Redline on 97 4.3l Vortec?
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RE: Redline on 97 4.3l Vortec? - 2/20/2007 8:23:27 PM
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swartlkk
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From: Waterloo, NY
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With a stock cam, you should be fine with the stock springs. Now if you were to put a set of higher ratio rocker arms on... Then you may need stiffer springs or you may get valve float above 6000rpm.
I'm not sure what the stock redline is... But I'd say it's somewhere around 5500rpm
If you aren't doing anything to improve the hp output at the higher RPM, increasing your rev limit isn't going to net you a whole lot of gain.
Hypertech Dyno Graph (2000 4.3L v6) shows the stock graph. I guess it would be slightly beneficial to open things up to 6000rpm redline, but to go any further would not be advisable simply from a HP at shift point of view.
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2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto
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RE: Redline on 97 4.3l Vortec? - 2/20/2007 9:17:07 PM
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Jackal
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Yeah the software i have is telling me that Hp starts to fall @ 5k rpm. I am running the stock cam. I told them to set my rev limit to 6200 rpm. The heads are ported, polished and have custom valves (standard size). Also are these heads considered "Canted, or Wedge" heads? Thanks Kyle for the info!!
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RE: Redline on 97 4.3l Vortec? - 2/23/2007 4:11:51 PM
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2000BlazerSS
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Jackal: Your engine noses over at 5000 rpm, even with what you've done going past it won't give you squat. The camshaft is what determines how high you can get horsepower, and unless you change THAT your just wasting time. Even 1.6's, which increase lift by .030 will gain you maybe a couple of hundred rpm at best.
If any of you BS artists want to prove it take your car to a dragstrip, put the lever in Drive (NOT OD!) and make a couple of runs, then shift it anywhere your heart desires and see what happens. Been there, done that, know whereof I speak.
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RE: Redline on 97 4.3l Vortec? - 2/23/2007 4:23:18 PM
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swartlkk
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Who exactly are you calling a BS artist? Inorder to do what you say and shift where you want, the rev limiter would have to be lifted to actually note any change.
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Kyle-
2004 Rainier
1970 Chevelle - Resto
1974 K5 Blazer - Resto
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RE: Redline on 97 4.3l Vortec? - 2/23/2007 6:56:12 PM
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drperry
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Power starts falling off at like 4500RPM, the computer lets the engine revs to 6000rpm, there's no power that high, but it'll go there... Sounds like it's going to explode at anything above 5K but it goes there, lol.
I might have a little more oomph above 5K now that I Hyperteched it, but not a whole lot difference...
And the cam itself doesn't determine the redline of the engine, only WHERE the power is according to the RPM of the engine. You'll need stiffer vavle springs if you want more RPM, but I still wouldn't reccomend anything higher than 6500 or 7K at an absolute max, without getting better bearings for everything.
That's assuming the transmission can survive at high RPM like that, and all your accesories can too...
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RE: Redline on 97 4.3l Vortec? - 2/23/2007 8:19:18 PM
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Jackal
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"OOOOOOOh he's an angry little elf!" LOL Quate from Elf...the mov. Anyway there are alot of factors that are to be considered into how hi to rev an engine. I have ufortunatly seen this argument way to many times. Put it simple enough, i am a believer that you want to rev any engine past its peak power so when it shifts it falls closer to peak power. You get an higher averag amt. of power. In my opinion) Power is just work over a period of time. Any engine that breaths better than stock you can squease a little extra out of the top. This truck wont be for racing anyway. I know a bit about engines and such, but im always looking for the opertunitay to learn....hence why i build what i build :). Who int there right mind builds powerful Blazer....one who wants to learn from what affects each mod has had. Sorry for the 12 pg disertation, and thanks for the input also !!
p.s. i'll keep the rev limiter @ 6200 rpm...
< Message edited by Jackal -- 2/23/2007 8:21:29 PM >
_____________________________
97 Blazer LS 311k RIP Rebuild to Come soon.
High CR/Will Be Turbo
http://www.cardomain.com/ride/2377252/1
My Turbo Dialy Driver
http://www.cardomain.com/ride/2336011
"The Hulk" http://www.cardomain.com/ride/2568605
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RE: Redline on 97 4.3l Vortec? - 2/24/2007 12:23:32 AM
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2000BlazerSS
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Listen to drperry, he knows what he's talking about. You can put ice cold air and have an open exhaust and rev it to the moon and you won't get squat more power out of it. The camshaft limits where the POWER is produced, and the stock cam in a 4,3 cam is all done at 5000 rpm, MAYBE another couple of hundred with 1.6's which give the cam .030 more life (and your starting with nothing to begin with.
FYI: What your/we're doing when we add a cold air intake, larger MAF, free flow exhaust is raising the horsepower UNDER the maximum RPM the cam design will allow. I think it's called "under the curve". Anyway, if you've ever seem an engine on a dyno you'll see what happens when the engine runs out of cam and noses over.
PS: I WANT you to reprogram your computer, I WANT you to reprogram your tranmission to shift at 6200 rpm. PLEASE do these things. For me?.
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RE: Redline on 97 4.3l Vortec? - 2/24/2007 11:08:16 PM
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Jackal
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My truck won't shift at 6200rpm, thats where i moved the fuel cut to. I can get it to shift at 6200rpm if i floored it and held it down untill shes done shifting. The pcms already on its way back here, will be here on tues. 2-27-07. I simply moved up my redline to 6200, not 7k. Ans i still may put a Lunati cam in! I understand power falls of @ 5k. Put it to you this way A 750hp nascar engine doesn't make peak power at REDLINE, no engine does! So ever seen the in car video of them as there shifting....uh they take it to redline. Your turn to explain to me why that is? I was just trying to explain that in my last post. I'm mean all this peacefully man, i realy do.
What the heck are you talking about? I'm sure but, there is some sense of sarcasme here, i'm not real sure why. My angry little elf comment was just to try to lightin things up in here....its my favorite part of that movie...it usually makes people laugh when i say that
PS: I WANT you to reprogram your computer, I WANT you to reprogram your tranmission to shift at 6200 rpm. PLEASE do these things. For me?.
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_____________________________
97 Blazer LS 311k RIP Rebuild to Come soon.
High CR/Will Be Turbo
http://www.cardomain.com/ride/2377252/1
My Turbo Dialy Driver
http://www.cardomain.com/ride/2336011
"The Hulk" http://www.cardomain.com/ride/2568605
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RE: Redline on 97 4.3l Vortec? - 2/24/2007 11:32:39 PM
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2000BlazerSS
Posts: 45
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I'm sorry jackle I'm off my meds.
Unless or until you put in a cam designed to rev to and/or past 6200 rpm your best shift point is 5000 RPM, that's with a stock cam. This is NOT where it makes it's highest horsepower but just past it. The cam in a 1997 4.3 is mild at best.
Just because the engine will turn 6200 RPM, and I wouldn't even TRY to see if my 2000 4.3 with roller ROCKERS stock (lifters have been since about 1992). I have no need to abuse my engine for no earthly reason.
Reving past the peak power point. The reason for this is when you shift (or in the case of an automatic it shifts for you) the engine will drop back to peak power. For example, on the dyno my wife's 454 with a .550 lift hydraulic cam makes peak power at 5300 then noses over. The shift light comes on at 5600 and she hits the lever there. It then drops back to 5300 and pulls again. You "shifting past peak power" is an old wive's tale from way back when. The best shift point is the shift point that gives you the best ET, 9 times out of 10 when you find it it's much lower than you would expect. My Corvette will go to near 6000 RPM, I can easily shift it at 5500. The best ET comes when it's shifted at 4700, I let it shift by itself at 4400 (I lose a tenth over 4700 but it's consistant aas HELL!). This is a stock block and cam and heads 1985 TPI engine. And this car has been raced for 22 years.
Now you can do whatever you want, I've been bracket racing for 42 years, I KNOW what I'm talking about. I begged you to shift it at 6200 RPM because if you do that the engine will scatter in short order.
You and all the other "experts" the 4.3 V6 is 3/4 of an old style 350 V8 truck engine. There is NOTHING high performance about it. If you want high performance you have to do the same things to it that you would a 350 truck motor.
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RE: Redline on 97 4.3l Vortec? - 2/24/2007 11:41:23 PM
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Jackal
Posts: 48
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I DO NOT PLAN ON RACING MY TRUCK. Im simply saying the pcm's already been programmed, but i'll let it shift normally. It's not a vette lol. Its not a 454. Iget no joy out of using 30 yr old technology. except my pc its an old apple pc, it doesn't even use windows.
_____________________________
97 Blazer LS 311k RIP Rebuild to Come soon.
High CR/Will Be Turbo
http://www.cardomain.com/ride/2377252/1
My Turbo Dialy Driver
http://www.cardomain.com/ride/2336011
"The Hulk" http://www.cardomain.com/ride/2568605
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RE: Redline on 97 4.3l Vortec? - 2/25/2007 8:00:46 PM
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pilgrim
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The fact is that if you rev much past the power peak in any car, you're not accomplishing much or accelerating very fast. The time lost due to slow acceleration after you pass the power peak is generally not going to be recovered by having the next shift drop the engine into some (imagined) spot in the power curve.
You lose time one place or another, but revving the motor higher than it's designed to is just asking for premature wear and engine trouble. Torque generally peaks at much lower RPM than HP, and in the Vortec V6 the peak is about 2800 RPM. The HP peak in this engine is reached at 4400 RPM. The way it adds up - after 5000 RPM what you're doing is mostly revving to hear it rev. IMO, without a planned and integrated set of engine mods, raising the rev limit to 6200 RPM is pointless.
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RE: Redline on 97 4.3l Vortec? - 2/25/2007 8:37:13 PM
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Jackal
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I completely agree! Believe it or not. It's too late for that though. I made a mistake on the of moving the redline to 6200 . Thats actually why i was asking. I am not going to mod the engine to any extense that would enable it to rev any higher actually. I don't want it to rev past the where power it becomes useless. My goal with pcm was timing and afr, among other things. Now that i look at my calculations i see clearly that after about 5k power, and torque fall off more dramatic than previously thought by me. Just for the record, i sent as i made my first post here. i emailed the guy on the rpm side of things without any answers also. p.s. i am admiting i was wrong the vortec in my case will not be any good, as in reving it higher.
_____________________________
97 Blazer LS 311k RIP Rebuild to Come soon.
High CR/Will Be Turbo
http://www.cardomain.com/ride/2377252/1
My Turbo Dialy Driver
http://www.cardomain.com/ride/2336011
"The Hulk" http://www.cardomain.com/ride/2568605
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RE: Redline on 97 4.3l Vortec? - 2/26/2007 7:09:41 PM
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drperry
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From: GP AB CA
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You can get cams that shift your power band, so it could theoretically produce power PAST your redline, and if you're running forced induction, the more RPM you make, the more power you'll get.
Nascar engines are made to breath like crazy at high RPM, because that'll make the car go faster (turns the transmission faster) The reason they shift at or near redline, is because they're tuned to have peak power close to redline...
And when you change gears, you don't want the RPM to land ON the peak power, then power falls off without much use... you want your RPM to fall just UNDER peak power on a shift...
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