What Mods can be done before reliability suffers ??

[spybot]

When moding an engine what can be done before they effect reliability ?
Say piston scalloping this helps the flow but it also effects the reliability.
Where as smoothing the intake flow helps reliability.
What are the pros and cons of each mod ?

High Compression Heads skimmed .30 thou
Port Matching
Intake path smoothed out.
Pistons and Rods statically blanced
Exhaust polished to mirror shine
Intake polished to dull finish
Ports chamfered
Piston and Block Scalloped

If someone could give me the pros and cons of each please.
If its a Pro why is it and if its a con what is that makes it so?

Disregarding the time factor in doing some of the above as i know some of them will take hours to complete with very little benefit if any at all hence the questions.

what kills reliability most of all ???
The above is based on a V4 but it should apply to all engine in theory.

[rude tim]

RPM is what shortens engine life the most. Raising compression is the easiest way to increase power. You must remember that you will need to use better gas with higher compression.

[phillnjack]

lots of questions, but most dont realy mean much to what your doing to your motor.
your just making a realy bad strangled version of the v4 block into a decent built block.

look at like this, all the mods you listed are what should be done to an engine in the first place for it to run good and to be very reliable.
its the difference between an expensive hand built motor and a cheap mass produced production motor.

Most mods you have mention that will give a power gain will also give more reliability .
IF KEPT WITHIN CLOSE PROXIMITY OF ORIGINAL RPM LIMITS.
when revving to the moon the motor can wear out faster obviously.
just because a well built motor could reach 7,000 rpm for example dont mean you have to run it flat out, keep it at 6500 and it will last a lot longer.
if racing its a different matter, and 1st place often means you dont care if engine lasts long.

just for a bit of useless information about the v4 motors

in 1984 the price of a Evinrude/Johnson....90hp with power trim was £3,403
in 1984 the price of a Evinrude/Johnson..140hp with power trim was £4,213.
so it was another (25%) £800 for the extra work done to the block from the factory.