I have a custom 351W motor and I am wondering how I would determine what a red line is for the RPMs. I used a seasoned block, a stock crank, and the stock piston rods, everything else is new.

So what factors go into determining what a red line would be for a motor? What about performance parts like a supercharger or nitrous, are those a factor in determining a red line?

I have a rev limiter and I want to make sure I put in the right limit on the RPMs.

Thanks.

 

I would take cam choice in consideration.
you need to keep in mind the rpm limit of the rotating assembly, but if you choose a cam that only makes power to 5500, I see no reason to rev to 6500.

Stock bottom end, with no arp bolts or main bearing girdle, I'd say about 6k all day long and 6500 max. I have built a few stock car motors that revd 6500 all day long with stock bolts and no issues. But I wouldn't reccomend it.

But go with cam selection for max rpm. If cam is good to 5500, put a 6k chip in the rev limiter. For boost, your cam selection is most likely 5-5500 anyway. Nitrous is a little different because you don't want to hit rev limit while spraying. You'd use a window switch to turn off nitrous just below your shift point that way you aren't spraying when you throw the clutch or, like me, don't let off the gas to shift.

 

I have a lot of the specs for my cam but nothing that mentions what you said. Is there a way I could figure this out or should I just call where I got the cam?

 

What cam is it.
if its a custom cam for your application I'd still say its max will be in the 5500-6000 range.
Boost requires shorter duration and overlap unlike a high rev cam.
If you got the number of the cam manufactur I'd just call them. Theyade it, they know the limits and specs.

 

With hydraulic lifters the motor should be limited to about 6500rpm but there's also no point reving the motor beyond peak HP so my suggestion is to use a dyno sim program to figure out what that is and set the ignition limiter about 500rpm above and a shift light right at peak HP.

 

Rev it till she blows then subtract 200! Just kidding don't do it

 

the only real way to see what is an optimal redline is slap it on the dyno. then use the "intel" gained by the dyno pulls to set your redline. . .since im assuming you have an automatic, you want to then "tweak" your redline so that you have a happy balance between shifting right after peak hp, and allowing the rpm to fall back to an optimal range. there is a happy relationship between utilizing the peak hp (and sometimes revving past it) and keeping it in the power band after the upshift. for example, if you had a drag truck you would set the redline according to the dyno, take it down the track, and keep bumping it up each run until you lose time. . .you dont have to do it on the trakc, but this real-life trial and error teamed with the info gained by the dyno graph is the only way to optimize your redline/shift points.

 

I'd say 5500-6K. You said you've got new parts, did you upgrade the valve springs at all? I'm assuming you've got hydraulic lifters too. Unless you've got big ports, high compression and big valves, no sense in spinning an otherwise stock engine very high.

 

This is your best option especially with a power adder; when HP and torque fall off at the same time.

However, I personally would keep it below 5500 unless you have upgraded the rotating assembly hardware and valve springs.

 

new Trick Flow heads. Hydraulic rollers, yes (I did the retro fit kit). I have stock compression (at least when the supercharger isn't connected) but I do have big ports and valves. 205cc (polished) on the ports and 2.02 intake valves.

 

so is the charger not hooked up?

 

Well, nothing is going to be hooked up now, the motor took a crap last night so I gotta take it out, no ideas yet.

But, my plan is to run the motor with this setup (stock injectors and no charger) for the first 500 or 1000 miles, then it is ready to be bolted on. Well, I have a little metal fab to do but that won't take long. The mounts and all other connections are ready for me to install it and connect it up, probably take 30 min. when I am ready.

 

good idea, keep the boost off for a while. i suspect youll want to dyno tune it anyway once youre all setup, so thats the perfect chance to get the info you need to start your redline/shift points. just another reason i hate autos. . . .

 

If you're running a blower you'll need to determine how much boost pressure you want/can run, and determine at what engine speed with what diameter pulley you'll hit that mark. Dyno it and see where the power falls and adjust max rpm and pulley size to get the most power where you can use it. Trans choice and rear end ratio will play a large factor too