4500 rpms in your IDI???

[IDIoit]

screwin around in different forums tonight, and i ran across this on FTE....

think ill keep mine below 4k

watch post # 13.
altho it sounded great initially,
the end result was some wrench time for the guy!

FYI, NEVER FREE REV YOUR ENGINE

http://www.ford-trucks.com/forums/1413137-4k-rpm-what-do-we-worry-about.html

 

[FordGuy100]

Some better valve springs and he more than likely would have been alright.

 

[IDIoit]

it turned out it was just a rocker nut, but could have easily been more....

 

[The Warden]

He's actually not the first person to do it...someone who used to post on here did it with an otherwise stock engine and posted a video. You could hear the valve floating as the RPM's came up.

I figure this...that much rotating mass spinning that fast...even with upgraded valve springs, you'll get away with it for a while, but sooner or later things are going to scatter. There's a reason why big truck engines generally don't turn above 2500 RPM or so (and cruise closer to 1600 RPM IIRC), and the engines in large cargo ships barely crack 100 RPM. A person can do as he sees fit with his engine, but I strongly contend that it's taking a big gamble for not that much gain. Longevity's important enough to me that I wouldn't even think about doing it.

JMHO...

 

[IDIoit]

now if i could just get to building my drag truck......
but thats a whole different animal entirely

 

[icanfixall]

Installing the GM 6.2 6.5 governor spring will get you around 4400 rpm. We do not have nuts holding the rockers in place. We have bolts. Guy guy sure had a sad ending sound to his voice. Free reving is a not for me thing nor is running the rpm up much past 2500. I just really like my engine in one piece and not many broken pieces in the street.

 

[Kevin 007]

10-4. I have no desire to run any engine any higher then necessary. Been there, done that.....the novelty wears off fast. Also.... like to achieve as good of fuel mileage that I can during any circumstance.

 

[fsmyth]

Hell, 4500 is taxing on a GASSER big block (with a lot lighter set of moving parts).
There is a reason God made governors.....
If I ever loan the winch truck out, it will have a rev limiter set at 3750.

Although, I did used to run my SS396 up over 6500 a time or two. Don't tell anybody, please.

 

[IDIoit]

i can get my poncho to spin 7100
but thats another story lol

 

[fsmyth]

Back in the day, we were running A/FX. 327 4-bolt block, reground 283 crank,
moly pistons, aluminum rods, and SERIOUSLY ported heads. Tunnel ram (very
new at the time) and 2 1050 holley 3-barrels.
Made 10k. For 2 runs

 

[laserjock]

Used to turn a 402 bbc 7200 on cast crank and rods. [emoji15]

 

[dunk]

Hell, 4500 is taxing on a GASSER big block (with a lot lighter set of moving parts).
There is a reason God made governors.....
If I ever loan the winch truck out, it will have a rev limiter set at 3750.

Although, I did used to run my SS396 up over 6500 a time or two. Don't tell anybody, please.

Maybe 4500 is taxing on a BBC, but no prob for a 460. There are also a few oiling system improvements to be done for truly high RPM (4500 ain't it) or sustained high RPM. Used to shift mine at 6500 somewhat regularly and there are plenty of guys with solid cams spinning a bit higher. I built a 289 that peaked around 7500, that thing was a blast to drive.

Not sure what the weak link in the IDI is... Rods I'd guess since the factory turbo got a stronger rod?

 

[hce]

Hell, 4500 is taxing on a GASSER big block (with a lot lighter set of moving parts).
There is a reason God made governors.....
If I ever loan the winch truck out, it will have a rev limiter set at 3750.

Although, I did used to run my SS396 up over 6500 a time or two. Don't tell anybody, please.

Had a stock 454 down to the quadrajet in a farm truck, when pulling 12 head of cattle would always bounce the tach up to 5000 grand going up a certain long hill. Probably would have wound it a bit more with a little more camshaft.

 

[fsmyth]

Maybe 4500 is taxing on a BBC, but no prob for a 460. There are also a few oiling system improvements to be done for truly high RPM (4500 ain't it) or sustained high RPM. Used to shift mine at 6500 somewhat regularly and there are plenty of guys with solid cams spinning a bit higher. I built a 289 that peaked around 7500, that thing was a blast to drive.

Not sure what the weak link in the IDI is... Rods I'd guess since the factory turbo got a stronger rod?

The 396 was bone stock. And the only 460 I ever had was DEFINITELY not happy over 5500.
There are quite a number of things that need to be done for anything to live at high RPM's, but
none of them are going to keep something with that much mass to spin and bump up and down
to live long. Personal experience with an old 432 Interceptor engine (closer balance and better
rockers on a hotter cam - option on police bids). Scattered all those nifty parts and pieces all
over the road in an attempt to nail the local badass (327 all nicely maxed). Almost got him
Engines in racing tune were not actually part of the original discussion. I just got off on a
tangent. Sorry.
And there is no way to compare a small block to a 444 cu.in. diesel. Apples and peanuts.

 

[FordGuy100]

He's actually not the first person to do it...someone who used to post on here did it with an otherwise stock engine and posted a video. You could hear the valve floating as the RPM's came up.

I figure this...that much rotating mass spinning that fast...even with upgraded valve springs, you'll get away with it for a while, but sooner or later things are going to scatter. There's a reason why big truck engines generally don't turn above 2500 RPM or so (and cruise closer to 1600 RPM IIRC), and the engines in large cargo ships barely crack 100 RPM. A person can do as he sees fit with his engine, but I strongly contend that it's taking a big gamble for not that much gain. Longevity's important enough to me that I wouldn't even think about doing it.

JMHO...

What it is is piston speed. The larger the stroke, the slower the rpm generally. If you have a stroke of 2" at a certain RPM, and a stroke of 4", the piston/rod combo is going to be traveling at a much higher velocity for the 4" vs the 2" stroke. Those extremely large engines turning 100 RPM's do so because of this.

Ever wonder why formula 1 engines can turn rediculous RPM's? "Big-bore, short stroke: F1 V8 engines are currently limited to 2.4-liter and 98mm maximum bore, or 3.858 inches. That means the maximum stroke for that bore is just under 40mm or 1.566 inches." Short stroke = higher RPM.

IDI's have a stroke of 4.18". That means at 3300 RPM's the piston speed is about 38 feet per second (FPS). At 4500 rpm's it increases to 52.25 FPS. 4500 RPM works out to be 15.9 Meters per second. F1 Engines are in the 28+ MPS range. For many decades OEM engine designers considered 3500 ft/min (17.8 m/s) to be the threshold.

Now talk about the G force on the piston/rod. Think at the bottom and top of the stroke, piston speed goes to 0, and then halfway in the stroke it reaches it peak piston speed.
Chevy 350
Engine RPM/ Piston Velocity mph / G's exerted on rotating mass.
6000/ 62.20/ 1140.15