pizza_guy

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I posted the following, then looked at the stickys. I apologize and will do it the other way around next time. Feel free to respond, though.
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I recently got my orig L69(125K miles) running again...except this time the timing is being contolled by an aftermarket ecm.

The timing map I have is from a TPI motor, and my 1984 heads seem to like quite a bit more timing than this map provides 2000rpm and up.

I've changed the inital timing from the TPI map, but it's a trade-off every time. Better idle/low end versus 2000 and up.

What kinda timing curves do you guys use on your older heads?? My longblock is untouched stock. Except the replacement valve springs.
I don't need a whole map, just the basics like:

Initial: XX
Total Mechanical: XX by XXXX rpm
Total Vaccum: XX

I could develop a map out of those numbers. Any other tips you might have would be great.

And a side note not as important: Is it possible/smart to run these motors 15.0-15.5 afr in cruise?? How lean is safe with detonation monitering?

Jproz1167

iTrader: (3)

Base timing is 6 degrees .... and I've read somewhere that a LG-4 total advance was 32 degrees and a L-69 was 36 degrees. I have a factory service manual if it can be of help to you

pizza_guy

Are those total advances at WOT I assume?

I changed the map...by bringing the advance in 500 rpm earlier it's a bit happier. Apparently the L69 likes more than the later tpi's.

Does higher compression require a faster ramp-up, or is it the 20+year old heads? The slightly larger cam??

Jproz1167

iTrader: (3)

I think there could have been various timing curves for TPI motors. since some had a peanut cam and ohers had manual transmissions. TPI was about torque they generally ran out of steam at what apprx. 4500rpm where as the L-69 redlined at 6,000rpm or was it 5,500 (can't remember) So I think thats where one of your issues is. Maybe someone else can tell you what the max timing is for TPI bu I do know the L-69 was 36 total degrees of advance.

pizza_guy

Well, I've tried all sorts of timing schemes, but I'm still getting the same issues.

Whenever I approach 2000 rpm, I get minor mis-fires, soft pops out the tail pipe and it refuses to climb any higher. Does that indicate fueling issues??

Fast355

iTrader: (2)

Factory Monte Carlo SS timing table. Sorry, don't have one for a F-car, but it is very likely the same as the SS.



This is what I ran in my 305 Van that was converted to TBI. HO 305 with headers and 2 1/2" duals.



This is how it ran with 3.08 gears and the stock torque converter.

http://youtube.com/watch?v=Oi_n0goatA8

pizza_guy

I apologize for not clarifying this, but I'm not running GM ECM's. I don't know anything about the software aspect of them.

Does your software include ANY other modifiers for those tables during run-time?? Add timing during TCC lock-up or this "Highway Mode" I hear about.
The maps posted are incredibly helpful, if I can clear up a thing or two.

It appears to be about 26* or so at cruise, and I don't think that is correct.
It seems to only have about 10* vac. advance. The 100kpa column looks good, but under vaccum, shouldn't there be more timing?? Maybe 6*-10* more by 40kpa?

According to the sticky at the top of the section, shouldn't I be about 45* to 50* at cruise?? (1600-2000rpm and bout 50 kpa)

Fast355

iTrader: (2)

The L69 does not have a lean cruise timing mode ("Highway Mode"), nor does it have PE spark mode. It does have compensation against coolant temperature, but it is 0 at the engines normal operating temperature.

My TBI map for my LE9 engine is what the resultant was. The highway mode and PE spark tables were zero'd out.

Given that both Monte Carlo SS and my Van are heavier, you might be able to get by with a couple of more degrees of timing advance at low-loads and rpms, but probably not.

In all honesty I do not see needing more timing than what was in my timing map, that is enough. 45-50* is TOO much.

I am linking these, just to give you an idea of the resultant timing advance at various loads and RPMs.

pizza_guy

Thanks for clearing that up! I'll start getting this thing going.