[71 Ventura II]

Growing up we always felt it safe to run 100, 125, & 150 HP with the proper tune up and fuel on top of cast pistons. Now I'm older and hopefully wiser I've started to re-think all this...

Depending on which calculator used my engine is making +- 380-435 HP NA. Now, maybe you can run 150 HP shot on an engine making 250 HP but it makes sense to me my engine is a different animal.

How much nitrous could/would/should I run on my 400? There's a link to the basic combo albeit there have been valvetrain changes since then. But the TRW L3035F "Cast" 8 relief pistons and Factory rods w/Milodon bolts are the same. What do you think? Be honest! JD

[BVR421]

As an occasional buzz I wouldnt hesitate but spraying 4-5 times every weekend it would have a cumulative effect on my nerves LOL

[David Holmberg]

With a small shot, 150, it's more about the tune up. Detonation or running lean will kill 'em. But like BVR said, I wouldn't make it a habit.

[Brian Baker]

If you're already at 400-HP naturally aspirated, hitting cast pistons with a 150 shot is risky. Sure, we've all done it when we were younger, but that was with milder combo's making between 250-300 HP naturally aspirated.

[Elarson]

I have no direct experience with nitrous along with cast pistons. But here's something to ponder. We run a loose piston-to-wall clearance and wider ring gaps with nitrous because of the thermal expansion issues. Cast pistons are typically set up to run a fairly tight clearance. So one of the possibilities is that you could heat up the piston quick enough to lose all of your clearance.

Just a thought....
Eric

[71 Ventura II]

Hmmm, pondering continues.... LOL

1. A small shot of 100-125 HP might be my "Nerve" limit!
2. 550 HP may be pushing it too far. (400 NA + 150 nos)
3. The heat expansion is a real concern I hadn't considered.

I appreciate the responses to help in this decision. I will run "Good" fuel in the 104-110 octane range, go to a colder plug, and pull the appropriate timing to be safe. I feel pretty good about 100-125 for one Summer. My goal is to run in the upper 10 second range which will require chassis upgrades and safety items for the track.

This engine is "old" in terms of years but has relatively low miles and runs on it, which makes it hard for me to justify pulling it out for a new build. Then there's lack of funds right now, especially during the holidays, to do a build justice. At this point I wish I would have thrown the forged pistons in my 400 I sold last year.

At what ET/MPH is it required to have aftermarket axles? This is another "upgrade" I need to plan for. JD

[Region Warrior]

When i was young(late 70's) and didnt know any better, used a 150 shot on a known good stock 455 block with 70-RAIII heads/intake/cam all summer long.
Back then octane was cheap.
All was good on winter tear down.
BTY, seen more engines hurt running to rich vs lean.

[TIN TIGR]

the mix and distribution are what counts..100hp shouldnt hurt any american v-8 engine, period..if it does,you did it wrong..and if ya do it wrong, forged pistons wont help..so there..start at 100, and edge it up..elarson has a very valid point, and it's one that many people bypass and pay for in the end..

[TIN TIGR]

if the engine runs on pump gas now, tune for it..same with plugs..you should not need the artificial help, and the different fuels and plugs may fool you..

[69Goat1]

Beware as it may turn up like this one did on a "small shot".... FWIW it's not mine...

I hear driving over your crank builds character...

[71 Ventura II]

Originally Posted by Region Warrior

When i was young(late 70's) and didnt know any better, used a 150 shot on a known good stock 455 block with 70-RAIII heads/intake/cam all summer long.
Back then octane was cheap.
All was good on winter tear down.
BTY, seen more engines hurt running to rich vs lean.

Originally Posted by TIN TIGR

the mix and distribution are what counts..100hp shouldnt hurt any american v-8 engine, period..if it does,you did it wrong..and if ya do it wrong, forged pistons wont help..so there..start at 100, and edge it up..elarson has a very valid point, and it's one that many people bypass and pay for in the end..

Originally Posted by 69Goat1

Beware as it may turn up like this one did on a "small shot".... FWIW it's not mine...

I hear driving over your crank builds character...

Crap that block is TOAST! It sure makes me think about it even more and makes me more interested in getting it right. I hope to avoid running over the crank! Fingers crossed... I think that is Lances block... Good to see your still out there Johnny! Merry Christmas!

I calculated some estimated increases with the nitrous; I've decided the 4.30's are definitely coming out and the 3.70's going back in. If I were running 1/8th mile I'd keep the stiffer gear but in a full 1/4 mile it will definitely run out of rpm's. It's unclear if the combo will suffer or improve NA with the 3.70 gears but it may just be a sacrifice to make it run right with the nitrous.

Thanks to all for the valuable feedback! Merry Christmas! JD

[PONTIAC DUDE]

100/125hp is a no brainer and staying together.

Most cast piston combos that bit the dust might have been because.......................

Installed a plate withbig jets on a used engine with miles and most cast pistons will wear out ring lands qucker then a forged pistons.

Increasing the pill size while still using stock ring gaps.

Tight wall clearance for hp used.

Going over the what I call magic number of 175 hp and still maintain stock type combo settings.

Most also fail to realize that basic cam LSA and cast pistons will build cylinder pressure and then ya add nitrous.

With a properly built cast piston combo 200hp shouldn't raise a sweat.

[71 Ventura II]

Originally Posted by PONTIAC DUDE

100/125hp is a no brainer and staying together.

Most cast piston combos that bit the dust might have been because.......................

Installed a plate withbig jets on a used engine with miles and most cast pistons will wear out ring lands qucker then a forged pistons.

Increasing the pill size while still using stock ring gaps.

Tight wall clearance for hp used.

Going over the what I call magic number of 175 hp and still maintain stock type combo settings.

Most also fail to realize that basic cam LSA and cast pistons will build cylinder pressure and then ya add nitrous.

With a properly built cast piston combo 200hp shouldn't raise a sweat.

Thanks Ken, I'm going to use the old school "ICE" brand plate kit which was the forerunner to the BG nitrous kit. With the "Small" noids of this kit I doubt it would flow more than 150 HP pushing it to 175 HP would be a stretch. imho For my intention a good 150 shot would be plenty to get me in trouble. I'd probably get where I'm headed on a 100 shot depending how the heads handle it. On the cam timing I intentionally went with the ICL 108 over the ICL 106 suggested to see if it would help move the power out a tad and work better with the nitrous. I'm not sure but can't wait to see.

On the new engine being scienced out it will have the forged internals and the ring gaps to handle a little more nitrous if needed! LOL Thank You for the help! Merry Christmas and Happy New Year!!!! JD

[PONTIAC DUDE]

Having messed with non adjustable plates back in the day, wink, wink, stock holes, LOL......................
If the plate has no jets, you need to "pin" (size) the holes in the plate to see what size they are and can figure flow or HP from there.

You can also use mini drill bits to measure.

[62fatcat]

there is no reason to be runnig that low of a gear with a pontiac.
change the gears and run it the way it is. you might be surprised how much better it runs. a 4.30 gear with your hp level, you are defeating the torque of the pontiac engine.
we have never run quicker with a lower gear in the 1/8 mile. our cars run best in the 1/8mile when they are geared correctly for the 1/4 mile. just something to think about.
150 shot is fine as long as the tune up is correct as stated.

[Region Warrior]

I dont know fatbob? He's has a 400 with a 247/252 cam.
Maybe 3.73 or 3.90 with larger tires.

[BruceWilkie]

A friend put 100hp of N2o to his bone stock Omni 2.2 with individual fogger nozzles (200 hp if v8). Scary handling is all I can say. He Beat the snot out the thing. The motor never failed. The automatic transaxle had severe case wear(it wore thru). Initial tuning it burned up plugs real good. Had a lot of laughs intimidating others on the street. Who'd expect an omni to be able to do a burnout starting at 30 mph roll?

FWIW my son has a heavy 64 Bonneville Brougham 4 dr hdtp 389 305 hp (stock rating) presently has ported small valve 1970 #11 heads on it, modified 3 tubes off my old firebird, performer intake, a 600 Edelbrock with all the stock 64 AFB internals(except jets, 1.65 rockers Crower valve springs, a new silent type timing chain(iron gear). Everything else is as delivered in 1964. Original pistons and rings, minimal wear and taper in the bores, very good oil pressure, he decided the head swap was good enough. (it doesnt use oil and it runs ok on 91 or better octane he usually uses 93.) He has a NOS adjustable plate kit. He started at the low hp setting(100 iirc) hurt a few spark plugs and learned as he went just what his car wanted for timing curve etc. His NA tune is very near stock jetting and vacuum advance(he has an HEI with adjustable vac canister) covers the economy/cruise side. His self imposed redline is 5k but rarely manually shifts.(stock column shifter) The superhydramatic shifts on its own just fine at about 4800. He eventually stepped up to 150 level and so far hasnt had any issues since resolving the burning spark plug strap issue(went to slightly richer jetting on the secondaries). Spark plugs are Autolite 85's gapped at .035. Its held together so far all with completely stock shortblock 5 years now. Probably no more than 100 hits though and probably half of those 1/8 mile or less. With 235/70 15 regular radials(Walmart?) he has managed a best of 1.92 60ft 13.21 101 mph in that yacht.(the "ricers" dont like him) We think there is high 12's in the car if he gets some sticky tires on it. The old superhydramatic seems unphased so far. He may try it with a 455 he's building.

Detonation and high combustion temps are the biggest killers of cast pistons. Like cast rods rpm will eventually be an issue with them as well.(though on a Pontiac stock block something else will probably let loose first.) Forged pistons are certainly more forgiving.

FWIW tried to break a stock piston out of a rusted up old Pontiac 400. It took a heck of a beating before it broke. An equally rusted Ford I did the same thing but the piston broke by the 3rd whack using the same hammer and steel bar.

[71 Ventura II]

I really appreciate all the feedback!

Ken, my "ICE" brand kit is adjustable! lol I have to order some more jets to get the proper stagger for a 100 hit though. We ran it on my neighbors 377 SBC with a very FAT 150 shot resulting in a .83 ET drop and gained 9+ MPH. The bottle pressure on that run was only +- 600 lbs.

On the "Low" gear theory I believe it holds true more so when dealing with 455 or larger engines not so much with the 400's. As an example my car with the 400 dropped .391 in the 1/4 mile by swapping from the 3.70's to the 4.30 gears. IIRC I have tested 5 cams, 2 intakes, 3 converters, 4 carbs, 2 ignitions, and 3 sets of tires to get the car to run 11 seconds. I feel I have an abundance of information through trial/error to pull from. LOL
NOW, with the addition of the nitrous it is definitely going to be over geared! I will swap my 4.30's out to the 3.70's for the nitrous, but will do some NA runs to see how it responds. If I was over geared the car should go faster, following the torque logic, but if it slows down then it was the opposite. I can't wait for Spring!

Just to clarify, I had to pull the Crower #60311 solid cam out from 4 lobes scuffing badly (Best ET/MPH with it was 12.51 @107 shifting at 6500 rpm.). I've been running the Comp XE284 cam for a while (Originally it got me down to 12.24 shifting at 5600 then with the new fuel system got the 11.95 shifting at 6000). They won't let us update the combo thread anymore so I added my current combo to my signiture.

Bruce, your information follows my logic about the horse power concerns. What I mean is, your sons car has +-305 HP plus a 150 HP shot showing maybe an optimistic 455 HP net. My engine is pushing close to or more than 400 HP NA! Now add the 150 HP on top of those cast pistons we could be looking at +- 500-550 HP. Is it safe to "think" the cast pistons will handle 500+ HP safely as long as the tune up is good? My pistons are TRW brand not stock with a weird part number #L3035F, but they are definitely cast not forged. I mean I can see this experiment going high 10's so I'd like to be prepared... JD

[62fatcat]

gears!

[71 Ventura II]

Originally Posted by 62fatcat

gears!

I started with a set of 2.56 gears but sheared the teeth off the pinion before ever making it to the track! I ran the 3.70's w/28" tires for a long time before trying more gear. In reality the 4.30's with a 28" tire was too much gear because the car picked up when I switched to the 29.5" bias ply slicks. The 4.30/29.5" combo proved a good combo for both 60' time and getting close to my shift point as I crossed the finish line.

With the added power of the nitrous it should run very strong with the 3.70's! JD