I have a little problem and I'm not sure what to do. I'm building F20C motor for the FI use and now I have the following problem.

The block is sleeved with Darton MID sleeves and the bore is 87,5mm and I have CP 9.1:1 pistons for it. The problem comes with the crank itself or more with the main bearings and rod bearings.

The connecting rods are Crower rods and while we were putting the motor together I noticed that one of the old rods (OEM) bearing were with different color code than the three other. I understand that this means different size of the bearing.

I have following letters in the crank BBBB, and the OEM rods had 3332 (not in order, i really don't know which cylinders rod it was, if there is any matter with it). Now when I have Crower rods, are the ACL race series con rod bearings (std size) right bearings to use with? I'm reasoning that the crank shows BBBB so every journal is identical, but the OEM rods weren't. Now when I have Crower rods (I'm assuming STD size) I can use ACL std size bearings for it?

Other problem is with the main bearings. The block itself has letters CCCCC and the crank shows 34433 for main bearings. I have a set of ACL race series engine bearings for F20C1 (5M1913H-STD) so I'm supposing that I cannot use those as a main bearings, because 2nd and 3rd journals are different sizes? Do I have to use OEM main bearings instead of ACL if I don't decide to machine the crank ?

Also the one more question is about the F20C OEM bearings sizes. Which codes are the standard size for the main and rod bearings? BBBB and 3333 for rod bearings? CCCCC and 33333 for main?

Is the only option to send the crank to you for balancing and get right bearings ordered in the same?

Ps. sorry for the bad English, I live in Finland with the polar bears and Santa

 

I have never built a F20, but in building D and B series Honda motors I have never run into a better choice than the OEM Honda bearings. They can get somewhat pricey, but the reason for the color codes is to be able to maintain consistent rod/journal and crank/main clearances all the way across the engine. this helps to equalize oil pressure in all of the bearings and journals to keep consistent high rpm reliability and minimize bearing wear.

If you were to hone the crank journals and mains, then it would be OK to use the ACL bearings as long as the clearances were within Honda OEM specs.

 

I urge you to get a micrometer and measure the journals on both main and rods. Then compare the measurements to the specifications. The measurements muist be within the specs or the crank needs to be turned and new bearings for an undersized crank will need to be obtained. I would not build a new engine with the old crank without having the journals at least polished to get rid of any irregularities, but that's just me.

 

You'll need to check all bearing clearances with a good quality micrometer. You can't assume the standard rod bearing will work with your Crower rods. Crower and ACL may have different oil clearances than stock as well.

I've had to set up B-series engines with Eagle rods and it takes a full set of OEM bearings to measure to set the oil clearances accurately. Some "builders" like to slap in a set of greens and let it ride, but I 'm not one of them.

The OEM bearings are very high quality, and don't need to be replaced by ACL "race" parts if you don't have too.

If the crank is within standard specs I'd start with the OEM bearings coded for it. Unless it needs to be reground I wouldn't touch it.

 

This is the only thing you said that I question. I always at least have a used crank polished to get rid of any minor surface imperfections that are "above" the surface of the journal. It does not change the diameter so why not make sure the journals are smooth?

 

The reason I said this is I've found quite a few machine shops that can't polish a crankshaft without cutting the journals undersize.

Getting bearings for an undersize crank is just about impossible.

A good friend of mine sent a brand new B20 crank to Crankshaft Specialties in Memphis to be polished and lightened. It came back with journals cut .010 under and the rod throw counterweights cut below the main journal diameters. $1000 crank turned to junk.

 

I understand. You need a good machine shop to do it right. I use a local shop that builds competiton engines for track and drag strip and even they have to send some things out to others. I seem to recall that the old crank can be built up with a powder weld techniqe and then cut to original size. I'm not sure that would work on the cranks for the F20

 

Good workshops use a special crank pin polishing cloth. It feels like a cat's tongue (if you have ever felt a cats tongue). It burnishes the crank pin to a mirror finish with only minute dimensional changes.

I would suggest assembling with ACL plastigauge to check the clearances. Check all the main pins in the one assembly/disassembly job.

Chris