure it doesn't ping or start hard.
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Replace the cap and rotor, don't just scrape it. Try advancing the timing more, just make sure it doesn't ping or start hard.
Oh I plan to.. just scraped it now to get by.
That's actually a question I have.. how far can you go on BTDC before you shouldn't go? Or is it go to where it simply doesn't ping? Like say you went 18 BTDC to get it run properly? Is that to much?
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If your motor is totally stock disconnect the vacumn from the vacumn advance and plug it so you don't have a vacumn leak. Then set the timing to factory specs which is probably 8 deg btdc. The other way which I personally think is better is to have some one power brake it and bring the rpms up to right before it starts to break loose. Then advance until you hear a pinging and back it off til no more ping. Let her get to full operating temp first so when you shut her down you make sure there is no run on or dieseling as it is called. Fire it right back up if its hard to start like a weak battery just retard it a bit til it turns over easier. This should be the optimum timing for that engine with whatever upgrades it may have.