I'm having a 383 built, I plan on LE3 heads and cam. Forged rotating assembly, forged steel crank, SRP flat top pistons. Compression ratio at 11.1 without milling, im aiming for 11.8:1 which should keep my DCR at around 8.8. Im double minded about whether to go with nitrous or not.

I would need larger clearance for the rings and possibly a nitrous cam, so I need to decide before work starts. I was thinking if my bottom end can handle a 250shot (wet), then maybe I should satisfy the forged assembly and do it. Wondering if there are any serious drawbacks. Would the fuel pump handle it? I dont want crazy piston slap or something like that. I know i'll need some sort of timing retarding ignition as well.

I have a walbro 255 with stock wiring, pacesetter longtubes on the way, 42lb injectors, all the boltons. I'm running a 10 bolt and street tires cuz i cant afford a 12bolt for now. I've never raced on a 1/4 mile track or off the line so Im thinking my 10bolt might last me a bit. Let me know your opinions and reasons. thanks!!

p.s. goal is for a fast weekend warrior with nitrous as backup against a forced induction setup

 

First off, if you can't afford a 12-bolt then you cant afford a "proper" nitrous system. I would worry about the 12-bolt then start thinking about the nitrous setup.

For comparisons, I am finishing up my solid-roller fully forged LT4 383 motor. Jordon musser ported/polished the LT4 heads and the LT4 intake manifold. We are looking at about 475rwhp through a TH-350 and a 12-bolt. My motor is also 10.5:1 compression and setup for Nitrous. We are going to spray a 350 direct port shot onto my motor.

But I would worry about all the supporting mods, like definately a 12-bolt, proper fuel system, blah blah blah

 

Med -

Two things I can tell you, and all my nitrous experience is 20 years old:


1) Whatever HP you make without the juice, divide that by two and THAT number is the PRACTICAL limit for how much juice your engine can eat.
(That's a rule of thumb that can be violated, a little bit; but there are flow limits to your head that affect the nitrous, not just the airflow.)

2) Take your naturally aspirated HP number, multiply it by 1.5 and THAT will be the power level your engine, transmission and car must be built to withstand.


Let me add this...

The engine you described might well be putting out 500hp already. You didn't mention a cam, but I assume it will be compatible with the LE3 heads.

That Walbro and the 42lb injectors you mentioned should supply your engine with no problem. I think. I haven't actually bothered to use the injector calculator since that's something you can do yourself, but it should be OK.

HOWEVER...

If you add a dry nitrous system, I would think that you might want to consider using a larger pump and get the impedance converter so that you can run bigger injectors.

OR...

You need to run a wet system with it's own dedicated fuel supply. I personally think that's a better idea anyway, especially for a larger system, because you can use race gas in the extra tank.


But understand this...

Even in the old days, before all the fancy electronics out now; a GOOD nitrous system wasn't cheap, or easy.

Someone else mentioned that if you can't afford a 12-bolt rear that you shouldn't be looking at nitrous. Well, that's true.

If you are going to absolutely INSIST on running nitrous anyway, then you should probably use a 100hp or less ZEX dry kit and opt for the Walbro 340 pump.
Based on what I have seen others doing, that seems to be a reasonably foolproof setup, to the extent that any of these things ever are.

But honestly...
You should really skip the laughing gas for now.

Get your new motor in, sort it out and do all the suspension/drivetrain upgrades that you need to do, INCLUDING a stronger rear end; and do that FIRST.

You will be happier and better off in the long run if you do it that way.

 

II would get better pistons if you plan on running anywhere near a 250hp shot of nitrous. You need a "nitrous" piston to play at that level with a reasonable expectation of longevity, IMHO.

Rich

 

Is it worth doing the rebuild with the larger clearance and nitrous cam and pistons now, and then installing nitrous when i can afford a 12-bolt, clutch, and suspension (eyars from now)

Other option is to go with standard le3 build and then.... do another engine when I want to add nitrous.

 

It is, in my opinion, ALWAYS worth building the best bottom end that you can; UNLESS you know that you will never do more mods.

What you're asking is slightly different. You want to know if you should put in the nitrous specific parts now, then add the actual kit later.

As long as you definitely plan to add the nitrous later and you understand that the specific nitrous friendly mods do compromise other aspects of your engine; then yes... Do it.

Having said that, you may want to consider building a more "normal" engine and backing off the laughing gas plans a bit.

See, your problem is that the nitrous specific mods in terms of clearances; are not actually good for N/A power production and street life. Looser clearances and bigger end gaps I mean. Sure, that's good for nitrous but that's because the nitrous use will make those mods more "normal".

That's a bad explanation, but it comes down to this: Those types of mods are for cars that see a LOT of nitrous use, perhaps at the dragstrip.

For a street car, with street motor clearances and ring endgaps, you are probably better off keeping your added power to no more than 200 so that you can get away with occasional nitrous use and not have to compromise your build to accomodate frequent "big" shots.


Everything I said is oversimplified, like usual. However, the basic premise is useful. Unless this is an engine for a drag car with little to no street use, you'd be better off with a smaller shot and "normal" clearances.

 

I'm building a similar set up,
What lifters did you go with and if you don't mind saying what kind of lift are you runing?

 

I'll have to ask Jordon as to what lifters I went with. I know they damn sure weren't cheap.
The cam is a ~.640 intake/~.610 exhaust, I believe. I can get the exacts this Saturday.
Matt

 

I think I'll go with the LE3 head + cam setup, slightly looser rings, and plan for a 150 wet shot in the future (fuel from the rails to mix with nitrous out the bottle). Thanks for the help guys.

 

383 le3 motor. haha should have bought my brand new one and saved tons of money. I've had it in the for sale section forever..I'll even sell the heads and cam seperate...

 

I think the rear will hold as long as you dont spray off the line. Get moving and hit it past the 60 foot just after the shift into second.

 

You say you are staying with the 10 bolt because you can't afford a 12 bolt right now. If you build a LE3 383 and spray it with 250+ HP. You will blow your rear end to hell. If you are seriously going to spray it to that level you need to lower the compression ratio a bit and make sure you have the best pistions, bearings, and rings you can buy. Nitrous use at that level requires a bullet proof bottom end.

I would spray it with 100-150HP and only on the street until you have a better rear end.