Great section with lots of good information, I had a couple questions:

-Is zero decking a block common practice when building a Honda motor?

-What is an acceptable gram difference for pistons when balancing them? how much can be taken off and from where?

-Same question as above but for rods....also balancing big ends (and small ends) with one another or just total weight?

-measuring and assembly room temps and part temps...what is the proper temperature for both?

thanks again guys, I'm having everything done professionally I just like to be informed before talking to someone.

 

I think you'll be surprised with the quality of OEM Honda parts. Going off my last build (kinda basic GSR road race engine) everything was pretty dam good without any changes. I made a jig to balance the small end of the rods, once the small end is balanced I check total weight. Small ends were fine however the big ends took a very slight amount of material removal. I take it from the outside of the big end near the rod bolt, a quick run over a belt sander is all it takes. The small ends were within 0.1g, total weight was within 0.2 g once finished. You should technically weigh the rod bearing as it rotates as well, however I have never found them to be different (at least not more than 0.1g).

I think you’ll find that the pistons won’t take any work. I used USDM ITR pistons from ebay with the coated skirts (Nippon), make sure to weigh them with the matching wrist pin.

Room temp for me changes as my shop fluctuates in temperature depending on the time of year. If I know I’m measuring engine parts I won’t turn the temp down when I leave the night before. Just try to make sure that everything isn’t stone cold or in the process of changing temperature when measuring. I’ll leave my shop at 20* and after a day or 2 everything (chest height) is about the same temperature.

I don’t square deck the block. I’ll measure the piston the deck height at each cylinder and find the one with the lowest amount of clearance; this will be my ‘0’. From there I’ll set my piston the head clearance, usually 0.040” by either decking the block or adding a thicker HG depending on where I’m at.

Hope this helps, I’m not a machinist by any means, just like to have fun messing around.

 

If I recall correctly, zero decking is getting the piston to deck clearance as close to zero as possible.

From my understanding of things, you may or may not wish to do this. And I don't believe it's typical for every Honda motor build. There are a great many factors to this. The main two are quench and squish area. Your Head design (combustion chamber design) really affects this.

The ideal gap for quench seems to be between 0.035" and 0.040" from my understandings.

So based off of that, if your head combustion chamber has a large flat area going towards the valves and then turns up just before the valves to create a small combustion area.... If you zero deck flat pistons... You will have to have a head gasket that has a crushed distance of at least .035" which is a fairly thick gasket. Thicker the gasket, the more opportunity to fail usually depending on the gasket.

So sometimes it's better to have .010" piston to deck clearance and then you will only need a .025-.030" gasket to get the same quench.

So really it depends on the Head's combustion chamber design and your pistons, on whether you will need to zero deck to get your proper quench and squich areas.

I hope that makes some sort of sense as it's a rather large set of variable at play all interconnected so changing one changes them all.

Factory Service Manual states 68° F which translates to 20° C for measuring.

I have not seen anything mentioned about specific temps to assemble, probably as all the measuring is done already? Not sure.

 

depending on motor redline, rods and bolts etc you probably dont want it to be much less than .035-.040 pth or you will have issues.

plus, if you zero deck and then need a resurface for some reason your in some ****. better to use hg thickness and a bit of head milling to meet your specs imo

 

Thanks for the information guys, makes complete sense.

I weighed my Wiseco +8.2cc 81.5mm pistons and from the lowest to the highest there was a 3.678 gram difference and the tapered wristpins had a difference of 0.039 grams from low to high.

How close can a machine shop get them balanced, within a 1 gram of each other, within 0.1 gram of each other? Can you take out more than 3 grams from a piston?

thanks guys

 

Wow, that's a far bigger difference than I would have thought... The wrist pins aren't a problem being out such a small amount; you could pair the heaviest wrist pin with the lightest piston and vice-versa to lessen the deviation.

Pistons, wrist pins, piston rings, C-clips, and rod small ends reciprocate. Rod big ends, rod bolts, rod bearings rotate. keeping things in their respective groups you can pair things together to try and make up for that piston being out so far.

 

another question: How/what is the best way to measure valve spring install heights?

 

An Installed Height Micrometer is the best way, but I don't know of any to fit OHC heads like a Honda. I think PAC makes a small OD mic for beehive springs that may work.