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Discussion Starter · #1 · (Edited)
I need help getting the proper squish

I have a 04/05 motor with a 6mm falicon crank and falicon knife rod with a spacer kit and Athena 98mm cylinder, with a CP piston, the piston is a 03-05 13.5:-1 or a 06-13 13.75:1 compression ratio so I do not know which one it will be with my set up.
I have web 943 cams and if needed I can look up the specs of the cam.

I have 2 head gaskets, one is a Athena that I measure at .049 thickness and I have a cometic that I measure at .053 thickness. both are measured before it is mashed down if that matters.

With no gaskets my piston is sticking up over the cylinder .074" in dead center and the rear of the piston is .042 and the front is .039 ( I only have one ring on so the piston is probably cocked a tad and so maybe the equal amount would be .040 -.041 ) I have the spec sheet on the piston if that is needed.

I do not know if the head has been resurfaced and the head is at MMAD so I probably should ask him to check that if it will matter.

I do have 2 base gaskets, one is a Athena and it measures .026 and the OEM measures .023

I need to figure out what size base gaskets I will need ( I will need 2 )
Any help would be great.
 

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Discussion Starter · #2 · (Edited)
If my thinking is right would I need .060 thickness divided x 2 so 2 base gaskets at .030 each when using the cometic head gasket ?
And if so then I could use the Athena at .026 and get one gasket at .035 if they make one that size.
 

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this is the procedure I use when dealing with SPACER PLATES .

having all the extra gaskets just adds places for leaks and does nothing positive towards making a solid platform for correct and stable head torque values !

your decked head won't affect the squish ,but will decrease piston to valve clearance, and increase compression slightly.

your stroker crank will raise the comp even more.


measure the deck height over the wrist pin c/l on each side of the piston without any base gaskets .

I would use the Cometic head gasket, and measure its thickness where there are NO raised embossments (where all three layers are flat).


shoot for .038"-.042" squish clearance.


after you take your measurements call Cometic and order the correct copper or aluminum spacer-gasket (add 6% to the measurement for the copper gasket).

Yamabond the spacer plate to your cylinder and don't bother with any standard base gaskets, only use a THIN`ish ,EVEN LAYER on both surfaces, not a bead , let it skin over some then hold it down or clamp it together snugly till cured !!

Yamabond, then clamp the spacer-gasket to the bottom of the 6mm spacer plate, after its cured, assemble the piston-cylinder then put a thin`ish layer (as above) of yamabond on both the spacer-gasket and cases ,let it skin over, then assemble it all and bolt it down snugly (BUT DONT TORQUE IT DOWN YET) let it cure some first !


clean all surfaces with brake cleaner before applying the Yamabond,
and use fresh Yamabond !!

or you could just order a new thicker spacer plate with the added thickness you need and just Yamabond it alone to the CYL , it would cost more but is a better way to do it.
 

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going by the measurements you gave of

deck .041"
head gasket .053"
leaves .012 quench
shooting for .040" quench
needs .028" added

a .030" metal spacer gasket or
two .015" base gaskets would net .042" quench


double and triple check your measurements !!
 

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if that piston is a 13.5-1, with your stroker your going to have some hella compresson !!
using some quick FUZZY math , I put it around 15.77-1


you could have the head cc'd while its a Jeoffs.
and find out what the TRUE true dome volume is, dome displacement should be on the piston build sheet.
 

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Discussion Starter · #6 ·
Thanks, what is cc'd ?
I will post on the piston specs Sunday.
And I did measure the head gasket with the raised embossments so I will re-measure and post.
I did not realize I would have over 15. compression, not really what I wanted, I had the piston before the motor and purchased the motor that needed a new piston so I was just going to use that piston because I had it.
 

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CC'd is a term for measuring the volume of a depression, in this case a heads combustion chamber.

It's used to find the true volume of the chamber ,only with having the accurate info can we make the correct modifications.

using a calibrated burette filled with a colored, low surface tension liquid and a plate of thick glass with a small hole drilled in it, the plate gets clamped to the head over the chamber and you fill the chamber up so there isnt any air left inside, then you measure how much fluid you used to fill it.

The graduations on the burette are in 1/10 Cubic Centimeters hence the term CC'ing.

It's used after, port work (heads and intakes), valve deshrouding ,chamber polishing , new seats, different valves (larger dia or flat faced instead of dished) to see what the actual volume is after the work is done.

To do it correctly you need thick enough glass so it doesn't bow in when clamped and mess up your measurement.
You can use lexan but it needs to be thicker than glass, but its easier to drill the hole.

The gasket surface needs to be coated lightly with grease to seal the plate to the head, don't get any in the chamber.
Position the small hole in the plate at the very edge of the chamber and raise that end slightly higher so all the air can escape, and you get a complete fluid fill.

use plate glass, and drill it with a carbide spade bit.
and use rubbing alcohol with red food coloring.

its not head cc'ing but here is a pic of a YFz and TRX I needed the dome volumes on.
I called Venom and they wouldn't tell me the dome volume on the TRX piston !! (said it was proprietary info) WTF !!
 

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Thanks, what is cc'd ?
I will post on the piston specs Sunday.
And I did measure the head gasket with the raised embossments so I will re-measure and post.
I did not realize I would have over 15. compression, not really what I wanted, I had the piston before the motor and purchased the motor that needed a new piston so I was just going to use that piston because I had it.

If you were going to use race gas anyways ,youll love the extra compression !
 

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this procedure just determines the true piston dome displacement and crevice volumes from zero deck height.

most use just the pistons build sheet info , but that isn't nearly as accurate.

this method measures ALL the crevice volume down to the top of the compression ring , for an exact volume value.


it's an easy enough task

install comp rings on piston.

place a dab of grease on both rings end gaps.

insert piston in CYL.

push piston down to bottom of CYL.

wipe a thin layer of grease around the CYL bore 1.5" down.

push piston up until the highest part of the piston is level with the top of the CYL deck (use a straight edge) or the glass plate.

clean all grease off the piston and CYL wall and use a feeler gauge and paper towel to clean between the piston and CYL above the top ring.

using a height mic or caliper measure from the CYL deck to the piston compression height (outer circumference of the piston where its flat).

calculate the volume of the CYL for that depth measurement,
if it measures .125" down that's 3.175mm.
on a 95mm bore, at that depth the CYL volume measures 22.49 CC
95 x 95 x 3.175 x 3.14 /4 = 22.49

grease the head gasket area and clamp the glass plate onto the CYL with the hole at the very edge of the bore , clamp it in place, position the CYL with the hole at the highest point so it won't trap air and it gets a complete fill.

using a filled and measured burette, fill the space above the piston until fluid just touches the bottom of the hole in the glass plate.

now figure out how much fluid is missing from the burette.

if you used 15 cc of fluid, then you have 7.49 cc of piston dome volume.

22.49cc cyl volume
-15cc open space = 7.49cc of dome displacement.
use that figure inserted into a compression calculator to get your exact comp values.

be sure the piston stays touching the glass plate, ring tension and grease cohesion should hold it snugly ,and watch for leaks past the rings (look under the piston).

just takes some time ,worst part is cleaning the sealing grease out of the ring grooves and oiling holes !
 

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Discussion Starter · #17 ·
What does that mean ? I purchased the piston as a 03-05 13.5:1 or a 06-13 13.75:1 compression ratio.
I still need to measure the head gasket, I do not have the correct calipers to measure that way so I need to run it to a friends house to find out.
 

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Pretty good info in this thread.

What compression where you hoping for, and what fuel do you plan to tune and run in the motor?

The stroker cranks are based off the 04-05 cranks, so any piston spec-ed for the 04-05 will be used. However that all goes out the window with long rod stroker motors. Don't forget you will also need adjustable cam gears, and degree the cams for the new assembled motors deck height.
 
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