Boost referenced timing retard

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scottylack said:
anybody know of a good ignition system for a Paxton blown 360???
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I have a Vortec-blown (10-pounds of boost) 360 Magnum and drive it on both the street and strip.

When I built it in 2006, I bought an ignition system called an "MSD Boost Timing Master." It has an ignition module that replaces your orange box and incorporates a dash-mounted control knob that will retard your timing (it has a boost/monitor line running from the intake manifold) either zero, one, two, or three degrees per pound of boost, (depending on how you set the knob,) up to a maximum of fifteen crankshaft-degrees.

It is an analog ignition system and does not have the "multiple-spark-discharge" feature that MSD units are famous for.

I think its output is 42,000-volts. I have never had a misfire under boost, so the voltage must be enough.

Summit sells this unit for $259.97.

http://www.summitracing.com/parts/msd-8762/overview/

Hope this helps...
 
you can hook your vacuum advance canister up to manifold vacuum, when i hits boost it will go back to "static" timing.
 
MSD has a 6BTM box.
Same as a 6 series but with the tining retard Bill is describing.
I saw one for sale here, maybe MoparDude318 had it listed.
 
805moparkid said:
you can hook your vacuum advance canister up to manifold vacuum, when i hits boost it will go back to "static" timing.
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I don't see any reason why that wouldn't work well, especially if you modified the slot (in the distributor mechanical advance mechanism) for mechanical advance so that it was limited to about 8 crank degrees. That would enable you to set ten degrees initial, for easy starting.

That setup would provide the 18 degrees mechanical you'd need for boosted power, and a lot more, once the vacuum advance kicked in after the boost goes away, for cool-running and better fuel economy.

The best of both worlds...:cheers:
 
Bill Dedman said:
I don't see any reason why that wouldn't work well, especially if you modified the slot (in the distributor mechanical advance mechanism) for mechanical advance so that it was limited to about 8 crank degrees. That would enable you to set ten degrees initial, for easy starting.

That setup would provide the 18 degrees mechanical you'd need for boosted power, and a lot more, once the vacuum advance kicked in after the boost goes away, for cool-running and better fuel economy.

The best of both worlds...:cheers:
Click to expand...

Turns out it not QUITE that simple almost, but not quite.

There are TWO methods of using vacuum for purposes of creating spark advance, and they are different in the degree of vacuum they utilize.

MANIFOLD vacuum is a strong signal and is what exists in the intake manifold, whenever there is a vacuum there. It can range up to 20-inches of water (or is it mercury???) and, beyond.

VENTURI vacuum comes from the carbureter and is a comparitively weak signal, but is also used to actuate the vacuum advance canister on the distributor, but with a weaker spring in the diaphragm to match the weaker vacuum signal.

Most slants had this second system, I think.

The strong signal from a manifold, both on boost and generating a vacuum would likely rupture a vacuum diaphragm that was intended to see only venturi vacuum... and, the spring in that distributor would be too weak for our purposes.

So, this will work, but only if the spring and diaphragm come from a distributor that was designed for a vacuum signal from a manifold and not the weak, venturi-vacuum signal from a carb...

If I have missed something here, please tell me...


THanks for you patience!!!:blob:
 
Bill im just gonna run a uber loose dizzy in the blower car. 10 in the dizzy all in by 600, so 20 total. see how it goes from there.

but what you do is lock the mechanical to what ever you "boost" timing number is. then use the vacuum can (on the manifold vacuum) to achieve your off boost number. as soon as you hit boost your back to your correct number for boost.
 
Throw the retarded stuff in the ditch and run race gas.
 
805moparkid said:
Bill im just gonna run a uber loose dizzy in the blower car. 10 in the dizzy all in by 600, so 20 total. see how it goes from there.

but what you do is lock the mechanical to what ever you "boost" timing number is. then use the vacuum can (on the manifold vacuum) to achieve your off boost number. as soon as you hit boost your back to your correct number for boost.
Click to expand...

"So, this will work, but only if the spring and diaphragm come from a distributor that was designed for a vacuum signal from a manifold and not the weak, venturi-vacuum signal from a carb..."

Isn't that what I said???

If you don't get a distributor out of a car (for this usage) that had an engine with manifold vacuum, you stand a very real chance of having that diaphragm fail, and that will not only deprive you of the desired advance, but will create a dandy vacuum leak that can lean-out your mixture an undetermined amount.

Cheap insurance... I'd do it, if I were you..
 
On my Dakota with a W/A inner cooler I run 32* locked with 1.5* retard with a 6BTM on 10# I liked the 6BTM unit worked for me.
 
What's your plans with this combo? (Pump gas, street/strip use, race only?)
And give us some details of your build. (Boost PSI, intercooler, water meth injection?)

If you're running meth injection, then pass on the retarded garbage (as stated)

Im running 6 PSI of boost,32° total timing, pump gas, no type of intercooler, on the street.
I need the ability to retard the timing. Several reasons, occasional bad tank of gas, hot weather, and traffic. I drive over 200 miles sometimes and sometimes get caught in crazy traffic. It's common to take over an hour to cross the George Washington Bridge. Several factors lead to me dialing back the timing. Slow vehicle speeds limit air flow thru the radiator, and my uncoated headers add to underhood temps. The March underdrive pulleys again limit water flow and mechanical fan speed. Also the fuel return line to the fuel cell recirculates hot fuel, due to the hi under hood temps. The fuel cell acually gets hot, not warm but hot. Lol, so with a combination of all these factors, I can hear engine ping. For me the 6BTM works.

On my next build I will use coated TTI headers, OD water pump pulley and a cooler on the fuel return line to reduce the underhood temps, water and fuel temps.
 
just a Paxton at 6 psi on a 360 ...J heads with 2.02 valves, performer intake, demon 750, push button auto, dougs headers, 9.1 comp, high energy comp cam, 2800 stall
 
Bill Dedman said:
"So, this will work, but only if the spring and diaphragm come from a distributor that was designed for a vacuum signal from a manifold and not the weak, venturi-vacuum signal from a carb..."

Isn't that what I said???

If you don't get a distributor out of a car (for this usage) that had an engine with manifold vacuum, you stand a very real chance of having that diaphragm fail, and that will not only deprive you of the desired advance, but will create a dandy vacuum leak that can lean-out your mixture an undetermined amount.

Cheap insurance... I'd do it, if I were you..
Click to expand...

think about it... its the same vacuum Bill, just different times... manifold vacuum is when ever the manifold is. venturi vacuum depends on throttle angle and rpm. but in the end will still be the same overall number... the engine only produces X amount of vacuum. your talking about something that dosn't matter...
 
I run the MSD 6531 Programmable by laptop. you can save multiple ramps for say pump gas and race gas and be able to swap them in and out. Plus it has a start retard and a couple rev limiters such as a launch limiter and others..
 
HOTMOPR said:
I run the MSD 6531 Programmable by laptop. you can save multiple ramps for say pump gas and race gas and be able to swap them in and out. Plus it has a start retard and a couple rev limiters such as a launch limiter and others..
Click to expand...

yea i like those!
 
HOTMOPR said:
I run the MSD 6531 Programmable by laptop. you can save multiple ramps for say pump gas and race gas and be able to swap them in and out. Plus it has a start retard and a couple rev limiters such as a launch limiter and others..
Click to expand...

Actually I think it 6530. I'll check.
 
scottylack said:
just a Paxton at 6 psi on a 360 ...J heads with 2.02 valves, performer intake, demon 750, push button auto, dougs headers, 9.1 comp, high energy comp cam, 2800 stall
Click to expand...

scottylack said:
think Ill go with the 6BTM
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Not cheap, but looks like a good option for you Scott. As I said before, i'm not boost savy, but i can see you'd have some more left with that box especially if you decide to step up the pressure a little further.
 
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