Max RPM of Jeep Engine

[John]

I have only worked with the 12 cw cranks, but there is a 4 cw hanging in the rack that will be working with next, even with always thinking the 12's were stronger, thinking to do a old school build with a Paxton sitting on it.
John

[TurboTom]

To answer a few questions about my Turbo 4.0.
Long story short 14 pounds of boost
I quit at 4500RPM due to the pushed out head gasket, and later found 2 cracked pistons.
No problem...I will fix it and get ready for round 2

Also I got the cam out of my 4.0 today.....If that baseball bat is flexing, bending or or being a harmonica, I'll kiss your......Ummmm I would REALLY be surprised.

[1bolt]

You might be surprised... somewhere on the intertoob there's a video from a spintron showing a NASCAR engine revving to 7k...

The pushrods take on this scary S shape... And they're supposedly chromoly.

[TurboTom]

You might be surprised... somewhere on the intertoob there's a video from a spintron showing a NASCAR engine revving to 7k...

The pushrods take on this scary S shape... And they're supposedly chromoly.

I doubt anyone here with a jeep 6 cylinder is running 450 pound of open spring pressure.
And if the Nascar engine is only turning 7k, it must be from 1990
The latest cheater Nascar pushrods are carbon fiber, with a thin skin of metal wrapped around them so the Nascars tech inspectors magnet sticks to them. (As per the rules)
The pushrods are 3/8 inch..that lump stick I took out of my motor is not the problem...if one exsist.

[1bolt]

Thats true but then I wasn't going for a litteral comparison between a NASCAR engine and I6. More of a statement about the kind of severe forces at work on things we tend to think of as solid and inflexible, like chromemoly push rods. Anyway I guess I didn't make that obvious. The forces happening in there don't really lend themselves to a hold it in your hands appraisal. Grab any steel push rod and try to imagine it bending in an S curve 3000 times a minute... Its not just NASCAR engines where pushrods flex, all pushrods flex and it gets more severe as the RPM's increase. There are cam harmonics in other engines that have equally stout feeling camshafts. Hell there are even harmonics that break crank shafts, and they are way more beefy than a cam...

[TurboTom]

True.
Hey I could be wrong, there has to be a first time for everything
But with the cam turning 2850 rpm coupled with the spring pressures we generally see. I would just bet that it is not the problem...if there is one

[1bolt]

Hell right now I wouldn't bet either. But there's definitely something going on that doesn't seem consistent. I'm not convinced it isn't just OEM components that were never meant to see 6,000 RPM... G. Hill's experience with regularly stretching double rollers (while relating another 4.0 racer not having any such stretching problem) and Johns first hander with a spit out dizzy all certainly indicate something is up at higher Revs... Lee Hurley says the fix is expensive additions to the block to allow extra helper bearings to be added (frankly sounded like he was making shit up but who am I to judge)...

I'm not sure it isn't the stiffness of the block itself that's the weak link (read the G. Hill thread)... And that might be the easiest to fix...

[TurboTom]

Hey if Grant Hill's camsahft would not go in until he "lifted" the front of his block, then it would not have turned after he installed it. No mention of this?
I have not heard of anyone that "can't turn their crank" while on the engine stand... so much for the droopy block.
This is BS.....another urban ledgend is being born....The block is "Droopy"
Lee Hurley has money to make if the stock block is "weak"... never forget that.
I am going to turn mine to 6000- 6500 and make 475 HP... and forget about all the myths that come with this motor.
I trust SixPak.. he and his dad have raced this junk for 20 years.
i will eat my words later if need be.

[yuppiexj]

i will eat my words later if need be.

I finally have a sig.

[1bolt]

Yeah Lee Hurley invented G. Hill, posted to the Yahoo group in the year 2002 with a made up interview, and Plechtan is also Lee, he came here pretending to think the exact same thing you do, doubting the harmonic, only to pretend call the (fictional) Mr. Hill (actually himself) so he could further the rumor by mentioning multiple stretched double rollers and plant the droopy block rumor... And to make it super believable he even threw in the bit about another racer not having ever stretched a chain or having any RPM related issues even spinning up to 9k.

So all of this is a wicked conspiracy to get cheap ass Jeepers to buy HESCO's diamond encrusted Aluminum block which address' a camshaft harmonic that doesn't exist!

Seriously, not intending to dog on you, just good natured ribbing I mean that sincerely. I can't wait to see someone with the balls to do so; dyno flog his engine in search of breaking shit, I look forward to your findings... Start a new thread call it something catchy like "flogging the wee out of the I6" and write it all up with pics and I'll sticky it. I suspect you're going to break weak links until you reach the point where it's too expensive (or unfun, or tedious) to find the next weak link...

[John]

I like that wee wee 6.........
John

[yuppiexj]

Start a new thread call it something catchy like "flogging the wee out of the I6" and write it all up with pics and I'll sticky it. I suspect you're going to break weak links until you reach the point where it's too expensive (or unfun, or tedious) to find the next weak link...

Since the renix has no rev limiter and I'm replacing its engine in the spring...

That sounds like fun...3 cameras rolling (gauges, oil-pan, and top of engine), even some data capture on the dyno.

[1bolt]

Do it man

[TurboTom]

1Bolt.
I knew the Hesco/ Lee hurley thing was too much!!
Remember, sometimes I post after drinking

But really, if one would have to lift the block to get the cam in. Why would it turn after I let go?
What am I missing?

Hesco, I am sure is a fine company and does have alot of research into the Jeep 6. I truly meant nothing against them.

Guess i will add to MY sig!

[Delk]

Tell me if I am wrong but the way I read the Hesco stuff it was to machine the block to install extra bearings for the cam. This would be complicated and expensive but adding two bearings on each side of the dist drive gear would really help the cam.

Delk