Timing question

[OldsFan]

I just joined, but I've already got a few hundred questions, lol. 

First one that's really bothering me is the timing on my truck - it's waaaaay advanced.  Looks like it is sitting at 27 degrees on mechanical only at idle (700 RPM) in park.  Seems to only advance out to 34 or so at 3K.  The previous owner has a vac cap over the line that goes to the advance canister, so I know that's not having any effect.  It makes starting the truck pretty hard at times which is why it's bothering me - and the starter's only a couple of weeks old (as are the battery cables).

Yeah, I confirmed that the balancers original, not slipped and used a piston-stop to do it....  It's really that advanced.

It doesn't ping, it doesn't buck or do anything else strange - in fact, for a 305, it runs like a thief.  Anyone have any ideas?

Oh yeah, with all the accessory drive and related stuff in the way, is there any better angle to see the timing tab on this engine?  I have to sit up on the core support and look down over water pump to see it...

[rich weyand]

34 degrees of total advance (once all the centrifugal advance is in) is about right.  36 would be no problem.  Sounds like there is less than the normal range of centrifugal advance (20 degrees).

You should have the vacuum advance connected.  Not sure what's up with that.

[bd]

Is this on your 85 C10, 305, 350C?

Check the advance weights, springs, bushings & pins under the rotor.  Make sure the reluctor rotates freely on the distributor shaft and isn't sluggish or seizing in an advanced position.  A broken or missing spring, sloppy weights and seized reluctor are common problems.  Is the rotor installed correctly, so as not to bind the advance mechanism?  Is it possible the PO changed the springs & weights to recurve the advance?

[454Man]

Is this on your 85 C10, 305, 350C?

Check the advance weights, springs, bushings & pins under the rotor.  Make sure the reluctor rotates freely on the distributor shaft and isn't sluggish or seizing in an advanced position.  A broken or missing spring, sloppy weights and seized reluctor are common problems.  Is the rotor installed correctly, so as not to bind the advance mechanism?  Is it possible the PO changed the springs & weights to recurve the advance?

X2, the initial is commonly found@ 10- 12° hints the reason for such a hard start. I wonder if the previous owner tried to lock out the timing. 34- 36 @2500- 3000 rpm is where you want the mechanical to end up( it's why it runs like a thief :-)) now it's time to get that initial lower

What's under the hood??? If you have to ask maybe we shouldn't race...

[OldsFan]

You should have the vacuum advance connected.  Not sure what's up with that.

Heh...  I hear you on that.  Just for kicks, I started up the motor, put the timing light on the pointer and hooked up a vacuum tester to the canister.  It holds vacuum, but no matter how much vac I put on it, it doesn't have any effect.

Is this on your 85 C10, 305, 350C?

Check the advance weights, springs, bushings & pins under the rotor.  Make sure the reluctor rotates freely on the distributor shaft and isn't sluggish or seizing in an advanced position.  A broken or missing spring, sloppy weights and seized reluctor are common problems.  Is the rotor installed correctly, so as not to bind the advance mechanism?  Is it possible the PO changed the springs & weights to recurve the advance?

Yup, my 85 LWB.  I am going to pull the cap and rotor today (weather permitting) and I'll let you know what I find out.  If it is screwed up, hilariously bubba-fied or whatever, I'll post pics.

X2, the initial is commonly found@ 10- 12° hints the reason for such a hard start. I wonder if the previous owner tried to lock out the timing. 34- 36 @2500- 3000 rpm is where you want the mechanical to end up( it's why it runs like a thief :-)) now it's time to get that initial lower

What's under the hood??? If you have to ask maybe we shouldn't race...

Race???  Haha...  This truck was a neighbor's grandpa's truck.  His grandpa stopped driving years ago and when he passed away, the grandson couldn't sell it or scrap it - reminded him of his grandpa too much.  So for years, it just sat.  He sold it to me for a few bucks with the promise that I don't scrap it.  No problem there, I like it way too much already.  But for now, I think of it like I imagine his grandpa - old and a little stubborn, but full of character and happy to work half days in retirement. 

Thanks for the suggestions - I am a little unfamiliar with it because this is the first time I've dealt with the 5 pin HEI module with knock sensor, etc. but hopefully it isn't too bad.

[OldsFan]

Well, I did a bunch of work today just trying to figure out what's going on with the timing.  I opened up the cap and rotor and found that there's nothing too rigged up and overall the cap and rotor look ok for now (though they could probably use to be replaced soon).

• First pic is just an overview of the engine bay which needs a cleaning. That's going to have to wait until I get these other issues worked out though.

• Second is the cap removed, rotor sitting in plain view.  Doesn't look bad, moves around against the springs fine, no binding.

• Third is the rotor removed.  You can see the 5 pin HEI module in all its glory.

• Fourth is me messing around with the weights to make sure things aren't bound up.  Looks ok, but the springs seem a little heavy.  I think I have some weight sets for Olds HEI's around in the basement.  I'll probably put a lighter weight spring in there (assuming there's no difference between Olds and Chevy HEI advance mechanisms).

Read up in the next reply - I think I figured a few things out, but the next picture is important and I can't add it to this post.

[OldsFan]

Ah, the fifth picture - you get to see my awesome graphic editing skills in Paint.  This is the pin (red arrow) is the end of the vac advance canister.  It is jammed or stuck.  Completely.  It doesn't move at all and I didn't want to try to force it.  Ok, I did want to force it, but I held myself back.

So, here's what I know:

• The timing was set at 26 degrees.  I timing tape to make sure I got semi-accurate results rather than just counting on my new-fangled timing gun (long story behind that one).
• At 3K RPM it was kicking out over 40 degrees. 
• The vac line to the advance canister was steady at 20 inches Hg.  No matter what.  Revving or not, even when I turned the truck off it stayed at 20 inches.  Yes, my vac gauge works fine, but I started to question my sanity.    It took around 15 seconds for it to bleed all the way back down to zero after the engine was off.
• The truck was really hard to start.  Took lots of attempts, cranking slowly and sounding like the battery was about to die.

Here's what I did:

• Set the initial timing to 15 degrees.  Beyond what it should be, I know, but read on.
• Set the all-in mechanical advance to 32 degrees (which caused 1 above).
• Saw the vac advance line suddenly start varying like it should.  Dropping and rising with manifold vac.
• Started the truck 15 times or so over a few hours.  It now starts like it should.  For the first time since I've had it. 

I am guessing that it will probably feel really unresponsive now.    I am going to try to use some spring sets I have from Olds HEI's to try and get a little more timing advance capacity.  Hopefully get the max to 34 and the initial down in the 10-12 region.
Now for the questions:

• How could it not be pinging like crazy at 40 degrees?  My Olds would not be happy with 40+ degrees under load...
• Did the vac advance jam up and the PO just try to get annoyed by crappy cruising gas mileage and then keep setting the timing more and more advanced?  I mean 40+ degrees under vac advance for part-throttle cruise would be fine...
• Can I change the vac advance canister without removing the entire distributor?
• Does anyone have any idea why this would be setup this way???

Sorry for the long post, but I appreciate any advice... 
Thanks,
Mark

[OldsFan]

Well, I figured out why the distributor is so advanced.  The HEI coil pack connections stick out far enough to prevent the air cleaner from sitting down onto the carb if the timing is set right.  Advancing it a lot (twisting CCW) puts those connections right next to the cruise control vac motor and out of the way of the air cleaner. 

Any suggestions on what I can do from this point?

[rich weyand]

There's a ton of headroom above the air cleaner.  Put a spacer between the air cleaner and the carb.  I had to do that to get my air cleaner to sit down on the Edelbrock carb because it is a different shape than the Qjet.  Cement the spacer to the bottom of the carb with 3M Weatherstrip Adhesive and then mount the air cleaner on the carb until the adhesive sets up so you don't have to deal with the darn thing all the time.

You can get spacers in whatever height you need to clear:
http://www.jegs.com/webapp/wcs/stores/servlet/KeywordSearchCmd?storeId=10001&catalogId=10002&langId=-1&Ntk=all&Jnar=0&itemPerPage=90&Ne=1%2B2%2B3%2B13%2B1147708&searchTerm=air+cleaner+spacer

Of course the other thing you can do is index the distributor correctly.  Sounds like the distributor was pulled out and put back several teeth out from the stock indexing, which is why you have the conflict now.  It certainly didn't come out of the factory that way.

[bd]

Remove the cap and unbolt the distributor.  Pull the distributor straight up just far enough to disengage the distributor gear from the camshaft.  Rotate the complete distributor one tooth CCW then set it back into place and adjust the timing.  Know that when you try to restab the distributor, the oil pump drive probably won't line up, so you'll need to bump the engine around until the distributor drops all the way down and seats.

[rich weyand]

Note the relationship of the rotor to the distributor body before you pull it up, so you can be sure to have it in the same orientation when you restab it!

[OldsFan]

There's a ton of headroom above the air cleaner.  Put a spacer between the air cleaner and the carb.  I had to do that to get my air cleaner to sit down on the Edelbrock carb because it is a different shape than the Qjet.  Cement the spacer to the bottom of the carb with 3M Weatherstrip Adhesive and then mount the air cleaner on the carb until the adhesive sets up so you don't have to deal with the darn thing all the time.

Rich - great suggestion!  It should've been my first thought.  I was sure I was going to have to pull and reindex the distributor, but it is like 30 degrees outside today (was around 50 yesterday, cold snap  ).  After reading it, I just got a Mr. Gasket spacer kit from Advance Auto which they actually stock locally.  Lo and behold, one of the kids at the counter actually knew what it was (said he races SBC cars with his dad).  I had to dremel a couple of little notches into it to get the stock air cleaner to fit down on it properly.  Regardless, the trucks's running again (minus the breather tube which doesn't reach) and has decent timing, too.

Note the relationship of the rotor to the distributor body before you pull it up, so you can be sure to have it in the same orientation when you restab it!

I probably wouldn't have forgotten this, but thank you for mentioning it..  Ask me how it feels when an Olds engine that some idiot (me  ) setup way off backfires up through the carb at you.  For anyone reading this in the future, make a mark on the distributor where the rotor is pointing so you don't forget later.

Remove the cap and unbolt the distributor.  Pull the distributor straight up just far enough to disengage the distributor gear from the camshaft.  Rotate the complete distributor one tooth CCW then set it back into place and adjust the timing.  Know that when you try to restab the distributor, the oil pump drive probably won't line up, so you'll need to bump the engine around until the distributor drops all the way down and seats.

This is what I was planning on doing, but I have a couple of questions:

• The truck has vacuum based cruise control.  Can the HEI cap even clear that module?  Maybe it needs to be behind the cruise module?  I guess it is trial and error.
• Can I line up the oil pump drive ahead of time somehow (screw driver or something)?  I was thinking of setting the engine up to TDC on #1 when I do this and I'd want to drop it back in at the same point... 

I haven't worked much on SBC's before, but it seems like things could get hairy if the oil pump shaft doesn't line up and I run the starter...  Wouldn't the cam then be out of sync with the rotor?  I mean, would the engine turn until the shaft lines up without turning the rotor?  Then when things do line up, wouldn't the rotor be out of position?  Maybe I don't understand what you meant...

[OldsFan]

Take a look at the pic attached.  Not sure if the terminals of the HEI coil will fit past the cruise module.  The HEI coil terminals are what is preventing the air cleaner from just dropping back into place.

Glad I dug into this, though, because I found a bunch of rotted vac hoses and resulting vac leaks.

[rich weyand]

If you pull the distributor all the way out, you can rotate the fuel pump shaft with a LONG blade screwdriver into the slot in which the distributor shaft tang fits.

I think on the HEI connector, you need someone on here with the same setup to take a look see where their connector comes out.  Could you be far enough out on the distributor that the stock position for the HEI connector is between the cruise module and the firewall?

[bd]

If you pull the distributor all the way out, you can rotate the fuel pump shaft with a LONG blade screwdriver into the slot in which the distributor shaft tang fits.

I think on the HEI connector, you need someone on here with the same setup to take a look see where their connector comes out.  Could you be far enough out on the distributor that the stock position for the HEI connector is between the cruise module and the firewall?

Did you mean to say "oil pump driveshaft?"   

Take a look at the pic attached.  Not sure if the terminals of the HEI coil will fit past the cruise module.  The HEI coil terminals are what is preventing the air cleaner from just dropping back into place.

Glad I dug into this, though, because I found a bunch of rotted vac hoses and resulting vac leaks.

Why not measure the protrusion of the connector pod off the cap and compare the measurement to the available space between the cap and cruise module?

...I haven't worked much on SBC's before, but it seems like things could get hairy if the oil pump shaft doesn't line up and I run the starter...  Wouldn't the cam then be out of sync with the rotor?  I mean, would the engine turn until the shaft lines up without turning the rotor?  Then when things do line up, wouldn't the rotor be out of position?  Maybe I don't understand what you meant...

When stabbing a distributor on SBC & BBC engines, the distributor gear engages the cam gear before engaging the oil pump drive.  As long as the distributor housing is within ~3/8" of seating on the intake manifold, the distributor is indexed with the cam gear.  Bumping the starter repeatedly (1-3 times is typically all it takes) until the distributor drops the remaining ~3/8" is an accepted method; using a long standard blade screwdriver to align the oil pump drive is also an accepted method, as is using an old distributor drive shaft.  Setting the engine on TDC compression before disassembly is the conservative approach that always works....  Use the method with which you are most comfortable.