Have you Decked the cylinder

Ok I am thinking about adding the a stk base gasket (doubling up with the cometic .012) changing the deck to .030 and expecting the following.


Cylinder Head Volume (cc) 38
Cylinder Head Vol (cubic in.) 02.318
Piston Head Volume (cc) -8.6
Piston Head Vol (cubic in.) -0.525
Gasket Thickness (in.) .025
Swept Volume (cubic in.) 26.637
Gasket Bore (in.) 3.508
T.D.C. Volume (cubic in.) 02.325
Cylinder Bore Diameter (in.) 3.508
Gasket Volume (cubic in.) 00.242
Deck Clearance (in.) .030
Note: Neg. nubmer above deck, Pos. number below deck Deck Volume (cubic in.) 00.290
Stroke (in.) 2.756

Comp 12.47:1

Now how about the squish on this one?

[dhines]

Well, I just spent the better part of an hour reading through this thread in its entirety. There is an amazing, and frankly overwhelming, amount of information.

Based upon the collective information gathered by the main posters in this thread is it possible to come to a collective recommendation for the average user who is looking for the best piston combination ( I don't even want to throw cams or carbs into the mix).

Based upon the people I talk to and the majority of the threads on this board, most people who mod their 400's are wanting a 416 piston and are looking for a reliable increase in power without using race gas and without having to do any decking. Based on that, can we get a recommendation on the following:

Manufacturer: (JE, Ross, etc)
Compression ratio:
Flat topped or domed:
Any other custom piston recommendations (i.e. reduced weight, custom wrist pin, etc):
Recommended base gasket:
Recommended head gasket:
Other info:

Or is there already a kit out there that provides a reasonable and accurate compression ratio, with a relatively flat topped piston (which apparently give better performance than those that are more domed), and the appropriate head and base gasket combo to get us to the magical squish area (or is it quench?) of .040?

If possible, it would be nice to get the same info for a 440 kit as well.

Maybe I'm hoping for too much, but I figure it's at least worth asking.

Best,

Dennis

Dennis (damn was I hoping it was Duncan )

good thought but every time I have tried to get anything with a mod on this quad to be simple it just doesnt happen.

One of the main reasons I resurected this thread instead of starting a new one was that there is so much excelent info here anyone could determine how to properly set up their existing or future piston no matter which size or MFG it is.

And it also shows why a properly preped 416 motor could out pull a 440 and then get completely left in the dust by another.

And though you could almost say that the info I have posted on my experience will give you a basic guide on what to expect from both the pistons I have used there are still some variables that will require things to be assembled and measured before you can answer your questions.

The diff in design and compression etc between the 11:1 flat top J&E (it could have been 10.8:1 also?) and the 11.2:1 Ross dome top are pretty big and both require diff mods to work right. And this can also change motor to motor.

I am just glad that I had the chance to get this info in the first place and that there were other members who had this knowledge to share.

PS.
Its looking like I am going to try the dbl base gaskets .012 and .020 and shoot for the 12.4:1 comp as posted above, wish me luck and any idea on squish (damn I am gonna have to find how to figure the squish and stop being a pain in the arse)

[MIKE400EX]

Without over complicating it, squish = head gasket thickness + deck height. In other words, if the gasket is .025 thk. compressed and the piston is .020" "in the hole" at TDC, the "squish" would be .025 + .020 = .045". If the piston were .005 out of the hole (negative deck height) then it would be .025 + (-.005) = .020".

thanks Mike.

Hmmmm then I am getting a little high on the squish with that dbl gasket set up.

I am not thinking thats good with the dome top and higher comp. Damn this is never gonna end LOL

[powerslider]

That's why I suggested you modify the piston so all else can remain the same, that is what I would do in your case....

That's why I suggested you modify the piston so all else can remain the same,

I am deff looking into it, thanks.

[joeroadking]

this is the best thread I have read so much usable info, I am currently having the 440 wiseco bore Kit intstalled and now think I am going to have my cylinder decked by .010-.012 and am going to use a thinner cometic base gasket and head gasket getting me closer to the 11/1 compression ratio ? thinking I will be in the 10.5/1 range with these mods,please correct me if I am wrong .Will I be able to run super unleaded gas? I do not want to run race fuel.fyi has stock cam , Joe

[BigThumper33]

is there a set standard on squish? Is there clearances that are too close? Also if squish is deck height + compressed head gasket width then quench is distance from piston to top of dome? And if it is, how would you measure quench? Measure the dome distance to the head mating surface and then add that distance to your squish?

[Matt Fisher]

As much as I'd like to say "here are the best combo's to use", that ain't gonna happen.

When I first started looking for a 440 piston, my primary concerns were weight and compression.

Due to the fallacy that a 406/416 will outperform a 440 due to piston weight, I made that my first priority. JE was less than helpful, while Honda Jim at Ross was able to come up with some very good info (also on the JE's since he designed their piston too). BTW, there isn't a real significant difference in weight between the OEM piston assembly and any of the aftermarket ones, and it's possible to make them equal.

Not only was the Ross a couple grams lighter than the JE, but they also had special lightweight alloy wrist pin available. Additionally, they offer a service to mill the piston for additional weight reduction. Yes, I did both, although I needed to purchase 4 pistons for them to do the milling.

As a side note: My seemingly anal fixation over a few grams really is quite silly given how little a gram weighs. Hold a dollar bill in your hand. That's a gram. Not much huh?

I struggled with the Wiseco due to knowing that their pistons often were coming up short in the CR dept (see the info posted by Mickey Dunlap). Being a flat-top piston, that made sense. The key, however, is in the piston to pin height. A flat-top can easily have the same/more compression than a domed one, if it's height is greater to begin with.

The problem I ran into was when I decided to set the squish. That's the distance between the outer edge of the piston and the head, when the piston's at TDC. A smaller squish will create turbulence, which increases power and reduces the chances of detonation. If it gets too small, the piston can hit the head at high RPM's , and gets very sensitive to carbon build-up (.040 isn't much space).

However, as you decrease this distance, you cause the compression ratio to increase. This was a problem for me because I didn't want to run race fuel, so I needed to keep the CR to about 11:1.

I ended up milling a bit off the piston's dome, as well as unshrouding the valves, which resulted in a 2-3cc larger combustion chamber (I did 2 motors). After all that milling, cutting, measuring, cussing, etc., I'd bet that if I'd just assembled the bugger with the 11.3:1 piston from Ross I'd only lost out on about 3 hp.

My suggestion- if you have the time and patience to "do it right", then by all means- go for it. If not, I'd suggest 2 options for a pump gas motor. 1) Pick up a Ross piston (and spend an extra $20 on the lightweight alloy wrist pin), drop it in there, and go have fun. 2) Get a Wiseco piston (I think www.thumper-racing.net has specially milled ones), and then mill about .020 off the cylinder to up the CR.

If you going to run race fuel, then don't leave power on the table. Run the same Ross piston, but mill about .020 off the cylinder. You'll end up with about a 12:1 motor.

A couple of tips-
-I wouldn't even consider using the stock cam with a 440, and the XR is also too small, IMO (ok, maybe for a tractor motor). Try a Web 450/451, or the Web 479 with some Kibblewhite valve springs.
-Mickey Dunlap's oil cooler is a killer idea. I used his basic design, then made up my own custom cooler. But for the limited amount of money he wants, it's a no-brainer. Especially when you consider that (according to him) hardfacing the rockers is unnecessary when using his design.
-These websites may help in figuring out compression ratio's- http://www.rosspistons.com and http://www.kb-silvolite.com
-The stock squish is about .085+/-