All Small Six Ignition Timing Map

[xavier296]

I am diligently working on a friend's 66s Mustang 200 auto that she bought in the early 70s but hasn't been driven for 20 years I have it running well, except it heats up at highway speeds (reached 205 after 10 miles on the highway, and it was still going up, despite outside temp being 70 and AC being off).
Short list of mods:
- Sniper 1100
- DUI distributor
- All cooling components new: 3-core brass rad, hoses, waterpump, 180 thermostat
- New head gasket

The distributor gives a lot of vacuum advance: 15 degrees total. My understanding is that adjusting the VA only changes when it engages, not how much, unless I install a limiter. It ran great with 15 btdc initial (30 total) at idle, but I believe the high timing at cruise (50 total) is creating some of my highway speed heatup. I bought all the parts for the HEI to let the sniper control the timing, but haven't found any definitive guidance on creating a timing map. My thoughts:
~20 idle timing under vacuum, 14 low vacuum (probably check my total idle timing with a vacuum gauge)
~35 timing by 2500 rpm at WOT
~45 timing by 2500 rpm at cruise (Is this too much?)

Looking for recommendations to make developing the initial timing map easy.

 

[awasson]

I'm watching this conversation to see what more experienced hands have to say but it seems to me that ~45° timing by 2500 rpm at cruise is a bit high. I would have expected it to be around ~35° maximum. Does the sniper control the advance and does it have a knock sensor to retard the timing if it's too high?

Also, I have found that mine likes a lot of initial advance but I am running an aftermarket camshaft so the stock 12° is just not adequate. My initial on an HEI distributor is somewhere around +25° at idle and it gets +10° on ported vacuum. I have +14° mechanical so close to 40° max is what I would expect on mine but I don't know what mine sees at cruise at 2500 RPM. My 2-core rad and factory 6 blade fan keeps it right around the middle of the temp gauge and it has never overheated since I've had it.

Hopefully someone more knowledgeable than I am can add some insight to help you out.

Cheers,
Andrew

 

[Frank]

I am diligently working on a friend's 66s Mustang 200 auto that she bought in the early 70s but hasn't been driven for 20 years I have it running well, except it heats up at highway speeds (reached 205 after 10 miles on the highway, and it was still going up, despite outside temp being 70 and AC being off).
Short list of mods:
- Sniper 1100
- DUI distributor
- All cooling components new: 3-core brass rad, hoses, waterpump, 180 thermostat
- New head gasket

The distributor gives a lot of vacuum advance: 15 degrees total. My understanding is that adjusting the VA only changes when it engages, not how much, unless I install a limiter. It ran great with 15 btdc initial (30 total) at idle, but I believe the high timing at cruise (50 total) is creating some of my highway speed heatup. I bought all the parts for the HEI to let the sniper control the timing, but haven't found any definitive guidance on creating a timing map. My thoughts:
~20 idle timing under vacuum, 14 low vacuum (probably check my total idle timing with a vacuum gauge)
~35 timing by 2500 rpm at WOT
~45 timing by 2500 rpm at cruise (Is this too much?)

Looking for recommendations to make developing the initial timing map easy.

Do you have the distributor vacuum advance on manifold or ported vacuum? This will not affect high speed cruise timing, but does affect idle timing. Your post, sounds like manifold vacuum. With manifold vacuum to the distributor it's "engaged" all the time. Only ported vacuum "turns off" the advance at idle.

 

[xavier296]

The Holley sniper only has manifold vacuum, not ported, so I have vacuum advance at idle also. When I switch to having the sniper run the timing, there will no longer be a vacuum canister, and all advance will be handled by the CPU.

 

[awasson]

The Holley sniper only has manifold vacuum, not ported, so I have vacuum advance at idle also. When I switch to having the sniper run the timing, there will no longer be a vacuum canister, and all advance will be handled by the CPU.

Manifold vacuum explains the high advance at idle. Your distributor would have been designed for ported. The DUI has an adjustable vacuum advance canister. It will take an Allen key (I think it’s a 3/32). They usually come set to full advance and you can back it down to zero. Clockwise increases advance, counterclockwise decreases. You can also adjust mechanical advance with springs to control when it comes on and bushings to control the amount of mechanical advance.

Have you ruled out a vacuum leak? That will heat up an engine for sure.

EDIT: What camshaft are you running? Stock should be at around +12 degrees initial for idle and most aftermarket cams want somewhere close to +20 degrees.

Also, how much vacuum are you pulling at idle?

 

[xavier296]

I checked, and my DUI, purchased about ten years ago, does not have an adjustable vacuum advance canister. I am not actually worried about that, as I am going to convert it to allow the sniper ECU to control the timing.

For now, I'll start the table with 13 degrees base idle timing (no vacuum), 34 degrees WOT timing, and 42 degrees cruise timing. I can then use my laptop to look at vacuum levels at idle while I adjust the idle timing up to give it vacuum advance..

Stock camshaft, but I haven't actually checked idle vacuum. Plenty I think.