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MSD advance springs
MSD comes with heaviest springs in it. Full advance comes in at 4000 rpms. I have read on this forum about replacing the heavy springs for lighter ones. Bought the kit to do so, however it comes with a lot of different springs/advance curves. One set of springs will bring in full adv @ 2500 rmps the other @ 3000 rpms. What set of springs would you guys install? I want it to come quick however I don't want to detonate. My rear end ratio is 3.64. The different curves could bring in full adv @ 2000 2500 3000 3500 or 4000. For a car this light I am thinking 2500 or 3000. What do you guys think?
Thanks |
2500 to 3000 would be safe.
You need to shorten up the advance also,so you can run more initial. |
Hey Robert;
I believe Roushs specs are 16deg initial, 18deg advance for a total of 34deg. The black adv stop bushing and heavy "truck" springs were their recommendation when they were trying to sort out the "hesitation" problem, which turned out to be due to their re-jetting of the carbs. MSD has an instruction sheet which explains how to set your dist curve. They (Roush)want the advance all in by 3000 rpm. If you need the inst sheet, give me a call. Ted Suncoast Cobra |
Make sure you check your base timing and full advance timing. In other words at idle and at 4K rpms. The neighbors will love you!! Do not exceed 34 degrees!!!
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I would also verify what you have in there, in other words rev the engine until it quits advancing while someone watches the tach.
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Thanks for the input. Right now mine has the blue bushing 21 deg total adv. and the heavy springs. Total timing is 35 deg @ 4000. Not sure what the initial is I guess 14 deg. I know this can make the car quicker, I am just not familiar with timing and distributors and do not want to hurt anything.
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My full mechanical MSD was curved by Keith Craft. I believe he installed the light blue and light silver springs. The curve starts early (around 1700) and the advance comes all in at 3000. Of course the curve is dependent on the specifics of your motor. You might want to get the car on a dyno to experiment to find the optimal setup.
Keith was pretty adamant about making sure that I check the total advance, more so than the initial advance. If your total advance is right, you are checking two things: the advance mechanism advances, and it stops advancing at the right place. Basically, you just open the throttle while you are looking at the timing mark with your light. My initial advance is 10 deg, and has the 25 deg (silver) stop bushing installed for a total of 35 degrees. Just be your usual careful self when you change the springs and bushings, and make sure you check the timing with the motor reved up and you should be good to go. |
Good article on ignition tuning in Kit Car Mag: http://www.kitcarmag.com/techarticle...ine/index.html
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That was an interesting article. They seem to be recommending boosting the initial timing way up (as much as 18!), and of course keeping the total between 34-36.
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I have my initial at 20 deg with the total around 34 deg with the light blue and silver. It starts to advance just above idle ( which is 1150 for my 514) and is all in around 2800 rpms. 4 Seconds Flat makes a 12 deg bushing for the MSD, which ended up closer to 14 deg. I wouldn't think you need to rev it as high as 4k to get the total. When you do rev it up, don't do it for long without a load.
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native1,
It appears you have a Roush, why would you want to manipulate the factory setttings? |
Here's another article from Henry - this one is about how to tune a Roush 427: http://www.automotiveu.com/tuningperformance.htm
Using the Barry Grant initial timing guide we decided that 18 degrees of initial timing would work quite well with the camshaft that is in this engine. We then recurved the distributor so it would give us 16 degrees of mechanical advance that starts advancing at 800 rpm and is all in by 3000 rpm to give us 34 degrees of total mechanical advance. The MSD distributor that is in this engine did not come equipped with a vacuum advance and since the reason the customer selected this engine package is maximum power the vacuum advance was determined to not be a priority. We then reinstalled the recurved distributor into the engine, set the initial timing at 18 degrees BTDC and confirmed the total advance to be 34 degrees BTDC. The tech literature that came with the engine specified the total timing was not to exceed 35 BTDC. |
Thanks everyone. Good info!
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-Dean |
If you read the second part of the artical, there is a chart of exhaust gases plotted against the air fuel ratio from 10:1 to 18:1. They state that maximum HP is made at 12.5:1 A/F. O2 levels hit near zero at about 14:1 and they state that EFI O2 sensors can only read in a very narrow range around 14.7:1. EFI with an O2 sensor would not be capable of closed loop control at 12.5:1 as the O2 sensor is not able to measure that low. This would put EFI at a disadvantage when trying to make maximum HP. Some one around here stated that EFI on the exact same engine makes less HP in many dyno tests. I think this explains it.
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Dean,
I use to have it at 14 like fords spec sheet suggested. When I bought the new BG from 4 Seconds, he had me bump it up to 20. I have the Power Master gear reduced starter. It grunts a bit when hot ever since I had the engine rebuilt wether at 14 deg or 20 deg. Scott |
MSD advance springs
My KC 373 engine, which I recently re-dynoed had all the advance in at approx 2500rpm, I wonder if this is to soon, as in this case I have 308 bhp at 4000rpm, this increases by 200bhp at just over 5000rpm, but not a lot below probably 3500rpm and I would like to avoid detontation or "pinking"
Having said that the car has not done any track work yet, so I am curious to know why you guys have the advance in so early at small rpms? |
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MSD advance springs
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Well I put in two blue springs which according to the chart should bring in full adv at 3000. It had the two heavy springs in it before. I can't say that I noticed a big difference. It did not ping or buck at all even at low rpms. I am looking for a little more low end spunk. So I am going to try one blue and one silver spring to bring in full adv at 2500. Of course I don't stomp on it with the rpm too low. Thanks for everyones insight.
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