RPM limits of this setup
RPM limits of this setup Fresh engine, done with break-in and took it to a dyno. Didn't spin it more than the stock RPM limits, but at 6500 power was still climbing so now I'm trying to figure out the limits of this engine as I know I should be shifting well after peak power especially if it flattens out and doesn't nosedive.
stock gen IV crank
forged I beams (lightweight) with ARP bolts
forged 4032 pistons (lightweight)
ARP main studs/head bolts
Cammotion cam with soft lobes sub 600 lift
Morel 5315 lifters
3/8s pushrods
PAC dual springs with titanium retainers
hollowstem valves
trunion stock rockers.
stock gen IV crank
forged I beams (lightweight) with ARP bolts
forged 4032 pistons (lightweight)
ARP main studs/head bolts
Cammotion cam with soft lobes sub 600 lift
Morel 5315 lifters
3/8s pushrods
PAC dual springs with titanium retainers
hollowstem valves
trunion stock rockers.
TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
I would push it to 7500rpms and see how she acts. If you still aren't experiencing any valve float or anything like that, then I would keep going until you're happy. With the right cam, intake, and exhaust you could probably spin it all the way to 8000 pretty easily assuming your oil pump is up to the task.
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A response is worthless without knowing what the heads flow, intake, cam specs.
All I'm asking is the *physical* limits of my setup where I can safely spin without blowing it up.
I've already stated that the power was still climbing at 6500 where we stopped the pull.
Any stock intake hits a flow wall at around 6400-6600rpm and flat lines after that. +1 on that!
And just because intake flow flatlines at a certain RPM does not mean that power stops climbing. And just because power stops climbing and simply flatlines does not mean that it's time to shift. There are many instances, especially in roadracing which I will be solely doing, where holding onto a gear will help even though the "flow" or power flatlines.
Thank you for all those that have responded so far. Seems the consensus is that I can safely take to at least 7000.
Last edited by redtan; Apr 17, 2016 at 03:59 PM.
Lol @ some of these responses you're getting.
When you go back to the dyno, you could probably make pulls and each time raise the rev limit 500 RPM or so. Just sneak up on it and see when the curve starts breaking up, then backing off from there.
When you go back to the dyno, you could probably make pulls and each time raise the rev limit 500 RPM or so. Just sneak up on it and see when the curve starts breaking up, then backing off from there.
Hydraulic lifters can only go so much past 7000 safely. I'd trust your setup to 7500 in short bursts.
Staging Lane
Joined: Jan 2012
Posts: 61
Likes: 0
I had the same question at one point. I built my own LS7 using Johnson slow leak lifters, BTR cam, TSP heads with titanium intake valves and all titanium retainers and CHE LS7 rockers. If I'm not careful the engine will rev right past 7000. On the road courses I have driven I will turn between 7000-7500 on the straights for a long time because I don't want to end up shifting right before I need to brake. incidentally, I recently discovered a broken valve spring when I just happened to inspect the top end after using the car for street driving. Called TSP and upgraded to PAC springs. Car ran flawlessly at the track last Saturday.
Jason
If you plan to road race a lot and you didn't spec the cam specifically for road racing, you can always install it +1 or even +2 to shift the power band (and peak) down 200-300 rpm while picking up some mid range.