Setting 240z timing

[inline6]

I read this in an old post:

"Much better to set your timing using total advance of 32 Degrees BTDC with the vacuum advance off and plugged @ 2,500 RPM. So, no matter what the initial mechanical advance is setup for, you'll know you've got it right."

How is everyone setting their timing? I have a "Euro" distributor with single points D609-52 I think is the number on the side. When I set the timing at 17 BTDC (at 650 RPM as the workshop manual states), it runs fine but not as well as when I set it closer to something like 27 BTDC at the same RPM. Yeah, I know, that's a lot. And when I rev it while checking with a light it definitely is going past 36 degrees BTDC although at that angle, it is hard to read with the flat scale that is on the block.

Details: 77 L-28 shortblock - no mods

E88 head -not shaved with stock cam, stock Su's with SM needles

I run 89 octane gas.

Seems like setting it so that it just pings ever so faintly with full throttle in 4th gear from 30 to 40 mph works best for power.

Also, how are you reading 32 BTDC on 240's if you just have a pointer on the timing cover and 5 lines on the pulley? That only gives you 25 degrees, right?

Garrett

[LanceM]

Timing is a funny thing. With the timing too advanced static you can have cold start problems and low speed problems, though yes it seems to give you the best power warmed up and running. Since your engine is mostly stock my recommendation is to do it how we did it in the old days, lug it like you are doing in 4th gear and keep reducing the timing until the pinging stops, pinging is bad. Now if you have problems cold starting or low speed continue backing it off until you have the best of both worlds.

One of the things to remember now that these cars are older is that the springs in the distributor are tired and the weights may be worn. This will change the curve of the distributor, the amount of advance to rpm. In a perfect world there is a perfect advance, giving you spark at the right time to make the most power at that particular rpm. When things get tired you get too much advance to soon causing pinging in the midrange until the engine rpm catch up to the spark advance. Remember that every ping is a little chunk blown out of the top of your piston, like I said not a good thing...

So by setting it so you don't have a ping through out the rpm range you know that you are not exceeding the advance curve no matter what your static setting is and hopefully getting the most power available from you advance curve.

Clear as mud right

Oh and to get higher timing marks, put a timing tape on your dampner and use the zero mark on the case as the reference point. I don't know any more who or if anyone has them anymore but once again that's how we did it in the old days It just divides the dampner into 360 degree marks using the TDC mark as the zero point.

Ah if it was just 30 years ago and I still had my 454 Monte Carlo SS I'd show you Boy am I glad I'm not buying gas for that today!

[Victor Laury]

Lance's advice works. It's the same as my father instructed me 30 years ago.

Advance the timing untill it pings under acceleration, then retard it untill it will only ping if you bog the engine down in high gear.

I've been using this rule on cars where the scale just doesn't seem right. I have my Roadster club guys over from time to time for my help with tune ups. Every so often a car will pop up that WILL NOT RUN with normal timing adjustments, which leads me to believe something wasn't set up right during an engine re-build.

Using my Dad's formula for these "hard cases" has worked so far.

Garret, if your car isn't pinging like crazy with the total advance "well over" 35 degrees BDTC, I say the scale was funky.

Find you self a hill, advance the timing till it starts to ping, then retard it till it stops. Old fashion? Yep. Hard to track your adjustments? Yep. Works? Yep.

[inline6]

Thanks to both of you for the info. I just played with the timing for a couple of hours. Although seat of the paints is not scientific, there is enough of a difference between 17 BTDC and 32 BTDC to feel a difference. 32 BTDC or as best as I can currently read it, is where the pinging goes away in 4th with full throttle at 30 MPH. At this setting 6000 RPM comes a bit quicker in 1st, 2nd, and most noticeably, 3rd. Also at this setting, when I operate the throttle by hand with the timing light on it, I show something in the neighborhood of 45 degrees of total advance. Seems to be fully advanced around 3000. Also, I am not having any cold start problems.

That just seems bizarre to me. I checked TDC with a screwdriver in the number one spark plug hole and the marks on the pully are correct. I have the euro pully with just one groove. The mark furthest left when facing the car from the front is TDC. Each of the other marks (I'm assuming) is 5 degrees.

I wonder how many Z car owners are setting their timing by the book and missing out on a couple of HP?

Garrett

[PrOxLaMuS©]

so then for an all stock L28e...

what is the best timing range?

the book says 10' BTDC/700 RPM for my automatic.

but change it to 32'? what's the best range?

[LanceM]

Does it start and run well at 10? Then that's a good place to set it. If you want to play a bit and see if more is better read my post above and work from there. Every car is different, what is good for one won't work for another.

[Kerrigan]

I've a stock 1971 FairladyZ and I'm going to try doing it the "book way" and set it at 17 degrees at 750rpm for running with 92 octane fuel. Seems to work out that way if I remember from the last time I set it.

[madkaw]

Wow - 11 year revival

[Kerrigan]

Some subjects never die ...

[Zed Head]

Initial timing really depends more on the advance curves of the distributor that is being used. If you have a reman. distributor with different weights, springs and vacuum advance canister than factory stock you probably wouldn't want to run factory initial timing. Just an observation that could be overlooked.

[Mark Maras]

Being an old timer :-) Everything you've been told is correct. You can get as deep into advance curve theory as you desire but if you just want to have a good running car, retard the timing until it won't ping at anytime or perhaps barely when lugging the engine ridiculously low. It doesn't take many pings to break a piston ring in an old engine. (Hi-Lux PU, rarely pinged). I think you may want to put away the timing light. If you time it by ear you'll know it's right.

[siteunseen]

I'm going to try and set my total timing today after finally getting the fuel levels right.  Does this sound right?

1. idle at 750 rpms

2. plug vacuum hose

3. set to 17 degrees

4. set light offset to 34 degrees

5. run it up to 3,000 rpms

6. adjust distributor until "0" pulley mark hits on light strobes

Thanks for any advice and my ZX distributor has 8.5 stamped on the weights.

EDIT, I have know idea what pinging sounds like so I'm using my high dollar light. 

[siteunseen]

I found the Excel spreadsheet Walter Moore made.  I have the D6K8-05

10 degrees at idle

17 weights

20 vacuum

47 total @2,500 rpms

Thank you @Walter Moore

D6K8-05

10

17

20

47

2500

27

M

1979

 

[siteunseen]

If the vacuum is unhooked do I still add the 20 into my total? Should it be 47 or 27? 

Or should the vacuum advance be hooked up instead of plugged?  Thanks for any help, I'm confused once again.

[siteunseen]

I think I'll need a vacuum pump to get to 20 off the distributor?  Then I eliminate that from my total. So with a vacuum pump I need to dial back my light to 27?

Sorry to be a pita but the unknown scares me.

[siteunseen]

Can you help me out @Jeff G 78 

[djwarner]

I have a D6K80-03 from a 1979 280ZX AT in my Series I. I found the following specs for it and used it in setting my timing. Doubt it will be significantly different than yours.

Centrifugal advance 0 @ 600 RPM, 8.5 degrees @ 1250 RPM.

Vacuum advance 0 @ 5.9 inches of vacuum, 5 degrees at 9.8 inches of vacuum.

Please remember that vacuum decreases as you open the throttle, so the only time you would see both high rpm and high vacuum is letting your foot of the throttle at high speed. During this period of engine braking, you are at low pressure during the compression stroke and actually need the additional spark advance and won't see a knock.

If you are drawing vacuum from the carb port, check to see what vacuum you are actually drawing at idle. These ports are designed to only port vacuum while decelerating and will read zero at idle. If you are porting vacuum off the manifold, disconnect and plug it when setting the timing.

The timing spec given in the factory manual is for engine off with a test light (not a strobe) directly connected to the points. This is known as static timing. When setting timing with a strobe, there will be a component of centrifugal advance as well as this static timing. If you have vacuum connected, the two advances will confound your readings and idle speed as you set the timing.

To figure the expected timing at your desired idle speed you have to calculate the amount of centrifugal advance at idle. For mine at 750 rpm, it is 150/650 times 8.5 degrees or about 2 degrees. (650 rpm is the difference between no advance and max advance rpms.) If the static timing was 5 degrees at 0 rpm, you should observe 7 degrees at 750 rpm and no vacuum. If you see significant change in idle speed as you adjust your timing, reset your idle speed and then idle mixture and recheck your timing. repeat until your rpm and timing  are on spec and  you have adjusted for best idle mixture.

All that said, the idle timings specs for our cars has varied over the years. As a rule, they are retarded to control pollution rather than to avoid knock. This gives you some room to err on the advance side without risking harm to the engine. While most manuals typically set timing to 10 degrees BTDC at idle, I routinely set mine to 17. This conforms to the earliest non-pollution controlled models.

 

 

Edited July 3, 2016 by djwarner

[siteunseen]

Thank you Mr Warner.  I'll have to read that a few times to wrap my head around it though. 8^)

[Stanley]

Me too. Don't know much except that if the timing isn't on, you're throwing away a bunch of potential speed.

My Z did fine with stock US timing and regular gas and the stock head. With a newer, higher compression head it was pinging so I went to premium (91 in CA) gas, OK. Then got a FSM and a light and put it at 17 deg per book for my new euro distributor. I was burning rubber all over the place and it's an automatic. Pinging badly though so I put it about 10 deg. at 1000 rpm IIRC. So I guess I learned something. Feel like there's more to learn though. Feel like I'm shooting from the hip with this. How much ping is OK? 150K on the engine and I don't want to hurt it; but also don't want the CRX's to beat me. Ran the rock drill in my youth so my ear's not great.

[madkaw]

Cliff,

I think the best of Both  worlds would be to limit the vacuum advance so you can run max total timing WOT.  Meanwhile I would run about 17 initial and disconnect the vacuum while you play around for best power. There are threads somewhere where folks have limited the travel on the rod connecting the vacuum . 

[siteunseen]

So simply put, set the initial to 17 degrees at 750 RPMs.  Since I have 8.5 weights, add 17 for a total of 34 degrees on my dial back light.  At 2,500 RPMs with the light set to 34 I should adjust the distributor until the big notch (TDC) on the pulley lines up with the pointer, 0 degrees.  That would give me total advance of 34.  Drive it and see how it performs?

What should the vacuum pull on the front carb be at 2,500 RPM?  I'll hook my vacuum gauge up and get some numbers and report back.

Thanks guys

[siteunseen]

When my dizzy is spinning with the motor at 2,500 rpms those weights are out?  The vacuum advance should stay unhooked and plugged at high rpms too like setting initial timing at idle?

I'm going to understand this one way or the other!

[madkaw]

Minimum of 2500. 

Yes - disconnect vacuum and set dial back to 34 total . As far as figuring the vacuum on top of that - not sure , but I would say just add in the vacuum advance on top of the 34 at 3000 and see where it stands. In the end Cliff, your motor will tell you if the advance is too much. I bet you will have to either limit the vacuum portion of advance , or just reduce  your timing- period