Piston and rings for 540 nitrous engine

[BrianB]

Looks like I need to redo the 540 for my boat. Something went through a cylinder and beat up the piston and cylinder wall (heads are ok). The bore will have to go to 4.530. This is the first nitrous engine I've worked with, so what do you guys recommend for pistons and rings? Compression will be about 10.75:1 and I'm hoping for around 800hp on the motor, plus a 300-350 shot. Also I'm still debating on the vacuum pump - this part just depends on what kind of deal I can get since I gotta pay for these other parts.
Brian

[subhuman415]

Wiseco pistons and Total Seal TNT rings are my choice for my 415. I plan to spray a 300 shot on a 700hp engine.

[strokedTA]

You're going to get 20 different opinions about this one!
I went with Tool Steel top rings in my motor, but would probably go with the Hellfire rings next time, from SpeedPro.
Pistons, doesn't really matter and top brand will be fine. I used BME's with pin buttons.
I'd use a vacuum pump no matter what! You will be crating a lot of crankcase pressure on the spray.
Plus you can get the rings with lower tension and gain even more power with the pump.


Dave Brown
www.wheelsupracing.com

[BrianB]

The closest piston I have found is the SRP for the 4.530 bore, 4.25 stroke, 6.385 connecting rod, that is 10.4:1. Will the SRPs hold up to a 300-350 shot of nitrous? Only other option would be to order a custom set but that seems to add around $300 or more for the set. I have contacted Wiseco, SRP, Ross and CP (but they wouldn't give me a price - have to be a dealer).
Brian

[Maximum Race Engines]

I run Hellfire rings in alot of engines that see a decent amount of nitrous, of atleast up to 300hp. A real nitrous ring will cost a bit more, but be worth it. I would use a stainless ring rather than the tool steel. The tool steel stuff tends to not seat very well. The hellfire ring will be fine for what you are doing. Just make sure they make it for the bore size you have. As for a piston, well you are looking to make over 800hp on motor with pump gas compression? What cylinder head is on this? If you are running race gas for nitrous why not just run race gas compression? Either way with that much power, and that much nitrous, every dollar spent in a custom piston is well worth it. SRP is not a piston you want to run in anything seeing 1,000hp+. They are not made for 300-350 worth of nitrous. I would go with a custom Ross or CP if you know a dealer for them. As for a vacuum pump..should be a no brainer..I would definitely go with it.

PS..Just because you go with a vacuum pump does not mean you have to run the low tension rings to use it. You will still see a power gain from the pump alone, seeing 13" of vacuum. The low tension rings will create too much oil in the cylinder and does not work well with nitrous. Stick with standard tension rings with the nitrous.

[BrianB]

Joe,
What brand of stainless ring do you recommend? Is there a "zero gap" type stainless ring?
The reason that I don't want to have high compression is that I want to be able to run pump gas when I'm at the lake, then be able to go to races and put race fuel in it and spray the hell out of it.
Thanks for the help,
Brian

[Maximum Race Engines]

Brian-
Childs and Albert Stainless top ring. Didn't inquire whether or not it was a zero gap. I don't tend to run zero gap stuff. I really wouldn't bother with the stainless set, priced them out $350 bucks. The Speed Pro Hellfire will work with the 300 hit you plan on running and be half the price. I use the stainless stuff when the hit goes 350-500. Other thing is, why would you go 4.530" on the bore? Why not just go 4.560" OR 4.600"? Piston is readily available at that size, and for the amount of nitrous you are going with, a Ross will be more than fine for that level, and you gain in cubic inch. I wouldn't worry about the cylinder walls, at 4.600" the walls are still over .250" thick unless you are not running a Dart or Merlin, then I can understand..

[BrianB]

Joe,
I can't find anything like that in Ross' online catalog. If you know of one, I would sure like to check into it further.
Brian

[Maximum Race Engines]

Brian-
What size chamber in the heads and what compression are you looking for? How far is the piston the hole? Head gasket being used? Piston that was being used? They don't list everything online...Besides, it doesn't have to be a Ross, just a better piston than SRP, like CP or J/E. I will be looking into dealing with Diamond as well so keep me posted, I am sure I can find something for you.

[E T Engines]

Thanks for such a great board and advice on here! I ran across another option the other day for moderate compression 2618 material pistons. Probe makes a 9cc dome piston for this application. They usually have a good price on them too. Any one have any thoughts on the Probe pistons? Have already used a set of their pistons and pins in a circle track engine, have worked great so far. I'm not a dealer but check them out at: www.probeindustries.com they are listed under the products>forged pistons>sportsman race series>chevy>Chev 454>dome top Hope that this helps.

[BrianB]

Joe,
Chamber size is 119cc. Current setup has piston about 0.021 in the hole, the block has o-rings and I will be decking the block to get rid of them. I suspect that if I was still using the old pistons, the deck would be near 0.000 with the o-rings gone. If the deck ends up at zero, I'll use a Cometic 0.040 gasket. I'm looking for compression in the 10.5-11.0:1 range. I think I can still run 92 octane with the 11.0:1 and the timing backed off slightly and the engine running cool (boat). Then at the track I can fill the tanks with race fuel, turn the timing back up and blast it with the nitrous.
Brian