Lightning what do you mean clearance it?
Tldr
The short answer is
Make sure you have enough room above the piston.
These forums call it squish but in reality it's called the quench area. You need a certain amount of clearance there between the piston and the head combustion chamber. No one ever explains it so here we go down the rabbit hole. I tend to set up my stuff with no room for carbon build up. Read that as my personal tools and toys with any number of cylinders. Others go in what I call the grey area and that is fine for them. If I leave more room for carbon build-up on a cylinder that isn't mine then it becomes a give and take to figure how much extra to leave behind. What oil is being used is high on the decisions list, flat dish or popup dome, the fuel being used, thermal expansion expected on the dome, cylinder temperature, cylinder expansion amount, rpm window of operation and the bore size. The piston material, and they are all different so, you need to know the expansion rate of it vs how much of it you have there on this individual piston. Lean spots are the enemy, period. Not getting onto that here.
Nothing will destroy and engine faster then metal to metal contact in the quench area but tossing out a few con rods. Bearing failures are eminent.
This personal ripper of mine is setup tighter than most and does not follow the five thousands an inch rule. Just go look it up and you will understand all this much better. Wiki is a good place to start. At least on there we can all make corrections so the information being put out is accurate and timely. They list the references.
My current one is a base gasket deleted. If you do that on 99% of he 361s or 2s you rarely can get away with it. In essence the piston will hit the head when its cold. Cold not hot and that isn't a typo for this particular engine. Sanding out the squish band for clearance is proper or your going to regret it running anything but alky. You need room for your con rod and piston to "grow" and your jug mostly as not to not **** up your day in this motor. Doing maths is how you get there or beat stuff up.
I could add five more maybe ten reason we haven't covered like o-rings, nitrous oxide feeds, nitromethane, diesel fuel, propane, pumping losses, angles, inversions, bla bla so on and so forth. Many haven't even touched the tip of the iceberg yet. They just do what they're told or what they read. Four strokes over a four inch bore pretty much go with the rule but not much else imho. Five per inch is like a common SBC 355 cid rule for ten to one compression, flat top piston on pump gas so it must be gospel by now lol
See now that was clear as mud
