What RPM should my motor spin to?
 

Just finished the cam and spring install- Comp XE 282 HR+987 dual springs with titanium retainers and 10 degree locks. The motor runs good and pulls like my friends' cammed LS1's. It seems to make power for ever. Comp lists the RPM range as up to 5800, but it seems to pull past that. What "should" the redline be for a 350 with a cam like this one-230 intake duration, 236 exhaust @ .050 (possibly more with 1.6 rockers) and .544 lift, .555 lift?

RPM intake
750 Holley HP DP carb
complete comp valvetrain

Put it on a dyno. Anything else is just a guess.

You may feel like it registers as "pulling" on the butt dyno, but with real test equipment you'll find that its HP peaks somewhere, even if it doesn't crater immediately right above that. Wherever it peaks, is about as fast as you need to be spinning it; it'll go faster if you shift.

I'm guessing it'll be done at around 6000. It might go to 6300 or so if you have a rev kit and you zero-lash the valves.

I did a search on the rev kits by AFR and Isky. Do you know any where I can get one?

Is the bottom ends stock? Crank, rods and pistons?

Even though you peak hp might be around 6k, can your bottom end handle the repetition? Just something to think about.:)

Crank and rods are stock pieces that have been balanced and treated to good hardware. the pistons are flat top hypereutectic pieces. I am not worried about the motor coming apart, I would just like for the redline to be at 6500. I read that TRAXION turned his bone stock L98 to almost 6800 rpm with no problem. i have the video and it sounds awesome.

Sounds like you got it covered. I have spun my stock L98 up that far also. Dont know how good it was for it. lol.:D

Like Rb said, get it on a chassie dyno. Find out were the peaks are at. Then take it to the track and see what rpm you are at when you cross the finish line. You then can adjust the rear tire size or gear for optimal performance at your peak rpm.

You can get an AFR one from AFR, and an Isky one from Isky. You can also get at least some of those products from Summit and Jeg's and maybe your local speed shop or machine shop.

Comp, Crower, and Crane also make them. Probably Lunati too but I've never tried to get one from them.

Every one of those companies has their catalog on their web site, easy to find. Just go look.

www.airflowresearch.com
www.iskycams.com
www.compcams.com
www.cranecams.com
www.holley.com
www.crower.com

There's a BIG difference between "it'll turn xxxx RPM" and "it goes fastest if it turns xxxx RPM". You've got a hydraulic cam. It's going to be naturally rev-limited by that. Whatever valve springs you have, the valves will float at some RPM. Whether the bottom end will survive RPMs beyond that is a worthless non-academic exercise, because the motor should never be forced to go there, because even if the bottom end survives, the valve train won't. Your induction system has a flow limit beyond which no further gain in output is possible once that RPM is reached; again, it's pointless (or actually negatively pointful) to try to go beyond that.

All of this about "so-and-so spun his bone stock 38 Hupmobile to 9400 RPM" crap is pure useless monkey-spank. It doesn't apply to your motor. You can't go by that. That guy might have just got real lucky. And he also might have gone alot faster if he had shifted at 3600 RPM or 6100 RPM or 7500 RPM or whatever other RPM caused his motor to be back at its torque peak after it reached the new gear. Again, you have no way of really knowing that.

If you want your "redline" to be at 6500, then go get yourself one of those r¡cer 8" tachs, stick it out in the open where everybody can see it, and turn the big red pointer to 6500. Then you can tell everybody your "redline" is at 6500, for whatever good that's going to do. Meanwhile, your engine is going to do whatever it does at whatever RPM it does it at, and it would be best to learn the reality of what that is, and screw a bunch of this "what you want your redline to be" nonsense after you've already built it. It is not founded in reality.

without knowing what heads you have i'd say redline would be about 6500 and shift point should be around 6200-6400.

If all your parts say the same range (i.e. 3500-6500) does that mean your range should be exactly that? Is it determined by the keast restrictive or weakest part? To what degree can the intended end be planned?

The entire reason I swapped the cam was to gain a few more rpm than the HOT cam I was running. HOT cam .050 duration is only 218 degrees but will pull to 6000 and sometimes more. I did the typical HOT cam+Vortec combo on a budget, then I upgraded everything else on the motor but I was running the same cam. I knew there was more power left in my combo so I swapped camshafts.

What I was looking for, was someone who has a cam with similar duration and lift, and a simlar setup to see where they shift their car at.

It just doesn't make sense that my combo would pull hard to 6000 with a 218 cam and also with a 230 cam with narrower lobe separation.

I guess it is off to the dyno for me again. Here is a snap shot of my best dyno with my old HOT cam and edelbrock valve springs. the red line is with Vortec heads, and the blue line is after I changed to E-Tec 170 heads. These are Rear wheel dyno numbers.

Looking at your graphs, the correct shift RPM is fairly obvious.... with the red setup, it looks to have been at about 5400 RPM; with the blue setup, about 5700-5800.

The goal is to keep the engine within the RPM range where it produces the most power. That means, in most cases, you should shift at the RPM where the engine returns to about its peak torque RPM after the shift.

In fact it might very well make sense that you'd shift at the same RPMs with both cams, if the cam isn't the limit to the engine's flow. If something else is limiting it, you can change cams all day long, and not get past that. You're right, that the bigger cam should move the whole curve to the right; but only if all the other flow-related parts support it.

Your motor's torque curve falls off ALOT as RPMs increase. It's not flat with a broad peak like you'd want. It has the same "shape" as a stock LG4 one or something; which shows signs of being induction-limited. There's something holding it back. The red motor was worse. I'd guess, just as a guess, that it's the exhaust; but I could be wrong.

Putting a cam with closer lobe separation will make the peak torque higher, and lower the RPM at which peak torque occurs somewhat compared to a wider lobe separation. I would expect that the XR282 will put down well over 400 ft-lbs to the wheels, at about the same 4500 or so that you have now; and peak HP will occur at the same or lower RPM than it does now, and not be much higher. All of which will make it more obvious even as you drive the car, just from the butt dyno, where the optimum shift point is; you'll be able to easily "feel" the peak.

Next time you go to the dyno, do an open header run if possible. See how much difference it makes. I think there's some power missing in there somewhere.

You must remember to go that fast (spin) would require higher quality parts. Eventually, the people who spin theres to X,XXX RPM would do major engine damage. Stock components are not made to hold up under high power and revving conditions. Once in a while is OK, daily or weekly is asking for trouble.

This was with open headers. Keep in mind that this was my old setup. I think I had poor valve train control. How much better could the induction be for the street?

750 Holley HP carb+ Perfromer RPM intake

I am shooting for 375 hp and 400 tq at the wheels. I will be going to the dyno on friday and i will post back on how it went. I may even spray the 75 shot on top of it.

I hope you get the numbers your looking for. Im interested to see where you end up at.

I'd just like to give everyone the chance to call me an idiot
 

Once I dropped my tranny into 1st gear around 45-50 mph. I slammed on the gas and noticed I wasn't hauling ***, then I realized what I had done. In any case, my 200k+ mile stock TPI350 survived a trip into 6k-7k+??? whatever rpm it was. Still no problems.

I've heard from a mechanic who's worked on his fair share of TPI engines, 3rd gens, C4s, etc, and had a pretty fast 71 barracuda, that the stock tpi bottom end can handle 8k rpm. Comments anyone?

Re: I'd just like to give everyone the chance to call me an idiot
 

"Can handle" and "Make power at" are two different things.

Re: Re: I'd just like to give everyone the chance to call me an idiot
 

I'm aware of this... not only did I provide the example I did, but I also said a "stock TPI bottom end", not a "stock TPI engine". A bottom end of an engine won't make ANY power without a top end and vice versa. Hence the reason why I said bottom end. Sorry if I insinuated the idea that a stock TPI engine could make power at 8k rpm.

Okay. And? What's your point?

I never said stock tpi motor. I just said that an engine being able to handle a certain rpm is totally different than an engine making power at a certain rpm. Regardless of whether is has stock heads/cam or not.

Stock GM cranks are not strong, neither are th rods or cast pistons. Very porus and brittle. Sure you can take a stock bottom end to X,XXX RPM and it will survive. Take it there repeatidly and it will perish at the hands of centrifical force and such.

went to the dyno and it did not look good
 

First pull it seemed to struggle once it got passed 5500 rpm and it was very lean. It made less power than my HOT cam. Then i jetted it up from 80 in the rear to 84's and the power got better as seen in the blue graph. We took it to over 6000 just to see what it would do and it seemed to hit a rev limiter but there was no valve float and I DO NOT have a rev limiter. The motor seemed to fall flat on its face. I t did not even have a steady decrease in power like it should it just died as you can see in the graph.

I have an old dyno pull with my LT4 cam that we did take to 6200 rpm and it made a nice curve. The only thing that I can think of is that the lifters are the culprit. When I changed to the ETEC heads I also changed the roller lifters to "new" ones from mellings from Autozone. I may try to put in my old lifters and try it again. It is doing the same thing with two different sets of valve springs.

The dyno started getting rich as the engine went over 6000 which makes me think that the valves were not seating. My actual dyno sheet is exactly where Desktop dyno said it should be up until 5300 rpm then the valvetrain goes wild and power just dies. I don't think it can be the heads, or the induction, or the headers, so I am goin to replace my lifters and see what happens.

This is the reason I stoped building so called "hot small blocks" well anything under 400 cubes.

I dont think the lifters are a factor, I would do as was suggested by RB, get a rev kit and set the lifters to zero lash.

Although this is USUALLY the case, it is not set in stone. You need to look at the nature of the power curve and look at the gearing to figure out the true shift point. Depending on the way it is geared it is POSSIBLE that you can still make more power to the ground by leaving it in one gear as opposed to shifting to the next. Only after you put more power to the ground in the next gear should you shift.

What you will likely find though is that your cam is still pulling very hard until you just don't feel safe spinning it any further. In this case you're giving up E.T. if you shift it at any point below that.

Edit -- Looking at your dyno graph I agree something is wrong. If you're gonna be turning that kind of RPM you might want to invest in some Comp Cams Pro Magnum R lifters. They are specifically designed for higher RPM operation.

i have a bigger cam than yours(Comp cams 294S). My car would fall flat on its face at 5500.It turns out my ignition system was holding me back.I recommend upgrading the ignition to MSD.

You need to remember he has what is basically a stock bottom end. Shifting later and later might not be healthy.

See sig. I do have a total MSD ignition. Distributor, wires, and CD box.

I just got done replacing my lifters. I waited til the engine was up to temperature, then adjusted the rockers to 1/4 turn past zero lash. i also port matched my intake to my heads. The performer RPM ports are small like stock Vortec heads, not like ETEC ones. The Vortec port is wider at the bottom as where the ETEC ports are the same bottom to top.

BTW I sprayed a 75 shot on the dyno and made 427 hp and 596 torque at the wheels.

Post that 75shot chart ^_^
It does sound like something must be happening, possibly aircleaner restriction? Is the fuel pressure staying where its supost to be set?

I have the same cam with 1.6 rockers and sportsman 200cc iron heads with a home port job on my 10:1 355 and it made 348 rwtq@4800 and 350rwhp@5900. Like yours it starts to fall off a cliff after 6000rpms. The motor will go to 6500 no problem (which is what the cam card recommends for max RPM), but it stops making power before that. This was with stock roller lifters, and I'm sure part of the problem is valve float. I have since replaced mine with comp-R lifters but have yet to go down the track or dyno it since. A rev-kit is in my future along with some AFR's to make a little more power.

The other part of the problem is it is a 110 LSA cam which makes great midrange torque but at the expense of not being a high RPM spinner. If this cam was on a 112 LSA it would peak a couple hundred rpm higher. You can retard this cam 2 degrees to shift the powerband up a couple hundred RPM, but thats about it. I would be curious to see what just lifters and a rev-kit would do.

Also you might be reaching the limits of your heads and/or intake. As asked before, are there any restrictions with your air filter setup? Have you done a pull without it to see if it made a difference.

One last thing on cam choice...224/228 on a 114LSA 1 deg adv with .582 lift on my buddies LS1. To me cam seemed a little weak, but it pulls to 6700 rpm and the power curve is flat up there. Put 443 rwhp down too. Insane power. You might want to rethink cam choice or possibly call comp for a recommendation.

Sorry for the long post

I did not do a pull to see if the air cleaner was restrictive because I have seen people loose power with no air cleaner to help straighten the incoming air. I am running a 14x3 triangle edelbrock air cleaner.

Lo-Tec:

Thank you for the first hand input! That was what i was trying to understand. Since my lifter install the motor runs quieter (no tapping valve sounds) and it is much more responsive. I have not yet taken to redline but I think I fixed the problem. I would like to put some 2210 1 3/4 inch long tubes to squeeze out a few more HP out of it. I also need to jet my nitrous plate 2-4 jets leaner on the fuel side since my a/f was off the scale rich ( 10:1). I believe I can come very close to 400 rwhp/400 tq on motor and 500hp/600 tq on a "75" shot.

Did you go with the comp-r's for lifters? Mine quited down alot at idle after install also (used to sound like a sewing machine). With the air filter, you might be surpised. I had a supercharger style top hat and 3" tubing to a large K&N cone filter to fit under the stock hood (this is on top of a single plane DFI 4bbl throttle body). Only made 308 to the wheels. Removed it and got 350. The top hat has that restrictive. Worth a try next time you're on the dyno.

Damn:D

1. Lose the Edelbrock "Triangle of Death". It's costing you ALOT of power, and will cause you even worse problems some day.

2. Your RPM limit is probably valve float. The reason the GM cam didn't do it, is that its ramps are much more gentle. Also, the GM cam has a wider lobe separation, which tends to reduce the peak value of both the torque and HP curves, but tends to flatten them out toward higher RPMs. The tighter lobe sep gives a higher peak, but the motor will seem to "crater" sooner after the peak. You probably need either more valve spring, or a rev kit, to overcome valve float, if that's what's going on; although it won't go too much farther. Although, I'd try getting a real "go-fast" air cleaner on it first, instead of that stupid "lotsa chrome" POS.

What is that? :confused:

for some odd reason carbs love the foam of those edlebrock air cleaners
I've heard of quite a few carbs and even seen one first hand where the carb just did the best job it could of getting that air cleaner inside itself to eat it
or rather not the whole air filter but the filtering foam inside the carb

Those things are a big piece:doh: I run a 14X3 open element K&N on mine

I've seen them suck into motors, catch fire :eek:, I've even seen the screen piece come loose and go in the carb (as far as it could anyway....)

They're for street rodders that want to jam more square inches of chrome under the hood, so all the 7-year-old boys will ooooh and aaaah over it in the parking lot. Doesn't matter if the car even runs at all or not, let alone how good it runs, or how fast, or if it's faster than it would be with some other air filter. Strictly for looks. The car will go faster with almost anything else on it. Especially if there's a hood. Look how close the top of it (air intake surface) comes to the hood; it's mostly a blockage with the hood closed, not a filter.

Altogether evil.

I think he has this one--the 14x3 triangular one.. This one looks great and doesn't want to jump inside your engine.

Well it seems like top-end woes roll call. Count me in too.

XR282HR-110, Comp R lifters (1/4 turn past zero lash), 987 springs
200cc Alum. Topline heads
HSR
MSD probillet, coil, etc. (rules out an ignition problem)

No power after 5500rpm.

What is good about only doing a 1/4 turn past full lash vs the recommended 1 full turn?

Well, if the engine has sufficient fuel supply, and ignition, then it sure looks like a case of valve float.

Like somebody mentioned (I think), if it were just an intake or exhaust choking off airflow, the power curve would show a gradual decline, not a sharp drop.

I'd check fuel pressure and volume supply first just to be sure.

You said you're using hydraulic roller lifters? I've heard those are a disadvantage at high rpm due to their weight. You may need a spring upgrade, maybe the new Comp "bee-hive" style would help. A call to their tech line ought to sort that out.

I've run into the valve float problem before on a 502 on the dyno. At about 5400-5500 rpm, the rpm suddenly falls off like there's a huge drag on the motor, or like you pulled back the throttle. (In our case the valve springs were inadequate to handle the heavy hydraulic roller lifters and the big-*** big block valves. )

Does this sound like what your motor was doing?

Supposedly if you run less valve lash you can get more lift.

I know this post is old, but I would like to know if anyone solved their problem. I am running a 383 with AFR heads and an AFR rev kit. 114 LSA 525 intake 532 EXH @ .50 with 226 and 232 respectively. Using Miniram intake.

I have tuned the chip rich and lean to no avail. I can make power (Dyno proven) to 5700 and the motor just goes rich and sounds like it is going to shut down. I usually have to rev it a couple times to clear it out.

I have checked cam timing. did a cylinder leak down test, and checked valve spring pressure. They all seem to be fine.

I am thinking that maybe I am having some electrical problem with the harness to the ECM or the stock distributor with MSD ignition module and coil is not cutting it

I am thinking that you need to finish tuning it and post a dyno graph.

What makes you think it is not tuned??? It drives great. I changed the timing and fuel mixture at 5500 to 6000 in the map to see if I could reveal a problem, or possibly make the car rev past this stopping point. Unfortuneately, it did not work. I will try and post a graph tonite, not that I have anything to prove, but if anyone would like to see the correlation of AF to HP and RPM then that info will be available.

According to the graph the car is making power to 6000 and then it bogs and the AF on the ECM and the dyno WB read rich and you have to back out of it. We may try changing the valve springs tonite, and make a couple runs.

What makes you think it is not tuned?

Fair enough,,,, I did not specify what I tuned rich and lean.


I am using a speed density system. I started off with a 1222730, but have recently changed to a holley C950 for ease and speed of tunning.

What I tuned were map values from 5000- 6500 RPM and 80-100 Kpa. I used the high RPM 8d patch on the 730 (to no avail) and the C950 I set the high RPM value to 6500. I have also played with timing in this range. I can change the AF from lean to rich and the HP varies with timing, so it is my guess I am not out of adjustment on either one.

This weekend a buddy and I changed valve springs and dropped the exhaust. THis did not help. It rev limits itself at 6000 and almost dies. And before anyone says it we have checked the rev limiter MULTIPLE times. We even put in an early one for a test at 5500. Which shockling leaned the engine out up top when using the C950. That will have to be remedied when all is said and done.

Just a follow up incase anyone is looking for a solution. I found the problem with the motor dying a 6K. THe type of spring that was being used was going into coil bind. Replaced the springs with 918 Behives and the car ran great.

Get rid of the junk dual springs and put some beehives on. MUCH more stable above 5500 rpms than a dual valve spring.

Not all dual springs are junk. Here's my "junk" dual springs singing at 6500 on the dyno: VIDEO :idiot:

It depends on how aggressive the cam is of course. There are plenty of setups that can cause a dual valve spring to get unstable at 5500 rpms