*7M Crank RPM Limit*
- Thread starter IJ.
- Start date
im such a pussy, i havent even hit redline... but im 160,000 miles on the block..
still pulls hard at 6k,,
still pulls hard at 6k,,
Funny when mine was NA I can't remember hitting a limiter at all!
(don't even know if NA's have one)
(don't even know if NA's have one)
In case anyone's wondering what I mean by 6M and 7M Cranks the early 7M's used a crank that's marked 6M and didn't have Counterweights on all of the throws then in 89 they got the 7M crank that's fully Counterweighted.
Look at #2 and #5 throws!
Top 7M crank Bottom 6M
Look at #2 and #5 throws!
Top 7M crank Bottom 6M
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joel w. said:
Hahaha Well i have. Here we go,
I was cruising at ~60mph with cruise control. I came to a light so i went to disengage the clutch, thinking the cruise control would cancel like it should.
Well my car has a auto->R154 swap and the lazy ass second owner thought it best to leave out the clutch switch. Yes, that is the thing that cancels cruise control when you push in the clutch... And i didnt have one.
Sooo, I push the clutch and slowly begin to slid down in my seat with the "oohhhh shhhiiiittt" felling as my tach takes off. For a second or two i was as confused as my car was thinking, "WTH is goin on!" So i frantically swing around in a blur looking to stop this. I dont remember exactly but im sure i engaged the clutch 1000 times after putting it in neutral hahaha. Then i thought for a 1/2 sec and flipped the CC stalk toward me. The people i was passing must have been like wtf is that damn person doing.
All in all, I think my engine barked at me about 5 times as it bounced back of the limiter. To bad i was too busy looking for a way to make it stop i didnt look to see how high the needle went. lol not safe, not fun, and almost dramatizing. I was somewhat in shock the rest of the way home. I did pull in to a near parking lot to make sure that it was ok.
Im starting to think my engine has had a past rebuild... I wish i knew.
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Valvetrain has nothing to do with the reliability of the crank. The crank would fail at the same rpm no matter what springs you have up there. Melloyellow I believe runs his 7m up into the 8k range. High rpms under a load or in a quick rise then fall is much safer than "hanging rpm" Meaning that if you run your motor up to 8k rpm and hold it there harmonics will will set up and tear your crank apart. How you balance your rotating assemby and how you drive will be the factors in crank life.
if WOON can spin 94mm to 9500 rpm. The 7m crank at a measily 91mm should get thier provided the supporting mods. 
Run my new motor to 7200 no problems at all but it's not your average build.
I'll run it to 8000 but will take some time working up to it in small steps.
With the right supporting mods it's still pulling like a freight train at 7200 and I suspect will do the same at 8000.
I'll run it to 8000 but will take some time working up to it in small steps.
With the right supporting mods it's still pulling like a freight train at 7200 and I suspect will do the same at 8000.
ROFLMAO if you do it and don't post a vid I'll come there and make you suffer!figgie said:you are going to make me push the 9k limit aren't you
Mine sounds awesome at 7200 and very different to a JZ engine at the same RPM! (7m sounds wicked revving the JZ's sound like a sewing machine)
(NOT hanging shit on JZ's they just sound very different at high rpm)
So everyone says that the valvetrain needs to be upgraded before reving to 7500rpm. Has anyone actually tried and see how high the stock valvetrain will run before it spits a shim or floats?
Tubbie: I sort of doubt many will have explored the limits on stock gear as to get around the stock limiter generally requires a standalone and by that time you've installed good springs anyway.
The stock springs are quite light seat pressure and most motors have sacked out 50.000+ mile old springs that have even less pressure!
The stock springs are quite light seat pressure and most motors have sacked out 50.000+ mile old springs that have even less pressure!
Indio: It shouldn't "break" unless you have some big cams in there!
It'll just float the valves drop off in power and sound really bad till the rpm drops enough for the valvetrain to stabilise!
You can just about change out old stock springs using your fingers they're so soft!
It'll just float the valves drop off in power and sound really bad till the rpm drops enough for the valvetrain to stabilise!
You can just about change out old stock springs using your fingers they're so soft!
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