How can I figure out how much I would need to shave off the head to raise the compression .4? How many thousands of an inch?

 

bumpy

 

simple question and yet no one knows?

 

two words. try searching

 

two words

I have

I haven't been able to find a strong answer that is backed. Just a lot of guessing.

 

With an 88mm bore, decking the head 10 thou on a h23a motor will give you roughly a .4 increased compression ratio.

 

If this helps at all, i'm planning on running type-s pistons and raising the compression to 11.0:1 by milling the head. The stock bore of the h22 and the h23 is the same correct?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matgallis &raquo;</TD></TR><TR><TD CLASS="quote">If this helps at all, i'm planning on running type-s pistons and raising the compression to 11.0:1 by milling the head.</TD></TR></TABLE>

That makes NO sense. If you run Type S pistons then you WILL run 11:1 cr on otherwise stock internals.

What is your setup? if you have the JDM h22 with stock 10.6:1 compression then about a .020 mill will put you up above 11:1 easily.

otherwise answer your own questions using this:http://www.c-speedracing.com/h...c.php and other info that you can find on this board

 

unless the piston to deck height is close to 0.000" then it'll be higher than 11:1cr

 

the stock Piston-to-Deck height is very close to zero. Arias Pistons reports it to be .005".

I did a typo if you have the JDM then about .015" will get you pretty close to 11:1

 

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PirateMcFred &raquo;</TD></TR><TR><TD CLASS="quote">

That makes NO sense. If you run Type S pistons then you WILL run 11:1 cr on otherwise stock internals.
</TD></TR></TABLE>

How does that not make sense? type s pistons are 10.6:1 compression right? My current pistons are 10:1 correct? swap those, mill the head for 11.0:1 compression...

 

No, regular jdm pistons are 10.6:1 Prelude Type S are 11:1. This has been covered before, several times. Searches will turn up threads like this one: https://honda-tech.com/zerothread?id=438456

 

JDM H22= 10.6:1
USDM H22= 10:1
H22 Type S=11:1




Modified by 93H22ACX at 6:15 AM 6/8/2004

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matgallis &raquo;</TD></TR><TR><TD CLASS="quote">
How does that not make sense? type s pistons are 10.6:1 compression right? My current pistons are 10:1 correct? swap those, mill the head for 11.0:1 compression...</TD></TR></TABLE>

the reason that that makes no sense is that there are a few different pistons for the H22a. there are 2 types of 10:1 in the US: pressed-in wristpins and floating wristpins (h22a1 = pressed, h22a4 = floating) then the same goes for the BASE JDM that are 10.6:1 (they have better octane ratings there so can run a higher stock CR) then there are the type-S or S Spec 11:1 compression pistons.

so breakdown is like this (assuming std B/S of 87mmx90.7mm):
USDM = 10:1
JDM = 10.6:1
JDM Type-S = 11:1

So if you have a plain jane JDM h22a then you can mill the head 0.015" for the extra 0.4 CR for an 11:1 CR
or you can get the Type-S pistons for a "stock" 11:1 CR. mill that .015"and you will get close to 11.5:1
or mill the bejesus out of a USDM head to get 11:1 CR (~ 0.040"). Cool?

the Pirate

 

oh dman I always thought the type s was just 10.6... hmm so the type s pistons will work with the h22a4 rods correct? (are the type s wrist pins floating also?)

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by flyrod &raquo;</TD></TR><TR><TD CLASS="quote">No, regular jdm pistons are 10.6:1 Prelude Type S are 11:1. This has been covered before, several times. Searches will turn up threads like this one: https://honda-tech.com/zerothread?id=438456
</TD></TR></TABLE>
damn I wish that one had come up in my searches. Very good info...
When reading through the posts I saw that when you shave the head, you lose volume but gain compression. What would the consequences of this be?(loss tq? but hp gain?)

 

not really...i think the only consequence is having a closer piston to valve clearance.

You should gain hp and trq not loose

 

I think i misworte it

If I have JDM 10.6:1 pistons, and I shave the head to achieve 11:1 compression.
I lose the amount of air being compressed, thus less power? I would make more power off type s-pistons without shaving the head correct?

 

when you shave your head it will result in higher compression ratio, this means you will get some additional little ponies and alot of ponies if you its high enough with a more aggressive cam setup etc etc

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matgallis &raquo;</TD></TR><TR><TD CLASS="quote">If I have JDM 10.6:1 pistons, and I shave the head to achieve 11:1 compression.
I lose the amount of air being compressed, thus less power? </TD></TR></TABLE>

wrong. Compression is defined as taking a certain volume of air (this being your bore and stroke) and squeeze it into a smaller container (your 53.8 cc cumbustion chambers). when you mill the head you make the cumbustion chambers smaller making higher compression. you see that the only whay that you are going to lose displacement is if you magically decrease your 87mm bore or shorten your 90.7mm stroke. It has nothing to do with milling your head.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Matgallis &raquo;</TD></TR><TR><TD CLASS="quote"> I would make more power off type s-pistons without shaving the head correct?</TD></TR></TABLE>

no. The only difference between milling the head and the type-S pistons is that milling the head will retard the cam timing.

 

ah gotcha, I was thinking that it would have changed the stroke somehow... thank you for clearing everything up

 

you will have a extremely miniscule decrease is combustion chamber size but obviously having so much higher compression ratio extremely offsets that incredibly tiny loss in volume