Cast Crank Strength

[Dusterb318]

How much spray can a balanced cast crank handle. I'm trying to decide if I wanna go to a stroker motor or build another 318ci motor that takes a about a 200 - 300hp shot of nitrous. Basically I'd like to see the 10's out of my street/strip Duster. I'm running 11.85's now with a 100shot and I figure a 200hot should get me into the 10.90's along with better compression, head porting and a roller cam. I wanna keep the motor on pump premuim but I don't mind mixing in some race gas for the track for nitrous use. I think if I get some H-beam rods and some good pistons; have the rotating assembly balanced the cast crank should be fine. I know of guys running more power on the cast stroker cranks. Also anyone have any experience with the KB pistons and spraying over 150 shot on them? I know you have to set the ring end gap to their specs. I have always been told a 100-125 shot was about max with them. I'm leaning towards the nitrous motor because I can make it have great street manners and run on pump gas, cost less money cause I already have some of the stuff and I wouldn't need any more block machining and I can up-grade stuff in steps. Would I even need H-beam rods? They would probably be lighter that a set of stockers that were re-worked.

 

[340mopar]

If you go faster than 11.49 you will need a roll bar and when you get to 10.99 then comes the aftermarket axles, well at least at a NHRA track.
I would be more worried about the KB pistons than the cast crank with a 200hp+ nitrous. A hyperuetectic piston is still a cast piston, just a stronger version.
That .90 of a second will probably end up costing you just in safety equipment alone $750. For what just so you can say your car runs 10's? There is no shame in running 11.85 and is still a very fast street car. My drag car runs low 11's and for awhile was trying to get it into the 10's and decided to leave it were it is because of the added expense of the axles alone. It is very consistent and that is the ultimate name of the game in racing. If you want bragging rights just exaggerate a little, everyone else does.

 

[dusterdood]

I'd like to know the same thing. Anyone have luck running more than 100 shot on the hyper pistons? The 4" crank, balancing, and special pistons would make it more expensive than getting a 360 short block, and getting forged pistons. I'd think the extra 50 cubes isn't worth the extra $. Maybe go 360, and then spend the extra on the upgraded axles?
I've got a stock 318 ('86) in my street duster, and I used a few bottles full and the only thing I could hurt was the 999 tranny. I'm seriously considering swapping my trucks 360 in, and it was built with hypereutectic pistons. Or maybe leaving it alone, and building a 408 out of my spare 360 block. How much cheaper are the hypers in comparison to the $500+ forged stroker pistons?

 

[Dusterb318]

$250 for a set of hyper pistons. I e-mailed KB's tech dept and asked them how much of a shot they can take. I am not going to go to a 360 block. I want to to keep the 318 block.....that and I have 4 of them so I don't need to go buying another engine. I am not going to exaggerate that is lying and it's not right....only chevy, ford and import guys need to do that. As far as safety equipment I have no problem doing that...I already ahve the 5-point harnesses and the roll cage should be going in this winter. Upgrades axels are on the way.....going with Yukons. I already have the longer studs so I am NHRA compliant.....safety stuff and driveline strength go hand in hand and I'm not going to cheap out on that stuff that just being stupid.

 

[BJR Racing]

We have shot a 350 shot on KB hyperutectic's and they are still running. Have them in a 6.0 headsup engine. Since then we upped the power and don't use that much anymore.

 

[Dusterb318]

I think they can handle the 200 shot.....I'll just need to get the rotating assembly balanced and make sure the tune doesn't go lean and it should be okay. I'm also leaning at going to a 2-stage set-up on the nitrous.

 

[dodge freak]

Just make sure your fuel lines, pick up are 1/2 inch and have a good fuel pump. Thats how engines go lean the fuel system can't keep up. The best racing gas won't help if there is not enough of it flowing.You might be allright for awhile, just don't be surprise if its does go kboom one day. At least 318 blocks are dirt cheap.

 

[Dusterb318]

Already done....-8an supply and return. I'm also going to go to a dedicated fuel pump for the nitrous system when I up the shot to a 200hp level.

 

[dusterdood]

The dedicated pump is smart. I'm suprised the hypers are so much cheaper than the forged ones. The forged ones shouldn't be over $500 like they are. IMO.

 

[dodge freak]

Yeah but forged are better, maybe much better. They can take much more abuse without cracking up. But even still with those the block could give out. Which is why some racers spend $2000 for the R block

 

[Dusterb318]

I just got my e-mail back from KB's tech guys and they say as long as the igniton is retarded and I have plenty of fuel the pistons will be fine. I also have to make sure I use their ring end gap calc numbers too. He tols me to start out with the mix rich and lean it out which is what I do anyway when tuning on nitrous.

 

[sheets55]

I just got my e-mail back from KB's tech guys and they say as long as the igniton is retarded and I have plenty of fuel the pistons will be fine. I also have to make sure I use their ring end gap calc numbers too. He tols me to start out with the mix rich and lean it out which is what I do anyway when tuning on nitrous.

best of luck keep us posted :thumbup:

 

[moper]

I wouldnt use them over 150hp. It's more than detonation when you start going with a hevier shot. The piston itself is under much more stress. Think of it like this. Detonation is a hammer blow. Hard, and very abrupt. It creates a lot of stress over a very short amount of time. But the forces from pressure from the burn and from the directional changes all try to deform and break the piston too. The materials in a forged piston are very strong, and can take the stress by deforming slightly or "flexing". Cast pistons can also do this, but to a lessor extent. Hypereutectics cant, because the material is like tool steel. It's strong and light, but brittle. So instead of flexing, they fracture. There are limits on what the cheaper stuff can do. In addition, you are talking about adding stress to the block, the main caps, and the crank itself. Cast Mopar cranks are good, but the reason the 4" ones can take so much is they were designed from the get go to be very strong. They have large radii and are thick where they need to be. A factory 318 crank is light, strong, and will far exceed the stock hp levels. But to ask it to go to 500+hp under nitrous IMO is a recipe for a short service life. They will crack. You may not notice until the whole thing comes apart. Also, being that nitrous is a sudden power increase (and decrease) the block and mains are under a lot of stress. The mains at minimum should be studded, and the weights of rods and pistons should be kept as light as possible. Now, all that being said, you have got a nice foundation for a safe car with the right stuff to support bigger NOS use. So if you have 4 of them, and can sacrifice one, perhaps doing a ring and bearing job on one and them gassing it until it expires would be fun AND educational..lol. The Neon 2.0SOHC took over 250hpo of gas before it lost a head gasket with a hasty tossed on Cheater setup. So why not? I would either decide to "do it right" or dont spend more than a minimum and go have some fun with it.