Whats the stock redline on a 97 Blazer LS? Also what are these engines safe to rev to? I sent my pcm out to get reprogrammed. My friend told me you don't need special springs, or lifters under 6200 rpm. What you all think? Thanks Bill

 

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.

 

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!!

 

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.

 

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.

 

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...

 

"OOOOOOOh he's an angry little elf!" LOL Quatefrom 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 wayto many times. Put it simple enough, i am a believer that you want to revany 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 overa period of time. Any engine that breaths better than stockyou 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 buildspowerful Blazer....one who wants to learn from what affects each mod hashad. Sorry for the 12 pg disertation, and thanks for the input also !!

p.s. i'll keep the rev limiter @ 6200 rpm...

 

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?.

 

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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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 thatgives 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 heads1985 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 RPMbecause 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.