Hello to all. Have some blower motor questions as I have never owned a blown car before and I acquired this one already built (first car I have owned that I have not built myself). The car is a 671 blown 401 AMC and has an old Mallory HyFire VI ignition controller. My questions are what would be a good upgrade for ignition controller or will this one work ok? Ignition timing? Best ways to protect motor, I have seen/heard about the use of MAP sensors but don't really know much about that. Any suggestions would be appreciated, I am getting ready to rewire the car from front to back and want to setup the ignition accordingly. Thanks in advance........
Kinda depends on the boost level you plan on using. First step is to curve the distributor to stock specifications and have a few degrees taken off because of the boost. Also make sure the ignition is limited at that setting. Then based on boost level adjust intial timing from there ..
How much timing it will tolerate depends on the blower drive ratio, cam, compression ratio, fuel, gearing, etc. You didn't tell us any of those things, so we can't answer your question. If it's a typical street setup with less than 8 psi boost, and 8:1 or less compression, you can probably get away with stock timing. If you have more, then you might need boost retard, or just back the timing off a bit. I'm not too keen on mallory electronic stuff, and I've had good luck with MSD goodies. but that's just my opinion.
From recent news that we read here, older is better with Mallory stuff. I have an old hyFire box running as an amplifier(?) on a chevy points dist, driving an MSD Blaster coil. It works and has been trouble free. I'm using it to have less amp load on points. The rub block still wears, but the points always look good. It comes with a jumper wired connector that will take it out of the circuit if something goes wrong.
Msd 6530 would be my pick. You lock out you ignition timing and then set a timing curve up on the box. It also has an input for a map sensor so you can run a boost retard. Hands down best cdi unit under $400.
also to answer your question.. a map sensor is a manifold air pressure sensor. this sensor detects the amount of pressure in the manifold and converts it to an electrical signal between 1v-5v. this si used in blown engines to either adjust the fuel mixtures in an efi setup or to program in timing retard to a cdi unit like the one i mentioned above. great investment for any blown car. i am running this box with my blown cleveland in an aus falcon and its fantastic. no more dizzy regraphs or no more checking the timing.
what type of fuel system and carbs are on the blower? Get a msd distributor, box and coil, depending on how much of a performance engine this is, timing should be about a total of 32-38 degrees, you dont need alot of advance. its quite simple to make a 6-71 reliable without electronics
how can you say that he needs that amount of timing when you have no idea about what comp ratio he is running, what ammount of boost he is running and also what camshaft he is using. This is the basic info required before asking what fuel he is running, if he is using alloy heads, and also what carbs he is using. that is just a recipe for disaster, until all these variables are known you could not possibly tell him that running 32-38 degrees is a good idea. to the op do alot of reading and learn alot about blown engine before going out and spending your hard earned on what people tell you to do on a forum. also try other forums such as www.turbomustangs.com there are guys on there that are a wealth of knowledge with supercharging and turbo charging and maybe they can help you understand the fundementals behind forced induction and how it is alot different to natural aspiration. what works n/a does not work for forced induction.
But also realize that a mild street blower setup has simpler timing requirements than a high boost turbo car. You can get away without using the fancy electronics. Which is something we value here on the hamb....long live simple mechanical solutions
I am with Squirrel on thsi one. I like mallory ignition until it comes to control boxes. MSD ignition contolers are a better piece of equipment. MSD has a new box that you can use a boost sensative switch and dial in lag on your ignition in 2 degree increments. Squirrel is also correct on ignition advise. We can give you generalizations but without the information he mentioned we cannot give you good solid advice. Your best bet is to get your ducks in a row and contact GMC Bubba for good solid advice, he is mister ignition.
Mallory HyFire 6 box 6852 is just a C.D. Digital Ignition Control. The 685 Box is that and also has the capability to be used in conjunction with a MAP sensor for boost proportionate control. You would need a optional harness with that also. MSD's version is the 6 BTM or 6462, the sensor is built in, there is a little fitting on the side of the box for the manifold pressure. That unit would replace your Mallory entirely. Guys that already have a MSD box whether 6,7,8, or 10 can just upgrade to the Boost Timing Master, to be used with thier existing box. Crane cams also has a Boost Referncing box that must be used with a MAP or Manifold Absolute Pressure sensor. As already stated, at low boost, correct compression ratio, and a correctly curved by Mr. GMC Bubba distributor and you will be fine for everyday street use. Hope that helps. Dont over complicate your situation if you dont have to. Sofisticated ignition systems can get VERY exotic, with the ability to control each cylinder individually, starting retard, boost reference retard, nitrous retard for one or more stages, top gear retard, and on and on, I think you get the picture, TR
Sorry, to help you understand the MAP sensor, it takes the signal of vacuum from the manifold under pressure or boost from the supercharger or turbo compressor. Then you have a control knob that will allow you to tell the ignition controller/the box, how much to retard the timing in degrees in relation to the pressure of pounds of boost. For each pound of boost pressure, you adjust the amount of timing retard in degrees. The electronic box does the rest, TR
I've had good luck with my MSD digital E-curve. You have plenty of ignition curves to choose from, plus I love the built in rev limiter. Leave the funky wire seperator off the top of the cap and it has old school points distributor looks. Super easy to hookup too.
I'm running a Mallory dual point dizzy cause it fits in front of the firewall on my 32. Only one set of points active to control MSD box. Running 32 degrees advance locked down, 7.5:1 static compression, 19% under-driven with an old B&M blower cam so pretty tame. As others have said ignition timing required is dependent on cam, compression, blower drive ratio etc.
Thats how my blower motor ran best,too,about 32 degrees of timing .Mechanical advance locked down,no vacuum advance.5-6 pounds of boost.
I appreciate all the input. The heads are cast iron, I am going to have to pull the motor and find out what camshaft is in it as I got three cam cards in the stack of paper work that I got, but I don't which one applies. The pistons are JE dished, I believe the compression ratio is around 7.5 to 8 from what I have researched in the paper work. The carbs are 2 750 Holleys. Fuel system is a Mallory 140 pump, the lines seem a bit small as they look like -6 going in from the cell to the carbs. I will provide as much information as I can as I would like to get the car lined out and make it run better than it does.
TK, you can " plot " the cam at the valves to fiqure out which one you have. Better than pulling the engine, unless of course you want to.
If you dont know for certain already, I would also think about calculating the blowers percent of under/over drive. Count the teethe on each pulley and record the numbers, and then you can easily calculate what you are currently running. Good info to have. You also mention getting it running better than it does, let me therefor make a strong suggestion- do a LEAK-DOWN first. Now cut the oil filter open and go through it with a fine toothe comb. If it gives the indication of being that tired, consider pull the pan and check out the bearings too. TR
TK, now that your in the world of boost, there is another topic you should know- Final Compression Ratio. The 7.5-8.0 that you mentioned is your "static" or "calculated" compression ratio. Knowing the "final" C.R. is important for blowers or forced induction engines for street use. This helps with knowing your meeting your fuel requirements. Altitude is another variable for people running in areas significantly higher than sea level this will also have an effect on C.R. of a blown engine. This is called the " corrected " C.R. for a blown engine. This goes hand in hand with the previous post I made #19, regarding calculatingyour boost levels. I have formulas for either calculation when and if you need them, or if anyone else needs them, TR
Well because i have about 15 street blowers and racing blowers sitting here in in invetory, years of building and running them on the street, running blown injected alky engines, I at all times own a blown street car...I am far from Austin Coil but i know how to set up and run one. About the timing, i know what they like, i dont need to know his compression to get it in the ball park. Anyone that puts a 6-71 on a engine is going to be making horsepower, if its a street car 8-1 or 11-1 that timing will work, depending on how well it is built is how much power its capable of making, part qaulity, air flow, blower type, carbs and then on top of that, we can set it up to run perfectly effecient and if the engine does not have the parts to handle doubling that horsepower, kableeewie! Knowing all this we can decide to upgrade engine parts, down size blower, change pulleys for boost and then move to tuning the carbs and timing for final tune up.
You have a nice set of pistons if they are the Je blower piston, what blower do you have? Is it a stock gm blower or a new production copy? And also when you say, you want it to run better than it did, what are you referring to? Did the engine not turn on ( i mean it, does it not make boost and come alive when you stand on it?) Do you have a good fuel pressure regulator? I would upgrade that fuel pump as well. What is the air temperature where you drive the car? What pulleys do you have on the engine? Can you tell me if its a hydraulic cam? I would also look into checking and probably replacing the cam and valve springs if your going to freshin it. And yes in most cases blown engines like the timing to be locked out
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