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Timing and TDC

Started by 71-440, January 21, 2018, 03:18:51 PM

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Chryco Psycho

You are welcome Joe  :twothumbsup:

headejm

Thanks @Chryco Psycho! So I assume each engine build has an optimum initial timing. I know you like to set timing without a timing light but what are the best indicators besides experience and engine sound? Can they be measured? Like vacuum reading, rpm, etc.?

Chryco Psycho

adding advance at idle the rpm will increase Vacuum will rise , the engine will become more responsive off idle , less accelerator pump shot needed without having the engine stumble , less traction , go too far & it will not increase rpm & can be hard to start


HP_Cuda

 :iagree:

Had mine set at the high end and it was hard to start, even worse in the winter!

:bricks:
1970 Cuda Yellow 440 4 speed (Sold)
1970 Cuda clone 440 4 speed FJ5
1975 Dodge Power Wagon W200

shawge

#49
What is the rate of advance added with the vacuum advance? Something like 2 deg / inHg?  And we want to shoot for ~15 deg vacuum advance?

Edit: followed the link to the article, They have a 2 deg / 5 inHg vacuum advance and end up at 14 deg.
1970 Challenger, 451 MS3Pro EFI
Colored wiring diagrams
Wheel spreadsheet

Chryco Psycho

I have found using the vacuum advance lengthens the advance curve so to run best at higher rpm you have to remove timing at idle , no win ,
the vacuum advance can be adjusted using an allen wrench inside the vacuum hose nipple on the dist & can be changed from approx 15 * to zero , turn the screw CCW to reduce the amount vaccum can add to the curve