Delco Voyager for 454 with a B&M 250?
04-15-2016, 02:03 PM
#1
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Delco Voyager for 454 with a B&M 250?
My TB-IV is acting up, and I'm considering replacements. I am not very happy with MSD stuff so I'm considering dumping the Merc ignition for the Delco Voyager. I've heard that it has a good curve for a mild-to-mid blower motor set-up.
454, B&M 250, 525 EFI roller.
I'm embarrassed to say that I do not know what the base timing is with the V6 module (that decided to start seriously misfire through the blower), but I do know that it's set at a max of 30 degrees.
What do you guys think?
454, B&M 250, 525 EFI roller.
I'm embarrassed to say that I do not know what the base timing is with the V6 module (that decided to start seriously misfire through the blower), but I do know that it's set at a max of 30 degrees.
What do you guys think?
Last edited by TomZ; 04-15-2016 at 03:26 PM.
04-15-2016, 02:24 PM
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I run a mallory marine version of the delco. THe curve is 20-22* all in by 2800 rpm or so.
Note that cheapo modules often don't have the curve built in. The Delco 1965A and GM & Mallory equivalents do.
Great system that is easy and reliable IME.
Note that cheapo modules often don't have the curve built in. The Delco 1965A and GM & Mallory equivalents do.
Great system that is easy and reliable IME.
04-15-2016, 02:38 PM
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04-15-2016, 03:31 PM
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I think I was reading that there may be more power available by making some changes with how the curve comes in... not sure of what the best curve would be... just know that most have used the V6-14 module with blower set-ups forever. I think Joe (Mild Thunder) was mentioning something about a change in curve structure away from the norm, but I can't remember where I saw that post. Perhaps something for another thread.
Going to look into the Mallory.
Going to look into the Mallory.
04-15-2016, 05:22 PM
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From what I have seen, a roots blower combo, doesn't like all the timing in very early. It likes alot of initial for idling, but, in the midrange, it likes a little less timing.
If you look at the timing curves for a 525SC, 600SC, 800sc, you'll see they don't bring max timing in until nearly peak rpm. The 525sc had 34 or 35* total, and 33* total on the 600sc. I think the reason they got away with the higher timing, is due to their timing curve. An engine turning 3000RPM, simply doesn't have the piston speed it does at 5200RPM, and therefore, doesn't need as much timing there.
I think this "30" degree timing bit for every big block with a supercharger, stemmed from the old days of running any more timing than that with a blower, meant detonation. This was the days of guys running inadequate fuel supplys, improper jetting combos, too small of blowers, locking the distributors, and so on.
There's a thousand factors that come into play , and every engine is different what it will like for timing. Chamber design, intake temperatures, piston speed, boost pressure, air fuel ratio, piston design, and so on. Retarding it past what it likes, is no good, and advancing it past what it likes, is no good.
Timing isn't a power adder, or reducer. Its simply just one part of properly tuning the engine. I saw the light, when I went to a programmable ignition, and some dyno time. When you pull 10 degrees out of a blower engine in the midrange, and it makes MORE torque in the midrange, it's eye opening. What did that tell me? That 10 additional degrees THERE, was not what the engine liked, and putting it much closer to the danger zone. At 6500RPM, it LOVED a little more timing, 1 degree picked up nearly 20hp.
Think of it this way. The engine liked 35 deg at 6500. It did NOT like , 34 degrees, at 4000. It liked 25 deg better. Now, imagine if I gave it 44 degrees at 6500? People would call me a moron, and we would expect to be replacing pistons . Well , 9 degrees too much at 6500, is no worse, than 9 degrees too much, at 4000.
I would say, that I have seen more meltdowns at a fast cruise, than at wot in marine engines. On something like you have Tom, I'd rather have more total timing at max rpm than 30*, and less timing in the lower rpms. Ultimately, it would be a safer setup, that also makes more power. Firing the plug too early down low, can lead to preigntion, firing it too late up top, can lead to tuliped exhaust valves, etc.
If you look at the timing curves for a 525SC, 600SC, 800sc, you'll see they don't bring max timing in until nearly peak rpm. The 525sc had 34 or 35* total, and 33* total on the 600sc. I think the reason they got away with the higher timing, is due to their timing curve. An engine turning 3000RPM, simply doesn't have the piston speed it does at 5200RPM, and therefore, doesn't need as much timing there.
I think this "30" degree timing bit for every big block with a supercharger, stemmed from the old days of running any more timing than that with a blower, meant detonation. This was the days of guys running inadequate fuel supplys, improper jetting combos, too small of blowers, locking the distributors, and so on.
There's a thousand factors that come into play , and every engine is different what it will like for timing. Chamber design, intake temperatures, piston speed, boost pressure, air fuel ratio, piston design, and so on. Retarding it past what it likes, is no good, and advancing it past what it likes, is no good.
Timing isn't a power adder, or reducer. Its simply just one part of properly tuning the engine. I saw the light, when I went to a programmable ignition, and some dyno time. When you pull 10 degrees out of a blower engine in the midrange, and it makes MORE torque in the midrange, it's eye opening. What did that tell me? That 10 additional degrees THERE, was not what the engine liked, and putting it much closer to the danger zone. At 6500RPM, it LOVED a little more timing, 1 degree picked up nearly 20hp.
Think of it this way. The engine liked 35 deg at 6500. It did NOT like , 34 degrees, at 4000. It liked 25 deg better. Now, imagine if I gave it 44 degrees at 6500? People would call me a moron, and we would expect to be replacing pistons . Well , 9 degrees too much at 6500, is no worse, than 9 degrees too much, at 4000.
I would say, that I have seen more meltdowns at a fast cruise, than at wot in marine engines. On something like you have Tom, I'd rather have more total timing at max rpm than 30*, and less timing in the lower rpms. Ultimately, it would be a safer setup, that also makes more power. Firing the plug too early down low, can lead to preigntion, firing it too late up top, can lead to tuliped exhaust valves, etc.
04-15-2016, 07:00 PM
#8
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Joe, if you were going to replace what I have, what direction would you go?
I very much appreciate your thoughts and explanation on all this. Thanks!
TZ
I very much appreciate your thoughts and explanation on all this. Thanks!
TZ
