Need A Little Help With My 331

madmike1157 said:

Using a CR calculator shows me a 8.75:1 CR for your combination.

Ideally, more compression is desirable in a high output, purpose built nitrous engine,...but a 100-150 shot of nitrous is far from that. MOF, that 100-150 hp shot is w/i the confines of what can be safely dumped into a engine sporting near stock internals.

Big nitrous use requires that you pay attention to three things specifically.
Spark timing, fuel octane, and what your plugs look like. (and you gotta know what to look for)

The timing thing is easy, and there are several recommendations from different mfg's out there to serve as a guideline for that. Typically, you remove 2 degrees timing for every 50 HP of nitrous injected as a starting point.
So,...if you are running stock timing curves and total advance of say......32-36 degrees total,.....you'd remove 4-6 degrees from that to compensate. If you don't want to continually get under the hood w/ a timing light, Several MFG's make timing retard boxes that will allow you to run stock timing right up to the instant that the n2o is activated, then retard the timing to your desired setback.

The fuel thing is a catch 22. Use a fuel with enough octane to cover detonation and keep it in check, but not so much as to slow the burn down to where it starts causing the engine to make less power.
That said, there's no way in hell I'd use 118 in a low CR/low nitrous injected engine. I'm thinking that you should call somebody at VP or Rocket to be sure, but I'd bet they'd cap you at 100-110 instead.

The plug reading is a direct indication of whether you are safe at your chosen HP level. The plug color will be a tell tale of that. Now that I think about it, you're gonna have to know what kind of alloy the pistons that are in the engine are made of.

A true forged piston will be more tolerant of abuse, however the industry has put out a bunch of confusing info about what the word "forged" means, and it doesn't automatically mean that you have a good piston that will tolerate getting rattled if you have something go wrong.

A 2618 alloy is a true forged piston, using the best aluminum that can be used in high HP applications.
It is more "soft" and less brittle and consequently can absorb more abuse. The negative to a 2618 piston is that they are noisy in the engine,..and you can hear them rocking as the engine runs. They grow w/ heat, so the engine has to be finished honed w/ more sidewall clearance to allow for that.

A 4032 alloy forged piston is made w/ a higher silicone content, and as a byproduct expands way less than a 2618 piston does. The engine builder can run tighter clearances because of that, and that nets a quieter running engine that typically lasts longer, and has better ring seal. But,...

The piston is more brittle because of the higher silicone content, and less tolerant of detonation.

A hyper-eutectic piston, typical of what KB uses is the least tolerant of the three, and is considered a cast piston. They transfer alot of heat to the rings, and the ring end gap has to be set huge because of that. They are NOT suited for a power adder, and should only be considered in a N/A application.

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Brandon Palmer said:

Shouldnt it being boost built motor make the ring gaps tight? Meaning I should gap them more for the bottle?

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Brandon Palmer said:

10/4, thanks fellas. Will be finally put together and driving by July I hope. If I can ever find time to work on the thing.

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