Guest Anonymous Posted December 31, 2001 Share Posted December 31, 2001 What exactly determines Redline? I mean the base engine I had was at 5500, now that I have put a new cam, intake, heads, lifters does that matter? I guess I'm asking, because I wasn't watchin my tach, and was getting on my car and it pulled all the way to 6000 like it was nothing. I saw the tach and stopped immediately, kinda scared. Thanks for the info. Sean Quote Link to comment Share on other sites More sharing options...
Brad-ManQ45 Posted December 31, 2001 Share Posted December 31, 2001 Generally, redline is the highest engine speed that the bottom end (reciprocating assembly), top-end (valvetrain), intake and exhaust system are designed/built to support. You didn't mention new valve springs, but if you bought a cam kit that had the springs in it then your valvetrain would definitely support the rpms you saw for the engines lifetime. Since we already know the induction system and exhaust let you pull the stated rpms, the only real question is - what was done to the bottom end? Most stock bottom ends should have no problem with 6000 rpms (Pontiacs possibly excluded). As long as you don't keep the rpms up there a lot and only wing it occasionally, no problem. From an engineering standpoint, the higher you go, the less life to the bottom (and top) end - more stress/fatigue). Hot rodders have always been willing to sacrifice a little engine life in order to spin higher and produce more power. They also, depending upon bucks of course, have options that most manufacturer's won't take advantage of when building their bottom ends (for production cars) - forged cranks w/generous fillets, cross-drilling, longer rods. Grumpyvette posted a link to an LS-1 article that will give some insight into what goes into designing an engine - the trials with oiling was an eye-opener. Manufacturers are starting to pull out the stops again in engine development - look at the Honda and Nissan high revving engines - short strokes and LOOONNNNGGGG rods, special (sometimes not forged) cranks (per LS-1). Remember, every buck saved is a major deal, leaving room for the hot-rodder to fill the need with better parts to make the engine last longer at higher rpms. I'm sure I haven't covered this very well, but look at a few of the projects the members here have posted at what they have done and you'll get the idea that we all have a case of "stock isn't good enough" and MORE POWER is only good enough until we need ---- MORE POWER. Power costs money - how fast do you want to go? Looking forward to more responses on this one! Brad Quote Link to comment Share on other sites More sharing options...
grumpyvette Posted December 31, 2001 Share Posted December 31, 2001 -------------------------------------------------------------------------------- on an engine with stock chevy parts its either piston speed reaching 4000 fpm or valve float which every is lower and in many cases 4000 fpm is realy pushing over the limit the engine will handle, to figure piston speed to divide 48000 (the number of inches in 4000 ft) by twice the engines stroke so on a 350 chevy (48000/7=6857 rpm max) on a 383 it would be (48000/7.5=6400 rpm max) but if you get to valve float at a lower rpm then you should figure your redline is a few hundred rpm lower than valve float rpm, if you want to avoid problems! remember the stress on the rotateing parts SQUARES when the rpms double so the stress on those rod bolts ETC. goes off the scale fast as the rpm gets over 6000 rpm in most engines, now of course if you add/replace parts with all forged , ballanced, high dollar parts the rpm can be raised slightly but even then with the high dollar parts 4500fpm is pushing things in most engines!!! NOW we all know people that spin their engines past those limits but its just a matter of time before something breaks as the parts are not designed to handle that level of stress,and stress is cumulative so every time they exceed the rpm levels the chances something will let go incresses! AND Brad-ManQ45 is correct that long rod to stroke ratios, short strokes to keep piston speeds low and good quality valve train parts are necessary to lower the stress on rotateing parts to get an engine to live at higher rpms.heres some stuff to read, http://victorylibrary.com/mopar/cam-tech-c.htm http://victorylibrary.com/mopar/rod-tech-c.htm http://www.stahlheaders.com/Lit_Rod%20Length.htm http://madlab.me.utexas.edu/~yspae/thesis/thesis/node46.html http://www.aros.net/~rbuck/rick/rodstudy.htm http://victorylibrary.com/mopar/chamber-tech-c.htm http://arc.engin.umich.edu/arc/conf97/wayne_tz.pdf http://arc.engin.umich.edu/arc/conf97/wayne_ch.pdf http://www.zhome.com/ZCMnL/PICS/detonation/detonation.html http://eric.virginia.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm http://www.tpub.com/engine1/en1-105.htm http://www.motortecmag.com/archives/2001/jun/JUN01-01/JUN010101.html http://www.torquecentral.com/techdocs/GM/ls1/LS1_Tech_article.htm http://www.c5registry.com/Documents/ls6/INDEX.HTM http://www.rapidline.com/calc/ http://www.carcraft.com/editorial/article.jsp?id=868 http://www.rapidline.com/calc/engine/pcpiston.htm http://www.superflow.com/support/support-engdyno-tt-torquevsspeed.htm I have several thousand more articles in the data files but if you read and understand these that should give you a small idea of whats involved! Quote Link to comment Share on other sites More sharing options...
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