I know the N* forum is on the other side of the creek but ya guys dont come around...unless ya smell something burning!
The Northstar has 2 each 1.425 intakes and 1.02 exhaust valves, can anybody tell me what the total diameter is for each so this ol geezer can relate how the engine breaths?? And also why did they choke the exaust so hard. thanx

were those diameters that you gave? and are you looking for total area?

not the area per se but the diameter the total area would equal of the intakes and exhusts valves as given above

Pi R^2 for area

intake valve area 1.5948 square inches (x 2 since it has two valves)= 3.1896

exhaust valve area .8171 sq inches (x2) 1.6342 total area

now remember overal valve diameter does not indicate Throat/bowl crossectional area which is smaller as the valve sits against a curved multiangle valve seat.

but for the same area of the two intake valves (3.1896 sq inches) a single valve would be 2.0152 inches in diameter vs two at 1.425

for the exhaust a single valve with that surface area (1.6342) would be 1.4424 inches in diameter

now a 2.0152 inch valve with the 1.4424 inch exhaust would require at a minimum a bore size of... 3.46 inches...and thats with the valves pretty much touching each other and the cylinder walls...not good so bore size would have to be larger than that min for clearance sake...and even then valve shrouding and (low lift) valve/port flow would suffer
this is why splated/canted valves are very good...as the valve opens farther it moves away from the cyl wall further improving flow by minimizing valve shrouding.

my 4.155 inch bore 400 sbc has 2.02 inch intakes and 1.6 inch exhaust valves...
but to put this into perspective with a N* you would have to calculate sylinder volume of the N* (one cylinder) and the volume of one of the 400 (or another engine) cylinders
so that you could see the relation of cylinder volume vs port/valve area which would tell you which engine is more LIKELY to have more efficient flow than another, though MANY other factors have to be taken into acount such as port crossectional area/shape/length/rpm... ad-infinium

most engine builders agree that they like to see exhaust valve area/size at least 70% of the intake...as the intake flows air at (presumably) 14.7 psi wherease the exhaust is flowing hot (high kinetic energy) high pressure expanding gasses....

as fer why they choked the exhaust so hard...i cant tell you...what i can tell you is that the new 4.4L N* factory supercharged/intercooled engines in the CTSV etc has very little in common with the prev N*'* as well (if i'm not mistaken) larger exhaust valves to compensate for the increased air pressure from the blower (over 14.7psi static air pressure) and other specs differ as well.

hope this clarifies things fer ya, and i hope i have answered your question to your satisfaction...my volume/area math is a little rusty as i have primarily been concerning myself of late with SI/SII deck heights/rod lengths and piston, compression height/ringpack spacing as i am trying to see how long of a rod a tall deck SI block will fit and its rod/stroke ratio vs the short deck short rod SII block
and it gets even more profitable to use the tall deck SI block from that standpoint when stroking the 3800 to say 4.2L (tall deck blocks are damn near always better for stroker engines to keep the rod/stroke ratio reasonable

Regards, James

The reason i posted this was I feel the engine is exhaust choked ,literally when I drive and the valve diameter difference and from a generation that only had 16 valves I couldnt put the difference in perspective. I'm putting a modest Holley nitrous kit in and slightly worry of an intake explosion Iif I throttle off hard after an agressive injection with the flow of gases governed. Which can easily be the case in a urban setting.
And that Sir was one of the most well written and comprehensive posts I've read in any forum and though it took two reads to fully understood what you said, I did and it reinforces an opinion. It really made me think for a change, and the why you layed it out helped alot.
My guess is they detuned the engine enough to quell managment/engineers fear that Pontiac owners would use the 300 Hp and cause warranty problems.
Do you or anyone have an opion about whether caddy heads would swap out or if LD8 heads could be reground to accomadate the caddie valves ?I'm not looking for the power you sound adept at achieving just enuff to lose the low end torque problem and with modest nitrous injection make it street worthy
James, i thank for enlightening reply. And wish I lived next door so you could build mine I appreciate the email link and will bookmark in cause I have similar questions. And by the way, BITCHIN SIG MAN!

yes it is a bit exhaust choked as exhaust valve size is ~ 71.5% of the intake (not quite as good as the ~79% in my SBC heads) and the exhaust valve area is ~51% of the intake area but i am willing to bet that its adequate for 100Hp of N2O porting the heads (pay specific attention to the throat/bowl area) and working over the exhasut manifolds will help improve flow, but even as stock as long as you let up on the GO-BABY-GO button before you go letting up on the pedal you should be fine I have seen a couple sand buggy'* at Glammis/desert (while i was in SoCal recently) that are running essentially stock N* engines with nitrous on them (specifically one w/o nitrous, 1 with 100 shot, and one with 2 stages 100Hp each-this buggy had head work done and headers but you get the point) but one thing i must point out is both of the juiced engines had PORT Fogger setups as this gaurantee'* equal mixture in each cylinder preventing lean/rich cylinders like a typical single point system.
So i would suggest spending the exxtra $ to keep your engine happy and together (thats the important part there )
regardless make sure your still at WOT a split second after letting off the funny gas (at 5K rpm it would only take a split second to clear all 8 cylinders) to prevent an intake backfire...which by its nature would be less likely with a port fogger setup as the mixture is injected closer to the valve and doesnt fill the main plenum
also i would suggest getting a simple rpm "window" switch to make sure the nitrous is only activated above a certain rpm (2500-3000) and shuts off at a set high rpm limit (redline or just under etc)
spend some time and talk with some of the tech guys at NOS etc as they can give you ideas or turn you onto some good books to fill your noggin with...


Thanks, its no problem, im glad i could be of some help. However by all means Check around...the biggest problem with the internet is people need to still do research to confirm data found on the web (it'* called "doing your Homework" and still makes me groan when i remember my years of school...but it is invaluable, you learn more and remember more of it that way...damn teachers...they were right after all )
I experianced the same thing with my SI/SII 3800 Hybrid project (better flowing symetrical port SII heads on the tall deck/long rod SI short block) i heard soooo much about how "it wont work" when i did a sh!7load of investigative work i could find no one who had even tried to do it...everyone just accepted it as fact...i did manage to find a fellow psychotic gearhead in australia who is working on it as i am...so whether succes or fail the info WILL be out there for others...hopefully succesfully!
besides i enjoy the challenge, and the 442 would be all the better to showcase it being as unique as it is

i wouldnt doubt it as manufacturers have more to deal with than maximum power from their engines...drivability, emissions, NVH (Noise Vibration Harshness), comfort, and of course warranty/longevity (both the engine and transaxle etc).

I honestly dont have any info on this for you, good luck hunting...i do believe however there isnt much in common dimentional wise between the Aurora 4.0 and the 4.6 N* but i'm not sure this pertains to your question. if you could expand on this question?

i'm not sure i'm understanding this right can you clarify?

I'm glad i could be of some help to you. I hear that enough that i think someone should build a GearHeadVille USA for all us psychotic gearheads (requirement is you have at least two project cars sitting around and car parts as lawn ornaments ). Got a link to your post/* on your project? let me know and maybe i can help ya more.
yeah i dig the sig too, we're doin our best to follow in the footsteps of greatness...the original Hairy Hurst Olds was one unique monster in its own right...we are going for a modern version...
check out the vid...13.81 at 98.21 on a 96* day with horrible humidity...and thats at a race weight of 4330 lbs...not bad for two essentially factory stock engines
http://videos.streetfire.net/Player....D-9486F01242C7

Regards, James

James, funny you mentioned sand buggies because thats where I got the idea to nitrous and one of the leading N* engine builders out there for sandbuggie/hot rod apps is Alan Johnson of Cadillac Hot Rod Fabricators. And his site and articles of his engines is where I've done alot the "homework" You spoke of.
But he has a whorish relationship with GM N* team and remains as tight lipped as GM about the engine. I found more info from articles about his engines then at his site. But theres is some info. he feels stock bottom good to 400Hp 10psiBoost.Thats an ok number and would be happy, but dont want to rely on nitrous to achieve it. Also if I ever sieze or scatter my engine or blow the intake through the hood I could buy an new crated XLR for $4500, but he wont sell parts or shopwork to GM cars owners, so have to go "around that issue".

The rpm window swich is a good idea and a definate upgrade but as yet the nitrous kit isnt here<ordered 8 days ago and told 8-10 days to ship. (Didnt have the kit that includes the N* on the shelf)

The question I asked in the beginning had to do with my wondering if my heads could be reground to accept the STS / LD8 stock exhaust valve @ 1.42 diameter. That and a TB bore plus some exhaust porting(nothing in the way of off the shelf headers found) should get some juices flowing in this N*. Please give me an opinion and anything else you might think of. Just trying to brainstorm right now.

I paid cash for new car(heavily discounted and the war chest is getting empty and still have alot of body mods to get done and very possible a marbelized custom paint job using the Cranberry metallic as base coat. One of my sons friends owns a custom body mod shop near me www.dreamakerskustoms.com He'* going to do all my work and I invite you to visit his site. The guys a wizard and does everything "in house" alot of nice photos of his work and ideas. Thanks, John

I have two Park Aves 91 and 92, and an 88 Ford 4wd in yard....and 95 GXP and Ram3500 Dually CumminsTurboDiesel in the driveway and enough car parts in the yard to keep the Lake Association on my A** all the time so...do I Qualify ???(I'll even drag the Ford down the road till it falls of the chain its pissed me off so bad
I remember the Hurst Olds It came out when I was still a teenager and only saw two in in that city(Denver) at the time and wonder how rare they are.
I vividly remember the Gold one out there blowing doors off the Mopars of the day.