OBDIICamaro

Ok I have decided that I am going to go all out on my 4 bolt for the 383 and it will take time and alot of cash. I was just going to take my dual nozzle kit off and put the direct port on and shoot 200, but a buddy has convinced me to do a piston swap and shoot more. So I am going to pull the engine that is in my car now and do a quick rebuild, .030 over and some ARP Rod Bolts. What compression will this TRW Forged piston give me if my heads have been decked .030 already and I plan on trying to deck the block about .010 or .020 whatever it will need. Of course I have the 54cc head.

2.4cc Dome Top, Press Fit or Floating Pin. Compression Ratios:

64cc Heads: 10.5:1
68cc Heads: 10.02:1
72cc Heads: 9.59:1
76cc Heads: 9.19:1


Also if we are putting this motor together just for temporary use for my fogger to squirt a 250+ shot in it, do you think it is woth it to spend the other 200 odd dollars to get the assembly balanced? How critical is would this be with that big of a shot of nitrous.
Yes just to let you know it will have the stock crank also, this motor will basically be a temp motor used for racing if I can see a month and a half of action out of it, I will figure it will be well worth it since I will have less then 400 invested.

Also those who say 250+, I currently am spraying a 200 shot home made dual nozzle setup through the complete stock bottom end. I have had it on there the whole summer.

Any info would be appreciated.

jonaddis84

If youre not worried about the powerplant having a meltdown, why not just spray that on the current configuration? Take a little more timing out and have at it. If you arent worried about wasting $400 then why not waste $0?

As for the compression ratio. Those numbers given dont do any good. There is a compression ratio calculator at the top of advanced tech. You need to know the exact distance the piston is in the hole, not the deck height.

If you were to base it on stock though, 9.025 is what it "should" be. Most all crank/rod/piston configurations end up at 9" so your piston would be down .025, that is the deck height you will plug in.

The parameters for the calc are listed, based on .039 head gasket

Input Parameters Are the Following:
Cylinder head Volume (CC) = 54.00
Piston Top Volume (CC) = -2.40
Cylinder Bore (Inches) = 4.0
Cylinder Stroke (Inches) = 3.48
Deck Height (Inches) = 0.025
Head Gasket Thickness (Inches) = 0.039
Computation Results:
Computed Compression Ratio is 12.2 to 1

When you say that you have 54cc head CC chambers and the heads have been decked .030, not sure which to believe or whatever. Stock chambers are supposed to be 58cc, but most are around 56 or 57 from what I hear. So maybe if they are decked .03 then you end up at 54cc, not sure. But you only need to know one or the other.

If you want even more compression, zero deck the block, but you might not want to do that if you plan on doing another rebuild, incase it would need to be decked again, might be dangerous

OldSStroker

As I understand it, you want to rebuild a stock 2 bolt 350 (LT1?) with forged pistons to get a very high CR, stock rods with APR bolts and do a 250 shot. Right? This will cost what? That's money you can't spend on your 383, and, IMO, it will be a very short term investment.

I agree with jonaddis. As long as you are building a disposable engine anyway, why not just start increasing the shot on the engine you have without the LBF (vulgar acronym) rebuild and see where it gives up? You'll be money ahead, and some of us could study the failed parts to learn a little more. You might also find the weak point in the driveline.

No flame intended, but if he were my buddy, I wouldn't be taking his advice on this unless he was footing the bills.

OBDIICamaro

I dont think the stock pistons would last long and then come april or may when I find this out, I am out a car for a month of racing season. I know the car with the fogger and the same 200 shot would go a 10.30-.40 I we figure if I throw some forged pistons in there, and up the anty to 250-300 I could hit the single digits.

As for more compression, with those pistons, that wouldnt be that much more compression then stock if you look at the ratings with the other cc heads am I right?

Also I made an error on saying it was on saying a 54cc head

jonaddis84

Im confused. You know you figure it will run 10.30? How do you know/figure? Forged pistons IMO arent gonna help you out much spraying that much, youd be taking a chance spraying 300 on an Eagle forged 383 with srp pistons. Just an example with cheaper forged stuff. Id rather be out a month of a car than $400 IMO, but if you have the cash go for it, wont be as cheap as you think though, unless you get machining for free.

IE youll want another good hone probably, head deck $~100, blcok deck same. pistons, head gaskets, ARP good rod bolts are ~$100.

Not worth it still IMO. Just spray it and find out, do it safely and you might not have any problems, get a goodass tune in there and retard a little more than normal, maybe a colder plug as well. Do it and send the broken parts out to guys like Oldss, or Bret to find out where and how a high spray stock shorty goes

OBDIICamaro

I would be using a TRW Forged Piston which we have awsome luck with it.

As for running a 10.30, I am running a 10.70 now with a dual nozzle 200 shot, so I figure the fogger is more efficent would have to drop me down some, not the pistons. Once I put the pistons in, I figure I could spray more 250+ and creep into the 9s.

Yes I have all access to free maching besides decking the block which I get charged 50 bucks.

jonaddis84

Go for it then. One thing you might consider is throwing rods in there as well, that would be the one other thing I wouldnt trust besides the caps. If you are building a 383, just buy some kickass 5.7 rods and throw them in as well, then just use them for the 383. Or even Eagle Hbeams can be had for $329, then sell them when you are done with them. Just a thought. As for the Comp ratio...you good on that now?

Edit #1: Oh, and when you said these wont be much more compression than stock, how do you figure. When they list them for different head CCs, they arent different pistons, just giving you an idea what the static ratio will be with those CCs. All you need to know to figure your ratio is following.

Deck height (depth of piston in the hole)
Piston dome/dish CCs (-2.4 in your case with those)
Head gasket thickness
Bore size
Head CC volume

All you are figuring out is the volume of the cylinder when piston is at BDC over the volume of the cylinder at TDC, and converted to a ratio over 1.

Edit #2: Looking at those figures again that you listed, I see what you mean by not seeming much higher than stock, but 64cc to 56ish CC is a big difference, play around with it in the calculator.

IE, same exact configuration on a 64cc head gets you 10.7:1, 54cc = 12.2

SStrokerAce

My god man it's just nitrous. What's a 250-300 shot going to do?
Harmless.....


As the old man said, we'll be happy to analize the parts once it goes boom. Hell might as well do this all on a 2 bolt with stock rods. The ARP bolts aren't going to help much on a stock rod with the same RPM range, the bolts will help with RPM but not compressive loads like a shot of juice. I really want to see these parts when you are done.

Side note, the Eagle H's should have upgraded bolts in them and should be NEW if you are going to throw a 300 shot at them. 400hp NA plus 300 shot gets into their breaking point. $150 for bolts is cheaper than a junked block.

Bret

Hot Rod Hawk

I sprayed 275 with a custom two nozzle two stage dry set up on
a 100% stock short block. stock LT1 pistons, stock rods, stock crank, stock 2 bolt maincaps, stock rod bolts, stock main bolts for two full seasons with only fresh rod and main bearings during winter down time!
What got me in trouble was getting gready with the WOT timeing.
At 30 degrees all was well at 35 degrees it was lean mean and a monster untill it lifted the top off a piston and sent chunks out the exhaust port
Stock rotating LT1 assy can make good power and live untill you listen to the voices that say "awe just a little more timeing your good on the 110 octane"

just my 2.5 cents

OBDIICamaro

Ya Im still debating what I want to do now.

As for getting rods, I wouldnt want to because if it does go and twist a rod or 2 then im screwed with those too.


Also now what do you guys think about the balancing part?

OldSStroker

You can always buy 1 or 2 replacement rods, just llike pistons.
The only way I'd not balance it is if the new rotating assembly had the same bob weight as the original within a few grams...maybe 1 or so. The chances of that are slim to none. Without balancing, we'll probably get to see the broken parts even sooner.

Eric Bryant

I think you might be surprised - I personally know one guy running flat 12s in his stock lower-end Impala SS, and another gentleman is now running flat 11s with the stock short block in his Impala. Giving the motor fuel and spark at the right time and in the right amounts is going to be more important to the engine's life than the manufacturing process used for the pistons, IMO.

I guess what I really question is the desire to spend money on a motor that's not going to get run for long before the 383 gets built. As others said, that's money that could be spent on doing the 383 correctly. If you're making money by racing, do what cha gotta do, but if you're just playing around, enjoy your current setup and put the time and money into the stroker motor. I know that patience is not easy to come by for most of us enthusiasts, but you sure can burn a lot of resources by being dissatisfied with what you've got.

n20ta2

If your not going to spring for rods than dont worry about balancing it,the motor your building is a granade with the pin pulled anyway.Why not at least go with a set of eagle forged sir rods they are only 190.00 I think thats cheap insurance compared with the idea of spending a few months without racing if it blows first time down the 1320.