6530 with 1 bar MAP sensor

[Murray2rude]

Hello I need clarification. I have installed a 1 bar MAP to my 6530 I need to know as the line moves from left to right in the boost curve map, is it adding timing or taking timing out? Non-turbo engine.

[Gaz64]

Your curve is sloping the wrong way, it should be pulling timing at MAP of 15 kPa, not pulling timing at 0. Gary

[Murray2rude]

Thank you for responding. I misspoke I meant to say as it goes from right to left.

[Murray2rude]

So is my boost retard map correct? If not where do I place my first dot? Does it not read vacuum from right to left?

[Gaz64]

Page 10 of the instructions: https://documents.holley.com/6530.pdf. On the top scale 0 is max vacuum, no atmosphere, 14 is 1 atmosphere, what is around us.
So your curve needs to run across the top from the zero point until you get to the point where you want to start to pull timing say 5 (1/3 atmosphere, 10 inHg), and then the curve goes down to the max you want to pull out.
The two curves are cumulative, so you set your total including this figure.

Gary

[Murray2rude]

OK, so I had it backwards, my boost retard map need to look like the image attached.
Does this mean if I want more timing at light loads, I have to account for this in my timing map? Thank you.

[Gaz64]

In the example you've attached, you can see the mechanical retard is all removed by 1500 RPM.
So this would be the desired total for mechanical advance in the "old school" thinking, what the engine wants under load say 30°.
Now the boost retard curve has not removed any while the engine is idling, so you need to account for whatever value has not been removed.
So you would set your total at say 40° at 1500 RPM while the "vacuum advance" is active.
Alternatively, you can disconnect the MAP sensor, and set your total at 30°.
Then whatever you remove on the run curve should have the engine idling at say 16°.
When you add the map sensor back it will add the 10° or so. Hope that makes sense.
An adjustable rotor, and a spare cap with a large hole drilled near number #1, will show what the rotor tip is doing with a timing light. Gary

[Murray2rude]

Yes, it makes sense now. I'll reset my total advance and play with the maps, and of course phase the rotor. Thanks for taking the time to explain it.

[Gaz64]

You're welcome. Hope you get it to work how you want. Gary

[gregski]

Page 10 of the instructions: https://documents.holley.com/6530.pdf. On the top scale 0 is max vacuum, no atmosphere, 14 is 1 atmosphere, what is around us.
So your curve needs to run across the top from the zero point until you get to the point where you want to start to pull timing say 5 (1/3 atmosphere, 10 inHg), and then the curve goes down to the max you want to pull out.
The two curves are cumulative, so you set your total including this figure. Gary

Thanks Gary. I noticed you have been offering help here quite a bit, and this thread is still fresh, so I figure I would ask. I recently purchased my 6AL-2 and have not installed it yet, and like most I feel comfortable with the RUN RETARD CURVE concept, but for the life of me I am still totally lost on the BOOST RETARD CURVE in terms of simple vacuum advance. I'm dealing with a dime a dozen Chevy Small Block 350 with a manual transmission in a '74 C10 truck. I'm not asking for the optimum advance curve, just help understanding the bottom graph on page 10 of the instructions.

Can you walk me through it like I'm 3 years old please, ha ha. When you say "On the top scale 0 is max vacuum" does that mean at max vacuum this sample graph pulls 0° out of the advance, in other words it does not retard it at all? And how did you get 10 inHg out of 5 (1/3 atmosphere). Sorry I'm a total moron when it comes to this.