CRANK MAIN JOURNAL TAPER

Goodmorning world!

So i am building a Honda B18C6 engine.

To make a long story short! Customer build engine with company X (engine A). They messed up the bore with cheap pistons etc etc etc.

Customer came in with a OE empty B18C core (engine B) for building it to 81.50mm. I had to reuce the old crank and build it to spec fot the new engine.

engine A have BBBBB stamps in the case and the new one have stamp CCCCC so i know there is difference in clearance.

when i measure the journal bore i always check the front & end of the bearing journal. to search for taper or strange out of shape signals.

with this engine i saw that bearing number 2 had a burned cap. So engine B had probably crank bearing problems.

Engine B is The problem that when i measure from the front side of the engine (timing belt) on journal number 2 i measure 0,01mm play. when i push trough and going to the journal side of the flywheel i measure 0,09.

i thought that since the main cap 2 had burn spots it would be out of round from the heat. So i used cap 2 with the bearings that i used for the measuring in engine A where the crank came from and i measure 2 perfect the same clearances. so the cap isnt worn out.

Is it possible that the engine blok is worn out on one side of the bearing? i don't see any spots of a spinned bearing or.

Since the bearing clearance is tight on this engine with this crank. i wil get it line honed to bearing spec. don't want to cut the crank. Crank is perfect perfect condition. But this is a point i need some advice because i never had this situation before!

Thankyou!

Sorry about the delay, I thought I'd commented before.

Usually, when there's any variation like that, it's because of one or both of two things.

The mating surfaces not being scrupulously clean - the dowel sleev makes it a bit more difficult, but some brake-clean, electrical cleaner, or somesuch with an old toothbrush as a scrubber, should make it possible to bring it back to a CLEAN finish on the block AND cap surfaces. Related to that is if a careless person marked the mating surfaces, slightly deforming them.

The second is usually down to microscopic debris, or dirt, caught between the shell and the bore, canting the shell slightly.

In this case, if I read your post correctly, you had a mains bearing fail, and this may have slightly distorted the bores? hard to tell from the pictures, but looks like there's a ridge instead of being perfectly even along the bore - this will definitely be a problem that will need remedying!

You CANNOT simply switch caps between engines, if that's what you've done, as even the smallest mis-alignment will cause an irregularity and almost invariably, bearing failure. That said, if you must, you can have the bores re-honed - sometimes this requires material to be removed from the mating surfaces of the cap and/or block, but some bearing specialists may offer special oversized outer diameter bearings to simplify this without extra material being removed, and a tighter 'clamping' force from more pre-load.

Hey Gord!

No problem for the late reply! glad that somebody wil help us out! To explain me wil in english and answer you on this -> You CANNOT simply switch caps between engines, if that's what you've done, as even the smallest mis-alignment will cause an irregularity and almost invariably, bearing failure.

I know this. But i tried to find what the reason was for the variaton. The main caps or the aloy block. When i place the main cap on the other B18C engine its straight. No difference. when i place it on the original engine. i have the difference from side to side. i measured even without the bearings itself and i measure exaclty the same as with the bearings.

The customer bought this empty engine to rebuild it. I think they had bearing issues and sold the engine empty without crank. So i have no further information from this engine.

Is there any other reason why the upper bearing cap can be damaged like that? i don't see 'spin' damage or anything.

It's a weird thing, other than a spun shell, perhaps there wasn't enough crush to hold the shells in place, and they fretted a little, causing the apparent (hard to tell from the 'photos) wear, while the tangs were just up to the job of preventing the shells from spinning?