We installed a new Crane roller cam in a block fitted with Magnum heads, which brings up another interesting benefit-with the better combustion chamber and port design of the Magnum heads, enthusiasts have been starting to retrofit them onto the earlier LA blocks by swapping the old-style lifters with the newer oil-through-the-pushrod type required to feed the Magnum heads valvetrain oil.
Because all of Crane's lifters are the oil-through-the-pushrod types, you can convert to Magnum heads at no additional cost. But if you want to keep your original shaft-mount rocker heads, that's no problem either-just order solid pushrods and drop them in.
Even though we did this installation on an engine fitted with Magnum heads, the procedure is the same, regardless of what engine you have. Follow along as we up the performance of our Close Ad. The Future. Join MotorTrend. Terry Delong photographer J. Nov 03, Oct 27, Latest Engine of the Week News. Jan 11, Jan 04, Dec 28, Dec 21, Dec 06, Nov 30, Nov 22, Nov 16, Nov 09, Nov 02, Oct 26, The big limitations are cost and all the other details that must be accomplished before you can take advantage of everything that hydraulic-roller cams have to offer.
Let's jump in and see just how deep the waters are, shall we? Small-block Chevys first came out of Detroit with hydraulic-roller camshafts in in some passenger cars. Because the small-block was first on the scene, this story will deal with just the small-block. You big-block guys will have to wait.
The concept was to reduce friction and improve mileage, which really didn't generate great results. However, the roller wheel on the end of the hydraulic lifter allows greater lift-curve capabilities, delivering much more lobe lift--and therefore valve lift--than a flat-tappet camshaft.
But there's much more to this puzzle than just rollers on the end of the lifter. Installing a roller cam isn't difficult, but it does require some specific parts depending upon the type of small-block you're working with. Early pre-'87 small-blocks require a retrofit-style hydraulic-roller cam and valvetrain while most 'and-later small-blocks can use much, if not all, of the original roller-cam valvetrain.
We'll get into a late-model small-block first to show you how the factory designed a hydraulic-roller-cam valvetrain. Then we'll get into the aftermarket version that reconfigures a flat-tappet block for a roller cam and lifters.
The most important point about roller lifters is that they must not be allowed to spin in the lifter bore for obvious reasons. The factory takes care of this by designing two small flat spots on the lifter that accommodate a rectangular alignment bar that slips over a pair of lifters that prevents them from spinning.
This requires the lifter to be slightly longer in overall length both for this alignment bar and to create room for the roller. Otherwise, the hydraulic part of the lifter operates the same way as a flat-tappet hydraulic tappet. To keep the alignment bar in place, Chevy uses an eight-legged "spider" that places one leg over each of the eight alignment bars in the lifter valley.
Roller cams also cannot be allowed to move fore or aft in the block for several reasons. CamQuest Online. Need help finding what you are looking for? Skip to the end of the images gallery. Skip to the beginning of the images gallery. Available Soon.
SKU Available Soon items may take weeks for delivery. Add to Cart. Wish List Compare. Product Attachments. Latest News Read about the newest product launches from our development team. View More. Email Us. All rights reserved.
0コメント