I have a stock 90 HO block that current bored .030.

What is the theoretical limit of HP the block will take?

I know Wendy made 577 at the wheels on hers with a turbo. To the best of my knowledge,.. that would put a block on serious borrowed time. But since a turbo doesnt initially shock the block with that much power like say blasting it with a 300 shot of nitrous would,.. or a blower at 20 lbs of boost. A turbo motor should be able to hold more HP together,.. or is that just a myth?

Is it the RPM's or the initial torque shock to the block that splits them down the middle?

I was always under the impression that 600 at the crank,.. or 500 at the wheels was the limit.

I just picked up a NOS Cheater kit and want to use it. Naturally I want to make as much HP as I can,.. but I dont want to destroy the block either. How much would you guys spray on a 306 motor? Would a 200 shot be too much?

Actually I think I better explain in detail what I have,.. then you guys can give me a better assessment.

Its a stock 1990 HO block. bored .030, decked .020.
Stock crank and rods, shot peened.
Pistons are KB Silvolite series with a 20cc dome.
Compression should be in the 11:1 - 12:1 range. I do not know for sure or how to find out.
Heads are AFR 185 #1387 heads. They originally had 62cc chamber but have been milled and are now 59cc. They have nitrous exhaust ports.
cam is 'supposed' to be a Comp Cams NX274HR cam. .555/.570 with 224.236 duration. Website advertises it as a nitrous/blower cam with good NA power to match. Its rated 2500 - 6200 rpm. Crane 1.6 roller rocker that Shaun says are bad ass rockers. Heads have titanium retainers, valves are supposed to be the sodium filled ones with matching springs for the cam but with stock hydraulic roller lifters.
Intake is a Vic jr
Carb will be a Holley 650 HP
and will have a MSD billet distributor and MSD digital 6+ box by the time I get this all together.

Obviously with a stock crank, rods and hydraulic lifters I'm limited on the RPMs,.. and the cam is only rated to 6200 anyway.

The motor is making good power. I went 12.70@110. The mph is there,.. the ET's will come down as soon as I fix the rear and lighten up the car. There is also 20 - 40 more HP to be had with a better exhaust, the Digital 6 box and the HP carb. Judging from the MPH and a race weight of approx 3600 - 3700 lbs. The math indicates the motor is making at least 360 to the wheels right now. How accurate that is I am not too sure. But its making at least 340 for sure. With a 200 shot,.. that should put me close to 500 at the wheels. Will the block handle this,.. or should I be safe and stick with a 125 - 150 shot?

Thanks guys,

Hurst

 

On stock compression you MAY get away with a 200 shot for a while depending on tune. I've asked around to several guys that are experienced nitrous guys same question. I was told with the compression I'll be runnning 11.5- 12.0 ish they wouldnt put more than a 150 on a stock roller block because you're already running high cylinder pressure and that a 150 may be pushing it.

 

If you are on the stock bottom end minus the pistons of course I would spray until you find out what it will take. You can always throw another block in there.

 

When the block splits,.. how much damage does it usually cause?

I have a spare unmolested 1991 motor. As long as the block doesnt take out my heads,.. I wouldnt mind finding out exactly what the limit will be and then just swap the heads over to the other motor and set that one up similar to this one,.. except then I will know what the limit is.

Hurst

 

john says horsepower is horsepower, it doesn't matter how it gets there. turbos are easier during the first 60 feet and then it unleashes a shitload of boost and then it's no different from nitrous or blower boost. typically when a block splits, it is at the peak of the horsepower output, wherever that might be RPM-wise.

to john, the compression isn't as important as the overall cylinder pressure. blowers and turbos deliver just as much cylinder pressure as nitrous.

if john was you, he would start at 150 and see how the car reacts to it. john's chevy II was 14:1 with a 250 shot. each motor reacts differently.

 

no way to tell. could be as little as an oil leak with low oil pressure or it could be you getting out of your car upside down. if the bottom end comes apart and a connecting rod breaks, it could send the piston up into the head.

 

Thanks Wendy.

I think thats what I will do. Start with a 125,.. then work my way up until I feel uncomfortable or it blows.

Was just curious as to what others had to say.
So the adage is true,.. 500 at the wheels is pretty much the limit.

I know you made 577 on yours,.. but I'm going to hit it off the line with what ever shot I spray. I dont have the money to setup a progressive shot,.. and personally I dont think it will really matter with a little 306 anyway.

Hurst

 

I can tell you its all in the tune!! Steve B a member on here had a stock short block in his car launching off the tranny brake with a 225 shot. I think the thing your going to have to worry about it the Keith Black (hypereutectic) pistons that are in that motor.

 

lol thanks for pointing that out shaun! john didn't realize that they were keith black pistons. heheheh he says forget everything he just said. DON'T SPRAY IT AT ALL!!!! lol

 

Very true,.. and though not exactly nitrous friendly,.. they should be fine up to 480 - 500hp level,.. no?

Come tax time I'll have roughly $2500 to play with I have so many idea's in my head,.. its like having ADD. As soon as one idea comes to light,.. I think oh yeah,.. I could try that,.. then,.. oh,.. wait,.. that sounds good too.

I'm thinking about ditching the 347 stroker idea and should just pick up a 351, put my heads on that motor and spray the 200 shot on it. That should be a safer way to go.

I'm sure come spring time I'll post up searching for ideas and suggestions.

Thanks guys.

Hurst