I've had a couple engines built (paid someone else to do it ), but I've never attempted one myself. I'm considering building my 4g63 on my own in a couple months. Not sure if I'll go with a stroker or a simple 2.0 yet. My question is, if you're not happy with your clearances between your crank mains or rods, what are your options? Do bearings come in various sizes? Or what do you machine to get the tolerances you want? Seems like a pain to order bearings and install them, and find out they're off by .002"'s from where you want, and then have to order a new set.

I searched, but seems every engine build somehow miraculously has proper tolerances.

Thanks in advance,

 

You have to check a bearing catalog for what range of sizes they have. They're made for a specific housing and shaft size such that when they're assembled, the clearance should be right. Before you install any set to check for oil clearance, mic the bearings and check that they're the right thickness to start with. Sometimes they can be far off. Don't count on it being right though because sometimes there is enough deformation in the housing (say 0.0003 - 0.0005") after torquing to require different bearings. You have to measure everything. You can swap bearings for free with most good vendors, as long as the bearings are back in their box and not scratched or bent, and it is done close to date of purchase. Standard dial bore gauge marks are ok.

You can mix oversize and undersize bearings to get closer to your target oil clearance but you'll end up with leftover bearings. Worth the extra money though.

The 0.002" off you talk about is really large. That is way off. You never ever want to machine a housing out just to get the cleaance, because the housing diameter sets the crush on the bearing which is really the only thing holding it in place. You can vary bearing thickness by changing bearings, or you can customize journal sizes, but you always want housing bore size to be exactly what the bearing manufacturer says it should be, or very slightly (tenth or two) on the tight side.

 

Be sure and use Plastigage to check the clearance dry . Then after you get the clearances right be sure to oil the bearings liberally during final assembly.

Milburn

 

IMO, plastigage is a last resort. I much prefer to mic journals and bearings, and dial bore gauge housing bores. If you can borrow the tools that you don't have, try to.