I guess I glossed over the part about blue printing. I want to elaborate on what Michael has written.
A blueprinted engine makes more torque, runs more smoothly & can survive abuse better. By definition I think a high performance motor should be blueprinted, so it can perform more "highly"
. I've done many quick & dirty rebuilds for people who just want an engine that doesn't burn oil, starts every time & gets them from point A to point B reliably. But if I was paid to build a performance motor & the client informed me they would be running the motor hard, I blue printed the motor. And priced my labor accordingly. I worked on cars in the evening & on weekends. It was a way of earning extra money. Blue printing meant many long evenings working on the details & hand fitting things over & over again. It's hard work, repetitive & tedious. Lots of cuts & banged fingers along the way. But I also found it kind of peaceful working late at night in the garage, slowly but surely making progress. The motors I blueprinted were like works of art to me. What a difference it makes in the way a motor's final assembly goes & in the way it operates.Setting 5 main bearings & 8 con rod bearings to the proper clearances is only a small part of the process. It starts with prepping the dirty block, grinding & drilling & chamfering & threading, all the dirty work that makes chips. If the lifter bores need bushing, I like to ream the holes at this point. Then its off to a machine shop that hot tanks the block & trues everything up & bores & hones the cylinders to perfection. The crank journals are align bored, the decks are zeroed & leveled (perpendicular to the bores, parallel to the crank). The bores are set perpendicular to the axis of the crank, their diameter & finish is the final & most important job.
Back home the bushings are pressed into the lifter bores & reamed to size (clearance measured in the 1/10,000's of an inch). Like Michael mentioned, each set of rings is hand fitted in its cylinder and set aside. Pistons, rods & cylinders are combined to achieve the same deck clearance in each cylinder (one reason I always spec floating rods). More than once I've had to return the block to the machine shop for a second decking as I have found the decks a little too far out than mixing parts can compensate for. The top & bottom of the cylinders & the lifter bores are chamfered to eliminate sharp edges that will create friction. The crank must spin easily when it is set in the saddles & they are torqued to spec. The cam is degreed & top dead center on cylinder #1 is accurately marked on the balancer (it is never accurate out of the box). The cam chain is checked for the absence of slack, this can be screwed up during align boring of the main bearing saddles. Once the lower end is just right, you start to work on the head. If you've worked hard to achieve equal deck clearance on all 8 cylinders it would be crazy to not cc each combustion chamber and set them all for equal volume. Builds of this sort always involve a trip to the head porting guy. There's the valve job itself, a multi angle job for good flow numbers at all lifts, and you must insure the valves don't recess into the head too much, else the low lift flow will be ruined. The guide clearances are set for the minimum tolerance. I always had bronze guides intalled, regardless of the condition of the head. The springs are measured for equal seat pressure, not equal height, but not installed until later. Mount those heads on the block & begin work on the valve train geometry, getting each of 16 rocker tips to sit properly on the valve stems and getting the angularity as close to 90 degrees at half lift as possible. Now is when you determine the proper push rod length & order up a set of custom push rods. Once the geometry is set, you verify valve to piston clearance and machine the valve reliefs if necessary. You make sure every clearance is perfect, every rotating part spins freely (oil pump, oil pump drive shaft, distributor). By the time everything is perfect, I've assembled the engine at least a dozen times, everything has been fitted & refitted over and over. Everything is about as perfect as I can make it using the machinery & measuring tools available to me. The motor then comes apart once more & the reciprocating assembly is statically & dynamically balanced, the block & all parts are meticulously cleaned.
During final assembly every surface is clean & flat, every gasket fits perfect, everything lines up right, there is no binding, no surprises, any problems were worked out during an earlier phase of assembly. Everything goes together smoothly, torques perfectly, there's no doubt that this motor will fire right up & purr. By this point you know this motor better than you know your spouse, you know it's measurements better than hers, you've spent a lot of quality time with this motor, lol. A known good carburetor is used for the first running, because break-in is no time to be fiddling with a carb. After break-in a trip to the dyno is a must to dial in the carb & ignition.
Is it worth it? Well, that is dependent on many factors, emotional, financial, the planned use of the motor, who is doing the work. Every gear head should blueprint at least one motor. Motors assembled this way are in a different class than the motors assembled on an assembly line, crate motors, etc. They can produce more torque & survive more abuse. and they purrrrrrrr. They are "tight".
Forgive me my engineering & gear head friends if I have left something out, I was trying to paint a mental picture of what blue printing is, give an idea of the investment in time, of the emotionally involving aspect as well.
George