Just ordered my Rebello 3.0, now what

[240260280z]

Orangetange

Could be caused by springs/weights/lack of lube in the distributor for the mechanical

or

shaft wear and wobble

or

spindle to distributor key wear

or

spark scatter caused by ambiguity on the trigger side.

When I rebuilt, lubed and switched to a ZX distributor, the high end rpms smoothed and so did the observations of the timing light at full advance.

You should try for 38 degrees at full you may pick up a few more HP.

[oranngetang]

38 degrees total? Unless I'm using the light wrong, with the engine set at a -10 BTDC idle, the advance to return the light to -10 at 4500 rpm is ~30 degrees. Total is ~40 I believe.

[Kurbycar32]

Rebello says to set the timing at 33 degrees at 5500RPM.

Blue I'm sure I've never lubricated my distributor which means it's likely never been lubed. I bet my vacuum advance is stuck. I did notice on my last motor the vacuum advance didn't seem to work and this is the same distributor. I'd love to get one of those 123 ignition units..

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[oranngetang]

That's amusing to me because he said 10 at idle for me. Haha

[240260280z]

I guess everyone uses the timing light differently.

I have an advancing light to I use a standard nulling method.

At idle I just dial in advance on the light in steps until the mark on the pulley matches 0 TDC on the scale. The value on the timing light is the idle timing point.

For maximum advance, I increase the throttle and watch the mark move until the mark stops then dial in advance on the light in steps until the mark on the pulley matches 0 TDC on the scale. The value on the timing light is the full advance timing point.

This can be repeated at any rpm to plot the curve as well as with vacuum in and out to see its effect.

When Rossiz and I tuned his Z (L28), 40 degrees BTDC total was too much advance. 36 to 38 was nicer and had more torque.

Edited July 12, 2015 by Blue

[oranngetang]

I did the same except from 10 BTDC

[Chickenman]

That's amusing to me because he said 10 at idle for me. Haha

Your possibly confusing idle or static advance ( 10 degrees BTDC ) with Total mechanical advance? Total mechanical advance is a combination of static advance and the mechanical advance in the distributor. So 33 degrees at 5,5500 is 10 degrees static + 23 degrees mechanical in the distributor = 333 degrees BTDC TOTAL advance at 5,500 RPM.

 

The amount the distributor adds as RPM rises varies between Distributor models and can also be modified. That why you have to check both figures.

[oranngetang]

I'm not confusing it. Dave told me to set the idle advance to 10 when I asked what the total advance should be. The numbers beyond idle seemed trivial and unimportant to him in the conversation. I have my idle set at a 10 degree mark on the pulley. At 4500 rpm the mechanical isn't swinging any further on my dizzy. To bring the mark back to my 10 degree starting mark takes ~30 degrees on my digital light. I believe this means the total actual advance at 4500 and beyond is 40 degrees +/-.

[Chickenman]

I use the same method as Blue mentioned. SOP is to make all adjustments with a dial back timing light at TDC. Makes things a bit less complicated and less chance for errors. " What you see is what you get ". Nothing worse than setting Total timing and then detonating the engine to death because you forgot to add that " extra " 10 degrees because you use the +10 BTDC mark instead of the +0 BTDC mark. 

 

Vacuum advance is always disconnected when setting timing. 

.

Total mechanical advance in the engine is a combination of Static advance ( idle advance ) plus mechanical advance that the distributor adds when RPM increases. Example values are 10 degrees BTDC Static + 20 degrees in distributor = 30 degrees BTDC.

 

Different plates and springs yield different values. You often have to shorten or lengthen the slots in the distributor plates to get the exact curve that you like. And every engine build is unique. But always best to error on the side of too little Total timing advance than too much. The former will cost you a bit of power... the latter can destroy engines.

 

 

 

 

 

 

 

 

 

[Chickenman]

I'm not confusing it. Dave told me to set the idle advance to 10 when I asked what the total advance should be. The numbers beyond idle seemed trivial and unimportant to him in the conversation. I have my idle set at a 10 degree mark on the pulley. At 4500 rpm the mechanical isn't swinging any further on my dizzy. To bring the mark back to my 10 degree starting mark takes ~30 degrees on my digital light. I believe this means the total actual advance at 4500 and beyond is 40 degrees +/-.

I'm very surprised he said that. You ALWAYS check total mechanical advance on any High performance engine. How does Dave know that someone hasn't modified the advance plates in your distributor. 

 

I think he's taking the position that 10 degrees BTDC is a safe setting. But your scenario indicates why it is not wise to assume. 30 degrees additional advance in the distributor is a LOT!! Normal values are more around 17 to 20 degrees. 260Z distributors have the maximum amount of mechanical advance at 23 degrees. So it sounds like someone has modified that distributor in some point in it's life. Probably lengthened the slots.

 

I don't know what you use for fuel... but 40 degrees Total mechanical advance is pushing it even with 94 Octane fuel and a higher compression ratios. If you're using 91 Octane and anything over 9.5 - 1 CR...I'd personally back the Total timing down a bit. That means pulling the Dizzy apart and changing plates or welding up the slots in the plates. You could temporarily set static timing to 5 degrees BTDC and that help.. but it's not the ideal combo.

 

Edit: Orangetang. I just noticed you live in Alberta. You using Petro Canada 94 Plus fuel? If so that may explain why you can get away with 40 degrees total timing. That's one of the top fuels in North America. Special formulation. Even better than Chevron 94.

 

On average Canadian fuel is much better than USA fuels. Our fuels factor in a higher percentage of RON vs MON. Higher RON values decrease detonation. We always have to detune our High Performnace cars a bit when traveling from BC to the USA. Gas quality Octane to Octane just isn't as good in the USA. I usually have to knock about 2-4 degrees out of my ideal setup when travelling to the USA. 

Edited July 12, 2015 by Chickenman

[oranngetang]

Dave dyno'd this engine with that dizzy in place, so he's probably going by what they used on the bench. I havnt taken it apart to see if he elongated the slots or not. I run 91 and 94, and I think I once heard a ping, but really it behaves pretty good. The engine is running a little over 10:1 but he's got a colder plug in it, possibly that may be avoiding said detonation. It's beyond my knowledge. Engine runs like a vtec.

[240260280z]

Great. Higher compression needs less total advance than stock. I forgot what you had

Edited July 12, 2015 by Blue