suggestions on advance curve?

[kingofapes]

L26 stock bore, MN47 head ported, 10,5:1 CR, Mallory Unilite (YH type Vacuum advance model - although VA now not used anymore),

triple DCOE 40s, header, 2,5" exhaust,

Cam:Intake Duration (gross):284 Exhaust Duration (gross):284

Intake Duration (.050?):240 Exhaust Duration (.050?):240

Intake Valve Lift*: .480" Exhaust Valve Lift*:.480"

Intake Valve Lash: .010" Exhaust Valve Lash:* .012"

RPM Range: 2800-6000+

I use 98octane unleaded (in Finland, not sure what is the equivalent in the US)

I'd like to hear any suggestions as to what type of advance curve to look for, especially if someone has experience on this particular type Unilite dizzy. I try to post photos of the advance curves available on this dizzy for you guys to see. I figure initial advance should be around 10deg, with total max around 33-35 but the guy who did the head, suggested even 33 may cause detonation and said I should aim at 30 which I did (already adjusted the dizzy to max at 20 degrees of mechanical advance+ 10 initial).

I have not done this before on this engine, so i don't really have first hand experience of the characteristics, so I'm just guessing it should be fairly linear and as with the triples i guess my idle will be around 900-1000, so mechanical advance starting around 1200 and it'll max out at what ever is that those curves will give. Any ideas? (please pay no attention to my early notes on the paper

[Travel'n Man]

Bring you car up to driving RPM's and then set your timing. That will help. I set mine at about 3300 RPM's.

[71Nissan240Z]

I wouldnt listen to anyone but you and your car. Set the timing in a reasonable range and run premium. U will never dial it in by ear tuning. You can only get it in a range. Dynos are good to see where u make the most power. U might be surprised. Also....all engines run a little differrnt. Some better than others.

[kingofapes]

I wouldnt listen to anyone but you and your car. Set the timing in a reasonable range and run premium. U will never dial it in by ear tuning. You can only get it in a range. Dynos are good to see where u make the most power. U might be surprised. Also....all engines run a little differrnt. Some better than others.

Yes, I am going to take the car to dyno eventually, but was interested in other people's experience when trying to determine a good starting point in terms of advance curve. I have the spring kit and my dizzy is disassembled right now so it would be a good time to see if someone with more experience could give an advice. My own guess for that starting point would be using something like brown and orange that should start the advance around 1200rpm and max it out around 3000.

[Travel'n Man]

We have had some members that have sent their dizzy's off to that the advance curve corrected for their individual cars - have you searched?

[madkaw]

I don't think you will find much info on hear concerning graphed timing curves. As posted above, using someone else's curve might not work for your engine anyway. There are very few L26 s with a MN47 head around here -let alone with your cam.

My only suggestion would be to make a good hearing device to pick up the sound of detonation. You can search for what others have done on the internet as far as putting a mic somewhere on the engine and wearing a headset of some kind to listen for pinging! They say the human ear is the best anti-knock sensor.

You can try all types of springs, but unless you have an accurate butt-dyno, it will be hard to tell your results. You could try the knock limiting approach and max out timing to just before pinging, but is that where best MBT is? Only a dyno would tell.

I would think the MN47 would be a very efficient head and you might not need to much timing to reach MBT. I have a small chamber head with my early e-88, and I run a lot of initial-18 degrees with no VA. I max out with 35(17 degrees mechanical) When I dynoed my car I started out with 37-38 total timing. I backed of the timing to 35 and saw no difference in MBT.

I would think with triples you would want more initial then 10-IMHO

[kingofapes]

Thanks guys, I appreciate this input. As for initial advance, I've had many different advices, varying from 10 to 16 degrees. Some people that I know, have dynoed their cars, one of them with somewhat similarly modified L28 and 12degrees initial. I'll definitely make some device to actually hear pinging. The first thing now for me is to get reasonable initial settings and later on take her to dyno.

[madkaw]

Remember , using a stock dizzy like I am limits me. To reach my total advance numbers I am forced to increase my initial advance, but I have no issues what so ever running 18 + degrees initial.

You have much more flexibility and with proper tuning should be able to extract more HP from your motor just with timing.

That's why I am installing MS and doing away with my dizzy all together

[kingofapes]

yeah although I'm not sure if the Unilite is the single best dizzy for a Z, nevertheless it is a handy upgrade because it has more flexibility than the stock one, and mine has worked very well in my previous setup (stock mn47 head with 4barrel Holley). I was going to go for MS too but then came across a set of Webers and was sold. MS is superior for certain aspects, but triples are also great in a Z, once properly tuned.

[Lazeum]

I used to fight with my dizzy, that was before

It was a unilite Mallory dizzy also.

To set it up, I was following 3 steps:

- idle: start the engine (hot) with loose dizzy. I was turning it by hand until I reach max rpm at idle. I was checking my timing only after.

- Total advance: I had a guess of how much timing I needed (34° roughly). Since I knew what was my timing at idle & my springs combo inside dizzy, I could adjust mechanical advance from dizzy. I have the shim set from Mallory but you can also use drill bits & some maths to set your dizzy.

- Advance progression: It was a trial & error process until I can find something that run ok. I ended up with 2 orange springs.

BUT....

I had issues to check timing. Spark plug wires did not go well with timing light so everything was a guess (timing light was telling me that timing at idle was 60° & 80° or so at high rpm...)

Since, I've removed everything & I've changed ignition management with Megajolt/EDIS system. Car has never run that good since then.

My engine combo is different than yours so you cannot use my timing map.

I'm running F54/P79 with major head work & 9.5:1 comp ratio

Street tight lash cam from Rebello. They don't share cam diagram but it is much more aggressive than Schneider Stg II cam I was running before, with a lot of overlap, 0.490" lift & asymmetrical profile. I have to run a lot of timing at idle.

Edited July 5, 2013 by Lazeum

[kingofapes]

Salut Lazeum, it's been a while Thanks for your tips. I'll give this whole timing thing a go today. My Unilite, by the way, has a system where the max advance is adjusted with a degree key. you loosen 2 screws, turn the plate, insert the appropriate key, turn back until the key fits snugly, then tighten the screws. In my case at the moment I adjusted it to 20degrees of mechanical advance, that will give me approximately 12-14 of initial, and if I end up having to use more initial advance, I can go down to 18 or even less of mechanical advance. I actually had determined that a good starting point might be using 2 orange springs, but of course only time will tell if that will work.

At the moment i'm just a little hesitant in letting the engine warm up as for some reason my temp gauge isn't working. it used to but now it doesn't so I am a little worried about it, because I haven't properly ran the engine since I put in the coolant and I can't be 100% sure if there's some air lock in the system or not. shouldn't since i put the coolant slowly when the engine was idling, but you never know..

I've thought about EDIS too, but this summer at least I'll keep the Unilite and maybe in the future I'll get the EDIS.

[Lazeum]

My Unilite could have been adjusted the same way: 2 plates with notches where you can insert some keys/shims.

When you tighten screws to lock everything, most of the time, plates move back to another position, not so easy...

With this system, you should find best timing at idle, try to get max advance where you want.

Adjust dizzy afterwards to get max power & readjust timing offset to get back to ideal timing at idle.

I have a excel file with all the curves overlaid to each other if you'd like. It was an attempt to get things better.