TurboAv

iTrader: (6)

Using these pistons in my motor: http://www.probeindustries.com/Chevy...ns_p/14510.htm

Forged H-beam rods and stock crank. I can't afford the blower right now, so I'm doing a ported FAST 90 w/ a direct port. Motor will probably make 450-475 bhp NA. What will I be safe to hit it with? I was hoping at least 300. Maybe more if the pistons will handle it.

00pewtertransam

with that much of a shot you need to make sure ring gap is safe for that shot. what is the ring lance depth. <(how far down is the top ring) and alot of it is of course tune. would highly recommend a progressive controller. a big 300 shot all at once could snap that factory crank.

TurboAv

iTrader: (6)

I am planning on progressive. Most likely a Microedge+ to get me started. Seems like a very good value for what features you get in the controller. I will talk to my engine builder and ask him about end gap and how far down the first ring is. I am using Hellfire rings, just not sure how he set them up. Thanks.

h0t

When I called the guys at JE they claimed that my SRP pistons would only handle a 150hp shot and anything more would burn a hole right through them. Basically you need a piston with a thicker top and with the rings moved down a bit...proper gapping as well. If it were my motor I wouldn't go past 150hp, especially with the stock crank on top of that.

TurboAv

iTrader: (6)

Hmmm. Wouldn't using a progressive controller help though?

TurboAv

iTrader: (6)

From the Probe website:

Edit:

Just got off the phone with Probe. They said 300hp is safe and they have guys doing 400hp.

00pewtertransam

well thats good to know about the pistons. but how much boost were you planning on? i know a buddy of mine just had his boost 385ci machine work done along side my 408ci nitrous motor and our rings gaps were damn near the same. we are both getting a lil crazy with our motors. i have a ring gap of 32 1/2. and my builder said that would cover up to a 500 shot. i dont remember my buds. i know he is planning on hitting 20 #'s, if not more. so if you were planning on alot of boost you might be ok. but double check. rings will expand and if they have no room to expand good bye rings and cylinder walls.

TurboAv

iTrader: (6)

My builder set my ring gap at .024 on the top and .022 on the bottom.

TurboAv

iTrader: (6)

Called Probe again and told them my ring gaps. They said I'm good to go for 300-400.

00pewtertransam

man i would contact your motor builder and get their opinion. everyone machine shop has their ways. thats a lot of nitrous, just becareful. and remember ur on a stock crank, they like boost a hell of alot better than they do nitrous. personally i wouldnt hit a stock crank with more than a 200 shot while progressing that amount. man its ur motor but if you want it to last to the boost part if its life, a 150 shot is the way to go.

TurboAv

iTrader: (6)

My only worry is that with my 9.3:1 compression a 200 shot won't be enough, lol. I'm planning on starting at 200 and working up. I also have to not make it too fast or the track will boot me. So it's going to be a combo of learning to drive the car, getting a cage put in, and saving money for the blower. My builder said 200 should be fine and 300 is pushing it. Probe says 300-400 is fine. As long as I'm not hitting it all at once the stock crank should live for a year or so. I'm already planning a stock stroke LSX block motor(4.125 x 3.622). 9000+ rpm and 20+ psi of boost is my future plan.

00pewtertransam

yeah your compression being that low is killing ya. alot of power being missed.
and yeah i have got my *** chewed out for running and i have a cage. lol well good luck with eerything i hope i have been of some help. just been trying to help you do the i and croos ur t's have fun nitrous is addicting by the way!! lol

TurboAv

iTrader: (6)

I appreciate the help. I was thinking about getting some new heads, but I'm unsure how low on combustion chamber size I can go. My current heads are 63cc as it is.

JL ws-6

iTrader: (50)

If the pistons are 2618 material, you can spray on them and have no problems, if they're boost pistons, chances are they are the right material. Ring is probably down a good bit too, and your ring gap is fine.

With the low compression, you do have one thing that's to your advantage.. your tuneup window will be rather large. That doesn't mean I'd start off with a fogger and a 32 jet off the bat, but you have a large enough window so that if it's not dead on you still probably won't hurt anything, as long as you get it right and don't keep hammering it with the wrong tuneup.

What are you planning on running for a kit/setup?

TurboAv

iTrader: (6)

I bought this off of Cal Speed. Nitro Daves installed a NX 4 solenoid direct port with a NX fuel accumulator on a ported FAST 90. Using the new versions of the carbon fiber solenoids.

JL ws-6

iTrader: (50)

I don't personally care for the log manafold type setup...... I like the smaller distribution blocks, they're known to distribute internally a little better, I'd have that setup flowed just to make sure that you don't have a cyl that isn't getting even distribution.

As long as there's no issue there, it should be good. Keep #6, 7 and 8 one nitrous jet smaller then the rest of the motor initially to start, and that should keep things happy.

TurboAv

iTrader: (6)

I was thinking about sending it back to Nitro Daves to get reassembled and flowed. That doesn't stress the crank when you run smaller jets in a few cylinders?

JL ws-6

iTrader: (50)

No, crank won't care, it will care alot more if those 3 cyl's are detonating.

TurboAv

iTrader: (6)

I've heard about 7 and 8 before. You are the first I've read say cylinder 6 also. What's the basis behind those three?

JL ws-6

iTrader: (50)

factory intake gets more air to the back 3 ports in the intake, back of the motor also tends to run hotter then the front but that has to do with the cooling system I think.

Alot of people find that it's #7, but when you start pushing things, #8, #6 and #5 also will become an issue.

It's mainly due to intake design. You have an opening at one end, a plenum that's the length of the motor and ports all along that plenum length. It lends itself to these issues.

Put a carb type intake on, and whamo, now you don't have the same issues (instead the corners run rich and the center cyl's are leaner) But, if the intake is ported right this won't be an issue.

Make sense?