Another timing question ???
March 4th, 2014, 07:23 PM
#1
Another timing question ???
I got a 1972 cutlass with a 350, this cars came with a TVS as posted in the picture, I wanna take it off and run eather manifold or ported vacuum to my distributor, I know my timing is goin to change and this is where I need help on, where do I start ? Keep in mind I installed a pertronix ignition and I have a digital timing light with advance, also the engine is all stock
March 5th, 2014, 04:06 AM
#3
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
Just look back a couple of years, and run your timing as specified for a car without the TVS and emissions-retard specification.
There is no difference between a 1968 350 and a 1972 350, other than the compression being lower in '72 (in most applications, cams were the same, or darned close, you can verify this yourself by checking the Parts Manual), so the timing that was recommended for the engines before they started with all the emissions stuff is still good for the later engines.
In general, if you are following the factory instructions, set it for around 5-10°BTDC at 1,100 RPM, then see if it pings, and try advancing a bit if you wish.
For best performance, you can set it advance fully by about 3,000 RPM, to about 34-36°, but to get the right numbers, you may need to use the springs from a distributor recurve kit (one heavy, one medium). After that, you may need to mess with the settings to get the idle timing just right, or you may not. This has been covered in depth in several threads.
- Eric
There is no difference between a 1968 350 and a 1972 350, other than the compression being lower in '72 (in most applications, cams were the same, or darned close, you can verify this yourself by checking the Parts Manual), so the timing that was recommended for the engines before they started with all the emissions stuff is still good for the later engines.
In general, if you are following the factory instructions, set it for around 5-10°BTDC at 1,100 RPM, then see if it pings, and try advancing a bit if you wish.
For best performance, you can set it advance fully by about 3,000 RPM, to about 34-36°, but to get the right numbers, you may need to use the springs from a distributor recurve kit (one heavy, one medium). After that, you may need to mess with the settings to get the idle timing just right, or you may not. This has been covered in depth in several threads.
- Eric
March 5th, 2014, 07:14 AM
#5
Thanks, im goin to try both, manifold and ported vacuum and see which is better, Eric it makes sense to look at other years for there timing marks, one more question, whats the best way to check if the vacuum advance canister that is on the distributor is good or bad ?
March 5th, 2014, 07:28 AM
#6
Connoisseur d'Junque
Join Date: Sep 2010
Location: The Hudson Valley
Posts: 21,183
Connect timing light.
Start engine.
Disconnect vacuum hose that goes to vacuum advance.
Suck on end of hose while watching timing marks with timing light.
Timing should advance.
Timing should stay advanced if you plug the hose with your tongue (ie: it shouldn't leak).
- Eric
Start engine.
Disconnect vacuum hose that goes to vacuum advance.
Suck on end of hose while watching timing marks with timing light.
Timing should advance.
Timing should stay advanced if you plug the hose with your tongue (ie: it shouldn't leak).
- Eric
Last edited by MDchanic; March 5th, 2014 at 07:30 AM.
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