I have been doing some searching and reading about nitrous installation and timing and have a couple of quick questions.

I understand that NOS reccomends 2* retard from base for every 50HP of spray.

My plans are to run a streetable 383, please correct anything that you don't think would support an extremely infrequent 175-200 shot.

Pistons: Forged 10.5:1 .060 oversized
Crank: 5140 Forged Crank
Rods: 6" H-Beam (5.7" ?)
Heads: Dart Iron Eagle Platinum
Cam: Moderate mechanical flat-tappet cam
This is a carbed motor.

Question: Will the timing retard affect driveability on the street when the NOS isn't in play?

I'd like to have good power off the bottle, and great performance on the bottle for the Infineon and Famoso track days.

Thanks alot,
Rob

 

Get a timing retard for the n2o or buy the MSD digital 6+. It has one built in. When the n2o is activated, it retards the timing to whatever you preset, and when you lift, it goes back.

 

The 6 box does that? Thats great! I was already going to buy that for my ignition, that just puts in into the "For sure" catagory.

Thanks for that, very useful.

 

You can back off on the engines compression ratio too.

The nitrous will more than make up the difference.
A more moderate cr will allow more NOS volume = more power. with more reliabilty.

Instead of being maxed out at say 170hp gain with pump gas while on the juice before detonation requires exessively more ignition retard, a lower 9.5:1 compression
ratio will allow the same motor to use signiffigantly more nitrous volume therefor much more power.

If you drop the cr I can easily see you using up to a 250+hp shot and going much faster, with the same or more safety.

We've run rediculess large racing nos shots thru street motors using lowly cast pistons with no failures, using lower(er) compression ratios along with some ignition retard and high octane fuel.

You'll want to get some type of automatic ignition retard that is adjustable for a dual purpose nitrous car.

Be sure to open up the piston ring end gap spec for your nitrous built motor. This extra ring gap especially on the top ring
will have minimul to no effect on N/A motors operation and power and will ensure the rings do not butt while running on the juice. The motor will not huff or smoke with this extra ring end gap.

Use a non projected tip spark plug.

 

This is gold, thanks for the info.

I was working on Desktop Dyno to get an idea of N/A power difference between 9.5 and 10.5 CR. What type of a loss in power would I be looking at Naturally Aspriated from 10.5:1 to 9.5:1?

I'm kind of wondering DDyno's #s. What type of power do you think i would be making from a Naturally Aspriated 383 motor with these build specs?

4-bolt 350 block .060 over
Crank: 5140 Forged Crank (3.750")
Rods: 6" H-Beam (5.7" ?)
Pistons: Forged 9.5:1 .060 oversized
Rings: std. with some end gap (thx)
Heads: Dart Iron Eagle Platinum (2.02int/1.60exh)
Cam: Moderate mechanical flat-tappet cam (comp cams no. 12-677-47)
Roller rockers
std. comp controlled Qjet
Intake Manifold: Performer
Exhaust: Hooker 2055 w/ AIR
built 700R4, 3.23 posi.

 

Looks good. Ring gap is the improtant thing. I would consider a hyd. cam if you are driving this car. Soild lifters take a lot of attention if you drive it much.

If you are not dealing with emissions, I'd step up to the RPM intake.

 

I'd order a custom nitrous friendly cam ground on wider 114 Lobe separation. you would install it a little more advanced in the motor. 7 to 8 degrees from "straight up.

I would pick the next size up 240+ -- 250+ @.050 duration. ground on 114.

A cam ground on a wider LSA than shown in the catolog will cost just the same as a catalog picked Extreme energy grind. Don't be afraid to call Comp cams and order it ground to your needs. Thats what they are there for.

Mechanical cams that are not super radical race only grinds that take the valve train to the limits of design do not require tons of lash adjustment. Exessive rpm and spring pressure do.

With a quardinated matching valvetrain package a extreme energy mechanical cam is a good choice for thisi motor.

A stock cc QJEt will need some mods to ensure it stays rich enought at high rpm with the NOS. large fuel inlet needle and seat. Hi volume fuel pump rod and jet tuning.
Are ya up to it?

I'd use a vic JR intake for a nitrous motor. Much more even fuel/NOS distribution on larger shots.

At least a Performer RPM. A lowly performer will hold this motor back.

To simplfy things I'd strongly consider swapping to a Holley 750 or Edelbrock 750carb.

A Qjet can work for ya but will take some mods to dial it in.
I would not use it in stock tune with NOS.

A 750cfm holley DP will be near spot on right out of the box.

I'd guestimate your N/A power to be right at 430-450 HP if you build to my specs. Good enough for mid to low 12's.

Can go high 10's on the juice.

What fuel will you be using? Would you be willing to install a small fuel cell under the hood to allow you to run 100% 110+ octane racing gas while useing the juice?

Goes a long way in ensuring that you don't eat up a motor allowing a more powerfull NOS shot, while still keeping the whole thing economical.

You'll sleep a lot better at night knowing that the motor is not being cheated on octane while juicing it. the extra investment in the fuel system will pay off down the road.

Nos motors don't really respond to a longer rod. 6" rods are going to be a waste. 5.7" will be just fine.

Just by employing a few of my recomendations on the engine build you'll end up way ahead of any power beneifit that a 6" rod might give.

Does this motor need to pass emissions?

 

Location: Santa Barbara, CA



Unfortunatley, yes. I live in California. I love it here, winter is 60* summer is 75. But this smog stuff is driving me crazy.

I was just going to abandon plans on the third gen. and go with a 72 nova just because of emissions, but one of the local shop guys around here is running an 87 Firebird with a 383 motor in it an blowing near zeros on the sniffer. Carbed.

I figured if I could do that, then toss on a plate system for those once-in-a-blue-moon situtations, it would be cool.

Anyways, seeing as yes, I do live in CA, I have to keep:

750 Comp. Controlled Quadrajet
Performer Manifold (What are some good manifolds with EGR?)
A cam that will be decent for smog (I am very, very bad with cam math btw.).. maybe I should just switch over valvetrains once every two years

Damn right. I have put a _lot_ of time and money into this car just to get it driveable, and the majority of the investment isn't coming back, so I think that I am going to get the most out of it that I can. Thanks for the information.

 

Look at thelast couple issues of Popular Hot Rodding. They built a smog legal 383 for the project G/28. I would mimic that build as much as possible. Talk with cmop cams about a cam that would work good for this with the NOS shot. They will probably say stick with the cam in that build, as you won't be using the N2O much.


AS far as intakes the performer is the best EGR one I know of.

 

patRIOTik - I work here in Goleta, live in Los ALamos, and run a 383, w/10.5:1, AFR 190's, Super ram, LT4 "Hot CAm" and a NX wet system and I pass smog and have managed a 117 MPH in the 1/4.

You have a California carb'd 86 V8? That actually has a lot of potential. No ECM?

I'm not trying pirate but you may want to check this out.

https://www.thirdgen.org/techbb2/sho...hreadid=310984

 

Dwayne, posted in your topic.

My car was originally a 4bbl 305. The previous owner dropped in a 350 and hooked up all the emissions equipment.

I am currently running a 4 bbl 350 with the stock 305 ecm ()

Man, I would love to take a look at your car. I was beginning to think that performance in California was a pipe dream.

What shot do you run on 10.5, at what octane fuel?

You can get a hot cam like that to pass smog?

tell me more!