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My Vortecpro 468 Timing

2K views 21 replies 9 participants last post by  Tom Mobley 
#1 ·
When I got this motor 10 years ago Mark's paperwork recommended no more than 36 degrees, all in at 2000 including 5 vacuum. This is a 520 hp/560 torque version. The car idles best with a lot of timing which is around 30 including initial and vac. I guess the best option for me would be to limit the mechanical so i don't get too much total I + M + V?

It seems to run better with more than 36 but i don't want to do any damage. Am I missing something in that total doesn't include vacuum? What are ideal advance curves?

I'm confused. Mark if you could comment I'd appreciate it.

Thanks,

Brian
 
#8 ·
Mark do you still recommend I stick to 36 total; that is I + M + V?

It runs very good at 18 I 12 V and 15 M. Never get any knock/pinging.

I have on occasion gotten a knock on cold start though. Never any other time. I does not buck starter.
 
#11 ·
initial and mechanical are added for the total timing;


vacuum advance is only there when there is some vacuum,

like idle and cruise;
under hard acceleration the vacuum advance goes away...


so most of us set our initial to 15*-22* and then limit the mechanical advance to target the total advance number of 34*, 36*, 38*, etc...
the vacuum advance does not get added to these figures as it is not always there...
 
#16 ·
I do understand how and when vacuum advance works. I was confused as to "total timing " meaning maximum possible timing. So if 45* maximum possible is ok then I'm good. Please correct me if I'm still getting the concept wrong.
 
#17 ·
Brian, as explained above total timing is measured using initial plus mechanical. Vacuum advance goes away when the engine is loaded, and only comes into play at idle and light engine loads. So timing at cruise speeds with a light load can be much higher than the 34-36 degrees you get from initial plus mechanical. And that's a good thing. Dave Ray's vacuum advance modifications are worth doing, and will help you optimize your advance curve, and avoid detonation.
 
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#18 ·
OP: you'll still want what we're referring to as "total timing" to be around 34-36 degrees. As you get higher, you can beat up your engine more....as my chasis dyno guy likes to say.

Mark is suggesting that you can keep pushing this figure higher until detonation starts to occur and then back off. Absolutely correct.

But please don't think that "total" timing (as defined above) of 45-50 is a good idea. It's likely too much.

I'd say that you better have good reason or be very conscious of going over 36 degrees.
 
#19 ·
Engines mostly idle better the more initial advance you throw at them; it doesnt mean it is best.

Brian, " It runs very good at 18 I 12 V and 15 M. Never get any knock/pinging." that 18/15 is close to where you need to be at. = 33 total. It might want a few more, +3 to 36 to make a bit more power. NOT INCLUDING VACUUM as its not on at WOT. If you do bump th einitial lead to 20/21, I would also cut the vacuum back.
 
#20 ·
"Please describe how the vacuum advance is set up, and what vacuum type is being used?"

What vacuum used, manifold, or ported?

45 degrees isn't excessive when the engine is on no load, as in coasting, and that would add yur vacuum advance degrees to the total of I + M.

Where we want the vacuum advance to go away is acceleration, that is for the mechanical curve to do. And, we want it to supplement the initial timing, to get between 22 and 24 IDLE degrees of timing.

Sounds like you don't know as much about vacuum advance setup and use as you might believe you do.

I have a vacuum advance package that I send out to get them set up right, they are FREE, ask for one, gmvacuumadvancemodifications@gmail.com
 
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