quick BORE question!

[kaplianablack]

Hey fellas, well i have a quick question, i was looking through machv.com which im sure all of you are familiar with. They sell an engine rebuild kit, you can choose oem size or .020 over size. What is better and whats the difference. Sorry but i am a newbie so please let me know. Thanks a lot for any comments. Peace out!

 

[Defiant]

Stock is better. Oversize if the bores need that much cleaning up. The displacement difference on a 4-cylinder is negligible.

 

[gurmanator]

.20 is cool,.40 your pushing it because the cylinder will distort under high boost.I went .40 but I found out that info after I bored(go figure)but I dont notice any problem.

 

[Julia]

Stock is better. Oversize if the bores need that much cleaning up. The displacement difference on a 4-cylinder is negligible.

I agree. Check the cylinder walls and see how much work needs to be done before you order the rebuild kit.
Julia

 

[92redman]

You are not planning on doing the rebuild yourself, are you?

 

[kaplianablack]

i was considering doing it myself with some friends...is this not a good idea..im a little short on cash and im guessing the labor would be through the roof. Let me know what you think!

 

[rkarkosh]

Rebuilding your own motor and be 'fun and rewarding' but you better read up first. I just finished my first rebuild (1000 miles and my fingers still crossed). Boring a block is a technique for restoring proper clearances in the cylinder and is not a performance mod. Cylinders can wear in different ways, some lose their roundness, some become tapered and most become larger. The terms overbore, .020in, .5mm etc refer to machine work required to bring a worn engine back to spec. The first step in rebuilding is to determine the amount of wear on the engine. Wear occurs in the cylinders and crank bearing journals. My cylinders were worn .008in. If I had just used standard sized rings and pistons (std.) my ring gap, where the ends of the rings meet, would have been too large due to the increase circumference of the cylinders and would have allowed pressure to escape into the crankcase. A machinist bored my block to .020 over which insured the cylinders were round and allowed use of oversided rings and pistons. This brought the ring gap back to spec. Likewise, your crank may need to be turned to restore proper oil clearances. This is done by truing the bearing journals in a lathe and using .020in oversized bearings to replace the removed material. I payed a machine shop $280 to do the machine work and supply the proper rings and bearings. Good luck.