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Max RPM?

This is a discussion on Max RPM? within the General Help forums, part of the LSx Technical Help Section category; What is a safe max rpm for my moto? Its an LQ4 with 65000 on stock bottom end,heads, cam, lifters ...

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    Member Edward-T's Avatar
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    Max RPM?

    What is a safe max rpm for my moto? Its an LQ4 with 65000 on stock bottom end,heads, cam, lifters and pushrods have about 1000 on them, when it was dynoed it was still making power at 6500 and it was smooth as silk from idle to rev limiter with no hesitation or anything, just wondering what a safe, realistic limit for these motors are.

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    Smiles for 9.5 Years cammed goat's Avatar
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    I know the LS1 redline is 6250. You should be fine as the LQ4 is an iron block.

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    Member Edward-T's Avatar
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    ok thanks bro!
    2011 GS

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    Senior Member Lunatikgixxer's Avatar
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    if you got it tuned on a dyno your tuner should of told you what he set the rev limiter at and where you should shift at.. atleast my tuner did..
    SLP Lid, TSP 233/239 112lsa with supporting mods, Pacesetter Headers and ORY, Magnaflow muffler, MSD Spark plug wires, Sportlines, HAL QA1 Adjustable Rear Shocks, BMR Adjustable torque arm, BMR Lower control arms, Monster Level 4 Clutch, 6K HIDs Lows and Fogs. Does 384rwhp 358ft/lbs tq on stock ls1 intake and stock heads, tuned by Jeremy Formato.

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    Member Edward-T's Avatar
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    well i told him to set it at 6200 after we did the tune, just to be safe, but since the tune i have a bigger MAF and 42 lb injectors i need to install then get a retune, and since it was so smooth to 6500 i was thinking that i should move the limiter up but wanted to stay safe as well.

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    Electrical Engineer KMdef9's Avatar
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    Quote Originally Posted by Edward-T View Post
    well i told him to set it at 6200 after we did the tune, just to be safe, but since the tune i have a bigger MAF and 42 lb injectors i need to install then get a retune, and since it was so smooth to 6500 i was thinking that i should move the limiter up but wanted to stay safe as well.
    42lb injectors and a bigger MAF don't justify a higher limiter. Just an FYI.

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    Moderator Firebirdjones's Avatar
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    In an ideal situation you want to shift the engine just above peak HP for optimum ET. If your dyno numbers show peak HP at 6500 (which is dictated by the cam and valvetrain) then ideally you need to shift above that, maybe ~6700ish. The question though is whether the bottom end is built to take that kind of rpm??

    Stock bottom ends spin to 6500 without much issues. I shift my stock bottom end LS1 at 6500 and don't sweat it, I even laid it on the limiter at 6700 in the traps for a couple seconds, but I don't make a habit of that.

    Your LQ4 6.0 is the same bottom end as an LS1, same stroke, rod length etc....just a larger bore. If it makes you feel better, I'm buzzing my bone stock 6.0 to 6,000 rpm with the stock cam . With the small cam, it would run out of steam before the bottom end complains.

    You really need to find your peak HP on the dyno, then decide if you want to spin it past that point. If it reaches a point where the stock rods are questionable, then dial it back a tad to save parts and live with it, or accept the fact that opening the wallet may occur at any time and be okay with that

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    I'm spinning mine to 7200, its a LS3 all ARP hardware..

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    Senior Member INMY01TA's Avatar
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    My stock bottom end LS1 has rev limiter set at 7,000 but I set the shift lite to 6,700. I've hit 7,000 a few tiimes.

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    Senior Member redbird555's Avatar
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    Quote Originally Posted by INMY01TA View Post
    My stock bottom end LS1 has rev limiter set at 7,000 but I set the shift lite to 6,700. I've hit 7,000 a few tiimes.
    thats really not too smart imo if you have better rod bolts then ok but the stockers are very weak around 6800 rpms some people do it without a problem but I would atleast back your shift light down to 6500 that way when you shift your probably at 6600-6700 anyway and wont risk damaging the bottom end. the little amount of gain you may get from shifting those couple hundred more rpms could cost you in the long run

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    Senior Member INMY01TA's Avatar
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    Quote Originally Posted by redbird555 View Post
    thats really not too smart imo if you have better rod bolts then ok but the stockers are very weak around 6800 rpms some people do it without a problem but I would atleast back your shift light down to 6500 that way when you shift your probably at 6600-6700 anyway and wont risk damaging the bottom end. the little amount of gain you may get from shifting those couple hundred more rpms could cost you in the long run
    Actually I think I do have the shift lite set 6,500 so I'll shift it at 6,600-6,700ish. I haven't raced at all this year so haven't been worried about it.

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    Member Edward-T's Avatar
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    Yea I know it doesn't justify raising rev limit. Tuner said my stock injectors were at 95 percent duty cycle that's the reason for the 42 lb injectors and I figured I may as well add more air as well with the bigger maf, also thinking of going with a 85 mm throttle body to, so what should I expect as far as gains? And since she was still making power at 6500 on maxed injectors shouldn't the limiter go up to find the peak?

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    Moderator Firebirdjones's Avatar
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    Quote Originally Posted by Edward-T View Post
    Yea I know it doesn't justify raising rev limit. Tuner said my stock injectors were at 95 percent duty cycle that's the reason for the 42 lb injectors and I figured I may as well add more air as well with the bigger maf, also thinking of going with a 85 mm throttle body to, so what should I expect as far as gains? And since she was still making power at 6500 on maxed injectors shouldn't the limiter go up to find the peak?
    You would have to put it on the dyno to answer those questions, it will need retuned anyway. Idealy you want to run the engine past peak readings slightly to find the actual peak.
    Last edited by Firebirdjones; 11-15-2011 at 04:29 PM.

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    Member Edward-T's Avatar
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    But isn't that kinda high to spin it? It never wavered or dropped off at 6500.this is my 1st LS engine, my previous car was a 95 T/A.... Good ole LT1-LOL so I'm not familier with it or what to expect but the tuner said with the 6 bolt mains I shouldn't worry to much, he says he turns them around 7 all the time

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    Moderator Firebirdjones's Avatar
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    For a stock bottom end,,,,,yes 6500 is getting up there. 7,000 though,,,,is really pushing the envelope. It's not the blocks integrity and the 6 bolt mains I worry about, it's the stock rods with stock bolts. You'll stretch a rod bolt and spin a bearing long before the block or crank gives up.

    If you were on the dyno at 6500 and power still was not falling off, and you have reached what you consider your limit to spin the engine, then I'd leave it at that. If you don't mind taking chances and can except the fact that it could be pushing the breaking point, and you have a thick wallet, then wind er' up
    Evidently the camshaft specs were ground far beyond the capabilities of a stock short block, or someone installed the cam retarded... (my opinion). At the very least an easy fix would be to advance the camshaft a few degrees and bring the peak down a bit.

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    Member Edward-T's Avatar
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    I don't know the cam was already installed when I bought it, its a TSP tourqer V2 595/598 lift on a 112, I added the heads when I got it, they are new castings LS6 ported/polished stage 3 with 2.08 intake and 1.60 exhaust, 5 angle valve job on the heads

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    Moderator Firebirdjones's Avatar
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    None of the websites I've seen actually list the intake centerline ground on any camshaft, I would need to see a cam card to know for sure what's been done.

    But with a 112 lobe serperation angle I can only guess at the ICL since it's ground specifically for Texas Speed according to what they want. If your 364 cubed engine is truly peaking well above 6500 then I'd guess they don't have much advance in that camshaft, (maybe on a 110 ICL??)
    With that said, it's also impossible to know where the cam was installed (only the installer would know,,,if they measured it).

    Theoretically, installing the cam straight up (without checking) it should be in there at 110 ICL, but that's a perfect world. That doesn't account for timing chain stretch (which retards the cam) and it doesn't account for discrepancies in quality control for certain parts. Such as keyways on crankshafts, keyways on the timing gears, keyways on the camshaft, or was the camshaft actually ground as the manufacture says it is???

    All these variables change the installed position slightly, which is why we always degree a camshaft to make sure.

    With that said, and assuming your cam might be ground with a 110 ICL, we could figure in some chain stretch (2 degrees isn't unusual after a few thousand miles) It's very possible it's running right now with a 111 or 112 ICL and maybe more. That would be a camshaft that is installed and/or running retarded. Which might explain the very high rpm peak well beyond what you care to spin the engine.

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    Member Edward-T's Avatar
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    Ok, that makes sense. Either way when I get my other parts on I think I will set it at 6200 or 6300 just for my own piece of mind, last thing I want to do is blow it up trying to get an extra pony or two. If I had built it myself I would have reworked the bottom end a little to strengthen it up.you guys pretty much answered my question that 6500 is about the limit for a stock bottom, thanks


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