Curious..... Like George - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


Bonneville GXP/ Northstar Powered Cars Discuss your Bonneville GXP and/or any other Northstar powered Olds or Cadillac... Including the 3.5L Twin Cam V6 (Short Star ) 4.0L and 4.6L Northstar V8's. Please use General Chat for non-mechanical issues, and Performance and Brainstorming for improvements.

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Old 09-18-2010, 11:21 PM   #1
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Wondering about cams...

What is the difference if any between the heads on the GXP and the STS, Besides the grind and Springs ?? Are they higher flowing ??

What is I picked up a set of Cams for the GXP ??

Or would it be better to grab a set of STS heads and build those then swap them out ?

Quote:
With any cam change, you need to replace the valve springs. If you over rev this engine, you can grenade a lifter and thus the whole engine. Look at the chart for the comparison over stock. These springs use the stock retainers to keep down the cost.

With a change in valve springs and some head cleanup, the middle cams will put out another 75 HP over stock.

Engines setup with blowers, superchargers, or turbos need a different cam profile and centerline setup. Choose from the cams above and use at least 10 deg more duration on the intake cams for single turbo installations, and 10 deg more duration on the exhaust cams for blowers. Twin turbo installations run on single pattern cam designs. Turbo engines also respond well to larger cam shaft durations.
On the Seat Factory Lift

Stock 275hp 48 lbs 98 lbs

300hp 59 lbs 109 lbs

Ours NS180 100 lbs 180 lbs

Also what about porting and polishing the heads ?

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Head work with our cams will really wake up this engine. Figure an increase of 50 cfm will produce 100 HP.
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Old 09-19-2010, 10:00 AM   #2
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hmmmmmm.... lots of views no input....
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Old 09-19-2010, 08:01 PM   #3
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The valve seats and all have a "secret coating" for tighter tolerances. They cant be polished. There are no valves available to do a regrind. All this and a few other things like a super thin cylinder liner also makes later N'*'* UNrebuildable. (Ya I see some BS rebuilders offer N*'*) Good Luck with them) To do so will ruin them. The PCM is engineered for the heads that are on it. Not even sure that a change would help if if could be "tuned in". The LD8 isn't really detuned. It makes 300 Lbs of torque out of it'* designed 275 HP. The relationship of HP and resulting torque are often misunderstood. Here'* the specs per GM

L37 high-output 300 hp (224 kW) and 295 ftlbf (400 Nm)
LD8 high-torque 275 hp (205 kW) and 300 ftlbf (407 Nm)

So what do you think your accomplishing by putting L37 parts or heads on? The LD8 is NOT detuned. It is RETUNED to deliver faster, and more torque. Mix/matching parts between the two engines isn't going to improve anything. The LD8 quite simply makes better use of HP and with a much more efficient power curve. Alot of people have been fooled by an old Admins here who hasn't a clue about engine dynamics. The L37 is not a superior engine. It is one designed for highway, not performance driving.

To that I will add the 04 LD8 came out with some newer and more sensors. Harness'* not likely to match up or work in our locked PCM scheme of things. And we can add taking the heads of L37/LD8'* is something GM Techs avoid like the plauge. The odds are you end up buying a vey expensive rezert kit, and good luck in getting things drilled out and put back together in a way that doesn't lead to a blown head gasket or warped/cracked head.

How'* that for some input???

Everything I mentioned here has been covered in this Section in the past and I feel like a "parrot" Drive your GXP as is and enjoy. You can Nitrous or mild turbo. All the moderate choices available after 7 years of aggregate brainstorming.
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Old 09-19-2010, 10:33 PM   #4
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Hmmmmm So what CHRF says is ughhhh.... I was Waiting to call them tomorrow and say Do IT haha
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Old 09-19-2010, 11:25 PM   #5
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Thats a nice cam/kit. But an expensive paperweight without a Holley Commander PCM Setup or higher. And Hardware/software. Programming. Custom Programming. Let me know how it goes for ya. I'll be the 1st impressed.
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Old 09-20-2010, 01:56 AM   #6
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Quote:
Originally Posted by GXP Venom View Post
Thats a nice cam/kit. But an expensive paperweight without a Holley Commander PCM Setup or higher. And Hardware/software. Programming. Custom Programming. Let me know how it goes for ya. I'll be the 1st impressed.
going by first hand experience the only way that the Holley Commander 950 works is to totally by pass the Stock PCM,, Then you would have to figure out how to make the trans shift (the 950 doesn't do the trans)

then the programming.... forget it..

Ask me how I know hehe..

But....

Maybe the self learning Avenger EFI on top of the commander 950...

Although I have been reading and reading, Spoke to a guy from TunerCAT and he once again suggested Westers Garage....

Quote:
Originally Posted by AJxtcman
I have the Seed & Key for this PCM and that is as far as I have gotten

Maybe Wester'* can help
Maybe I should explain. I have a Wilhelm reader and I have purchased several PCM'* and read the chips. The chip contains the Seed & Key and of course the calibration.
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Old 09-21-2010, 10:07 AM   #7
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There are no "buts" really. Unless IMO your a rich moron. The cost of a new PCM and setting up a program that will fly would be incredible. I have no confidence whatsoever in anybody just tweaking a tightly wrapped OEM program that uses so many parameters with/against each other. And relearns as it goes along. And ties so many things together in one PCM. I remember you being on the "turbo band wagon" 2 years ago and where did that lead? With the same thought I had. Alot of money for a big unknown and @ 6lbs of boost (if the engine can suck it without choking), why bother?. For the money just to get this engine tunable/tuned (and that only delivers a very modest HP gain), you could throw it away and go buy a crate/tune from CHRFab. 6 years of bullshit in this Section hasn't made one owner go an iota quicker. So exuse the pessimism, but money talks and bullshit walks. This really isn't about skill or the ability to do the wrenching. It'* about having the stomach to put out the funds needed to do a project that won't allow for a couple smaller mods for get up and go. I've sat here and read the musings of many people who believed they can do so for way to long, and it'* a pipe dream.
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Old 09-21-2010, 10:21 AM   #8
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I'm still thinking about Turbo..... 6PSI just isn't enough LOL.

But then again maybe it is
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Old 09-21-2010, 11:02 AM   #9
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Better put would be, "would have to be". Alot of fabbing there in that universal kit where room is a premium. Now that GM has shut done the Northstar production lines I wonder where shops like Mallet and CHRFab will migrate to. LSA? The grim reality is that the N* LD8 and L37 have been shipped down the same road as Caddy'* 4.9. Off to obscurity. I myself am wanting to get a lower mile one from Morad while we still can. I'm sure the car will outlast the engine. And one I would like to keep around.
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Old 09-21-2010, 11:20 AM   #10
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John I hear where you are coming from. My LD8 is still a baby with just a touch over 40,000 miles. If I ever need a new motor mayve something bigger !! Haha
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