im running a carbed LT1/4 motor with a stock 94 cam....
the heads are LT4's...

i have a MSD 6AL box and 8361 distributor (vacuum advance)
the distributor comes with the 21 degree advance stop bushing installed along with the 2 slowest springs...Since this motor is stock (cam wise) then i should theoretically be able to set the timiing to the stock setting and "tweak" it from there...

i set the base timing to were it ran the smoothest although im not really concerned with base...
i would like to know how much advance these motors run and what RPM full advance is in.,


thanks guys
Rob

 

Did i stump yall? lol

 

wow

 

Not too many people are running a carb and regular distributor.

It is hard to correlate your setup to the computer controlled one. Other factors such as engine load and temp are used to calculate amount of timing allowed. I can send you a screen shot of a spark map for a stock 1995 A4 if you want to email me.

 

.............BUH......................hhhmmmmmmmmm m.


Thats a good question,
-JOhn

 

yea id like to see that...

this motor is in a 91 GTA and its a 5 speed car 3.42 gears....as far as load were i live is tehre is MAYBE 200 foot elevatin change for like 50 square miles....its flat....ill drive it year round, winter dropping to the low teens, and in summer 95 is common...the thermostat is stock temp...the motor is stock LT1 with a carb and LT4 heads....

did i help any?....i can pretty much figure out how much it needs total...but im concerned with at what RPM full advance is in...

 

1995 A4 spark advance vs. RPM vs. MAP

 

Another thing to watch...

Just because the computer says it is giving 38º or whatever of timing, doesnt mean thats what the engine is actually seeing. It is much less in all likelyhood.

 

Right. There are other mitigating factors for timing, as mentioned before. The table I posted is just for MAP/RPM.

 

ok you have to tell me how this goes...lol
what am i looking at here?

 

You have to remember that this table is in the pcm. The left hand column is the RPMs. Across the top is the MAP, which is how the pcm senses engine load. MAP numbers correlate inversely to vacuum. The higher the MAP, the higher the load is on the engine. The MAP will generally be higher, the farther down the gas pedal is pushed.

You can read a little more about MAP readings in Injuneer's write-up .

 

RPM in verticle column, MAP in horizontal. Map is simply engine load more or less. 100 being pedal to metal. 25 = little or no load. All numbers within the chart is timing degrees.

This is how real men tune a car

EDIT, looks like shoebox beat me to post

 

ok i got it....i new what MAP was but i forgot how to read that type of chart...

so in order the figure out how much total timing there is and when its all in by youd look in the 100% MAP column...and i see its 33 degress and its all in by 2,800....am i correct?

 

hey atljar... i was looking at your site and i was gonna run longtubes but didnt want to give up ground clearance...hows the clearance with the LTs and y? Also how was the install?

 

Not necessarily. Notice that there is more timing at some lower MAP values (kinda like vacuum advance on a "normal" distributor). This would be like when you are cruising along at a lower throttle angle.