RPM

[305chevy c-10]

this may be a stupid quest but what determines the rpm of the engine ? in other words who or what  decides ur RPM .if u only want ur engine to turn say 5-6000 and no more .or is it ur foot .i know that spinning a engine out of range is asking for bottem end failure  spent bearring ,thrown rods and other problems that pretty much destroys ur hard work of building a motor . i really dont plan on spinning mine no more than 6000 rpm

[Irish_Alley]

your foot or a msd box with rev limiter

[bake74]

this may be a stupid quest but what determines the rpm of the engine ? in other words who or what  decides ur RPM .if u only want ur engine to turn say 5-6000 and no more .or is it ur foot .i know that spinning a engine out of range is asking for bottem end failure  spent bearring ,thrown rods and other problems that pretty much destroys ur hard work of building a motor . i really dont plan on spinning mine no more than 6000 rpm

     Are you asking the mechanical component that feeds the rpm gage, or like Irish said, the farther your foot goes into your gas the faster you go kind of thing ?

[305chevy c-10]

well kind of both .i was thinking it was something thats done when its built .so i can install something to limit the rpm . i just dont want to lose my bottom end from over twisting it .its only a 2 bolt main with pro comp studs .i figure if its not doing what it needs to do between 5 and 6000 then too bad .

[beastie_3]

A rev limiter as previously stated, or a shift light. You can program it so it lights up at a certain RPM and it will light up when you get there, telling you to let off. Its not the purpose of the light, but it will work. Might be cheaper than the rev limiter, but dunno what they hook up to.

[diphthong]

The amount of oxygen and gas fumes mixed at the correct ratio is the food of RPM'S.  This mixture, and the load on the engine is what determines the RPM's.  I think the most hands on way of controlling your RPM'S is the old fashion way.  That little red needle on most tachs.

[Captkaos]

Get a Tach and don't over rev it.  If this is a daily driver, and an auto, you have little to worry about.

[305chevy c-10]

ok thanks

[westsidek20]

How can i determine the engines RPM red line? There are several Tach's out there, some go from 0-8000 and some to 12000. What would be the redline on a 383? is there a limit on the RPM's on the crankshaft? or Is it determined by the operating  range of the camshaft? 

[zieg85]

That is a "depends" answer... How well the shortblock is built determines most of it and what the camshaft is designed to operate at and everything that feeds into it.  I am sure you're going to get some good answers on that... 

[Captkaos]

several things determine this, but first and foremost it is it a stock engine or not.  If stock redline is at 5300rpms, if it has been rebuilt was it a standard balance job or....   secondly the camshaft operating range will determine how fast you "need" to spin one.  If the range is 1000-4800, there is no point in going over 4800...  If building a motor, all of this would be determined in the planning stages of the rebuild...

You won't be spinning a SBC 12,000....

[305chevy c-10]

i think the camshaft  range is 5500 so is the intake .i took the block to the machine shop yesterday for clearancing and balancing ..can they tell me how fast they spent it or is this something different .also another quick question . Capt will it be ok for my motor to sit partially put togather in an   engine bag on a stand for say 3-4 months with botton end complete and pan installed ? or will it need to be relubed .or can i turn the crank every so often 

[Captkaos]

I don't know the background of your build, but the machine shop should be able to answer your questions.  If you are putting it together use assembly lube and it can be stored.

[Psycho71]

 

Cam and valve train is what I would concern myself with if I were you. The bottom end components will likely handle more than the upper end will, unless you have some high quality stuff up there. Valves not closing (floating) is the main thing that limits rpm, and a pushrod failure will usually be the first thing that happens if you are floating valves. Valve springs are the first thing to look at, and usually the limiting factor. Lots of other variables as well. If you run much more that stock srping pressures, you need to start looking at screw in studs, guideplates, etc.. But if I wanted to know what to shift an engine at, I'd make sure I had the correct valvetrain components for the cam I was running, then look at cam spec's. That would give a point of reference. Then I'd shift about 300-500 rpm less than the upper end of the cam's range. I've seen very few engines that wouldn't go faster by short shifting them a little bit. Well, streetable engines that is. Once comfortable that it's doing everything it should, then I might start pushing it a bit further, 200rpm or so at a time, until I found where it's starting to nose over. Back down a couple hundred rpm, and you have you're shift point.

Once you found that, there are many things you can do to insure you don't exceed that, rev limiters, shift lights, etc... But for the most part, a tach will do it. After a while, you won't need a tach, engine sound and the seat  of the pants dyno will tell you when to shift.

[chevymanrob]

dont worry about the engine "only" being a 2 bolt. rumors say GM tested them without failure to over 500 horsepower. i spun my 2 bolt 400 sbc to 6200-6400 often to the tune of 11 second quarters and both front wheels up about 2".
and if you're concerned with controlling your foot in the RPM range...get an msd 6a-l.