- Location
- North East Pa
If so what did you get? I did mine and I want to compare. My engine is "new to me" and want to verify if it has been cut or not. 
Has anyone cc'd a stock 64U head?
- Thread starter Big Chris
- Start date
- Location
- North East Pa
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
Did you find the rear held more volume?
I think a few people are confused about the 64u thing. 64u is a stock 701 head from a superjet. 64x is the 760 head with different domes front and rear.
I have not CC'd a stock head, or any head in the way that you did, but I did take a measurement of an ADA head installed volume, for what that's worth.
Info here:
http://www.x-h2o.com/index.php?threads/who-still-cuts-domes.192433/#post-2004522
I have not CC'd a stock head, or any head in the way that you did, but I did take a measurement of an ADA head installed volume, for what that's worth.
Info here:
http://www.x-h2o.com/index.php?threads/who-still-cuts-domes.192433/#post-2004522
- Location
- North East Pa
Storbeck, this engine came out of a '13 SJ. It is in need of a complete rebuild, which I am doing now. This engine is 62t cases, with a 61x cylinder and a 64U head. What I was trying to determine is if this head was cut by the previous owner or if it is stock. I suspect the cases were split at one time, because the case bolts were not installed in the factory locations ( the case bolts with the spacers under them were not installed in the center 4 locations). So since I think someone had meddled with it, I don't know if someone modified it. I have read your post you linked above and it seems you cc'd a 760 at 1.5mm overbore with an ADA head so there is no correlation there.
Everyone else,
The reason I cc'd just the head was to see if someone else had cc'd a stock head. This way we could compare numbers to determine if the head I have was cut. I would like to retain stock compression. I am super anal retentive about engine building, so I need to know this. The head shown in the first post of this thread measures at 36cc, both front and rear dome. I tried to measure the installed cylinder volume with the piston at TDC. But because of the feature inside the dome around the spark plug on the 64U head casting, I am not certain I got all the air out the cylinder. (see pic at bottom) I tried my best and tilted the engine repeatedly in an effort to get all the air out, and several large bubbles did surface. Although I am still not confident my number is perfect, but it is probably "close". I measured 32.5cc chamber volume. This is with the piston at TDC and the fluid level in the engine to the bottom thread of the spark plug hole, while making every attempt to remove air trapped in the head. Piston size is 80.25mm, stock base gasket, stock head gasket. I did not yet measure squish, and will do so using the crushed solder method.
I am relatively new to the 62T engine platform, however I own and operate a race engine shop. I build dirt oval karting engines. I have probably built more engines in the past two months than most people will assemble in their lifetime. On Oct 18th 2019, one of my engines took second place in the rookie class at the Maxxis Tire Karting Nationals in Neeses, South Carolina. I own a water brake dyno, a SF60 flowbench, Sunnen Hone, and a Bridgeport Mill. This is me www.rperacing.com
We live about 6 miles from a medium size natural lake (640 acres). This superjet is a father/son project for my 14yr old who is coming off a SX650. My build is pretty straightforward: new crank, fresh .25mm overbore, I'd like to retain stock compression, stock carbs, new stock reeds, TBM lightweight charging flywheel, MSD enhancer with stator at stock timing, Factory B Limited pipe, stock waterbox, stock drive line and stock pump/impeller.
Everyone else,
The reason I cc'd just the head was to see if someone else had cc'd a stock head. This way we could compare numbers to determine if the head I have was cut. I would like to retain stock compression. I am super anal retentive about engine building, so I need to know this. The head shown in the first post of this thread measures at 36cc, both front and rear dome. I tried to measure the installed cylinder volume with the piston at TDC. But because of the feature inside the dome around the spark plug on the 64U head casting, I am not certain I got all the air out the cylinder. (see pic at bottom) I tried my best and tilted the engine repeatedly in an effort to get all the air out, and several large bubbles did surface. Although I am still not confident my number is perfect, but it is probably "close". I measured 32.5cc chamber volume. This is with the piston at TDC and the fluid level in the engine to the bottom thread of the spark plug hole, while making every attempt to remove air trapped in the head. Piston size is 80.25mm, stock base gasket, stock head gasket. I did not yet measure squish, and will do so using the crushed solder method.
I am relatively new to the 62T engine platform, however I own and operate a race engine shop. I build dirt oval karting engines. I have probably built more engines in the past two months than most people will assemble in their lifetime. On Oct 18th 2019, one of my engines took second place in the rookie class at the Maxxis Tire Karting Nationals in Neeses, South Carolina. I own a water brake dyno, a SF60 flowbench, Sunnen Hone, and a Bridgeport Mill. This is me www.rperacing.com
We live about 6 miles from a medium size natural lake (640 acres). This superjet is a father/son project for my 14yr old who is coming off a SX650. My build is pretty straightforward: new crank, fresh .25mm overbore, I'd like to retain stock compression, stock carbs, new stock reeds, TBM lightweight charging flywheel, MSD enhancer with stator at stock timing, Factory B Limited pipe, stock waterbox, stock drive line and stock pump/impeller.
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hornedogg79
dodgin' bass boats
Haven't cc'd a stock superjet head (64u) but yours appears uncut. The ridge around the perimeter of the dome is normally gone after it's been cut. Stock should be around 33cc. Gasket will add around 7cc. I have an old WC head with interchangeable domes that still uses a gasket. Their chart read something like this. 27cc=190psi 29cc=185psi 30cc=170psi
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I see what you're trying to do now.
I would agree with hornedogg79, visually you can be pretty sure it's not modified, but I can understand wanting to actually measure and know.
I'm afraid you might not find anybody who has taken that measurement. Most of the watercraft builders don't bother modifying the stock head but just use aftermarket, you might try getting ahold of GroupK, they modify stock heads and might have the info you're looking for.
Also, I'm probably not telling you anything you don't already know, but if you are super concerned about getting it to stock spec, be careful about gasket thickness, particularly the head gasket, if you're not using stock. Aftermarket gaskets are often thicker, and also often have larger diameter "holes" for the cylinders.
I would agree with hornedogg79, visually you can be pretty sure it's not modified, but I can understand wanting to actually measure and know.
I'm afraid you might not find anybody who has taken that measurement. Most of the watercraft builders don't bother modifying the stock head but just use aftermarket, you might try getting ahold of GroupK, they modify stock heads and might have the info you're looking for.
Also, I'm probably not telling you anything you don't already know, but if you are super concerned about getting it to stock spec, be careful about gasket thickness, particularly the head gasket, if you're not using stock. Aftermarket gaskets are often thicker, and also often have larger diameter "holes" for the cylinders.
- Location
- North East Pa
The main reasons I'd like to stay conservative on compression are: My crystal ball can see long sustained WOT flat water runs. Jr does that now on his SX650. I'd like to run premium pump fuel in it, I dont want to mix Sunoco Standard 110 with pump gas. I do that now for my YZ250 and it's expensive and a PITA (Sunoco STD 110 is $10/gal locally). Secondly the rider is 105lbs.
I used WSM Platinum Pistons, and WSM head and base gaskets.
Observed head volume is 36cc
Gasket Volume (unfortunately I didn't measure the diameter of the metal fire ring in the gasket, so let's assume 81.5mm dia, but I did measure the thickness which was .060" uninstalled. So let's also assume a .050" (1.27mm) crushed thickness so that's 6.63cc for gasket volume = (((8.15cm/2)^2) x 3.14159 x .127cm).
Head volume + gasket thickness - piston crown volume = chamber volume
36cc + 6.63cc = 42.6cc.
My observed combustion volume was 32.5cc, if anything, this is probably a little on the low side because of air trapped in head. (read post #6).
So by my math, the piston crown occupies roughly 10cc. Does this sound right?
Hornedogg79: I have studied several aftermarket head manufacturers advertised volumes vs compression tester psi. I question these numbers. Are these the advertised volumes of the dome alone, or the total volume of the chamber as installed? I understand most of these use an oring rather than a gasket, so the gasket volume is eliminated from the equation.
I used WSM Platinum Pistons, and WSM head and base gaskets.
Observed head volume is 36cc
Gasket Volume (unfortunately I didn't measure the diameter of the metal fire ring in the gasket, so let's assume 81.5mm dia, but I did measure the thickness which was .060" uninstalled. So let's also assume a .050" (1.27mm) crushed thickness so that's 6.63cc for gasket volume = (((8.15cm/2)^2) x 3.14159 x .127cm).
Head volume + gasket thickness - piston crown volume = chamber volume
36cc + 6.63cc = 42.6cc.
My observed combustion volume was 32.5cc, if anything, this is probably a little on the low side because of air trapped in head. (read post #6).
So by my math, the piston crown occupies roughly 10cc. Does this sound right?
Hornedogg79: I have studied several aftermarket head manufacturers advertised volumes vs compression tester psi. I question these numbers. Are these the advertised volumes of the dome alone, or the total volume of the chamber as installed? I understand most of these use an oring rather than a gasket, so the gasket volume is eliminated from the equation.
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Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
With a stock head, running premium fuel is not going to gain you anything.......... You could run a cut head or AM Head up to around 170-175 lbs compression and run 92/93 Octane and run WOT all day long as long as your tuned right. With stock head. 87/89 Octane is fine.
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- Location
- North East Pa
I understand the octane/compression ratio/timing relationship. Again, this isn't my first rodeo.
The reason for conservative compression ratio is crank longevity, modern fuel quality (I'm old enough to have enjoyed gasoline without corn in it), along with the MSD enhancer's advanced timing curve. This is the reason I wanted to know what I had before I finished assembly.
I'd like to be "conservative" and get several seasons of trouble free reliability out of this build, my main concern is mostly with the MSD enhancer, which while retaining the 61x timing from 5500rpm to rev limit, is at a minimum 4° advanced from the 62t electronics for the same rpm range. See graph below, the data was borrowed from OCD's test bench and this thread.
http://www.x-h2o.com/index.php?threads/msd-enhancer-vs-protec-modded-cdi.183691/
Advanced timing + high compression + high engine load = trouble or at the very least a very small safe window. So by avoiding high compression I hope to achieve a larger safe window.
What I think is interesting, is apparently nobody here knew what a stock engine cc'd out to.............
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Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
I typed 180-185, meant 170-175
Big Kahuna
Administrator
- Location
- Tuscaloosa, AL
There are some that would, but not much traffic these days. Also, Many of us swap to AM heads to get higher compression. Also to run Girdle kits to make the stock cylinders stronger. Many also run AM Billet Cylinders........ So, the stock head volume is not relevant to many, but this is an excellent thread for anyone else that may be looking.
hornedogg79
dodgin' bass boats
I only mentioned the westcoast head because it uses the stock gasket. Oring head psi charts will be completely different. With oring heads the target squish is usually .045. Stock gasket is .052 so it would require some work to make your squish too tight with a stock head. Apparently you can cut .045 off a stock head, redo the squish angle and still have a reliable pump gas ski. I'm almost certain your head is stock with that lip still showing on the edge of the dome. I'm not a motor builder though. Just a jetski nerd.
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- Location
- California
Your engine will be perfectly fine with that head and just as reliable as stock.
Even if it were a cut stock head compression would never be over 180psi which is perfectly fine with 92 octane pump gas even running wide open all day long.
You will know the compression as soon as you get it together and crank it over.
At stock compression you are throwing away money using 92 octane fuel and gaining absolutely nothing.
The WSM head and base gaskets are not the best, best would be OEM.
OEM reeds aren't greatest being stainless steel and if the break they will trash the engine.
I have a stock head I can check if I get time.
Even if it were a cut stock head compression would never be over 180psi which is perfectly fine with 92 octane pump gas even running wide open all day long.
You will know the compression as soon as you get it together and crank it over.
At stock compression you are throwing away money using 92 octane fuel and gaining absolutely nothing.
The WSM head and base gaskets are not the best, best would be OEM.
OEM reeds aren't greatest being stainless steel and if the break they will trash the engine.
I have a stock head I can check if I get time.
- Location
- North East Pa
Thanks everyone
waxhead
wannabe backflipper
- Location
- gold coast
I just throw the stock heads in the bin. The squish clearance is way to large when you use a stock head and gasket so i simply dont care to measure it.
- Location
- North East Pa
Then there must be differences in the 64U castings. Or the more obvious, is are the head volumes different between the front and the rear. You appear to have done the front, and I appear to have done the rear. I measured this before, and I was pretty sure I got the same volume from both. I'll recheck.
See below.
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