The basics of my car are below. I have a nodular crank and shotpeened rods with ARP bolts. Would I be nuts to run a 125 or 150 shot on this?

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Black 89 IROC...Mods: 355, 10.5:1 comp, Big Solid Crower Cam, TFS heads, Victor Jr, Holley, and a 5 spd...12.72@ 116.9 with a 2.16 60ft time on BFG radial TA's

 

I'm using the smae stuff. I have some late-style GM forged rods and a 1 piece nodular crank that's all been balanced and the rods have been fitted with ARP wavelocs. The crank has chamfered oil holes and has been polished. The only non-GM rotating assembly parts I have are the TRW forged pistons. These parts are supposedly good up to around 6 grand and 500 HP as long as they're prepped correctly nad not constantly raced. They aren't designed as a HP part, but preform just the same. You should be OK. I have like 2 or 3 350 late model rotating assemblies in my garage for cheap build-ups. Parts are plentiful. polish the crank, magnaflux, polish beams perhaps, shotpeen rods, check them for straightness, heat-treat them. You'll be good to go. Make sure to balance. Look into prices though, sometimes it's cheaper to go with aftermarket rods due to machinework.

As far as pistons go, I don't think hyperutectics are the way to go, they're brittle. I considered the same, and not 2 weeks later I saw someone grenade a 355 when he hit it with nitrous. Cracked the piston in half and ate up the cylinder. Cast are somewhat durable like hyperutectics, but not as brittle. Forged are best for boost. Hyperutectics are best for N/A applications only. I agree with others who recommended this to me, in a nitrous or boost application, use cast before hyperutectics, forged are best.



[This message has been edited by dhirocz (edited May 12, 2001).]

 

Me personally, I don't think hyperutectic pistons belong even in a Geo metro. With nitrous I would go with forged pistons. A friend of mine had hyper. pistons in his supercharged mustang, putting out 7 psi he broke three of the into many pieces. All power adders basically do the same thing, add more cylinder pressure.

 

the key is to keep the motor out of detonation. i've seen hyperutectics take some crazy abuse. the motors were using almost pure 110,118 race fuels. 125-150 shot of oxide is fairly conservative. just make sure you get nothing lower than 110 octane(118 preferably). try and run it as pure as you can. don't forget colder plugs and less timing. if your already going 116mph you should be able to reach 130+. that's damn fast.

 

I also had this dilema. Go with Hyper parts or pay more for the proper forged parts. In the end I decided that the best thing to do was to pick up the hyper parts and, throw them away. Then I decided that I would go out and buy forged bits so that I wouldn't have to worry about anything breaking. Think of how embarassing it would be to be racing someone and, oh no, you smash a piston. He's just going to stop, laugh and then drive off and bring along some friends so that they can laugh. I know that's what I would do.

Scrap the hyper and just pay the extra for the forged. You wont regret it.

Robert

 

Scrap the hyper and just pay the extra for the forged. You wont regret it.
Robert

Dont think I could have said that better! DONT Squeeze on the Hyper's. Get forged.

 

I cant believe how many people give advice and drive 15 second cars. Its a old wives tale about hypereutectic pistons being brittle, they were when they first started being used. How many lt1 cars have you seen with blowers or spray? Any mustrag after 90 has them!! There are going to be some bad things that happen to any type of piston. Due to bd prep work or poor manufacturing.Ive been spraying hypers every weekend for 3 years now on a 175 shot with 93 octane and not even a slight sign of problems. Piston manufacturing has come a long way. Yes forged is stronger and I could afford forged. However hypers let you run tighter clearances which yields more power. If machining is correct and you stay out of detonation then you wont have a problem running 150 shot. Open up the top ring gap to .018-.022 inch.

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87z 383,afr 190's, comp hyd roller(242/248-.540/.562,114 sep),Ported and polished mini ram, 30lb inj, 3.42 gears, tremec 5spd, , 1,3/4" slp headers, speed pro bank to bank-wb02.

[This message has been edited by 87Z-ya (edited May 21, 2001).]

 

Start with a conservative shot like 75 maybe. Also polish those exhaust ports to a mirror finish and run either a nitrous cam or 1.6 rockers on exhaust only along with a good exhaust. n2o can get into the engine just fine but getting it out is harder. And like said tighter plug gaps (.030-.035) and colder plugs. I might even go as far as getting a timing retard when the shot comes in that way you can run enough timing around town then retard it 10 degrees when the shot hits.