Timing Vortec

[1966chevyc20]

Alright I have an L31 vortec crate engine installed in my '66 C20. I'm running a summit HEI distributor and having trouble getting it timed correctly. From what I understand I should have 10-12 initial timing with the vacuum unhooked and plugged. And somewhere in the 32-36 range total timing. I am having to use a advance timing light and when I try to retard the timing to line up the marks it dies. To get the marks to line up it is at a ridiculously advanced initial timing. Any ideas as to what could be going wrong here?? It also backfires through the exhaust when I speed it up.
Questions:
1. Is it possible to have the distributor off a tooth and still run?
2. Is total timing with or without vacuum advance hooked up?
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[truckster]

Yes, it's possible to have the distributor off a tooth and still run, but it wouldn't really matter if you're using a light to time it and you're on #1 plug wire. What matters is the cap's position relative to the rotor position.

The total timing is the initial plus mechanical advance.

Are you sure about your timing marks? Did you re-use the plastic cover and the Vortec balancer?

[geezer#99]

To answer your questions.
1. yes
2. Total timing is without vac advance added on.

What do you have for a timing tab and balancer?

[PGSigns]

Its not really a tooth off if you can set the timing. Usually when its off the vacuum advance hits something that keeps you from setting the timing. How are you checking the total and initial? Do you have a tape or using a light with advance on it? What are you using for a vacuum port? Also the back fire sounds like a wire crossed. Have you verified the firing order? What weights and springs are in that HEI?
Jimmy

[1966chevyc20]

I am checking initial timing as it is idling around 800 rpm or so. I am using a timing light with advance on it. For a vacuum port I am using the port on the edelbrock 1405 carb (port that is on the driver side of carb). I have not verified the firing order after I installed the distributor. The weights and springs are the stock ones that came with the summit HEI distributor. As for timing cover and balancer I am using the stock plastic cover (one without the crank sensor hole) and stock balancer. Thanks for the help

[geezer#99]

IIRC the plastic cover tab is not set right for your balancer.
Likely you need to reset it by verifying tdc #1.
http://www.crankshaftcoalition.com/w...op_dead_center

No cheating. Use a piston stop like in the link.
You gotta get your idle down a bit more to set timing. At 800 you might be just tipping into the mechanical timing.

The drivers side port is manifold vacuum.

[Captainfab]

With the plastic timing cover and a stock L31 balancer, the timing marks should be fairly close. Although it wouldn't hurt to verify that.

At what RPM are you setting your total timing?

[1966chevyc20]

Ok, I have now verified the firing order is correct as well as the rotor position is pointing at number one when #1 cylinder is TDC on compression stroke. However I am still having the same problem. The timing mark bounces around at idle slightly, and I can not retard the timing enough to get the marks to line up and run smoothly. It idles very rough and nearly dies when I get the marks close to lining up. However if I advance it the marks dont line up but it runs smooth. I am using an advance timing light (https://www.amazon.com/INNOVA-5568-P.../dp/B000EVU8J8) and trying to get it to 12 degrees initial. Any suggestions or ideas?

[geezer#99]

Try a different timing light.
I've heard some don't work well with an hei.

Maybe describe exactly how you're trying to set your timing.
Are you setting your light at zero and then reading the timing tab or setting your light at 12 and adjusting timing tab to zero?

[1966chevyc20]

I am starting it (idling about 700-750) and setting my light to 12 degrees advance and trying to line up the line on the balancer with the mark on the timing cover.

[geezer#99]

What's your motor combo like?
Stock L 31 or??
What's the elevation where you live?

[1966chevyc20]

Originally Posted by geezer#99

What's your motor combo like?
Stock L 31 or??
What's the elevation where you live?

Yep it's a stock L31 with headers, hei distributor, and edelbrock 1405 carb. Elevation is approximately 1,000 ft above sea level.
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[geezer#99]

Maybe you need to time it by 'ear'.
Advance it until it idles nicely and then test drive it. If it doesn't ping then try a little more until it does then back it off a touch. Then put your light on it and see what it reads. Leave the vac advance plugged for this test.
How did you prove your timing tab/balancer were accurate?
What did you use for a piston stop?

[1966chevyc20]

Originally Posted by geezer#99

Maybe you need to time it by 'ear'.
Advance it until it idles nicely and then test drive it. If it doesn't ping then try a little more until it does then back it off a touch. Then put your light on it and see what it reads. Leave the vac advance plugged for this test.
How did you prove your timing tab/balancer were accurate?
What did you use for a piston stop?

I used a small metal rod in the sparkplug hole and felt it as I turned it over by hand. I figured the balancer and timing cover should be accurate as they both came stock on the engine when it came in the crate.
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[geezer#99]

Never trust anything.
Confirm it yourself.
In this case your uncalibrated rod could be off 20 degrees.
You need something unmoving like the piston stop in the link I gave earlier.
EAsy to make one from an old sparkplug.
All in all it might be easier to try a different timing light.

[donut]

Just a thought, is it possible that the centrifugal advance is coming in at idle?
This "could" skew your readings and make it even more difficult to set.
(Though timing by ear could get you close, and at this point may be your best option.)

[garyd1961]

If that distributor is like my MSD you need to run the vacuum advance on manifold vacuum and use a vacuum advance limiter plate with that distributor. I haven't installed mine but if you hook to port vacuum above the butterfly plate it will have way too much advance.

[geezer#99]

Originally Posted by garyd1961

If that distributor is like my MSD you need to run the vacuum advance on manifold vacuum and use a vacuum advance limiter plate with that distributor. I haven't installed mine but if you hook to port vacuum above the butterfly plate it will have way too much advance.

I think we've discussed this before, but if your ported port is working as designed then you'll have no advance at idle.

[Bigdav160]

I am having to use a advance timing light and when I try to retard the timing to line up the marks it dies. To get the marks to line up it is at a ridiculously advanced initial timing.

I am curious how you are using your timing light. Does the statement above mean you are setting the dial to 10 and moving your distributor to line up the mark to the tab?

And you set the timing to get the engine to run and check the timing by turning the dial it's extremely high?

And it idles at 800 rpm?

It a "crate" engine but who is it from? GM or just a rebuilder?

I'd put a vacuum gauge on it, set the base timing to get 18-20 of vacuum and then check to see home much timing it takes. Maybe the camshaft is mis-timed or perhaps you have a vacuum leak. Bad carb?

[1966chevyc20]

Originally Posted by Bigdav160

I am curious how you are using your timing light. Does the statement above mean you are setting the dial to 10 and moving your distributor to line up the mark to the tab?

And you set the timing to get the engine to run and check the timing by turning the dial it's extremely high?

And it idles at 800 rpm?

It a "crate" engine but who is it from? GM or just a rebuilder?

I'd put a vacuum gauge on it, set the base timing to get 18-20 of vacuum and then check to see home much timing it takes. Maybe the camshaft is mis-timed or perhaps you have a vacuum leak. Bad carb?

Yes the statement I made earlier means I set the light to 10 degrees advance on my timing light and turn the distributor to line up the marks. When I set it to 10 degrees advance on the light it barely runs. When I time it by ear where it sounds good, the initial timings way too high. It idles pretty well around 800 rpm when timed by ear and not the light. The crate engine is direct from GM through Karl Performance Parts. The carb should be good as it is a brand new Edelbrock 1405.
Also, when I try to time it the mark on the balancer jumps around. I also hear an intermittent popping sound in the exhaust. I believe I might have a misfire. I have triple checked that I have spark at each sparkplug and my sparkplug wires are in the right order on the cap and run to the right cylinder. I am stumped as to what could be causing the popping sound and why I can't get it timed. I'm only 16 and this is my first engine swap so I lack experience. Any suggestions as to what to look for that may be wrong??
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[geezer#99]

Look in the carb when you have it idling. If you see any raw fuel at all then it's flooding slightly. Likely due to to much fuel pressure. Flooding will cause your misfire and popping and your mark on the balancer jumping around.
You might need a regulator set at 5 psi.

[69gmcc10]

What are you considering "ridiculously" advanced initial timing?

when I had my carbed L31 I messed with the timing allot to get it just right, lots of effort went into making right. L31 Vortec engines like a little more initial timing and less total timing due to the efficient design of the head. Your initial timing should be about 14 degrees, I have seen some run happy at 16 degrees. If you get much more than that the truck will idle fine, but stumble when you mash the pedal from predetonation. Your total advance (not including vacuum, so block that off until you get these two things sorted!) should be no more than 30, maybe 32 degrees.

The issues you are going to run into trying to get this sorted out are that first, most aftermarket distributors are designed to give 21 to 22 degrees of initial timing and for you that is way too much timing for a vortec head. I am not familiar with the Summit HEI, but it will need to be adjusted to limit the mechanical advance closer to 16 degrees. so your initial 14 fourteen plus the mechanical 16 equals 30. The next issue you will need to figure out is how to adjust the vacuum advance canister to operate in the 8 to 10 degree range.

Finally, after you get that all figured out, even though your carb is new, pout of the box it is not adjusted for your elevation or average temperature range, and while it will propel the truck from a to b some adjustments will need to be made to make it right for your application. Then you will need to check and readjust your initial timing back to 14 again after you get that figured out.

When I started adjusting my timing on my build I realized the distributor I had needed to be completely overhauled for my needs. I changed the springs, center plate, weights, vac canister, an even after I bought a new cap there was a hairline crack in it throwing off my timing and making the timing mark bounce around and I needed to replace it again. It originally idled good at 18 deg but the mechanical advance was way too much, finally after a bunch of adjustments I got it to 14 degrees initial + 16 degrees mechanical= for a total of 30 degrees and a modified vacuum canister that gave 8 degrees of timing. After I got it all figured out it ran like a top, but it took some time to get exactly what it needed.

Hope this helps and good luck.

[1966chevyc20]

I will have to get a fuel pressure regulator probably and see if that helps. I'm having to run a carter electric pump since the L31 isn't drilled for fuel pump pushrod.
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