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Advance timing from original specs by 2 degrees?

Started by eam, July 23, 2007, 08:09:01 PM

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eam

My 76 coupe de ville timing specs is 6 degrees befor top dead center.  What kind of a problem will I cause if I advanced the timing 2 degrees using an adjustable vacuum advance from Crane Cams in Florida.  If the engine does not ping and appears to be running real good is there any damage being done to the pistons.  This could possibly result in a little better mileage and a quicker response from the engine.  Any thoughts fellows?  EAM - CLC17806

TJ Hopland

#1
If the orignal vac advance is still working just try turning the whole dizzy 2* and see what happens. Check under the rotor and see what condition the weights and springs are in and check the vac modulator with a hand vac gauge/pump to verify its working. If you start changing parts make sure you know how much total advance you have now and how much you should have.  The shop manuals have charts that tell you how much advance there should be at various rpms and inches of vacuum. If you dont know what you are doing you can make things worse if you start messing with the curves since everything on that motor is a system and all works together.  I think most of the problem by 76 was the cam.  74,5,&6 must have had a bunch of new emissions because by then the mighty 500 was just a shadow of its former self.  I have read that the 73 was the best cam from the factory and 70 was the best year for the 500 because it didnt have that much emissions and it was still high compression.  I have one car that does ping under some conditions but Im the only one that drives it so I just dont let it stay in that situation.  If I back up the base setting by 4* it wont ping but doesnt have the same power it has when its advanced.
StPaul/Mpls, MN USA

73 Eldo convert w/FiTech EFI
80 Eldo Diesel
90 CDV
And other assorted stuff I keep buying for some reason

greg surfas 15634

Quote from: EAM- clc 17806 on July 23, 2007, 08:09:01 PM
My 76 coupe de ville timing specs is 6 degrees befor top dead center.  What kind of a problem will I cause if I advanced the timing 2 degrees using an adjustable vacuum advance from Crane Cams in Florida.  If the engine does not ping and appears to be running real good is there any damage being done to the pistons.  This could possibly result in a little better mileage and a quicker response from the engine.  Any thoughts fellows?  EAM - CLC17806

First of all, the 1975-76 500 inch motor is in an advanced stage of "de tune".  Carbueretors camshafts, ignition timing and compression ratios are all driven towards emission control to be used with the first generation catalyst converter.
I assume you intend to run premium fuel (93 octane) and your converter is still installed and functional.  Advancing the initial timing will probably not be beneficial in any noticable manner.

eam

Quote from: greg surfas 15634 on July 24, 2007, 11:56:29 AM
Quote from: EAM- clc 17806 on July 23, 2007, 08:09:01 PM
My 76 coupe de ville timing specs is 6 degrees befor top dead center.  What kind of a problem will I cause if I advanced the timing 2 degrees using an adjustable vacuum advance from Crane Cams in Florida.  If the engine does not ping and appears to be running real good is there any damage being done to the pistons.  This could possibly result in a little better mileage and a quicker response from the engine.  Any thoughts fellows?  EAM - CLC17806

First of all, the 1975-76 500 inch motor is in an advanced stage of "de tune".  Carbueretors camshafts, ignition timing and compression ratios are all driven towards emission control to be used with the first generation catalyst converter.
I assume you intend to run premium fuel (93 octane) and your converter is still installed and functional.  Advancing the initial timing will probably not be beneficial in any noticable manner.   GREG! I have owned this 76 since 1977 and as the factory suggests I have been using regular unleaded gas and the engine runs very well.  The converter is in excellent shape and I'll always keep it that way.  The engine never pings since I installed the adjustable vacuum advance from Crane Cams as I stated before.  I'm going to advance the timing one degree with adjustments to the vacuum advance to see the result if any and I'll let you all know the result good or no difference.  EAM

greg surfas 15634

Quote from: EAM- clc 17806 on July 24, 2007, 03:43:02 PM
Quote from: greg surfas 15634 on July 24, 2007, 11:56:29 AM
Quote from: EAM- clc 17806 on July 23, 2007, 08:09:01 PM
My 76 coupe de ville timing specs is 6 degrees befor top dead center.  What kind of a problem will I cause if I advanced the timing 2 degrees using an adjustable vacuum advance from Crane Cams in Florida.  If the engine does not ping and appears to be running real good is there any damage being done to the pistons.  This could possibly result in a little better mileage and a quicker response from the engine.  Any thoughts fellows?  EAM - CLC17806

First of all, the 1975-76 500 inch motor is in an advanced stage of "de tune".  Carbueretors camshafts, ignition timing and compression ratios are all driven towards emission control to be used with the first generation catalyst converter.
I assume you intend to run premium fuel (93 octane) and your converter is still installed and functional.  Advancing the initial timing will probably not be beneficial in any noticable manner.   GREG! I have owned this 76 since 1977 and as the factory suggests I have been using regular unleaded gas and the engine runs very well.  The converter is in excellent shape and I'll always keep it that way.  The engine never pings since I installed the adjustable vacuum advance from Crane Cams as I stated before.  I'm going to advance the timing one degree with adjustments to the vacuum advance to see the result if any and I'll let you all know the result good or no difference.  EAM
Please understand, I was not downplaying the 75-75 500 inch motor.  I have a 75 with 70K on it and it produces what must be considered Dynamo like performance.  No fuss, noise or harshness, but predictable and ample power.
The timing "spectrum" was developed by the original design team at Cadillac Engineering to provide the most optimum performance over an extremely wide range of climatical conditions and performance requirements.  Like any other engineering decision it is a compromise.  Minor changes in any of the settings are ususally tolerated, but some corner of the envelope of performance is changed.
There is great potential in this engine "platform".   There are minor, subtle and essentially invisible modifications that bring this engine to life.
Thanks.
Greg Surfas

eam

#5
Quote from: EAM- clc 17806 on July 24, 2007, 03:43:02 PM
Quote from: greg surfas 15634 on July 24, 2007, 11:56:29 AM
Quote from: EAM- clc 17806 on July 23, 2007, 08:09:01 PM
My 76 coupe de ville timing specs is 6 degrees befor top dead center.  What kind of a problem will I cause if I advanced the timing 2 degrees using an adjustable vacuum advance from Crane Cams in Florida.  If the engine does not ping and appears to be running real good is there any damage being done to the pistons.  This could possibly result in a little better mileage and a quicker response from the engine.  Any thoughts fellows?  EAM - CLC17806

First of all, the 1975-76 500 inch motor is in an advanced stage of "de tune".  Carbueretors camshafts, ignition timing and compression ratios are all driven towards emission control to be used with the first generation catalyst converter.
I assume you intend to run premium fuel (93 octane) and your converter is still installed and functional.  Advancing the initial timing will probably not be beneficial in any noticable manner.   GREG! I have owned this 76 since 1977 and as the factory suggests I have been using regular unleaded gas and the engine runs very well.  The converter is in excellent shape and I'll always keep it that way.  The engine never pings since I installed the adjustable vacuum advance from Crane Cams as I stated before.  I'm going to advance the timing one degree with adjustments to the vacuum advance to see the result if any and I'll let you all know the result good or no difference.  EAM
GREG!  Yesterday I checked the timing on my 76 and it was set a 5 1/2 degrees before top dead center.  Factory specs is 6 degrees.  I advanced it to 7 degrees and took it for a ride and found the response was better and the idle increased using the same amount of gas.  Bear in mind I have installed an adjustable vacuum advance made by Crane Cams which is used to modify these minor adjustments and continue to use regular unleaded gas with no ping whatsoever.  The idle is smooth and so is the takeoff.  I  understand the compromises the engineers had to make at the time the engine was put together, accordingly, adjustments have to be made within the adjustable vacuum advance to satisfy these changes which I think improves the engine response and gas slightly.  This isn't done for improved gas mileage which will never happen but the increased movement using the same gas has to result in very minimal improvement in gas usage-very negligable and hardly ever noticed. FOOD FOR THOUGHT!  EAM