[Pupsvette76]

ok so i have a twin turbo chevy 355 and i would like to have so reaasurance against detonation and one of my ideas to help stop detonation is to run a boost retard mechanism... i know they msd makes a 6btm box but it costs $363 i already have a streetfire ignition box which is made by msd and i dont feel like buying a new box... i know that msd makes an add on (boost retard master) my question is if anyone has used the boost retard master add on with a streetfire box... all the wiring on my box is exactly the same as the msd 6al... they should work together correct?
thanks in advance for your help

[68NovaSS]

My experience is with the full BTM, but you're talking about a universal boost timing master? Here's an MSD instruction sheet, it appears they can be installed on almost any system, even a points distributor.

http://www.summitracing.com/parts/MSD-5462/?rtype=1

[bentwings]

You might also consider a water/alcohol or water/meth system as they are called too.

A local guy has a tremendous turbo car that can run 9's that he drives regularly on the street. The car is really drivable but very, very quick. He has a water / alcohol system that really does the job. He also has 2 fuel tanks...one premium pump gas the other is racing gas. Two complete fuel systems changeable in less than a minute. Just a couple of ball valves.

The beauty of water inj. is that you don't have to give up power to use it like you do with the boost retard system.

[spinn]

The retard knob MSD control is universal. My Truck has 2 saddle 19 gallon fuel tanks on a dash switch. 1 Tank has 94 octane, the other 87.

[Pupsvette76]

two tanks isnt a bad idea except it will be a street car also and when i hit boost on 87 thats goona lead to bad things do you think i can run water inj on the 87 or maybe 93 and then still have another tank for just racing

[bentwings]

I'm not sure you can go for extended run like 1/4 mile on 87 at 8 psi boost. I run 87 occasionally when it's all that's available out in the country but I limit myself to short blasts. 0-60, maybe passing a truck etc.

I'm going to install a water/alcohol system this winter. Even with that I think discretion will be the better part of valor on 87.

Even with a fill of 87 there is still some 93 in the tank so real 87 would be very rare. I've filled with 87 twice in row a few times but I really have not had problems with it.

The 2 tank thing is cool but wow complex... and all the extra fittings and lines make it really impractical in my mind. I drive my car a lot and in all weather. I really don't need this stuff for street cruising. I have to have room for my chairs and tools. Another tank would use every bit of space I have.

[Pupsvette76]

i think i too have decided on putting a water injection kit in i"ll still use 93 but with water inj i think i will be much more than safe under even the highest boost i plan on running (15-20PSI)

[68NovaSS]

If you're going to run a roots blower, you might reconsider 15 to 20 pounds of boost. I realize you won't be under boost all that often, but on a street car? That's a lot of boost, build it forged everything, hopefully your static c.r. is in the 7.5 area, not over 8:1 and you're able to keep head gaskets in it.

As far as "being more than safe", the injection system will deter detonation and help save our pistons, but not lessen the strain on parts associated with a boosted motor.

I've never run a turbo, but hear they're much more forgiving, 20 #'s is common to those guys.

[Pupsvette76]

no blower this car is twin turbo but i know the deal i built it all forged internally thanks

[spinn]

A cheap boost retard alternative is one of GM factory tricks. Use a 5 pin module instead of a 4 pin. When the 5th R pin is energized the 5 pin module retards the engine 8-10 degrees. About $20 bucks.

-text- This module is a direct replacement for the 4 pin std 990 module, only it has an additional termal marked "R". This terminal when grounded, reduces ignition timing by 10 degrees. High compression engines have problems with starting when the initial ignition is too high. But with this "mod" the module will allow you to start the car with ease (and less abuse to the starter) with the flip of a switch. GM used this with a vacuum switch to at certain times it would pull timing back 10 degrees, or run normally. But this was done with a fixed timing distributor.
.
You can install this, then increase your initial timing by 5-10 degrees, use the EMR Pin "R" to retard timing at start, and then return to higher timing for cruise. This will now require modifications to the overall mechanical timing curve. As now it is advanced what you cranked up initial base timing, now needs to be removed from the mechanical timing curve. Once removed you will have a much tighter timing spread and have a overall much faster curve and more repsonsive engine. The area under the curve is fuller and will have overall higher combustion efficiency.
.
Example:
.
Base timing:-->10 degrees
Mech Adv:--->24 degrees
Total Adv:--->34 degrees
.
Modified with EMR
.
Base timing:-->20 degrees
Mech Adv:--->14 degrees
Total Adv:--->34 degrees

[Pupsvette76]

so the module shortens the mechanical advance curve? i heard you say something about a vacuum switch are you talking about the vacuum advance can?

[spinn]

No this is 10 advance retard off the module signal, or consider it inital mechanical. The example discusses the use with a vacuum advance and the 5 pin working together for driveability. The 5 pin will work locked mechanical, or not, and with a vacuum pod. Gm used some higher compression engines in the 80's and the 5 pin module is used in the lot of them. Use the R tang for adding or subtracting 10 degrees.

[jseabolt]

Originally Posted by spinn

A cheap boost retard alternative is one of GM factory tricks. Use a 5 pin module instead of a 4 pin. When the 5th R pin is energized the 5 pin module retards the engine 8-10 degrees. About $20 bucks.

-text- This module is a direct replacement for the 4 pin std 990 module, only it has an additional termal marked "R". This terminal when grounded, reduces ignition timing by 10 degrees. High compression engines have problems with starting when the initial ignition is too high. But with this "mod" the module will allow you to start the car with ease (and less abuse to the starter) with the flip of a switch. GM used this with a vacuum switch to at certain times it would pull timing back 10 degrees, or run normally. But this was done with a fixed timing distributor.
.
You can install this, then increase your initial timing by 5-10 degrees, use the EMR Pin "R" to retard timing at start, and then return to higher timing for cruise. This will now require modifications to the overall mechanical timing curve. As now it is advanced what you cranked up initial base timing, now needs to be removed from the mechanical timing curve. Once removed you will have a much tighter timing spread and have a overall much faster curve and more repsonsive engine. The area under the curve is fuller and will have overall higher combustion efficiency.
.
Example:
.
Base timing:-->10 degrees
Mech Adv:--->24 degrees
Total Adv:--->34 degrees
.
Modified with EMR
.
Base timing:-->20 degrees
Mech Adv:--->14 degrees
Total Adv:--->34 degrees

This is exactly what I've been looking for! This application is going on a car with a Bosch distributor. I've seen people replace the $100 Bosch modules with the 4 pin GM module but never a 5 pin.

Couple of questions.

I went to the autopart store and picked up one of these 5 pin modules. I know B and C connect to the coil. There is not an "R" pin on this module. Instead the three pin side is marked H L and D. H pin has a notch cut out above it.

Question is which pins connect to the magnetic trigger and which pin is grounded to retard the ignition timing?

I realize I'll need to experiement to see which pins for the trigger go to which. I've been down this road before with aftermarket boost ignition systems and trigger polarities but not sure which is the one that when grounded retards the timing.

Also what do you mean by "fixed distributor". Meaning the distributor cannot be rotated the adjust the static timing? In other words EPA mandated so you can't monkey with the static timing like you can with older cars?

They did have a module with an "R" pin but it was the 7 pin module. You said it was the 5 pin that replaces the 4 pin.

Thanks.

[spinn]

The 5pin modules should be similar. The factory pin is marked R they vary identification letter. Using a 3M snap on type connector, the wire splice is made without damage to the HEI connector, and attached to a switch that is grounded to the head. Enables my build to run 16-18 degrees inital and then crank for a hot start with a flick of the switch.

The upper left pin (tiny one) is the "R" pin. The thin "R" pin is for a connector that plugs in and goes directly outside the HEI. It went directly to a vacuum switch that apparently was grounded when whatever vacuum condition GM wanted was met, and it pulled the overall timing down by 10 degrees only. Same Mechanical and Vacuum advance, just offset.


Five pin modules were used for:
HEI-EMR (Electronic Module Retard)
HEI-ESC (Electronic Spark Control)
HEI-ESS (Electronic Spark Selection

At least two different 5pins were made. One is set up to retard timing based on a + voltage going to the fifth pin. The other is set up to retard timing based on grounding the fifth pin.

[1932bantam]

the alky/water inj. Is a smart move