setting a tach redline

grumpyvette

grumpyvette

Administrator
Staff member
jim said:
I want to set a tach red line for a 402 big block stock engine but I don't know what it is. Is there a standard that those motors should red line at?
thanks jim
Click to expand...


a 402 big block has a 3.76 stroke,you'll want to keep the piston speed limited to about 4000fpm, which would be about 6400rpm,at least in theory, but that's pushing past the reasonable upper limits if the valve springs are original, in a 35 year old or older engine with an original hydraulic lifter cam,and original bearings,valve springs, in my opinion.
you might want to consider what happens if a piston hits a valve
bent_valve.jpg

04907.jpg

Bent_connecting_rod.JPG

head02.jpg

read
viewtopic.php?f=53&t=343&p=1170&hilit=redline#p1170
 
is 4000 fpm a general safe speed for all motors or is it more dependent on materials and rod bolts?
 
philly said:
is 4000 fpm a general safe speed for all motors or is it more dependent on materials and rod bolts?
Click to expand...
Every Single Ford 5.0 Renegade guy ignored .
7,500-9,000 RPM was the Norm.
New Records Set Nationwide.
A few Revved to 10,000 RPM
I ignored too.
Good Top Notch metals.
Titanium is your Friend too.
 
first lets point out how you calculate 4000 Feet Per Minute, in piston speed, which in most completely stock chevy v8 engines is a reasonable durability limit
in one revolution a piston moves from TDC (top dead center )TO BDC (bottom dead center)and back to TDC, so you calculate the distance traveled as twice the stroke, and 4000 feet per minute is 12" per minute times the rpms
but anyone who understands engines understands that piston speed and rod bolt stress are far from the only factors limiting an engine rotational speed, most valve trains in stock engines, and valve springs and cam lobe acceleration rates are limited to about 5800rpm-6200rpm, and air flow rates or port stall speed could very easily limit power, as can a restrictive exhaust, an ignition systems, rpm limitations or a lube system, not being able to keep up with demand

thus if you have a 3" stroke, 4000 fpm=48,000 inches divided by 6"=8000rpm red line in theory, for piston speed, on something like a 283 sbc

thus if you have a 4" stroke 4000 fpm=48,000 inches divided by 8"=6000rpm red line in theory,for piston speed,
on something like a 454 bbc

yes your correct if your thinking that better after market forged parts like cranks, connecting rods and forged pistons, with light weight rings and tapered tool steel ,full floating piston pins,that will allow you to increase the FPM and maintain a safe margin, 4500fpm is not too hard to maintain for brief peak rpms between shifts with a properly balanced engine using all forged , light weight components and upgrades like 7/16" ARP 2000 rod bolts, but its the valve train stability, cam lobe acceleration rates, lube system or detonation issues that are usually the critical factors once the rotating assembly's been built to tolerate the sustained higher rpm stress.
I regularly pushed my racing crower injected, 13.7:1 compression 496 BBC engine in my 1968 corvette too 6500rpm , which is 4600 fpm, but it was balanced to 1 gram, ,and the only component that was from chevy was the block ,ALL rotating parts were 4340 forged steel, or 4013 forged aluminum and had a valve train that was designed to be stable at that rpm range


READ THESE LINKS
viewtopic.php?f=53&t=1168

viewtopic.php?f=53&t=343&p=1170&hilit=redline#p1170
 

Mean piston speed is a number that most people can understand, but it's only a
generalization of what's really happening inside the engine. Velocity(speed) is
not what breaks components, it's the acceleration that tries to pull things apart.

viewtopic.php?f=99&t=6636

 
Indycars said:

Mean piston speed is a number that most people can understand, but it's only a
generalization of what's really happening inside the engine. Velocity(speed) is
not what breaks components, it's the acceleration that tries to pull things apart.

viewtopic.php?f=99&t=6636
Click to expand...
Grumpy has safe zone redline guidelines.
Insures 100,000 mile reliablity.

Every Racer knows the ultimate risk pushing it to the limit & past.

There is more going on as you say Rick.

The new Huge cube Pontiac engines of 550-600 ci have 5.00" inch crankshaft strokes.
Not supposed to Rev over 5,500-6k.
But some ignore.
I posted recent a U-tube Vid of a Mountain Pontiac V8 turning
over 8,000 RPM.
Pretty sure it used Titanium rods, Ti Valves. Shaft rocker system .

Thing about Turbos is the Huge Torque Curve generated.
No need to Rev past 6,500.
You Won for sure.
 
4300- 4911 Feet per minute done by myself many times Grumpy.
I did the math again.
 
That mountain Pontiac Engine turned 8400 RPMS With a 5.00" crank stroke.
Equates to 7,000 Feet per minute piston speed.
More than I dare too.
You Bet McCartheys 1200+HP Poncho Ram Air 5 engine was filled with Titanium.
Only way to do it.
 
the issue with all piston motors is that they have to accelerate, slow down, stop, turn around, accellerate, slow down, stop, turn around. over and over and over, its probably the slowing, stopping, changing direction part that puts most of the stress on the bearings and bolts. if they just kept a speed it would be much easier, but they are reaching 4000 or 5000 fpm in a very short sprint and then decelerating and then sprinting again.
 
wow that really sounds like i am advocating a wenkel. not my intention
 
philly said:
the issue with all piston motors is that they have to accelerate, slow down, stop, turn around, accellerate, slow down, stop, turn around. over and over and over, its probably the slowing, stopping, changing direction part that puts most of the stress on the bearings and bolts. if they just kept a speed it would be much easier, but they are reaching 4000 or 5000 fpm in a very short sprint and then decelerating and then sprinting again.
Click to expand...
A few days back I posted on another old thread of Grumpys covering the same topic.
I can't give a direct link tonight , my internet is down.
Posting from my phone again.
But the greatest stress a connecting rod experiences is on the upstroke compression Exhaust cycle.
Stated in the article.
In another thread here I recall Titanium rods have a 2:1 strength to weight ratio of steel or billet steel rods.
Same I beam cross section when comparing the 2 materials in Rods.
Lessens the loads on the crankshaft, bearings, wristpins & pistons.
 
If we manage to get other real drag racers on board they are not going to go for 5,500, 5700, 6,200, 6,400
RPM Redline when they have turned 7,000-9,000 RPM'S for Years.
Are they Phil ???
Especially other Longtime Pontiac & Ford & Mopar guys.
No way.
My.02 cents tonight.
 
yea but its like grumpy sys... you can get 7000fpm but youre really rolling the dice

you have to accept that at those speeds you are gonna puke rods, you are gonna puke valves, you are gonna wipe out bearings, its just gonna happen.

in a race car you have the luxury of the trailer and a discretionary budget. i drive my "race" cars and i dont want to have to constantly worry about having a spare motor handy for the overnight swap out. been there, done that.
 
another good point grumpy makes is being able to dampen harmonics and if we are talking about 9k+ RPMs we should look at an aftermarket crank dampner, a belt drive for the cam, and an expertly blueprinted and balanced bottom end
 
philly said:
another good point grumpy makes is being able to dampen harmonics and if we are talking about 9k+ RPMs we should look at an aftermarket crank dampner, a belt drive for the cam, and an expertly blueprinted and balanced bottom end
Click to expand...
If You Do the Math on a 5.00" inch Crankshaft stroke,
4,000 Feet per minute mean piston speed equates to A 4,800 RPM REDLINE ONLY.

5 inch stroke crank is the foundation of every Big inch Aftermarket Pontiac Tall Deck 11.0"- 505ci-610ci Monster engine.
Its also used in Big Block Mopar, Fords, & Chevies up to 800 ci.
They don't settle for 4,000RPM.
Lucky if peak torque even takes place at 4k rpm.
A dirt track engine turns 7k- 9k rpm constant.
From 1,000 RPM -8K Instant. Over & over.
500 laps at times.
Sometimes for 20 minutes to 2hours long the race
Actually more torturous than drag race.
We never puked a Rod, piston, or crankshaft.
3.48- 3-7/8" - 4.00 inch crabk stroke used.

Now You Tell Me Phil.....

Fuck Bullshit or Not ?


I will tell You What those Racers will say Too.

BR
 
what are we even talking about? you cant argue that a motor that never spins past 5000 will last longer than a motor that spins 9000. its just a fact. its not even a discussion. i dont care what materials are used.
 
when we spec out a combination we decide, typically based on tire size and gear ratios, where we want redline to be, and work backwards from there.... whats gonna put me thru the traps while im still in the power? if thats 5000, 6000, or 10,000 rpm we have to build a combo for that and assume the risks that come with it. i wish i could have an 8 second car that doesnt spin past 6000 rpms (i bet it would last forever) but thats probably not gonna be the case. and as such, i have to accept that if im gonna be spinning it to 10,000 then i better be ready to deal with what happens afterwards.
 
philly said:
what are we even talking about? you cant argue that a motor that never spins past 5000 will last longer than a motor that spins 9000. its just a fact. its not even a discussion. i dont care what materials are used.
Click to expand...
The question is for You & Me....Do you want to Win Drag Races at the Track and on the street Consistent ?
Like 99 out 100 races ?
Or just make noise & burn rubber out of car show get together parking lot & impress kids & old
fart non racers ?
If you answered yes on the 2nd...you need a 305 sbc with a Comp cams Thumper Humper cam only.
Stay stupid & Gay.

Anyone that has been Street racing & racetracks know how fast cars have become.
Ask Rick.
He got smoked by the others at his Hometown Street Race Showdown
He will get there eventually and Win.

But he knows its not going to work at 5,000 RPM Refline too.
 
like you said its a calculated risk. and you have to be able to build around and prepare for it when those things eventually fail. really, were all on borrowed time so we should always be getting ready for when the next part breaks.
 
philly said:
like you said its a calculated risk. and you have to be able to build around and prepare for it when those things eventually fail. really, were all on borrowed time so we should always be getting ready for when the next part breaks.
Click to expand...
Why 1 455 Will be street.
5700-6200 RPM Max. Experience tells me its enough with Tallish gears for Chevy but not longstroke long rod Pontiac.

2nd TA Will Be Ultra Hi Pi Street & Race. That gets Titanium rods.
Turbo(s) ?
Likely Yes
 
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