318 cam timing

[AMP762]

New here and kinda new to Mopar so be gentle. I've got a 79 Aspen which needs a timing chain.I know in the 70s GM and Ford started retarding the cam timing for emissions,did Mopar do this also? If I buy chain and gears for 79 should I install stright up?

[thatwasfunny]

I don't think it matters if you don't degree it in.
Go ahead put it in 4* advance, you could only add to detonation due to too much advance already when installed in the 'mystery straight up mark',
Or advance it 4* from being retarded 6* from the 'mystery straight' up mark installation again.
Really, put it straight up or 4*advance but don't put it in retarded.

[DartGT66]

Why is the cam retarded for better emissions? If the cam is retarded, the intake valve closes later after the BTDC, I can't see how that would help the emissions? Retarding a cam moves the engines powerband to higher rpm, advancing it moves it to lower rpm. The effects of retarding or advancing some four degrees aren't huge, perhaps moving hte range 100-200 rpm. Commonly advancing the cam is "preferred" rather than retarding it. Many aftermarket cams have a "built in" advance of four degrees, meaning that if you install it with stock timng chain set that happens to be accurate, the cam will be four degrees advanced. Many aftermarket roller timing sets have a couple of different keyways to use, for advancing or retarding the cam timing if needed. They also may, or may not be accurate, so if using theses the true cam timing should always be measured in the final installed postition. If you are just renewing the timing chain set of a stock '79 Aspen, buy a new double roller timing chain set and install it straight up, unless you really arenät going to measure the true assmebled centerlines. Because of different tolerances, the end result may be whatever without measuring, but it's propably that even with the stock chain. I wouldn't use anything but a double roller timing set in a SB mopar, they are rpetty hard on the timing chain and gears.

[valiant64]

I agree w/ Dart on this. The factory "silent" gear timing sets are trash. Why they put a nylon coated cam sprocket on an engine that is notoriously hard on timing chains is beyond me. If just doing a timing set on an otherwise stock engine, #1 cyl @ TDC, line up the dots on the sprockets & go. Double roller sets can be had pretty cheap, I wouldnt consider anything less in terms of durability & longevity. Another good add-on is Mopars timing chain tensioner, part # P5007709. It takes the place of the stock cam thrust plate, and uses a sprung tensioner to keep tension on the chain after normal wear. A bolt in piece, & only costs about $30. I'd do it while you're in there.