Where YOUR engine makes the most torque, is it there you should se the most timing advance, is this statment correct?

When I have search the board on info about timing tuning. I found out that the vette alu heads dont like more then 30 of timing advance.
Why do I se up to 42 degrees in my stock bin?


Thanks

 

Is the 42° under light cruise? As another example Chevy specs the ZZ4 timing at WOT to be 32°.

RBob.

 

No, it's not universally true.

Under what conditions?.
SBC AL heads GM, that is, like a fair amount of cruise timing, and then limited WOT timing.

Chamber Volume, has alot to do with timing requirements, as well as quench, and turbulence.

 

I found my engine like LOTS of timing. It's over 40 at cruise, and in the 30's at WOT.

Question: how much is too much for the computer / distributor, and what happens when you go too far?

With this timing, power is better and everything is smoother, but it occasionally stumbles. Didn't do that before I advanced timing 10deg.

 

the max timing in my stock bin is 41 and its on the 50-65 kpa area, from 3500 to around 4500rpm. Semes alot..

 

There is a max advance value, in the code. To prevent the spark from cross firing within the cap.

I've run 44-46d with my DIS, and while neat for mileage, further review, showed the downsides were trading detonation and engine wear for mileage, I went to the lower detonation and longer life option.

 

so how can I tell if it's cross firing? Sounds like that could cause the stumbles I am feeling. Ignition system is stock, and pretty much everything has been replaced.

I'm guessing the fix would be to physically advance the distributor, then adjust the distributor base timing in the chip.

detonation is not an issue for me. Engine combo is pretty poor (low compression, med duration cam w/small LSA), but net effect is that it doesn't knock, even at crazy advance values. And it runs very poor at low advance.

 

How do you know this to be true?.
Are you just relying on the K/S?.
What are the plugs telling you?.

The K/S is an acoustic devise, and fooled.

If you can twist the timing all around and not generate ANY TRUE DETONATION. Then you are dealing with a rather none conventional setup, and while certain items might work for you they are the exception rather then the rule.

When you get to where timing changes make no real difference then you also might have a serious fuel problem that prevents you form even making enough HP to detonate the motor, and engine life will suffer at that stage.

You can have supossedly good numbers and have missed the tune.

 

I readjusted the base timing on my distruibutor. It was at 6BTDC. Now it's at 16BTDC. Also adjusted the base advance in the chip to 16BTDC.

The stumbles are gone.

Started knocking like crazy. Working on redoing my timing curves now.

Aparently, at 6BTDC base, I was running into some kind of limit. In areas where the timing was set at 36, I had to bring it down to 32 to stop the knocking.

Does this sound like I have a problem with the igniton system? Why would it not go to 36 with the stock base timing?

Thanks