Hey guys, I have a 66, 289, 3 speed and so far its stock and I keep reading about "max rpm" and I know that V8's are lower on average than smaller 4 cylinders and I was just wondering if there is a way to calculate my safe "max rpm" by what I have on my car (other than just going off of saying its "stock" because eventually it won't be ).

 

Well I found the Calculator from the link that is at the top of the page but I have a couple questions on that in order to do it properly...
What is "Head Flow at 28 inches"? and how do I figure that out?
and what is "Volumetric Efficiency (typically 100-127.5)" and yet again, how do I figure it out?

 

You don't calculate any of those...grasshopper.
Max rpm either limited by engine component material or valve float.
28 inches of mercury is how much vacuum they apply to test head flow.
Vol eff. is how well your engine breathes and is typicallly way less than 100% for a stocker. It can be figured out with dyno software and it varies with rpm.

 

ok thanks

 

And for the record....stop reading ricer sites that claim the 4 cylinders are faster than v8s because they can run a higher RPM...that rule of thumb doesn't work I have the redline set on my 408c at 7100 RPM....and it makes peak power at 7000.

Many motors will continue to increase in RPM, allowing the car to travel at an ever increasing velocity at an ever decreasing slower rate because you have passed the peak power point of the car but not achieved the maximum velocity the car is capable of going. I can't count how many times I have blow the doors of someone, hit 6500k in third, let off the gas, shifted into OD and slowed only to be passed by someone a few seconds later who was spinning high in the RPM range, buzzing like a bee and then claimed victory because they are an idiot pushing their little car well past where it makes peak power....I suppose they win some sort of moral victory of waiting 13-16 seconds to acheive 105 MPH and then the additional seconds to catch and pass me when the race was over .01 second after it started.



I'm in a weird mood today....I don't usually make such unsupported claims [:-]

 

Grasshopper..... I spewed coffee all over my monitor screen. KBunny: If your old tired and worn out 289 could reach maximum RPM, you would probably throw a rod. Just don't push that old engine until after the upgrade. It's not pretty seeing a rod going through the block. Trust me I know. And, if you question my age, do you remember S&H green stamps? Or the Howdy Doody show? How about the Creaking Door, and the Lone Ranger and Tonto? Big John and Sparky? I'm feeling kinda weird today too. [:-] We need some more emoticons, don't we? I have asked admin. to look into it. We'll see.

 

So... now I'm kinda wondering too... whats the max rpm and the best range for power on my 67 Mustang with a 289? It has a bigger cam, Holley 4 barrel, Power Plus intake manifold and a MSD ignition system and its all freshly rebuilt in Jan. Soon, the c-4 will be replaced with a t-5, so I'm going to need to know when to shift.

 

You will feel it when the valves start to float, unless you have a racing engine where the valves don't float. You get a flat feeling where there is no more pulling power. Check your tachometer when that happens, then back off a few hundred of RPM the next time you get it up there before you shift. All engines are different, even though there are recommended RPMs to take it to. On my 03 Mach1, the redline is 7 grand, but I have pushed it passed that, especially in 3rd gear. It was still pulling hard, so I didn't change into 4th until 7500. These old 289's can wind up pretty fast with mods, and somewhere in the range of 6 to 7K is where you will find that sweet spot. Dodgestang's winds a little tighter before shifting. Just don't expect that kind of performance from a stock wore out 289. On my stock original 65 289, I just take it easy and enjoy the scenery.

 

Very good point! Don't hold her down to get the last few RPM's. Things will go flying that were never intended to fly! Just be sure if you build the top end, cam, carb, intake, heads, that you dont forget to upgrade the pistons, rods, & crank if you're planning on getting into the high-RPM's.

I think the valve float for a stock engine is around 5200-5400 RPM's. It's really easy to get there fast in a lower gear. It was explained to me many years back that it was like having a built-in rev limiter. It kept the engine from spinning faster than the innards were designed to go.

 

Jeff and others, I just hope I got across the point that the original untouched 289 V8 Mustangs with a 2-V carb and intake should not be hotrodded.