sayanything

iTrader: (1)

I have an obd2 b18c1 with 81.25 USDM ITR pistons. everything else stock/oem.

so i am a little confused.

I had the block decked and the head resurfaced. from my understanding this means that i only had the bare minimum removed from the head and block, to ensure a good flush seal.

since i am running USDM ITR 81.25 pistons i understand i will have 10.8:1 compression ratio, but will running these pistons give me any piston to valve clearance issues? (asking because of the material removed from head/block)

do i need to run a different headgasket to accomodate the material removed from the head/block? Is there anything i need to worry about before i continue rebuilding my motor?

will i need to get some kind of tune when i start driving it? or retard the timing/use colder spark plugs?

i want to keep everything as original as possible, i do not want to go obd1 or have to mess with the ecu. i only got itr pistons because i couldnt find oem gsr pistons for a good price..

thanks for any help. and ive searched, but most posts are dealing with a lot of performance parts/different cams/etc

racebum

with a little bit of shaving you should be at 10:9-1 or 11:1 compression. if you had itr cams and a single runner manifold a p73 ecu would work near perfect.

the extra compression won't be a problem on an otherwise stock gsr, just use premium gas only

sayanything

iTrader: (1)

so i dont have to worry about piston to valve clearance right? and just making sure, OEM pistons with OEM rings come pregapped right?

OH_1fstgsr

iTrader: (2)

I ran USDM ITR pistons in my GSR block on the stock ECU for 1 year with ITR spark plugs. Never an issue. The block was decked a bit.
My head is ported and cc'd and I'm at 11.5:1, now.

racebum

don't even trust a pre gapped ring. always file fit if need be. it's beyond easy to do

sayanything

iTrader: (1)

this is pretty much exactly what i wanted to hear

thanks guys, and yes i do plan on measuring and filing the rings if needed.

1998GsRIntegra

I'll second this. Most oem rings are gapped and with in spec, but you may have to file them. Dont just slap them in and hope.

2LEM1

iTrader: (1)

Just to let you know, you're going to be over 11:1 c/r

I'm coming up with anywhere between 11.4 and 11.9 depending on how much you decked/surfaced. Not that it matters, like Idrivesideways said, just use premium gas. 11.9:1 is perfectly fine for a daily driver, and with some CTR/ITR cams it'll really wake that motor up.

Here's the calc I used. Make sure you have the bore @ 81.25 and I only took off .01 inch for your deck for the 11.4:1. .02 gives you 11.9:1.

http://www.zealautowerks.com/bseries.html

Edit: even with only 5 THOUSANDTHS of an inch milled, it puts you at 11.24:1. I'm guessing they took off at least 1 hundredth.

racebum

we also have the issue of cam timing if this much has been pulled off. the marks may not line up anymore and you'll have to degree the cams or risk guessing and being a tooth off. this of course means adjustable cam sprockets

JDMInteg96

oem head gasket is the way to go... i have the exact same build with a built head... 81.5mm USDM ITR pistons... stock cams and ecu... 01 gsr... runs great..

94 ls-r

Does it really make a diff? I am asking cause I never heard of this. I would think it would take alot to make any diff

fv8s

Even though you should not have any clearance issues you should consider claying the motor just to be safe.