As a former engine builder I can tell you that pistons are a consumable. You can put used pistons back in the same hole that they came out of with new rings as a an economy move, but you are going to loose compression as the cylinders will not seal as well as a fresh bore (with a block plate) and honed to fit fresh pistons. Taking pistons out of one engine and sticking them in another will lead to a rebuild sooner than you expected.
Mark IV (two piece rear main seal) blocks require roller tappets with a tie bar. Big blocks like lift, lots and lots of lift. Unfortunately such cams are very hard on the valve train and result in broken valve springs unless you check the valve springs for loss of spring tension (you can check the spring tension on the heads with a tool referenced below).
A 454 is close, but not close enough to use rectangular port heads on the street. You need around 500 cubes to utilize the flow capacity of 320 cc rectangular port heads, otherwise they will be lazy at low RPM as the port velocity allows the gas to fall out of the air flow. This is why the engineers at Chevrolet specified Edelbrock Performer RPM-O 280 cc heads with bigger valves for the ZZ502 street engine with a hydraulic roller , but used Edelbrock Performer RPM-R heads 320 cc rectangular port on the HO 454 with a solid roller that was designed to rev to 8K. Rectangular ports requires bigger displacement engine for idle to 4,200 RPM operation; or to twist the engine higher than you will ever encounter on the street for a 427 to 454 engine.
As to cams in general: Lift is useful every where in the RPM band and allows the engine to breath better. As I mentioned higher lift requires reinforcing the valve train (roller rockers with a stud girdle or shaft mount rockers, double or triple wound springs to dampen valve spring harmonics and control the mass of the valves, larger diameter push rods with matching push rod guide plates),
Duration is increased from the stock 182 degree to 196 degree range to larger numbers to hold the valves off the seats for a longer period of time. This is necessary to give air a chance to get into the cylinder as RPM increases. A longer duration cam gives you that rumpity-rump sound you hear on a race car that launches off the line at wide open throttle. That rumpity-rump sound is the sound of lost power. You are sacrificing bottom end torque that gets your car rolling off a stop light for HIGH RPM operation. If you are not racing you don't need that noise other than to feed your ego. Just don't be surprised if a Jap turbo car kicks sand in your grill.
Finally the issue of Lobe Separation Angle also affects that rumpity-rump sound. The bigger the number (the wider the lobes are separated the less noise, and the more power you will have for the street. That noise is air being pushed back into the intake manifold causing your carb to dump in more gas than needed; which causes the motor to load up. So a wider LSA with the same lift and duration as found on EFI computer controlled cars will run just as well on the street, but it reduces overlap (that rumpity-rump sound).
If you are buying an off the shelf cam my advise is to stay off the bottom of the page. Also consider truck pulling cams and Jet boat cams to get the numbers (lift duration and LSA) that you want in an off the shelf cam. I used to use custom ground solid roller cams in all of my cars (originally bought them from Harvey Crane back in the seventies, but changed brands over to Comp Cams in the eighties, then over to Lunati after the turn of the century as the quality at Comp of their roller tappets fell off ).
Find Moroso 62390 Moroso Valve Seat Pressure Testers and get Free Shipping on Orders Over $99 at Summit Racing! These Moroso valve seat pressure testers allow you to check the seat pressure on most assembled Chevy and Ford engines with roller rockers. These tools have built-in direct reading...
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Big Dave
