It came from a 77 impala so it was cast. After the 283 very very few sbc's came with a forged crank.

On top of that I would be concerned with the more rigid forging cracking under the severe torque spikes you see with nitrous. Castings are much more flexable and when manufactured and prepped right they are very resiliant even if they flex like mad.

At 300 even forged pistons will shatter crack or melt if one of the listed faults occour so if a solenoid fails or a piece of debris clogs a jet I'd rather not lose $5-600 worth of pistons ontop of tha other parts and work lost.

If I had the motor appart and wanted to hit it with N2O I'd look at affordable rods since in this case I think they are the weak point. LT-1 or better in my opinion, and forged would be good here since they should bend when they fail instead of break. Sparing the rest of your motor.



That too. One thing that has me holding back is the cost of running a BIG N2O system.

The basic wet kits start at $500 and are a great bargain but even modded to flow 300+ HP worth of gas and fuel they fall short when it comes to distribution and control.

You can easily have 2-3 grand in a port system with a controller and other essentials and it would be entirely impractical to use on the street. Doing so invites any number of variables that can cause you to eat a motor no matter how solid it's built.



There are 2 other factors to think about also.

#1 at 600-650 CHP you are coming up quick on the limits of the factory block casting.

High nickel blocks are a bit stronger and can be found still but if you spend several grand dropping forged everything in that factory case and it still splits your almost certainly out all that money if it lets go at full tilt.

#2 In the story they rebuilt the motor and turned up the N2O and right away ran into another limiter. The engine wouldnt accept any more N2O or fuel and that resulted in a cloud of gas and nitrous suspended above the carb.

If you hit this limitation in the car and it's all trapped under the hood imagine what a simple intake backfire would cause.

You will need to invest in a completely new set of heads and likely an intake, headers, valve train, cam etc.

I would think that the street oriented heads like vortec's and aftermarket production style heads would be a marginal advance if any at all.


So you can easily spend $10,000 on everything but the short block just to get to the point where the stock short block is completely incapable of staying together.

What this means to me is other than great N/A power production or endurance racing and barring any catastrophic failure the stock L98 in my bird could serve me as far as my ambitions will carry it. I dont plan on dropping money on parts that'll never be used to the limit.

 

If the engine relatively fresh, built with good parts, good attention to detail upon assembly and the RPM's are kept below 6k, I feel that 125-150 HP at the crank is a reasonable level for a stock bottom end 350. It's not "how much will it take before she blows" but how much is a "sane" level for a basically stock motor that is expected to survive many runs and be reliable.

My daily driver L98 (350) has all stock bottom end with the exception of Hyperutectic (?) cast pistons and good moly rings. Stock rods and bolts/cast crank. I have ran 200 RWHP shot which is probably around 250 at the crank with no issues. Total timing was 26ish and colder plugs. Now i run 1/8 mi so it's only for 7 or so seconds at a time and I shift at about 5800, but it works. This level does make me a bit nervous because I feel like I'm pushing the limit for a stock bottom end. Remember, we're talking about well over 500 RWHP on a stock motor! Honestly I backed her down to a 125 shot (150 at the crank) and feel alot better!

 

What jets were you running for the 200 rwhp shot? Also what kit do you have? You mention 7 seconds so you were running pretty quick that's for sure.

 

I'd have to check the jet sizes to be sure. It seems like 200 is 73/49 for EFI. I'm running a Cold Fusion kit and really think it's a quality setup. They rate their kits RWHP. Last time out I ran 7.69 with the 125 jets. I did some changes to my suspension so I backed down to 125 last time out. Probably step it back up to 200 hp next time to see what she'll do. The 200 level is big on these cars. Feels totally different than NA!

 

Car Craft did this same test about 5 or 6 years ago. Same results: takes a 350 jet run just fine. They then tore it down to inspect it and it seemed good to go.

A stock SBC seems to be able to take a 300 shot. For how long is the real question....

 

What else is done to get to that 500whp mark? full bolt ons is close to 240-250whp and another 200 gets you 440-450whp total. You have a cam?

7.69 1/8 with a 125 shot is close to 12 flats/11.90's in 1/4. Thats closer to 360whp i'd say, meaning your close to 240whp which sounds about right for a healthy L98 with stock/heads cam with bolt ons.
Another 75whp will push you darn close to 11 flats in 1/4 and maybe 6.x in the 1/8

Either way, thats good healthy load of spray on stock bottom end. Glad to see its working

 

I love all the info and opinions I've gotten from starting this thread . Keep it coming please ?

 

You're about right on. Dynoed at 240 prior to HSR, fully ported 083's (stock l98) chip programming and a freshen up. So maybe I'm closer to 250-275 NA. Cam specs are 212/218 w/1.6 rr, 9.7 cr, headers, exhaust etc. I may have been a bit optimistic with my 300 whp estimate. Still 450+ at the wheels is a great ride in a 3gen with 3.70 gears and full traction!

BTW 7.69 @ 92 in the 1/8th and there's still more in it besides stepping up the juice. I get awesome traction with BFG drags at the all concrete strip where I run. However, I'm still getting the launch down and have been a bit conservitive. 1.74 60' is the best I've been able to get so far off the line.

And yes, thats a load on a stock l98 bottom end!

 

Keep the posts coming .

 

I'm closer to you than I thought, I did a 7.71 in the 1/8th on a bone stock long block with 1.6 roller rockers, ported stock TPI, ET Street Radials and the .073 jetting BEFORE I went with the big solenoids. My car is on one heck of a diet though, it weighs 3200 without me in it and gas in the tank. I think it will get faster whenever I put a better posi unit in, my 9 bolt is DONE FOR, it was howling all last year after I ran it on some 8.5in M&H slicks.

 

Got to be hard to launch on the nitrous witha stick. Get that 60 down in the high 1.5x range and you'll be deep 7's in the 1/8

 

For sure! Traction isn't the problem- or at least I haven't given it enough off the line to blow the tires out! It's just getting that right amount of power down consistantly. Last time out was the first with the new TKO and 3.70 rear gear. Still getting it down. The stock 9 bolt is fresh with studs and girdle. I'm a bit concerned on how much it'll take off the line.

The nitrous is triggered by a limit switch on the TB. I try to give it 99% off the line with out hitting the switch. I'm gonna data log next time to see exactly what RPM the nitrous is kicking in- but it's pretty much off the line.

I certianly hope to hit the 1.50's with a street friendly suspension setup. This is still a daily driver...

But back to the subject. The car seems to really like the 200 hp level and as long as EVERYTHING is right- it doesn't seem to be a problem. But I do have datalogging/chip burning capabilities and can see if I'm getting any knock or lean out before it would be detectable otherwise. I am more comfortable at the 125-150 range. But isn't that really the problem? If you CAN go faster... Why not!

 

If you CAN go faster... Why not!
I like your way of thinking .

 

If you can keep it from detonating, you can spray as much as you want. I know guys who spayed 300 on a stock bottom and and it lasted for a full season because he knew what he was doing with the tune. There is no margin for error on a cast piston, better to error on the side of caution. There is a point where the stock heads will just not flow anymore and a 100 shot differnce will really not make much of a difference.

 

Keep posting I like to hear from everyone .

 

Still want to hear opinions on this .

 

Only thing done to mine really has been the LCA brackets, boxing the stock arms and the Spohn torque arm and I cut a 1.42 60' on nitrous. It's usually doing 1.6X 60' foots on the motor but, it's an auto plus 4.56 gears with slicks. Still, nothing fancy at all about the suspension, don't even know how old the struts and shocks are

 

I had the GM 350HO crate motor in my old 84Z. Cast Pistons, nodular crank, vortec heads etc. I ran a 150 hit and occasionally 175 on it all weekend long with no problems. Put it on the dyno made 270rwhp 310rwtq N/A, 395rwhp 509rwtq with the 150 shot. Through a built 700r4, 2200stall, 3:73 in 10 bolt. Fastest I ever went was on the 150 hit 12.0x @ 116mph.

Anyway, I ran it on the street, **** I passed a semi on the way to vegas on the jug. Nitrous is safe if you tune for it and run a shot that isn't completely overboard for you build