Timing issue

Hey guys,

Have a problem with timing on the new 464". What's happening is I can't find the '0' mark on the Romac balancer with the '0' mark on the TA cover. When I use a dial back timing light I've got to give it about 45-50 degrees for the '0' marks to match up. I've tried moving the dist. around but it doesn't get close. I've verified TDC with the balancer & rotor pointing at number 1.

So my question - is my HEI doing something wierd with total timing? Are my springs too light & total is coming in too fast? Would a vacum leak cause this? Here's the combo:

70 455 - .038 over
72 Stage 1 heads
Stock HEI w/ medium springs, adjustable vacum advance - not hooked up
TA 290/08H with 5 degrees advance
TA roller rockers 1.60
Holley 870 street advenger carb
B4B

Thanks in advance for replies, Wes

 

I'd look at the HEI unit

Many satisfied ignitionman customers. You may want to upgrade to MSD. Do a search, you will find much info...

 

It doesn't make sense Wes.

If you are sure you have TDC and the rotor is at #1 and your timing mark is at 0*, then You should be in the ball park when you run it.

Unless... all your mechanical advance is in at idle (I've seen it happen),

or

You have TDC but on the exhaust stroke, not the compression stroke. Be sure the air blows out of the spark plug hole as you are looking for TDC or that you watch the intake valve close and then rotate the assembly to 0*.

Put heavy springs in the dist to see if it makes any difference. And be sure the weights are free to move - and that they're not frozen open. I have springs if you need them.

 

I've posted this stuff at least 8 times here, but here goes again,

Take the dial back feature and turn it OFF, it DOES NOT WORK ON ANYTHING BUT COMPUTERIZED DISTRIBUTORLESS SYSTEMS, as in the latest Century with that strange, no distributor stuff under the hood.

Check timing with the vacuum advance hose DISCONNECTED AND PLUGGED OFF.

Mow, check the initial timing, this timing is the setting the engine has at ILDE, with the vacuum advance disconnected, and is NOT the idle setting, that will come in the next paragraph. Reset initial if necessary.

Next, check the TOTAL, and the rpms it all comes in, adjust the MECHANICAL CURVE if the total is not where you want it. Leave the initial in place as you change the mechanical for a different total.

POINT OF NOTE: ANYBODY WHOM STATES "JUST SET THE TOTAL AND DON'T BE BOTHERED WITH THE INITIAL/IDLE TIMING", IS SIMPLY NOT KNOWLEDGEABLE ON TIMING. SAME CAN BE SAID FOR THOSE WHOM SAY TO RIP THE VACUUM ADVANC OFF THE DIST, 'CAUSE "IT DON'T DO NOTHIN'".

THEN, reconnect the MODIFIED FOR LESS DEGREES vacuum advance to a FULL MANIFOLD VACUUM SOURCE, N...O...T...PORTED. The idle timing will go up, the idle speed will go up, so turn the idle stop screw down to regain the correct lower idle speed, and continue adjusting the carb.

And, yet again, initial for your engine should be between 10 and 14 degrees, cam is heavy duty and will need a bit more initial than normal from cam tioming bleeding idle and low speed compression back into the manifold.

Vacuum advance should be set with a 10 degree pin stop, .112. Then after getting the initial set correctly, add it to the engine on a FULL MANIFOLD VACUUM SOURCE, and set the rate with the Allen wrench through the hose nipple. PUT THE STOP PLATE ON THE OTHER SIDE OF THE PULL PIN FROM WHAT CRANE SHOWS, CRANE'S METHOD ISN'T CORRECT. Drill and tap hole, 8/32, then use an 8/32 hex head machine screw and #8 flat washer to hold the plate on the correct side of the pull pin.

Mechanical curves in large cap HEI nightmare travesty junkers's are set with three things, center plate, weights, springs, NOTHING ELSE, no stop pins, no bushings, nothing, just the curvature of the plate, weight profile and springs. Get the wrong combination of center, weights,springs, and you can tune the dist until the end of the world and not get it right, as there are over 450 different curves available with the parts available out there.

Try to find a 375 center plate, and 41 weights, then use one blue, one silver spring from your Crane 99600-1 adjustable vacuum advance, should give you the mechanical degrees you seek and very close to the correct rate speed. Shoot for start of mechanical advance at 100 rpms over out of gear idle speed, and total to come in between 1,800 and 2,500 rpms for the engine size/cam package you have.

Oh, you didn't get the Crane, there wasn't a stop plate and three spring sets in with it? Well, you'll have to make a different pin stop, and fight through the springs.

 

Dave, please explain the fact that dial back lights don't work. My MAC and Snap-on seem to work fine.

John

 

John, try a little test with your timing lights. After you check initial with the dial-back function turned off (say you got 10*), now turn the dial-back to 10*. Does the timing mark on the balancer line up with the 0* on the timing cover? I'll bet that you have to advance the dial-back wheel several more degrees than 10* to get the 0 to line up, but obviously they should be the same #.

What Dave said is right. I've wondered myself for years why my light was not reading the same way either way it was used. I finally gave up wondering and just stuck with one way or the other, and paid more attention to how the car was responding and less attention to the numbers. He finally clued us in during this thread. Here is another.

 

Okay, got it. I guess that explains why every once in a while I find myself saying. "I know I just timed this thing, why is it so far off?"
John