nitrous ring gapping

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17dartandbroke

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I want to eventually install nitrous on my 340 which I will begin assembling tomorrow. I do not have the kit, but I do have the fuel system to sufficently supply it. What i am asking is would you think that my motor would be sloppy while not on the nitrous with the additional ring gap ie: .032 instead of .017.
 
on a kb hyper piston? i know this will probably bring up all kinds of "dont spray hypers" but KB said it should be fine if the fuel is there. what do you think?
 
17dartandbroke said:
KB said it should be fine if the fuel is there. what do you think?
Click to expand...

I know of one person on another board who ran KB pistons with nitrous. Supposedly his carb got a little trash in it and it leaned out. End result was the rings butted and it broke the tops of a couple pistons. And he was not racing... just a little showing off on the streets.

I've never used KB pistons, but I was considering them for my motor. Have you read all their tech articles? The really caution about too small of a gap. In fact they almost promote bigger is better as far as gap goes.
 
the tech guy told me that .008/inch of bore was what he would reccomend for nitrous. he told me that they have a staged 600hp worth of nitrous on hypers
 
The addtional ring gap only applies to the top ring. The second will be to stock specs so I wouldn't worry about blow by. The Keith Black pistons come with an instruction sheet that will tell you what the end gap factor should be for the intended usage.

FWIW, Hypereutetic alloy is much stronger than the typical cast alloy used in pistons prior to the mid 80's (90% of the engines made since the mid 80's have a hypereutetic cast alloy psiton) but it's not a strong as a forged piston. However, the hypereutetic alloy is much more thermally stable than either cast or forged so they can be set up for tighter clearances which results in less ring and cylinder wear. The hypereutetic is also harder so it wears less. The down side is that when exceed it's strength it will shatter where cast and forged will distort (a less destructive failure). If you keep the nitrious to reasonble levels you shouldn't have any issues. Look at all the Mustang 5.0's and LT1/LS1 Camaros and Firebirds running nitrious with factory hypereutetic pistons.
 
I think most 5.0L Mustangs came with forged pistons from the factory.
 
5.0's after between 89 and 92 i believe


but thanks for your info. i did not even consider that the extra gap only applies to the top ring - my only reservation was running into blowby. it seems that if i run the right amount of gap with a dedicated fuel system and proper timing that I should not run into any problems. the motor is sort of on the edge for pinging now, but i think that some retard should take care of that when it comes time for the nitrous.

thanks,
daryl
 
There is more to piston design than the material they are made from. KB positions the top ring groove higher on the piston to cool it. This helps to reduce detonation, but it also weakens the top of the piston and causes the top ring to run hotter. To compensate for running the ring at a higher temperature, you have to run a larger end gap. If the rings butt, the piston will break.

The KB tech articles explain this in great detail. I am not trying to say these are bad pistons, or that you shouldn't use them with nitrous. It's just that they require special setup and even then there is a chance something could go wrong.
 
The .008/1" of bore is good. .032 is not enough that you will notice a drop in performance, especially only being the top ring. If you are "on the edge of detonation" you may want to install a progressive retard, or just drop the usual 2* for every 100hp shot, and figure to use the bottle when you need the power. And, make sure your dedicated fuel system's regulator is set with the solenoid open and flowing (like into a bucket), otherwise there will be a large drop in pressure when it's activated.
 
thanks for the info guys. i said the hell with it tonight. did it at a loose .032 to give it a little extra room.


loose meaning the feeler gauge was not that hard to get in between the rings when in the bore. ill keep you guys updated. nitrous shouldnt be in the car until around chrismas anyways.......i have to get some suspension and motor twekaing down once its all together

thanks again,
daryl
 
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