Timing woes, I wish I wish I hadn't killed that fish! Options

[mike_the_man]

Hi all,

My car was running like piece of poop recently (74 2.0L with F.I.), but backing off the timing a little made it run a fair bit better. Today I took it for a little drive, got it nice and warm, and decided to try and re-time it. It turns out that my timing was correct when it was running poorly, and now I'm very confused. I checked top dead center on the fan and on the fly wheel, as well as looking at the position of the rotor. Everything points to top dead center. I then put a new mark on the fan at 27 degrees as per the PP tech article. I also found the 27 degree mark on the fan, and it lines up with the mark that I made.

When I rev my car up to 3500 rpm and set the timing to the 27 degree mark (I disconnected the vacuum hose from the dizzy) the car runs like crap. But if I set the static timing (not revving the car up, but setting it at idle) to 27 degrees, it seems to run pretty good. I'm totally confused. Could it be that the mechanical advance isn't working? Is there any way to test the mechanical advance? What would the symptoms be?

I hope this all makes sense, and I'm sorry for the long post.

Thanks for all ideas. A (IMG:style_emoticons/default/beer.gif) to the first person that gets it right.

[415PB]

I just tested mine by using a mity vac. It didn't even hold any thing. I replaced the vacuum pot with an extra I had that held a vacuum. It runs a little better, but not much. Now I am back to the idle hunting until it gets warm.

[nebreitling]

mike, did your car ever run great, or is this a recent thing? if it ran well before, than i would check:

-points (hell, just get rid of them and install pertonix/crane)
-FI trigger points (this is my best guess for your problem)
-FI wiring (make sure all your connections are kosher. one loose injector wire or similar and you'll be in troubleshooting hell)

i doubt that it's a problem with the advance. are you plugging the advance hose(s) when you time the car? this can effect it a few degrees. of course, make sure that your rotor/cap are in good shape.

just for shits and grins you may double-check TDC #1, just to make sure that your TDC/timing marks are correct. insert a dow rod into the #1 spark hole. when the piston is at the top of its stroke AND the valves for that piston are loose (i.e. adjustable), you are at TDC.

adjust the valves while you're at it...

415PB: i'm sure you've heard the mantra before, but it sounds like a vacuum leak...

good luck,

nathan

[SLITS]

If you put a new mark on the fan at 27 and then found the existing 27 mark and they aren't on top of each other - something is bad wrong.

By popping the dizzy cap and applying vacuum to the advance pot, you should see the breaker plate move.

Do you have the advance and retard vacuum pot hoses hooked up correctly? If the are switched, the retard would be active during acceleration - bad bad.

[mike_the_man]

Thanks guys,

The car has never run perfect. I've replaced the points with pertronix, also replaced the cap, rotor, and plug wires. Checked and rechecked all of the injection wiring, and it all looks good. I'm not sure about the trigger points, though. Thats one thing I haven't replaced. My 27 mark, and the existing one are in the same place, so I don't think thats the problem. I don't think that the vacuum pot is working, but my car is a 74, so it has no vaccuum advance. I have the retard hose hooked up, advance port on the dizzy open to the atmosphere.

I will check top dead center one more time, just to make sure. Wasn't there a place to get a rebuilt dizzy with trigger points in for cheap?

Thanks for the brain-storming guys,

[SLITS]

My '74 2.0L has both advance and retard. If you dont advance timing under acceleration, it will run like crap. As engine speeds go up, the timing must be advanced to allow time for the F/A mixture to burn correctly (time to burn gets less and less as RPM goes up).

If I understand you correctly, you have the retard hooked up and under vacuum, you would be retarding the timing. If the advance is open to the atmosphere, there would be no advance beyound the mechanical built into the dizzy.

[mike_the_man]

As far as I know, the 74's didn't have the advance hooked up. I have no port on my throttle body for advance, only retard. As per Dave Darlings hose diagram on Pelican :"NOTE: Not present on many 74+ cars. If no fitting on throttle body, then leave that end of this hose not connected to anything." when referring to the vaccuum advance. That always seemed wierd to me, too, but I guess thats the way it should be. Mechanical advance is all I have. Is there any way to test if it's working?

[airsix]

The vacuum retard is only activated at idle when the throttle is fully closed, so this has no effect on the engine above idle.

Mike, try this if you haven't already:
1)Set your advance to 27 degrees BTDC at 3,500rpm per the book.
2) Slowly reduce the engine speed from 3,500rpm while continuing to watch the timing mark with the light. Continue slowing it down and watching until you reach idle.

You should have been able to view the advance being reduced until at idle you can't see the (red) 27 degree mark any more, and you should be very close to the (white) TDC mark now. If the 27 degree mark is still visible at idle then your advance mechanism is jammed up. As you rev the engine you should be able to watch the timing move in a linear manner from somewhere near TDC (white mark) to the 27 degree (red) mark.

If that checks out, the next thing I'd verify is that the timing marks are correct. Put the engine at TDC and get under it. Check the small hole at bottom center where the tranny and engine are bolted together. You will be able to see the bottom of the flywheel through the hole. there is a groove machined into the flywheel indicating TDC when the groove lines up with the seam in the engine case. Use that to make sure your timing mark for TDC is correct. Once you know if the TDC mark is correct you'll also be able to tell if the 27 degree mark is correct.

-Ben M.

ps - I'm just guessing, but I think a likely culprit is the installation of the pertronix. The screws holding the pickup in place, or the wiring to the pickup might be interfering with the advance movement. Just a guess, but you wouldn't be the first that has happened to.

[brant]

Ben and all...

is that mark on the bottom of the flywheel always going to be perfect...

I mean if I've had the flywheel off before and then just slapped it on.. could I have put it on in a different orientation than stock.. or is it pinned/dowelled so as to prevent that?

can't seem to remember if there is a pin right at the moment.

thanks
b

[mike_the_man]

Now that I think about it, it seems like the advance works. If I set the static timing at idle to the 0 degree mark, then rev the car up to about 3500, the 27 degree mark comes into view. and as I let off the throttle, the 27 mark disapears, and when I hit idle, I'm back at the 0 mark. So, I'm pretty sure that my advance is ok.

As far as finding top dead center, shouldn't the machined groove in the flywheel appear at the hole in the top of the tranny. Thats the way I've been checking. If you reach up to the top of the tranny, then you can feel the mark. Maybe I've screwed up my TDC marks. I'll pull off a vlave cover this weekend, and figure it out for sure.

Keep the ideas coming,

[brant]

Mike,

I think that you are right and the machine groove does appear at the top when on #1....

but what I'm not certain is if the flywheel could be assembled in such a way as to change that.

b

[SLITS]

There is a couple of other things:

1. If you have not popped the cap lately, take a look. I replaced a rotor with a different kind and didn't realize that while running, the rotor base was rubbing the Petronix unit creating bakelite dust inside the dizzy. I found out when the car started running real bad.

2. I had two hookups on my '74. One was the TB and the other was off the plenum with a rubber fitting that serviced the AAR and dizzy. See images:

(IMG:http://www.rccauto.com/ebay/914tb.jpg)(IMG:http://www.rccauto.com/ebay/914tb1.jpg)(IMG:http://www.rccauto.com/ebay/914tb2.jpg)After all this bull, if you need to try another dizzy, send me an address via email and I'll send you a '74 dizzy to try.

[brant]

slits,

where did you get an AAR boot that looks that good....

how is everybody else dealing with crappy-worn out AAR boots?

(oops sorry if I'm hi-jacking)
b

[airsix]

Mike,

I think that you are right and the machine groove does appear at the top when on #1....

but what I'm not certain is if the flywheel could be assembled in such a way as to change that.

b

I think you guys are correct. The flywheel mark will be at the top of the bellhousing at TDC. It'll be at the bottom when cyls 2 and 4 are at the top of their stroke (I line up the flywheel mark at the bottom when doing the valves on 2 and 4).

You can't mount the flywheel incorrectly. It only goes on the crank in one possition so you can't screw it up. That's why I suggested using it as a reference.

Mike, sounds like your timing and advance mechanism are set and working correctly.

-Ben M.

[SLITS]

slits,

where did you get an AAR boot that looks that good....

how is everybody else dealing with crappy-worn out AAR boots?

(oops sorry if I'm hi-jacking)
b

I have one (maybe another somewhere). The one I run is encased in JB Weld (IMG:style_emoticons/default/smilie_pokal.gif) (IMG:style_emoticons/default/clap56.gif) (IMG:style_emoticons/default/wub.gif)

[TheCabinetmaker]

Yep, timing mark on crank will be at the top for 1 & 3.
When it's there, make a mark on the bottom with white out or something so ya don't have to hug the tranni the next time.

[mike_the_man]

I have the one port throttle body, and I had the plenum fitting, but when I got my car everything was hooked up wrong, so I hooked it all up as per DD's diagram on Pelican, with the advance port open on the distributor. I'll try hooking it up with the advance, but I can't see that making a real big difference. I'm pretty sure that my vaccuum canister is screwed, but with only retard hooked up, it shouldn't affect too much, should it? Retard is only at idle, and only for emissions, isn't it? If not, then that could be my problem.

SLITS, thanks for the offer. I'll try a few things this weekend, and if I can't get it to work, I may take you up on it. I'm also going to order some new trigger points, just to make sure thats not the problem.

[brant]

yeah... my AAR boot is encased in clear silicon and glue.....

anybody find any good tricks out there to replace the worn boot?

b

[TheCabinetmaker]

Mike, the vacuum port on the throttle body goes the the diz side of the of the advance unit. Leave the other one open. The vacuum port on the plenum goes to the MPS. At least that's the way mine is hooked up and it runs most excellent.

[nebreitling]

trigger points