Re: 67 L-79 vacuum advance canister
Then in that case, enjoy your new cam. The Nostalgia Plus series from Comp Cams will give idle characteristics very similar to the cam it's emulating. At the same time, it will allow your engine to develop more torque across the entire rev range, than the original cam. This also results in increased horsepower, because that improved torque is carried somewhat higher in the rev range than the original. Your cam has significantly faster ramps than the original L79 cam, which allows for a narrower lobe centerline than the original. These two items combine to give very similar overlap to the original, which contributes much to emulating the original idle cadence/note/vacuum. The tighter LSA also enables earlier inlet valve closing, to give more cylinder pressure. The Nostalgia Plus series also delivers slightly more valve lift, at least, in the solid tappet designs, because of tighter lash requirements.
Is there a downside to all of these benefits? You bet. The faster ramps generally require stiffer valve springs, and the faster ramps, combined with stiffer springs will cause accelerated seat recession, and accelerated lobe wear. How much? Well, if you are careful in your valve spring selection, and give serious thought to utilizing beehive springs, then the accelerated wear will be minimized to near zero. If you use the lightest conventional spring (in your case, a single spring with damper should be all that is required) possible to achieve valvetrain control, then the wear rate may approach 30-40 per cent faster than the original cam/lifter/spring/retainer setup.
What this means, is that if you use beehive springs, which have less mass than conventionals, and use a smaller/lighter retainer as well, then valvetrain control can be achieved with lighter spring pressures as required for conventional springs. If you go this route, you can expect 100,000 or more valvetrain trouble free miles from your engine. If you use conventional springs, then you can expect 60,000-70,000 valvetrain trouble free miles from your engine.
######: This is all contingent on the assumption that you use motor oil with at least 1100 ppm ZDDP content, and change your oil at regular intervals.
Now, the next question is: "How many more years do you expect to be driving?"
Let's see.......worst case 60,000/750 = 80 years.
Then in that case, enjoy your new cam. The Nostalgia Plus series from Comp Cams will give idle characteristics very similar to the cam it's emulating. At the same time, it will allow your engine to develop more torque across the entire rev range, than the original cam. This also results in increased horsepower, because that improved torque is carried somewhat higher in the rev range than the original. Your cam has significantly faster ramps than the original L79 cam, which allows for a narrower lobe centerline than the original. These two items combine to give very similar overlap to the original, which contributes much to emulating the original idle cadence/note/vacuum. The tighter LSA also enables earlier inlet valve closing, to give more cylinder pressure. The Nostalgia Plus series also delivers slightly more valve lift, at least, in the solid tappet designs, because of tighter lash requirements.
Is there a downside to all of these benefits? You bet. The faster ramps generally require stiffer valve springs, and the faster ramps, combined with stiffer springs will cause accelerated seat recession, and accelerated lobe wear. How much? Well, if you are careful in your valve spring selection, and give serious thought to utilizing beehive springs, then the accelerated wear will be minimized to near zero. If you use the lightest conventional spring (in your case, a single spring with damper should be all that is required) possible to achieve valvetrain control, then the wear rate may approach 30-40 per cent faster than the original cam/lifter/spring/retainer setup.
What this means, is that if you use beehive springs, which have less mass than conventionals, and use a smaller/lighter retainer as well, then valvetrain control can be achieved with lighter spring pressures as required for conventional springs. If you go this route, you can expect 100,000 or more valvetrain trouble free miles from your engine. If you use conventional springs, then you can expect 60,000-70,000 valvetrain trouble free miles from your engine.
######: This is all contingent on the assumption that you use motor oil with at least 1100 ppm ZDDP content, and change your oil at regular intervals.
Now, the next question is: "How many more years do you expect to be driving?"
Let's see.......worst case 60,000/750 = 80 years.
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