I had all intensions of getting .25 oversized JDM ITR pistons, but I'm having a hell of a time finding them. With a GSR block/head, 3 layer HG and these pistons, it results in an 11.4:1 CR.

If I were to use USDM ITR .25 oversized pistons and mill the head .20 with a 3 layer HG, what would my CR turn out to be?

Without milling the head, it results in a 10.9:1 CR.

It would probably be smarter to mill the head, rather than use a 2 or 1 layer HG, correct?

With USDM ITR pistons, what would be the best way to get a 11.5:1 CR?

Thanks in advance.

 

I would use a thinner gasket before milling the head, but I would have the head milled slightly to be sure that it's straight.

 

I'm having the "Street Master" headwork done by Alaziz Technologies and milling the head is part of the package. (Also I made a mistake, they mill it up to .020)

So you think it would be a better idea to have it milled slightly and run the 2 layer head gasket?
I doubt I'll have any piston to valve issues. There should be plenty of clearance.

 

Run the 2 layer gasket. Also if you want to bum it up a little more get some high comp valves. With the valves and the headgasket you should see about .5 gain in comp.

 

I think pistons are the safest way to bump up compression you should be able to find a set of jdm itr pistons fairly easily search this site and look on ebay. Also I believe importselect.com has them for like 300 brand new with rings check there

 

importselect.com is out of stock, just like inlinefour and jdmhondaparts. I refuse to buy parts off private sellers since so many people get scammed. Search engines do a lousy job of finding sites that sell the parts I'm looking for, so I think I might just buy the USDM pistons and run a 2 layer HG and have the head milled slightly.

 

Try ipsracing.com or aj-racing.

 

FWIW, there have been sealing issues with people running 2 layer headgaskets. NOT everyone that has one has had problems, but it does seem to be somewhat common.

If it were me, I would mill. Some people don't like that because you can't get the material back, but its a fair trade off imo. You could also mill the block a tad bit.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blazin Si &raquo;</TD></TR><TR><TD CLASS="quote">I had all intensions of getting .25 oversized JDM ITR pistons, but I'm having a hell of a time finding them. With a GSR block/head, 3 layer HG and these pistons, it results in an 11.4:1 CR.

If I were to use USDM ITR .25 oversized pistons and mill the head .20 with a 3 layer HG, what would my CR turn out to be?

Without milling the head, it results in a 10.9:1 CR.

It would probably be smarter to mill the head, rather than use a 2 or 1 layer HG, correct?

With USDM ITR pistons, what would be the best way to get a 11.5:1 CR?

Thanks in advance. </TD></TR></TABLE>

With a 3 layer head gasket, JDM P30 pistons with stock bore, your CR would be 11:59:1... Oversize .25 will be around 11:8:1... You could still run that on pump gas if that's what you're concern is.

Avoid milling the head if you can

 

Thanks for the heads up. I want it milled a little, but I'd rather get the compression through the pistons. The only thing holding me back right now is locating the pistons.

If I don't find them this week, I'll have to go with the USDM ones.

 

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

With a 3 layer head gasket, JDM P30 pistons with stock bore, your CR would be 11:59:1... Oversize .25 will be around 11:8:1... You could still run that on pump gas if that's what you're concern is.

Avoid milling the head if you can</TD></TR></TABLE>

What compression calculator did you use? I used the C-Speed one and it turns out like this.

Block: B18C1
Bore: 81.25mm &lt;---------------- I'll have it bored to run .25 OS pistons.
Stroke: 87.20

Head: B18C1
CCV: 41.60

Pistons: p73-A0 USDM ITR
Piston Dome Displacement: 3.64 &lt;---------------- Maybe that's where I'm wrong.

Head Gasket: 2-Layer Spoon Gasket
It's a .45mm gasket
but it defaults 0.01933333 for 2-layer &lt;------------------- Maybe I'm wrong here, too.

Piston to Deck Height: OEM B18C1
Height: 0.030 &lt;-------------------- Is this where milling the head would effect this number?

Results: 11.16981984158335 CR

Did I make any mistakes?

 

why not just run p30's or pr3's?

 

Why use those pistons? According to the calculation table on C-SPEED, with the same exact setup and 81.25mm P30 pistons your CR will be 11:65:1

 

You know what... I didn't even think about it.

I figured the B16 pistons would lower the compression and didn't even try plugging those numbers into the equation. Where's that 'hammer to the head' image when you need it?

Thanks Mpir3 and LudeToAHatch... I need to get my head out of my ***.

 

Compression ratio calculator:

http://www.bojangs.com/calculator

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Blazin Si &raquo;</TD></TR><TR><TD CLASS="quote">You know what... I didn't even think about it.

I figured the B16 pistons would lower the compression and didn't even try plugging those numbers into the equation. Where's that 'hammer to the head' image when you need it?

Thanks Mpir3 and LudeToAHatch... I need to get my head out of my ***.

</TD></TR></TABLE>

haha... no problem