why does it matter?? do you wish to overspeed your engine? do you know what happens when an engine has been overspeed? Lastly are you the one who just recently did a motor change in your truck??

 

Lastly are you the one who just recently did a motor change in your truck??

:lmao:

"Are you the guy on transmission number 2 or blah blah blah?" <= You see how irrelevant that is?

The fact that I just did a motor swap has nothing to do with this thread, or an over sped engine.

 

Higher rpms has more to do with valvetrain and rotating assembly/mass than it does fuel delivery. So I'd say your idea of bigger injectors/pump would be useless for more safe rpms.

On another not these trucks don't produce anymore power past like 5800-6000rpm if I remember right so spinning them up even further without at least the cam to match would be pointless.

 

That is the point of this, I wanna know who has modified to achieve more.

Power range starts decreasing at 5500.

 

I know one or a few people have upped their rev limit a few hundred rpm but I don't think anyone has actually done the mods to the needed areas to wind these things up further. There is just no aftermarket support for these motors unfortunately. That means it would have to be a 1 off that someone pieced together from other engines or had custom parts made. At that price point there is absolutely no reason to go for more rpms in these motors when you can achieve far more power let alone more usable power with boost/n2o for a lot less money.

Would I love to see someone go nuts on one of these things like that? Hell yeah! Has anyone and will anyone? No :/

 

High RPMs = Floating valves (in OEM form)

 

This. There's a reason why GM puts a REDLINE on the RPM gauge, anything beyond that for a long enough period of time and the engine will eventually self-destruct, possibly chunking a rod through the block or the pistons will start smashing valves.

KABOOM. Full-stop, the end.

Unless you've got stupid amounts of money to modify/re-engineer the engine to push it's redline beyond what GM designed it for, I'd advise against it. Honestly I've never gotten mine beyond 5500 RPMs as a result when I'm "in a hurry" and stomping it in 3rd gear. Again, it makes more sense to throw money at either putting a turbo on the engine or dropping in a V8 IMHO to get more performance out of your truck.

Ultimately it's your truck/engine, so do what you will. At least if you do, please take pictures, we like pictures here.

 

I had my 4.2 I6 rev limiter set at 7k for a while. While it's true that power drops off after 6k, I found the extra range to be useful -say- in a 1-2 shift so that RPMs didn't drop off too far.

I think a 7k redline could be especially useful for those that are boosted. While a n/a loses power after 6K, the turbo could fill in potentially up to 7k. 15 psi at 7k would be pretty nuts on an I5.

 

Don't forget about your buddies over on the 4200 forum. I think a couple of them have swapped valve springs and pushed the rpms pretty far if memory serves right, but both were boosted and that one guy is running alky.

 

With my 5 spd swap I don't have then need to go passed 5500 rpm

 

Yeah Matt or AceX did the forged internals. I don't think he went over factory redline though, there should be some dyno sheets in his build I'm pretty sure he posted them after everything was done initially.

It's probably making some more power now though because I think he changed some things around and got the temperatures and a few other smaller issues squared away that he had.

 

when does god's rev limiter kick in? ( valve float ) cause the talk about turbo applications with 15 psi hitting 7-8 sounds interesting but would like some more validation on it

 

From what I've gathered on this forum, the 2.8/3.5 engines start seeing valve float around 6500 rpm. The 2.9/3.7 engines have beehive springs and don't seem to float the valves until somewhere north of 7000rpm.

Severe valve float shows up by the cam followers falling off the valves. They're just captured between the hydraulic lash adjusters on one side, the valve on the other side, and the cam on the top. When that assembly loosens up due to valve float, they kinda just fall off. This has happened to at least one person on here with the 3.5.

FWIW I've taken my 2.9 past 7200 rpm on a couple occasions and it's still in one piece.

 

That's what I thought. I don't remember where I read the beehive spring information, but it stuck in my mind from whenever/wherever I read that.

Some may get mad, but I have touched 6400 with the 2006 3.5 in my truck now. :shrug: Sometime's I wish my shift points on WOT were a little closer to that, but I love the new motor and don't need that extra push that often so I am content with 6250 shift points on this current tune.

As @limesquat said, that extra 500 RPM would be really nice between 1-2 shift.

That's interesting on the failure from valve float on the 3.5. Is upgraded springs what will fix the valve float or would it require a different lift cam to be able to handle the higher RPM's.

I'm not really looking at doing much to this truck now in terms of internals, since its my only DD but I love learning about this stuff (well really anything, I'm a nerd and proud of it) and would like to know a little for when I boost mine in the next 2-3 years. I'll be out of college then and hopefully in a situation where I could get another DD.

The later engines 2.9L and 3.7L have better valve springs if memory serves me right so they will probably get a little more than the earlier ones. I would have to guess 7,000rpm would probably be the limit on a stock engine but how long it would last doing that consistently before something lets go would be a guessing game. It also may go higher without floating, but honestly from looking at the design it's definitely not going to last long being put through that.

A 7,000RPM capable 3.5/3.7 with boost would be a true feat in terms of capability of these motors. The bottom ends seem well built from what I saw on my first motor, but it seems as though lubrication would definitely be an issue that would have to be addressed with these Atlas motors.

 

The later engines 2.9L and 3.7L have better valve springs if memory serves me right so they will probably get a little more than the earlier ones. I would have to guess 7,000rpm would probably be the limit on a stock engine but how long it would last doing that consistently before something lets go would be a guessing game. It also may go higher without floating, but honestly from looking at the design it's definitely not going to last long being put through that.

 

You could always swap in a Mazda engine..... Don't those rotary engines do like 13-16k rpm?


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Built yes.

Stock was still only around 8500 rpm depending on year.

 

More than just the valvetrain to take into account. Heavy rotating assembly and the fact that it's a tall motor (93mm bore and 102mm stroke) means it won't want to rev high. Its basic design is engineered for torque and midrange.

If money were no object I guess you could de-stroke and bore out a 3.7 to get it square or better. Of course follow that with hot cams, beefed up springs, new valves, ported head, intake manifold with a fat plenum, rocker arms, and a big throttle body.

Or... buy an L33, h/c/i and call it a day.

 

That would be an interesting build. It's funny that it is designed to be a midrange, yet most of our power is above the 3500 RPM range :lmao:

Yeah inlines seem to make better torque in the midrange anyways. You'd be better off building it to keep the power in the midrange and adjust the gears to match the rpm ranges you need.

I am regearing very soon, actually. This thread wasn't directly aimed towards my own truck, more of a discussion thread on what is possible

 

Yeah inlines seem to make better torque in the midrange anyways. You'd be better off building it to keep the power in the midrange and adjust the gears to match the rpm ranges you need.

 

Interesting thread

 

It started out real rough, then turned super interesting. I would say, success :salute:

 

2.8 at crank:



My 2.9 with rwhp:

 

@limequat @Supermodulation @Jaymes @FixxxerKH202 @LLV.MA5 so with my current project involving reground cams and head porting while also upgrading to the 07+ springs on my 04 3.5 I've been thinking about this more and more actually being a possibility.

Lime, you say you've seen multiple 4200 guys run up to 8k? Did they beef up the bottom end? Or just upgrade the valve springs? Lightened rotating assembly?

Could I rev it to 7k RPM and match the cams to that range better to take advantage of the extra RPM and have the engine stay together? Would it be worth it? I'd be more worried about the bottom end holding together with repeated runs to 7k.

 

@Skizzo What is the trucks best at the dragstrip with all your current mods? IWould be cool for comparison purposes after head and cams.

 

@Joe canyon best right now is terrible lol. Last I was at the drag strip I ran 15.8 at 95mph spinning each shift on the terrible Goodyear RSAs with an open diff.

Haven't been back since I put in the true-track and 3.73s because my 4th gear synchro is going out and I would be shifting into 4th right at the end of the track (assuming since I was pretty close to that with the 3.42).

I'd like to go back before I do all the work and swap trans/clutch but I don't want to blow my trans and be screwed either.

Yeah the 8K engines were all high dollar builds. Black Opel is the only one that shares much of anything. Forged rods, pistons, etc. I guess the crank is good for whatever you can throw at though.

The hardest part on the engine is the tensile load on the rods after the exhaust stroke. Seems like 7k would be fine on stock rods, as it's not a huge increase over stock. Beyond that...

@limequat I'd only want to run it to around 7k. I feel like any higher or even at that much I'd be pushing my luck. It was also asked by someone else... with higher lift cams would the beehive springs still be able to keep up at ~7k rpm?

Also, does anyone know if I'd be able to keep VVT with the re-grind and if so what benefit would it give me exactly?

@Sumner any input after your lakester build with the 2900?

 

Yeah the 8K engines were all high dollar builds. Black Opel is the only one that shares much of anything. Forged rods, pistons, etc. I guess the crank is good for whatever you can throw at though.

The hardest part on the engine is the tensile load on the rods after the exhaust stroke. Seems like 7k would be fine on stock rods, as it's not a huge increase over stock. Beyond that...

 

What is the normal shift point for a 3.5l auto? Mine shifts at 2100 rpm at first gear then 2000 rpm for second then about 1900 for third. Wanted to know if your guys trucks do this also. This is without hammering it down, just normal acceleration.

 

@Zr1Boy04 You'd be better off starting your thread instead of looking for an answer here. This thread is about high RPMs with the Atlas motors not everyday driving.

 

@Skizzo, the bump reminds me...

I posted in another forum that the return spring on my VVT phaser broke causing me to lose cam control (poor idle, engine knocking sound). I wasn't able to find any other people that had the exact same symptoms. Makes me wonder if it was the 7000 RPM excursions that caused it to fail. Might be something to consider for your build.

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Popped this piece off with two screwdrivers. It's a very light press, you could almost get it by hand

At this point the rattle is gone. So it must have been the spring. Going further, taking off the cover...

You can see the 4 vanes. The one vane is larger because it incorporates the lock pin. Speaking of which, the lock pin is the reason why I couldn't rotate the phaser. I'm not sure why I could on the new part. I went back and tried it again (now installed on engine) and I could not rotate the new one either. Perhaps they ship with the pin not locked?

And fully disassembled. The lock pin receptical is the circle in the top of the housing. the mate on the rotor is just a pin with a spring on it. When there's oil pressure, the spring is pushed back into the rotor and the rotor is free to move.

This seems to be my problem. You can see where it engages on the timing hub, but there is no corresponding feature for the housing.