Upgrading 420a

[Misuta Yancha]

ok I have another couple questions...

what is the difference between standard .020 and .040, as pertains to pistons?

what is the benefit/ use of thicker rod bearings and main bearings?

 

[99RedGs]

Those are bore sizes. They represent how much larger the bore is than the standard bore from the factory. So a .020 overbore would be the factory bore spec + .020. The difference between .020 and .040 is .020" . The .040 is a larger bore which can help add a little power, but its been pretty well accepted that a large overbore doesn't benefit very much. Most people go with .020 in order to ensure a perfectly round cylinder in case there was any ovaling of the cylinder for whatever reason.

 

[Misuta Yancha]

is that in inches... millimeters... centimeters?

 

[99RedGs]

inches

 

[Locke]

Red is on it.

The idea is to bore the cylinder as little as possible (or as allowable by readily available piston oversizes) to attain a concentric defect-free cylinder with no taper. This will leave you room to do further work on the cylinder in the future if something were to happen to damage the cylinder walls.

The same goes for the bearings. If the crank journals need to be ground down for whatever reason, you would need to purchase thicker bearings to make up the difference and maintain a proper oil gap size.

Don't purchase pistons and bearings until after your machinist has inspected the block and crank. If he is any good, he will let you know what size pistons and bearings you would need to order, even before he starts actually working on the block.

 

[Misuta Yancha]

so if I were to do the work myself... I would bore out all the defects then use a snap guage or something to that effect to figure out what size piston I will need?

 

[VelocitàPaola]

Boring isn't something you can do yourself unless you happen to have very specialized and expensive equipment. Some people either own or work in machine shops, and unless you're one of them, you'll be taking your block to a machinist to get this work done. It usually doesn't cost more than $150-$200 to get the standard shortblock treatment done at a reputable shop. They'll handle all the precision work and let you know what size pistons you need.

 

[Cinful526]

So how's this one coming along? Curiousty is getting me, i'm working on building mine. My biggest questions is how you're gonna do the wiring.

 

[99RedGs]

He hasn't posted since April so I am thinking he might have given up/ put this build on hold... Or maybe he is just lurking the forums and reading so he doens't end up wasting his money (what he should be doing )

 

[Cinful526]

Yea, that's what i'm doing, hah, so much info on here I'm spending like 8 or 9 hours a night researching, running figures, etc. I'm afraid to post a thread yet I've been reading up to make sure before i start asking opinions and help.

 

[bullettdsm]

Yea, that's what i'm doing, hah, so much info on here I'm spending like 8 or 9 hours a night researching, running figures, etc. I'm afraid to post a thread yet I've been reading up to make sure before i start asking opinions and help.

Nice

MB