Hey guys

Im planning on modifiing my 250 crossflow 4.1 EFI but im still learn A LOT!!! i been looking at people machining the
crank and cams to i think! like 10thou or 20thou I was wondering what dose this do to the crank and cam? and is it a
good performance thing or just motor recondtion thing


Also another thing id like to learn about is when you get a motor bored like, lets say 40thou im thinking.
Do i have to get the head done to suit the bore
(im refering to the area where the valves are around the edge to suit the bore on the block)


Umm what do you get from port and polish of the head? and is it worth it?


are getting larger valves installed and machined to suit a good performance idea?


I just want to know what i should do when i get my motor done up i want to do it right and top of range first time


Thx guys can't wait to hear what you got to teach me about
(man i love learning new things about cars)

pretty much it's just a reconditioning issue to make sure the crankshaft bearing journals are dead-on in terms of diameter, the bearing journal isnt out-of-round, on a taper, no grooves from worn bearings, or contaminants in the oil, etc

nope, the head will be ok, but IMO boring the cylinders out should only be to restore the bore to a perfect cylinder minus the scoring, lip, etc that you get on an older engine, boring for performance is a false economy, you lose out in terms of strength, (thinner bore walls=bigger chance of the bore blowing out into the water jacket, getting hot and bulging, or even distorting the bore so it is either tapered, oval, etc), cooling (thinner bore=higher temps on the coolant side of the block means the coolant can boil on the surface of the cylinder, and the steam bubbles effectively insulate the cylinder from the coolant, increasing the problem dramatically)
IMO boring a block for the few added cubes you get is an act of desperation and with the potential problems, its rarely worth it

porting/polishing the inlet/exhaust ports, as well as increasing valve diameter allows more of the air/fuel mixture to get into the cylinder (by making the flow easier, tho it can get to a point where its detrimental to the engines performace) and more fuel/air=more power