Stock engine specs

[eldiabloz13]

What are the factory specs of a 6 bolt 4g63 engine. What are the number of the cylinders and why does everyone bore to .20 over. What does 1mm over sized valves do. How can i tell if a block is messed up once its off. Cant i use a regular measuring tool to find the area.

 

[perley03]

what exactly are you asking for. be more specific when you ask questions. what specs are you asking about? there are many "specs", like bore, stroke, clearances, deck height, etc.

not everyone bores over to 0.020", you can custom order pistons to your boring needs. when an engine is due for a rebuild you measure each cylinder wall to see how out of round it is. then you determine how much you want to bore it to get it back to perfectly round. thats where the measurements come in, like .010, .020, .030,etc...

1mm oversized valves will allow you to flow more air into the engine....more air, more fuel=more power. it just allows the engine to inhale more air, and help get rid of the burnt exhaust gases.

as far as the block being messed up....you are dealing with many variables here. cracked cylinder walls, too thin cylinder walls, warped deck, cracked oil or coolant passages, crankwalk (sorry about the "C" word guys) etc. the easiest way to tell if a block is any good is to have it checked over by a machine shop. they magnaflux it and look for cracks, then measure all the tolerances and see if they are in "spec".

and as far as using a "regular" measuring tool, im guessing you will use a tape measure? no, micrometers and dial indicators are in need here. you are talking thousands of an inch (0.001") here. a tape measure or ruler generaly goes to 1/16 of an inch or 0.0625". that is not precise enough.
sorry if i sound like im being harsh here but its obvious you really dont know what to look for and how to check things out. if you need to have your block checked, tare it all down or have someone help you and send the block out to a machine shop and get it checked right.

 

[99gst_racer]

What are the factory specs of a 6 bolt 4g63 engine.

What specs, exactly, are you looking for?

- standard bore = 85mm (3.346")
- rod length = 5.900"
- compression ratio = 7.8:1

What else do you need to know?

What are the number of the cylinders

WTF ....4

and why does everyone bore to .20 over.

If the cylinders are out of round, then the block needs to be machined (bored) and it's usually wise to remove the least amount of metal as possible while machining a block. .20 oversized is typically the first step from a standard bore.

What does 1mm over sized valves do.

A larger valve head means a larger port size. It also means a larger intake port volume. That allows for more airflow.

How can i tell if a block is messed up once its off. Cant i use a regular measuring tool to find the area.

Take it to a machinist/engine builder. They will be able to determine if a block is usable and/or needs to be machined.