First, just run the car with the gap set to what the manual says. See what it does after a few hundred miles. Then check the plugs and re-gap if needed.
Additionally let us know how the MSD 6AL works for this motor. See any improvement in its driving characteristics?
First, just run the car with the gap set to what the manual says. See what it does after a few hundred miles. Then check the plugs and re-gap if needed.
Additionally let us know how the MSD 6AL works for this motor. See any improvement in its driving characteristics?
There is a thread somewhere in PFF where somebody already done that. This is what I am trying to find,
Explain what you read in this thread Share with us it can be useful.
Somebody already made tests and identify what is the best spark plugs gap when you install a MSD 6A or 6AL module on a 4.9 swap.
This is documented somewhere in a thread here in PFF and I can't recall the thread name. If I am looking for that thread to find back the correct information.
Here is my understanding of the effects of wrong spark plug gaps:
If a spark plug gap is too small, the electrical spark can fail to ignite the mixture if the spark happens to be in a locally fuel-lean zone. Also, the metal mass of the electrodes surrounding the flame kernel can quench the fire and prevent the fire from spreading in the cylinder. These problems are more likely to occur at low load / idle.
If a spark plug gap is too large, the voltage available from the ignition system may not be sufficient to cause an electrical breakdown in the compressed air/fuel mixture. If there is no breakdown, there is no spark, and you have a misfire. This problem is most apparent at high load / WOT.
If you have no misfires, then your ignition system is doing its job, and there is no room to improve the engine's performance.
There is no need to modify the gaps if your engine runs OK the way it is now.
Here is my understanding of the effects of wrong spark plug gaps:
If a spark plug gap is too small, the electrical spark can fail to ignite the mixture if the spark happens to be in a locally fuel-lean zone. Also, the metal mass of the electrodes surrounding the flame kernel can quench the fire and prevent the fire from spreading in the cylinder. These problems are more likely to occur at low load / idle.
If a spark plug gap is too large, the voltage available from the ignition system may not be sufficient to cause an electrical breakdown in the compressed air/fuel mixture. If there is no breakdown, there is no spark, and you have a misfire. This problem is most apparent at high load / WOT.
If you have no misfires, then your ignition system is doing its job, and there is no room to improve the engine's performance.
There is no need to modify the gaps if your engine runs OK the way it is now.
What is your experience with MSD 6AL and Cadillac 4.9 swap? As far as I know you don't have any.
The guy who wrote the thread I am trying to find back have the experience and have done the tests to determine the optimum spark plugs gap for this setup.
I have never complained about misfire or any other problem , I just simply want to retreive a old thread.
I have used MSD 6A ignition boxes on two different cars. I do not believe that an increase or decrease in the spark plug gap provided any benefit. While I have yet to install on one my 4.9L swap, my experience shows that the engine runs smoother with more economy below 3000 RPM's. Above that RPM I can't say that we saw any benefit as the unit could not generate multiple sparks as there was not sufficient time to fire them. The item that is holding me back from installing the MSD 6A on my 4.9L is that those boxes need to be put in a cool location with good air flow over them. With a 4.9L swap there aren't many cool places in the engine compartment.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Originally posted by falcon_ca: This is not what I read in the the thread I am looking for.
You said this is not what I read in the thread Me I said : Explain what you read in this thread Share with us it can be useful. Where is your answer ! if you can't say nothing on your memory thread. How you can affirm what we say is no good We try to help you
You said this is not what I read in the thread Me I said : Explain what you read in this thread Share with us it can be useful. Where is your answer ! if you can't say nothing on your memory thread. How you can affirm what we say is no good We try to help you
Claude, my answer is in the thread I am looking for. The thing I remember is what I am writing since the beginning of my thread, after installing a MSD module, done many tests, he adjust the spark plug gap, and had better performance. I am looking for that thread to re-read all that and review in details what have bee tested. You wrote that changing the gap will not help in anything, and yes, this is not what I read in that thread
pmbrunelle is talking about solving problems. I am not looking to solve problems, I am trying to retreive a specific thread that I can't easily found with the search engine
IMO anything more than the GM recommended .060" will not give a positive result. With the compression and RPM range that this engine is operated at, GM specified a wide gap that is designed for this engine. Too wide or too narrow a gap and the plug wont fire correctly. GM HEI ignitions already provide a hot spark The MSG will just fire the plug about three times but only up to 3000 RPM's. Beyond that the time is not there to complete multiple firing cycles and you get only one spark, especially so as it not a DEI system.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
