Hey guys, Im recently building a b20/vtec block. I have just received my ACL bearings and started to install them to check my clearance's. When I checked my Mains, im getting a .003 clearance which is quite large. Honda recomends .0009-.0017. Anyone have experience with running such a large clearance? I would rather it be a bit looser but, it seems a bit to much. It was measured with a digital caliper, im going to plastigage it tommorow just to make sure im not doing something wrong but, i have triple checked it and it comes out the same. Since this Motor will be boosted and seeing around 400whp what clearances do you all usually go with?

 

That is way too loose. Get some Honda bearings so you can get them sized correctly.

 

I had the crank micropolished, could this have caused such a big clearance?

 

A stock crankshaft being micropolish should not cause such a loose clearance. Trying the plastigauge would be a good idea. You said the motor will be boosted, I doubt the one size fit all ACL bearings were designed for that. Good luck. I have never seen any aftermarket bearing out perform or even come close to OEM HONDA.

 

Actually, I don't have a chart in front of me, but now that I think about it, I don't know if even a Honda bearing will get a .003" clearance down to .0015

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by B20bTurbo &raquo;</TD></TR><TR><TD CLASS="quote">I had the crank micropolished, could this have caused such a big clearance?</TD></TR></TABLE>

sounds like someone killed your crank

 

If the .003" is accurate, your going to need oversized bearings and probably from a inferior company made in Israel.

 

I have heard of people going with .002 clearance. If I can get it down to that should I stick with it then?

 

You should really use micrometers to meausure journals and such. And if you dont have bore gauges to mearsure the housing, I thing plastigauge would be your best bet.

I think that .002 is still too loose for the mains on a street car. Remember, if you make it too loose, oil will just sling everywhere and loose some pressure making it hard to reach the rod journals.

And micropolishing shouldnt take any material.

 

You should take the parts to a machine shop unluess you are already using precision measuring tools. It really needs measured out to 4 decimal places. If you dont have that option, the plastiguage will atleast give you an idea if your measurements were close.



Here is the chart I made after taking my parts to be measured. Mine were very tight even using a red bearing measurement. You seem to be at the other extreme.

 

A few things,

This is going to sounds pretty weird, make sure you check your clearance in a normal operating temp, 70 deg is optimal. Any direct heat or too cold, can expand and contract metal to give you flase clearance. I have had to play around and see a full color difference by having a crank and block at room temperature and at direct sunlight (evening ish).

So re-check the clearance at normal temp and see if anything changes. You can just get the OEM honda on that particular cylinder to get the clearance down. I always try to get .0015 on ALL the caps, simply becasue an equal clearance on every caps will get the crank to sit at perfect level, therefore spins easier. I have done some block to .002 before, it doesn't hurt to be a little loose, but I'll always to try to keep it between .0015 to .002 as much as I can.

Stan

 

My parts are at ERL now being machined to use the ACL bearings. THey would have had to be machined regardless even If i was gonna use the red bearings. They recommended .0018 on all mains and rods for 600 hp.