So I'm building an ls vtec and came across some issues and thoughts:

1. My rod and crank bearing codes are 3B all across which gives me a Green OEM bearing. I measured the rod journals and they are all 1.7712" +/-0.0001". I have not measured the rod bore. Now if you calculate the oil clearance using my rod journal diameter, green bearings(0.0590"x2), and factory rod bore(1.890"), you get 0.0008" oil clearance which is the tight end of factory B18a/b specs. Even when using the whole range of stock journal diameters(1.7707"-1.7717"), you get an oil clearance range of 0.0003"-0.0013" that barely gets into the B18c range. So my question is, are ls cranks and gsr cranks sized differently? As in, a "B" journal on an ls crank is not the same size as a "B" journal on a gsr crank. Am I on to something or am I totally off base?

2. Assuming I'm on to something in part 1, maybe one of the reasons so many people spin bearings on ls-vtec setups is because they go by the coding system and just drop in the correct bearings without checking oil clearances, whether by mic and dial bore or plasti-gauge. Because the correct bearings for an ls crankshaft will put you into the correct oil clearance range of 0.0008"-0.0015" which is pretty tight for a higher revving motor which requires an oil clearance of 0.0013"-0.0020".

Please let me know what you think and if I missed anything. Thanks.

 

Either nobody knows what I'm talking about or I stated something pretty obvious. So I guess I just want to help the beginner lsvtec builders by saying: Do not use the coding system to finalize your bearing choices. Use measurements from a micrometer and dial bore gauge and/or plasti-gauge. Because I'm pretty confident that the majority of the time you will need thinner bearings than what the codes tell you to get in order to achieve your desired oil clearance.

 

1) Measure the rod bore with a dial bore gauge indicator to confirm the factory rod bore. Most likely you'll find it will be fairly close and consistent to 1.890"...

2) The Bearing thickness codes stamped on the block may be useful for someone simply replacing their bearings as an easy rebuilt for a stock engine. However, ideally a set of micrometers and a dial bore gauge is your best bet to accurately calculate the achieved bearing clearance for your build.

3) I can't confirm the difference between the crank journal sizes between an LS and a GSR although I would assume they are nearly identical. I'm building a d16y8 engine for a friend and the y8 Crank Rod journals measure from 1.7712" to 1.7715" which is nearly identical to multiple b series engines I've built. The Crank Main journals are also almost identical. 2.1650-2.1652"

4) Exactly, if you don't take the time to accurately measure clearances then don't expect the engine to last. There's a lot of people that will slap bearings standard sized (OEM Green) bearings in and won't bother to plastiguage the clearances if not measure them. I build mine with 0.0018"-0.0020" of bearing clearance for built engines. I'm surprised that there aren't many aftermarket bearings that run looser clearances similar to the thickness of an OEM Honda pink or red color coded bearing. Or maybe I don't know where to find them yet...

 

Gsr and Ls cranks use the same coding system and the same bearing thicknesses, but a number of things can skew the clearances.
The B stamp indicates a small range the journal has from what I can tell. I had rod journals variate by .0001-.0002 on a crank using the same stamp for the journals. The bearings themselves for any given color can vary by several ten thousanths as well.

I cant remember for sure but I think ACL Race bearings are equivilant to honda reds (or they make a specific acl race that are thinner) honestly I just use oem bearings. I have extra main bearings I use to help me figure out what bearings to buy exactly.

 

the acl -HX extra clearance bearings for rod bearings fall between pinks and reds, ive had a few sets and measured them and its pretty darn consistent. im starting to lean toward using them for rods (still oem for mains) especially since they are "harder" they wont wear the upper rod bearing as much as oe for high hp or longevity builds.


you bring up a great point about having extra bearings. im doing that as we speak with a block. measure the codes, toss in the appropriate bearing and plastigage. each color you change is roughly .0002. so if you are green at .0015 and go yellow it should be around .0017.

you should build the motor for the rpm/power it will make not for what the factory manual suggests. that said, mains like to be around .0015, and rods can go up around .002. i would not run anything tighter than .0015 especially for rods. i did it once and it really kicked the bearings *** after a few thousand miles