Ok here is the deal I am getting ready to build an ITA spec engine. I know that I am limited to a 40 over bore and all parts must be OEM replacements. So my question is what pistons are people using to hit the 40 max limit? Since Honda only offers a 25 or 50 over? I know you can only port match up to an inch deep is there any "tricks" with in the rules that improve flow? That anyone has had some success with?

TIA

 

We have the factory honda 20 over pistons. It's a whole lot more reliable than aftermarket 40 stuff. If we had twice the budget, we might consider going 40 over, but it's just not worth it imo.

 

The rules also allow aftermarket pistons of the same weight, dome/dish as factory pistons. I'm 20 over with OE 1.6 liter pistons. Good luck on increasing flow through the head. There's a few schools of thought on head/valve work (weather or not fancy valve grinds are worth it), and those who know "tricks" aren't telling.

 

consult the SCCA rulebook, and take it to someone who's done this before

 

I did a lot of research several years ago and didn't find any .040 over pistons that were legal that I could pay for. I also used the 25s from the dealer after talking to several who had done the same and never felt that I was at a disadvantage.

As for the porting, I have never even done any IT porting within the allowed 1 inch rule as the Hondas have pretty good chambers to begin with. For the little gain that you will get from the labor of additional porting, there is also a chance that your port job may have negative effects that you'd never know about without a flow bench. I had Comptech do some radical porting on my unlimited Production head but have never bothered on the half dozen or so IT CRX heads. I ported the heads on my IT Corvair but the castings were very poor compared to the Honda stock. As far as I am concerned, unless you see a specific problem with your factory job, just make sure that your gasket matching is good and not causing issues then move on.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">consult the SCCA rulebook, and take it to someone who's done this before</TD></TR></TABLE>

I have consulted the book. Was looking for input as to what other people have been doing and whats been working for the 40 over pistons. But the two replies I got are the first factory bore size. Take it to some one who has done it before??? What build race engines? I have been doing it for 22 years in other aplications.

 

Thanks guys that is some of the info I was looking for. Looks like it is factory 25's for me then.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">consult the SCCA rulebook, and take it to someone who's done this before</TD></TR></TABLE>

come on RJ, its obvious he knows the rules by specifying the .40 rule, and he's HERE to talk it over with ppl who may have done it before... this post was not necessary.

 

Lee, there are currently .04 IT legal pistons availible today correct?

 

Correct there are .40 over pistons available....Weisco makes them. They are the same weight, shape, size....everything is identical. The only difference is they are forged. I know of many people running them, Tom Fowler had them when he won the ARRC, and they passed tech then. If there is any tech inspectors on this board speak up and let us know what your thoughts are on this.

 

also... be sure not to confuse inches with mm.....

I have seen them used interchangeably too many times.

Nash