Decking Nicasiled Cylinders

Canuck

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Does anyone have any experience with decking nicasiled cylinders? I'm raising the cylinders on my 92 Vmax-4 and I want to deck the tops of the cylinders to get my squish height back. I spoke to a Yamaha mechanic and he didn't think there would be a problem and suggested an automotive machine shop that has a good reputation. I went there and they didn't want to deck them because they feel there will be problems with the nicasil peeling after the machining. Does anyone have any experience with this? I suggested using a grinder and putting a slight chamfer on the top of the cylinder prior to machining but they said this would also cause peeling.

Thanks
 

I did some more checking and there are apparently two types of machines that are used to deck cylinders and heads. A surface grinder and a milling machine. The grinders apparently leave a better surface but the stones will load up with aluminum and they can only remove a little at a time. The milling machines are more common. I did find a shop with a surface grinder that will do the work but I'm not sure of their reputation. Taking into consideration that the grinder only removes a few thousands at a time I kind of question taking off around 40 thousands with it.

Someone must have some experience in this area?
 
I wanted to cut the heads but you can only cut about .015 - .020" off the heads and then you are cutting into the squish band. I wouldn't be able to take enough off the heads to get the squish back to a reasonable amount.

If I can't get the cylinders decked I will have to reduce the amount that I lift the cylinders and just stick with head shaving and a thinner gasket.
 
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My problem is too much squish so recutting the squish band would only make things worse. With my cylinder lift I'll end up with .076 deck height. I can cut the head to the squish band but I still need a head gasket. I'll end up with a squish height of .094, which is way too much.

Ideally I'd like to run my squish in the area of .060 - .070. The best (only) way to achieve this is to deck the cylinders but unfortunately I'm having trouble finding someone to do it.
 
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Your not making alot of sense. When you raise the cylinders to adjust port timing. You mill the heads and recut the squishband to whatever amount you need. Period I wound'nt f with decking the cylinders you will end up with a major headache more than likely...........SRXtreme
 
I am making sense, I just don't think you understand my problem. I will try and explain it in more detail so you can understand why I need to deck the cylinders.

Stock Motor
.016" squish clearance in head (varies slightly but this is the average)
.027" head gasket thickness
.038" deck height (piston edge to top of cylinder)
------------------
.081 stock squish (measured and confirmed)


Planned Lift with no other mods
.016" squish clearance in head
.027" head gasket thickness
.076" deck height (stock .038" + .038" lift)
--------------------
.119" squish (way too much)


Minimum attainable squish without decking
.000" head cut with zero squish clearance (you can't get less than none)
.018" thin head gasket
.076" deck height (stock .038" + .038" lift)
------------------------
.094" squish (this is still too much)


Squish with decking
.016" stock (or cut .010" for compression increase)
.018" thin head gasket
.038" deck height (deck the cylinder tops the same amount as the lift -.038")
--------------
.072" squish (or .062 with the head cut .010")


I can only cut the head to zero squish. With a cut head and thin head gasket I end up with .094" which is too much, my target is .060" - .070". The pro builders deck the cylinders to achieve the desired squish when you can't make it up elsewhere.

I was and still am looking for anyone with experience decking nicasiled cylinders.
 
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I just don't think you understand my problem
I understand fully.You should be able to cut the heads down the .038 you raised the cylinders. Then rechamber them for the desired compression and squish you are looking for.........SRXtreme

You can deck the cylinders worst case scenario is you might need to re-nic them. Pick your poison.
 
You can't understand fully. Yes I could cut the heads .038 but my squish will still be .094 which is too much. Explain to me how I would rechamber them for the desired squish? I'm cutting the head to ZERO squish and my squish height is still too much. The reason it's too much is the piston sits .076" down in the cylinder, which has nothing to do with the head.
 
as i remember the gasket on the sled is 3-4 layers. if you remove all but one that will take care of about .020. i have reused my head gasket on my viper over dozens of times. use permatex copper gasket spray(store upside down and shake well).
as for decking my viper was done .012 from the first two years i raced it a this one race that was a legal race. wanted to tech stock and increase compresion. what a headache now. every time i do something stupid to my sled i need to have a cylinder cut. I have a local machine shop do it. sometimes there is chiping but it is only down a .010, way above the ring line. if you can find someone whos cutter is designed to cut from the inside outward, not accross there would be no chance of chipping. also renicasiled cylinders seem to chip more than the factory ones. in my case atleast this has been true.
usually cost 20$ per cylinder
 
BV,

Thanks for your response. I considered using a dremel and very carefully putting a very slight chamfer on the top of the cylinder, the mechanic that I spoke to thought this sounded like a good idea.

For now I'm just going to do a .026 lift, cut the heads to zero squish, and try running a single layer of my head gasket .009". If I have any trouble with the single layer I'll pull it apart and deck the cylinders.

Thanks for your input.
 
Canuck said:
You can't understand fully. Yes I could cut the heads .038 but my squish will still be .094 which is too much. Explain to me how I would rechamber them for the desired squish? I'm cutting the head to ZERO squish and my squish height is still too much. The reason it's too much is the piston sits .076" down in the cylinder, which has nothing to do with the head.

go past 0 squish then rechamber them, if your'e rechambering it you can put your squish height wherever you want, take your 0.38 off of the surface of the head, then reset your squish zones 0.16 in, and if you can set the squish angle at whatever you want now.

if you wanna mill the cylinders you can do that to (I've had to do it same reason as BTV) I just did them on a mill, go slow and take your time, 0.005 at a time at the most, usually smaller cuts, leaves you a fine finish, then I usually scuff the cylinders with a 180block to help them seal


hopefully this is already resolved tho.
 
It's also possible to cut the head with a .038" step in such a way that the squish area actually sits down in the cylinder slightly. The last thing I would do is deck the top of the jug.

I dont know much about the V-Max 4 but I assume the goal was to raise the port timings? Why not just grind on the ports?
 
500Sabertooth said:
It's also possible to cut the head with a .038" step in such a way that the squish area actually sits down in the cylinder slightly. The last thing I would do is deck the top of the jug.

I dont know much about the V-Max 4 but I assume the goal was to raise the port timings? Why not just grind on the ports?

good idea!

decking cylinders isn't a HUGE deal, I wouldn't trust somebody I was paying to do it tho, you really gotta go slow and take your time.
 
Cutting the cyclinders down is not that big of a deal with the right equipment. Somebody said if you cut them from the inside out, the nicil coating won't chip. You could do that with a C and C mill and a circular interpulation program or grinding them would not be that bad with the right wheel and wax or kerosene to keep the wheels from loading up-but would take a while.
 


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