Recently had my engine bored and honed, and I had the chance to watch a machine shop check the bores with a dial bore gauge that read to the tenth (ten-thousandth). The bore was true to the thousandth, but varied about 8 tenths within that range (from top to bottom).

The engine is a b16a being built for FI. PTW is .004. Is it possible to have a hone done to the ten thousandth or is this an unreasonable request (considering the crosshatch). Thanks.

 

I don't think it's unreasonable, more like unnecessary. Unless you really really need that fine of a dimension, down to the thousandth would be sufficient. I think the engine heating up would remove any kind of clearance at that small of a unit and you may have too "tight" of an engine if it was spec'd down to the tenth. You could (for a neat trick) have them hone it with a slight taper from bottom to top(measured in tenths), tighter at the top than at the bottom, say 8 tenths out at the bottom and 3 tenths out at the top while staying in spec in the thousandth. Could help the rings/pistons seal up the chamber better. Kind of like an RC Nitro engine.

Nice engine in your sig, BTW.


Modified by King V at 9:43 AM 3/18/2008

 

I have to wonder why honda wants clearances to the thousandth but CP's PTW is .0035 (note the tenth digit). How can you accomplish .0035 PTW without a bore/hone to the tenth?

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by King V &raquo;</TD></TR><TR><TD CLASS="quote">Nice engine in your sig, BTW.</TD></TR></TABLE>

Thanks, it's still running after about 50K, but comp isn't perfect any more as I got pretty aggressive with timing on a 10.4:1 comp engine. Oh well.





Modified by cobra2326 at 7:21 AM 3/18/2008

 

Maybe its Honda's fuzzy logic. I really dont know. It is kind of dumb to say "we want bores to the thou, but variances will be in the tenth" Its been a while since I was in a metrology lab, whats PTW mean?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by King V &raquo;</TD></TR><TR><TD CLASS="quote"> Its been a while since I was in a metrology lab, whats PTW mean?</TD></TR></TABLE>
Most likely piston to wall(clearance).

 

Ah. Makes sense......

 

While it will likely work I would in no way consider a bore that had 8 tenths taper quaility work.

 

I would prefer a straight bore than a tapered one. RC engines (8th scale and smaller) use tapered bore because they do not use piston rings. Just my 2 cents.


Modified by q.c.autosports at 6:55 PM 3/22/2008

 

i saw a block that had been done to 1 micron yesterday

for a race car and money was no object but again that kind of level is way beyond most racers etc and for exceptional high end builds only seen by likes of very high end motosport

 

[QUOTE=q.c.autosports]RC engines (8th scale and smaller) use tapered bore because they do not use piston rings. .

[QUOTE]

Some do use rings, but those are on heli's and planes. But I digress. I really wouldn't say much about the 8 tenths variance and Honda's spec is .004 thousandth unless you paid a good amount of money for the hone.