How Much Nitrous Can The Stock Pistons Handle?

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Ant

Ant

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Possibly in the future I might want to experiment with power adders, like nitrous. I have a 1972 or 73 318 LA which is now a 323 with replacement cast pistons, a stock crank, stock rods and moly rings gapped within spec, but more towards the higher side (I forgot the numbers). The recommended safe shot from Nitrous Express is 100HP, which they told me over the phone years ago. But how much further can these cast pistons for the small block Mopars be pushed before they give up? And with addressing the ring gaps too?
 
I tried and ran one of the old Super Shops NOS systems way back in the late 70s early 80s. They were small.
Did so for short time. Did so at the starting level.
Gave -Sold it to a friend in a deal and he pushed it to the limits.
His power glide in 1st one night was reaching shift point (about what a 3 speed shift point is for 2nd gear ) this is when his stock bottom end gave up the ghost.
It was stock short block, Cam, Intake-Carb and headers.
Pushed all stock short block and you will find the flaws.
Remember thus is when you could still grab good stock old low mile small blocks at the junk yard
Same as getting a 3rd gen hemi now.
 
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You kinda answered your own question with the ring gaps.

A lot has been learned since nitrous has been popular on the street. Sadly why push a good running STOCK 318 past its limits when you can go get one - build how you see fit and run all the NOS you want. I feel if you want to experiment on a stock engine, you’re going to get stock results…. Psst, psst and then BOOM!
 
Ant said:
Possibly in the future I might want to experiment with power adders, like nitrous. I have a 1972 or 73 318 LA which is now a 323 with replacement cast pistons, a stock crank, stock rods and moly rings gapped within spec, but more towards the higher side (I forgot the numbers). The recommended safe shot from Nitrous Express is 100HP, which they told me over the phone years ago. But how much further can these cast pistons for the small block Mopars be pushed before they give up? And with addressing the ring gaps too?
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I have about the same combo but in a 360; stock crank, rods and pistons; with hastings rings gapped to their 250+ shot spec. As long as you keep detonation away and don't butt ring gaps together I don't see why you couldn't safely run over 100 shot.
The head gaskets are a concern, but as long as you back the timing off enough and progress the nitrous into it slowly, they should live long enough to have some fun and learn a little bit.
Also, I am going to run e85 in mine, just as a little safety net due to the cast pistons. Pump gas on nitrous isn't the best idea for stock engines.
 
Started with a super power shot nos system. Late 70s. 75 hp 125 hp jets. Engine no problems. Drive train needs attention,ujoints .etc .I used it only in 2 and 3rd gear, traction limited.Car was blast to drive. I run a cheater system on a nitros built 340 stroker now.14 years ,nitros converter, drag radials. Car is a blast to drive.
 
I’m guessing no one that has replied has personally found the limits of a stock engine with nitrous. Here’s the deal, if you can tune it AND it’s not octane limited, you can cram a bunch of nitrous through it before having a mechanical part failure. I watched a dyno session at westech where Richard Holdener put 300 hp worth of nitrous through a junkyard 305 Chevy.
 
I would trust factory stock Mopar cast pistons more than who-knows cast replacements.
If your nitrous (and engine) tune is good, maybe 150 (just not at the starting line. I'd use in second and third only). A hundred shot would be safer.
If the tune ain't great, a fifty shot can hurt stuff.
 
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4833A951-F9F6-4669-B138-B8396C652EAD.jpeg
Hmm, a 200 shot of N2O on a stock 1983 bottom end running 5PSI of boost at over 7000RPM…….
 
TT5.9mag said:
I’m guessing no one that has replied has personally found the limits of a stock engine with nitrous. Here’s the deal, if you can tune it AND it’s not octane limited, you can cram a bunch of nitrous through it before having a mechanical part failure. I watched a dyno session at westech where Richard Holdener put 300 hp worth of nitrous through a junkyard 305 Chevy.
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Opened the ring gap tho didn't he? What would you dare with (potentially garbage) replacement cast pistons and a normal unopened ring gap? 150?
 
D6D08AA4-1B8A-4647-BA32-5D633500BE7E.jpeg

Different engine, I found this in the pan of a MP crate 360CI short block after 10 years of abuse. Again running the same blower at 6PSI (smaller pulley) and a 150 shot. Hyper pistons skirts don’t exactly like 7000RPM’s. However the piston crowns were still intact…….And for those of you inquiring about how much nitrous can flow through a B&M 174 Blower before the rotors stall with a 6 rib belt is 150HP.
 
MiradaMegaCab said:
View attachment 1716434830
Different engine, I found this in the pan of a MP crate 360CI short block after 10 years of abuse. Again running the same blower at 6PSI (smaller pulley) and a 150 shot. Hyper pistons skirts don’t exactly like 7000RPM’s. However the piston crowns were still intact…….And for those of you inquiring about how much nitrous can flow through a B&M 174 Blower before the rotors stall with a 6 rib belt is 150HP.
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Was your car in one of the Mopar magazines about 20 + years ago ? I remember a Mirada with a mini blower in some kind of a streetcar shootout article.
 
33IMP said:
Opened the ring gap tho didn't he? What would you dare with (potentially garbage) replacement cast pistons and a normal unopened ring gap? 150?
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No he didn’t put ring gap in that one. There are a lot of variables to consider. In high school I put a 200 shot on a buddies cast piston 350 Chevy in a nova. Ran for years. I’ve personally only run 100 shot on a stock bottom end but I’ve also never shot the moon tune on one. If you run a separate fuel system with race gas or e85 I’d bet you could stuff 250-300 on a stock bottom end. On pump gas probably less than that. lol
 

MiradaMegaCab said:
View attachment 1716434830
Different engine, I found this in the pan of a MP crate 360CI short block after 10 years of abuse. Again running the same blower at 6PSI (smaller pulley) and a 150 shot. Hyper pistons skirts don’t exactly like 7000RPM’s. However the piston crowns were still intact…….And for those of you inquiring about how much nitrous can flow through a B&M 174 Blower before the rotors stall with a 6 rib belt is 150HP.
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Boost+nitrous is one of the best things on earth. I commend you sir.
 
The one's that I like are the one's that are all throttle and no bottle.
 
MiradaMegaCab said:
:popcorn:
Head gaskets are the weak link on a SBM.
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More correct it's the 4 screws per cylinder than the gasket. That's what causes the gasket to fail. A close second is the cylinder wall casting thickness. LA means Light A. That's why its so important to have your block sonic checked before an overbore. All other engine components were engineered for stock use. Anytime you are pushing past 500 hp, you are looking for trouble. Power adder engines should use power adder designed parts and engine modifications. So in other words? Follow manufacturers recommendations and limit to 100hp of nitrous or less.
 
B83AEEC0-CDD2-469E-95C5-EB601B3E1718.jpeg

4 screws or 4 ARP studs aren’t enough for added cylinder pressure and or Head Lift. Like I said, head gaskets are the weakest link.
The OP should look into full groove main bearings to supply full time oiling to the rod bearings as well as a colder Non Projected Tip spark plug. I see no problem with a 150 shot and a good tune.
 
Meh, ran 200-250 shots on stock 440's for years. Tune up is EVERYTHING!

Run em, they will end up smoking themselves, go grab another motorhome engine, cast/forged crank whatever, rinse repeat. Would a forged piston engine be a better deal? Absolutely.

If you want something that will give it a kick and last, run a 100 shot on it and pull enough timing to keep it safe.
 
Dan the man said:
The one's that I like are the one's that are all throttle and no bottle.
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Fast is fast. I usually don't care how. Unless of course, if you are slower than you should be with the equipment you have. (Example from a few, or more than a few, years ago. A 70 Bee with a 6-71 blown 440, running low 12s. Embarrassing.)
 
33IMP said:
Fast is fast. I usually don't care how. Unless of course, if you are slower than you should be with the equipment you have. (Example from a few, or more than a few, years ago. A 70 Bee with a 6-71 blown 440, running low 12s)
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I used to get the bottle is cheating BS. I'd tell guys build the biggest baddest mill you can, and I'll beat you with your own stuff adding a bottle to it!

I'd rather street drive around with a 450-500hp mill and a big shot on it than a 700hp non street friendly deal. We both have the same hp, just a different approach. Easier to hook 450-500 than that other thing when you can progressively feed in the juice!

Do it however you want, some like blonds, brunettes, redheads, does it really matter? Nope! Get yours however you like to go about it.
 
chisel said:
Started with a super power shot nos system. Late 70s. 75 hp 125 hp jets. Engine no problems. Drive train needs attention,ujoints .etc .I used it only in 2 and 3rd gear, traction limited.Car was blast to drive. I run a cheater system on a nitros built 340 stroker now.14 years ,nitros converter, drag radials. Car is a blast to drive.
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That's what I did second and third.
I did have plans to do the same on the 422six
Center carb gets a spacer as gets a shot under full power. So gets a laugh front and back.
nos3_17873760.jpg
 
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