ignition timing jumping -everything's new!

I hope someone can help me, I completly rebuilt my '71 350 three months ago, and still can't get it running right.

here's the specs:
'71 350-2 totally rebuilt, top to bottom
new carb
new points distributor
new flame thrower coil
new timing chain
new fuel pump

first off, the car is not getting the 350ft/lbs of torque it should have. the timing is jumping around. it retards 2-4 degrees every 1-2 seconds. again, the ignition is all new. I messed with all sorts of timing and dwell settings and still can't get it to run right. besides the timing jump, I can tell the timing is missing, but not at a consistant rythm. at first, it wasn't always getting spark at the plug end of the wire, but at the tower, but I think I figured that out to be low voltage at the coil. I temp. remedied that running a wire from the battery to the coil. I can barely get the tires to spin and get some popping here and there but I think that's the timing/dwell (I have been trying tons of timing/dwell settings) I can't seem to find the problem. I have to take it back apart to check, but I think the cam timing might be off, that may account for the lack of power. but before I go through all that, I need to get this timing jump taken care of.
first off CAN THE DISTRIBUTOR STILL WORK IF THE CAM-DISTRIBUTOR GEAR IS INSTALLED BACKWARDS? I thought that could cause a problem. I also thought maybe the harmonic balancer is sitting loose int he crank keyway, I'll have to check that. the timing gear shouldn't be jumping, because it's a new chain.
buy the way, this engine was build all to stock specs.
If it was say a loose balancer throwing just the timing reading off, it is still missing, with all plugs firing, so I don't think that is the case. PLEASE HELP! I'VE BEEN ON THIS FOR THREE MONTHS. I NEED THIS TO BE SOLVED SO I CAN FINALLY GET TO THE BODY OF MY SKYLARK! I've spent a lot of money and more time on this car and i wan't it on the road, I plan on usin it for my everyday car.
any insight would be appreciated, especially with the cam gear question.
thanks, Dave

 

timing

Make sure distributor is in the right spot if its 180 out it might run but it wont run very well dont know if that will cause timing mark to jump but it might

 

I just swapped in a motor and was getting a popping through through the carb when I accelerated. The thing also shook pretty bad. I went through the plug wires and had two wires crossed. Corrected the wire problem and the motor ran smoooooth.

 

Dave,
It will probably be something simple so check all of the basics.
1. good ground
2. correct voltage to the distributor. I think on a stock system you have a ballast resistor.
3. triple check the plug wires and firing order. Are the plug wires good. I have had brand new bad plug wires.
4. distributor shaft running true.. if the bearings are shot and the shaft wobbles that could cause the problem.

hope this helps

 

in my 340 the distributor had 1 big washer the set on top of the gear, but when I put my old gear on a distibutor out of 73 gs350 it used 3 thin washers. Make sure there is not play in the shaft. If u can move the distributor up and down, it might be doing like mine did the timing would not stay put. Once I got the washer in there to take up all play it has stayed set. Oh If your using a different cam, I would look into recurving distributor. Man it makes a difference.

 

Try the old coil...

There's often been reported problems with Pertronix..

-Also ..this might sound stupid, but did you forget to put the springs in the distributor, cause that would for sure make the car run like crap!!

-Just an idea..

Good luck
:TU:

 

Nightwrencher,

I gotta tell you I've had a similar problem for YEARS. Timing will jump around maybe 3-4 degrees. Makes it tough to set the timing!

I've changed every ignition component there is, except the MSD. I've had three different distributors, 3 different coils (internal in the cap like HEI and external like points), different spark plugs, plug gaps, heat ranges, different wires, etc. I am guessing the MSD is the problem (that's the only thing I haven't changed out), but I don't know how to confirm that. (And I've certainly heard of other people that have the same problem with no MSD).

My whole engine is computer controlled now (EFI), it still does it! I've checked the gap between the pickup / reluctor thing, that is fine (and didn't seem to make a difference when I did move it around a bit).

It's something I just live with. Not that I'm happy about that.

HOWEVER it hasn't cause any "popping", I don't think you'll get that because of your 2-4 degree "wandering".

-Bob Cunningham
bobc@gnttype.org

 

My experience has been, the majority of the "timing jumping" issues are actually not in the ignition system, but rather in the cam drive--either the timing chain or the gear drive setup.

I've had two vehicles now that used to exhibit this problem that was finally cured with a new timing chain.

 

timing chain

i concur on the timing chain cause . worn gears or bushings on the distributor will cause similar if the distributor jumps around a bit .

 

An interesting idea there on the timing chain.

One other point that (for me) might rule out the timing chain- for a while I was running an adjustable timing advance on the MSD (you know, that little know thing that allows you to retard the timing from the drivers seat). Well anyhow the further I retarded the timing, the worse that problem got. Maybe the problem was multiplicative, so if the MSD saw the timing jumping around (because of a timing chain), it would multiply that by the amount of retard I dialed in. Anything's possible.

Interesting nevertheless!

-Bob C.

 

Dave you didn't say what the timing was actually set up at. If the timing is retarded any more than 13* advanced you will be loosing a lot of power. Never set it for the origional 4* advance. Next the timing chain may be new but it could have stretched already. Where did you get it from? Is it a double roller chain? I know you have spent the money on the flame thrower coil but you should try a stock coil again. They are pretty cheap at the parts store. Good luck

 

Cam bumper?

This may or may not apply to your v-8's, but my '79 v-6 had a problem with the timing jumping around. It also developed what sounded like a rod knock, sooo apart it came for an inspection...

What I found was that the cam bumper spring had broken, and as I rotated the engine by hand, the cam would slide foreward a bit, then slap back against the block, creating my 'rod knock'. Dunno if it was the cam design that caused this, but a properly installed bearing-type cam bumper would prevent this, and keep the timing from jumping around.

 

?

If one makes this timing change (from 4 to 13 or more) how about total timing, is it not going to be to mucho No:

 

Snowmad welcome to the board.
To answer your question, No! 13* initial timing won't give you to much timing if you use an adjustable vacume advance and recurve kit on the dis. like you should. The factory timing was fine back in 1972 when the average gas was around 98 to a 102 octain. If your using the stock ignition then your getting some where around 50 to 57* while your crusing around on full vacume but only 4* at idle if your hooked up to manifold vacume. I recommend you bump up the initial timing to 10* and drive the car. You will be better able to spin the tires with this advance. If you can drive the car with 10* and get no detination then keep advancing it 2* at a time until you do then back of 2*. I think that you will find the advance to be around 13* when your finnished and you will be amazed at how much better your engine will perform.

 

Just thinking !

You say its is rebuilt, what type of camshaft stock or...?
You probably locked at this already, but anyway here is some wild "hints":
A Holley with wrong power valve can be the reason? opening and closing in stead of being closed at idle.
Also, check the color of the spark plugs, a bad (not completely dead) plug or wire can also be the reason
Try connecting to the wire 180* on the distr. cap what result?
Does the exh. sound ok
To weak,broken or missing distr. springs or to heavy weights? (engaging distr. advance at idle)
rotor in distr. bad?
the coil mentioned earlier in this tread?
the wire between the coil and the distr.?

 

yeah, I checked the wires several times, even tried a different cap and wire set, both which are new. I haven't had a chance to play with it during the week, but I will this weekend. I did also try advancing the timing (tons of timing and dwell sets) I did it last at 12 or 13 degrees, it seemed to get some more initial power, I got a little tire spin, but it is still very lacking in the power dept, flooring it doesn't seem to give any "oomf" at all. but most of all, the engine still seems to be missing, and the ignition jumps, those are my major problems. to answer your other question, the cam is supposed to be a stock grind. I ordered an engine kit from greenbay auto parts, whick put together a kit to my needs, and I did specify a stock grind for that year and engine set up. it did not come with a spec sheet however. If I don't get anywhere with tuning this weekend, off comes the timing cover (what a pain) and I will inspect the cam timing. also if anyone has hints on putting it back on, last time it was difficult to get it back on because of the cork oil pan gasket needing to compress. I don't want to break the seal on the pan and have to replace it. I was also told to suspect the cam to just be a "bad" or "inaccurate grind" due to the unlabeled box it came in with the kit. If I don't find any inconsistencies with the timing marks, I may have to get a reputable companies cam, and maybe a double roller chain, and see if that helps. I am still open to any suggestions anyone has, I really dread having to take this apart a third time and spent a whole lot of money on something that is not a guarantee to work. thanks for everyone's input.
Dave

 

???

Dwell 29-31* nothing else.
Loosen up, don't remove all other oil pan bolts and let it hang lose in the bolts, this way you will save the cork oil pan gasket.
But first, try with the old carb. if you still got it.
Lars

 

ok?

Have you fixed it?
Lars

 

What did you find Dave? I am having the exact same issue with my 71 GS 455. I'd prefer not to spend 3 months trying to figure it out.

 

Sounds like a bad distributor/bent shaft. he may have been watching a bad balancer along with it. It sounded like more then one issue.
Start with testing for timing chain wear. Pull cap off distributor. Turn with wrench one way mark rotor then turn the other and see how far it crank rotated before rotor moves.