IN VTEC

iTrader: (3)

I'm an amateur.

I noticed the slope with the dial indicator, just didn't know what to think of it.

NateTEG95

Yeah the slope is normal. I thought you were a machinist because of the Mitutoyo tools and the way you used measurments to describe everything.

IN VTEC

iTrader: (3)

Yeah, relative measurements are pretty much just stuff you learn to adapt from high school science. I really like the Mitutoyo stuff too. I also have a few Enco and Peacock gauges and mic's, but I rarely ever use them for motor work.

Side note about measuring tools: If you're gonna get a rod bolt stretch gauge, spend the extra money on the ARP rod bolt stretch gauge. The $70 Proform one is junk. The gauge face didn't turn with the outer face and the dial indicator is way too sensitive to be of any use for that kind of measuring. That's all.

Another update:

I had assumed it was at TDC just by eyeballing it from last time. Big mistake. After I accurately set the #1 cylinder to TDC, I found....

The piston-to-deck height clearances are actually about .005" further up than I had listed from the previous post. I'll put up the pictures and annotations later when I upload the pictures at home tonight.

FastSS

Fack.

Im seriously wondering what the hell I am going to do =/

I cant afford to change pistons, rods and bearings... im just going to have to figure out a way to make it all work

IN VTEC

iTrader: (3)

Setting the piston to TDC by looking for high point.


Dial indicator zero'd to the deck.


Intake side of the piston crown. [-.002"]


"IN" on the intake side. [+.006"]


Exhaust side of piston crown. [.000"]


"S" letter on exhaust side of piston. [+.006"]


on exhaust side to indicate front of motor. [+.0145"]


Anybody know the compressed thicknesses of the Spoon and/or Mugen headgaskets?

IN VTEC

iTrader: (3)

Poop. I forgot to rotate the picture. I'll do it after work tonight.

sickness

Nice build!

FastSS

I need to ask a few people a few things... get all of this sorted out =/

slow_dx

Bump...

I've currently got a b18c installed in my car with pct pistons in it, and I'm trying to figure out the compression ratio, but I haven't been able to find definitive numbers for piston -> deck height and dome volume. I've got a couple of question, and was hoping you could help me out.

You measured piston -> deck height right around 0.00, was that in a b18c or b16a block?

Did you measure the dome volume of the PCT pistons?

I'm a little worried, because I think compression in my car is right around 12.9:1 !!! If this is the case, I think I'm going to use a thicker headgasket to bring the C/R back down. Any help would be appreciated.

Thanks!

IN VTEC

iTrader: (3)

B18C block with .25OS PCT's. Block deck is unmilled.

I don't have anything to set the pistons in to get a dome displacement measurement, so I've been assuming C-speed's number. I'm also assuming the stock P72 chamber volume, even tho the chamber was opened up by Portflow. I still have yet to cc each of the chambers yet.

The engine will get a .045" thick head gasket.

That gets our motor a compression ratio of 12.62:1, but it'll probably be a bit less considering a larger chamber volume than stock.

We chose a .045" thick head gasket taking quench clearance, not static compression ratio, as the primary consideration. When you have quench pads like the P72 head does, you have to take piston-to-head clearance more seriously b/c the only thing separating the piston from the head is the head gasket, but at the same time you don't want to do away with too much of the quench clearance.

slow_dx

IN_VTEC,

Thanks very much; my car has a b16a2 head on it, so clearance betwee the quench pads is less of an issue. Running on 91, however is pretty important to me. I'm going to pick up a cometic gasket and push compression down to a more reasonable 11.5 : 1.

Thanks again; really appreciate you taking the time to measure and share this info.

IN VTEC

iTrader: (3)

If you're trying to hit 11.5:1, you've got a long way to go if you're gonna use the PCT pistons. You'd have to use a .060" or thicker head gasket, and lose all the quench that the PCT pistons give you to begin with.

If you want 11.5:1, use the P30 pistons with a thinner head gasket (.025") and .25OS pistons. Mill the head/block as necessary to go higher in CR. Going this way will allow you to keep your quench without going so high on the compression.

Use less dome, not less quench.

slow_dx

I agree with you in the general case of an ideal motor build, but the problem is that I've already got a motor that has been built in my car; taking the head off and installing studs / gasket seems to be a reasonable cost / performance compomise. Do you think that there would be a problem with this setup?

Headgasket would be the 0.067" cometic gasket.

With the pistons sitting up 0.030", wouldn't adding 0.037" to the gasket thickness put quench at just a little further away than stock?

I guess I could use a 0.057" gasket, run 11.8:1 and still feel good about running pump gas with conservative tuning. Quench would be a little tighter than stock, and compression would still be reasonable. What do you think?


EDIT: read another number for dome displacement; ~ 6ccs over at theoldone.com

I am going to try to pick up a CTR piston and some modelling clay so that I can get this figured out...

Thanks again!


Modified by slow_dx at 6:19 PM 10/7/2003

IN VTEC

iTrader: (3)

https://honda-tech.com/zerothread?id=130919
+6.15cc's here

If they are indeed in the +6cc range instead of +8.63cc's as stated by the C-speed sight, then you won't need nearly a thick of a head gasket to get around 11.5:1.

The pistons don't sit up past the deck, they're flush with the deck unless you had the block deck milled. So your quench clearance would be the thickness of the head gasket + the clearance of the head's deck to the top of the side of the combustion chamber. My friend's ITR head is out right now, so I can give you a clearance later on.

slow_dx

Some more evidence to support the 6.15 figure:

http://www.toda-racing.co.jp/p....html

Looks like pct pistons in a b16b have the same deck clearance as in a b18c, if you run the numbers through the c-speedracing compression calculator w/ todas headgasket thickness, you get the numbers to match up.

Also, if you recalculate the b16b using the smaller dome displacement and 0.00 piston - deck clearance, you get.... 10.8:1

Still, I'd like to get my hands on a pct piston *just to make sure*.

Integspeed21

That does look like hella fun. I just had a new motor placed into my car cuz i F****ed up 2 connecting rods and went ahead and bought a motor with low miles

IN VTEC

iTrader: (3)

Right on. I concur.

I guess I'll be re-running the compression numbers on our motor again.

joshwhe

nice rotary housing what year rotar is that

IN VTEC

iTrader: (3)

Dunno, but I'm pretty sure it's from a 13B with a NA (higher-comp) rotor, which makes it a FC motor.

joshwhe

series 4 or 5

IN VTEC

iTrader: (3)

Something like that. I don't ever work on rotaries and that one is a dead housing/rotor anyways. It's a collector's piece that one of our guys likes to keep around b/c he's a rotary jocking FD owner.

joshwhe

haha.. yeah i have a rusty one right by my tool box..... it was a gift from a friend when i got my rx7

joshwhe

if its a s5 na then its higher comp. then the s4

IN VTEC

iTrader: (3)

Series IV it is then. That rotor doesn't look like a higher compression unit unless my mind is exaggerating what I thought a higher compression rotor looked like from the one time that I did see one.

I'll let you decide.

gsrswapdcivic

IN VTEC Just wondering where you got the gauge and a part# also how did you shave the raised lettering and arrows off (what did you use)