The install causes the most problems. You HAVE to check the springs for proper install height. Make a solid lifter and rotate the motor over. At maximum lift stick a feeler gauge between the coils. You need some clearance there. Builders will differ on what they feel comfortable with. You NEED the proper spring pressures for your particular camshaft too. You NEED to check ptv clearance if you are running a BIG cam. Honestly if you are running anything under 240 duration and .550 lift you should be fine there. You NEED the proper pushrod length to do the job. Usually with a bigger camshaft with more lift a .10" longer one is key, you check this with a sweep of the rocker on the top of the valve looking at the pattern. You NEED a stronger pushrod for a bigger camshaft and guideplates too. You NEED to adjust the lash correctly. Some lifters require no more than 1/8th of a turn past zero lash. This is so critical. You NEED the proper head gasket. There are several thicknesses to choose from which can slightly alter compression. So many things that people do wrong on an install and then they throw the head porter under the bus when the problem is usually their own fault. This is just crap off the top of my head, but it's really basic for any motor.

 

The "extra" costs come from items you may not have considered thus far. Gaskets kits, timing chain, push rods, head bolts/studs, lifters, header gaskets, spark plugs (since you already have them out), radiator coolant, maybe A/C recharge, a good PCM tune.

And since you have to remove the intake, water pump, headers, heads, radiator some gaskets get trashed, hoses split, bolts break.

It all adds up as you go along.

Just make sure you put in the parts now that you may want to have in a future update, such as new lifters, head studs and a very strong timing chain. You don't want to go back later to install these and tear the motor all apart again.

Later ... Larry S.