YOUR engines RED LINE

[grumpyvette]

since no one else has directly answered your question about determining the red line,

red line(the rpm level you should not exceed without expecting to eventually do damage to your engine, this does not mean you can run at red line without problems, it means if your STOCK engine gets to that rpm but rarely it should be ok.) It is determined by the weakest link in your engine (usually rod bolts, or main cap bolts streaching enough for a bearing to spin) mostly by two factors,critical piston speed and valve float rpm, your engines RED LINE is just below which ever one is reached first. now valve spring pressure, lifter type, (hydrolic flat tappet,solid flat tappet ,mushroom base flat tappet,hydrolic roller, solid roller )lobe profile on your cam and valve train weight , use of rev kits etc. and harmonics determine valve float, but on stock engines useing roller or flat tappet hydrolic cams about 6300-6400rpm is going to be valve train red line.

piston speed is about at a reasonable max with stock components at 4000 feet per minute, now rpms alone do not have as great an effect as stoke x rpms in figureing piston speed.

example 4000fpm(feet per min.) is 48000 inches per min. if your stroke is 3.48 like in a 350 chevy the piston must go up then down in each dirrection once for each rpm(revolution per min) so 3.48x2=6.96 so 48000/6.96=6896 rpm, in this case the valves are more likely to float before the rod bolts snap from inertial stress, but lets try a 383 that has a 3.75 inch stroke,3.75x2=7.5" so 48000/7.5=6400 rpm max for the rod bolts(about the same as the probable valve float rpm.

btw long term highway cruiseing speeds should be kept to 2000fpm piston speeds for best engine life. and if youve got an all forged ,light weight rotateing assembly thats fully ballanced in a 4 bolt ARP stud block, solid roller cam and a rev kit 4500fpm is not all that hard to achieve safely.

 

and yes I am well aware that some guy at the track regularly turns 7500rpm with his 350 chevy,STRESS IS CUMULATIVE ,ITS JUST A MATTER OF TIME BEFORE SOMETHING SNAPS,A VALVE FLOATS ,A VALVE SPRING BREAKS ETC. AND THE MORE TIME YOUR ENGINE SPENDS AT OR JUST OVER THE RED LINE THE GREATER THE CHANCE SOMETHING EXPENSIVE WILL HAPPEN!

[Mikelly]

Damned good explanation of Redline... OK Grumpy, what is on the agenda next class session... You should teach this stuff!

 

Good Job!

Mike Kelly

[Guest kc6wfs]

Great stuff!!!!!

 

Thanks Grump.....

 

Dave

[Moridin]

What sort of redline do you think I could get with a 327 using stock steel crankshaft and a full solid roller valvetrain setup?

[grumpyvette]

"What sort of redline do you think I could get with a 327 using stock steel crankshaft and a full solid roller valvetrain setup?"

 

the formula holds, 48000/6.5=7385 rpm, now those solid roller lifters won,t float if the spring rates rocker ratios and the cam profile you picked is correct so thats your red line... (if )your useing good forged rods with ARP rod bolts and forged pistons because at almost 7400 rpm cast or hyper pistons will be at or past their strength level for long term use. and stock chevy rods will also be close to their strength limit.

[biohzrd]

if i only knew half the things grumpy knew. you are deffinantly the supreme engine guy. it's a great luxury to be able to bounce ideas off you. i'm just going to start calling you the human dyno.

[Peternell]

I agree, Grumpy has probably forgoten more about engines then I'll know. I thank you for sharing what you've learned. Additionally Grumpy is not the only good source of info on this board, there are several. Scottie GNZ comes to mind.

 

Anyway thanks for sharing

[denny411]

Q" How do you know when you`ve passed your red line? A" When the components of your bottom end will fit roughly into two five gallon buckets

[grumpyvette]

denny411

is correct here.... seeing your rods, crankshaft and partial oil pan in the rear view mirror thru a cloud of oil smoke at 160 mph is a fine indicator that your over the RED LINE!!!

[Tim240z]

seeing your rods, crankshaft and partial oil pan in the rear view mirror thru a cloud of oil smoke at 160 mph is a fine indicator that your over the RED LINE!!!

ROTFLMAO

You guys really crack me up!!

 

Big Kudos to Grumpy who is always willing to answer questions here, even when it's the same question over, and over, and over again

 

Not to forget all the others, way too many to mention individually

 

Tim

[grumpyvette]

Grumpy,

Does the rod ratio effect piston speed?

or does it only effect piston dwell time at tdc and bdc?

Curtis

theres two ways to look at that question,first look here,

 

5.70" Verses 6.00" Rod Length Comparison Chart

http://www.iskycams.com/techtips.html#2005

as you can see the aceleration away from tdc with the longer rod is slower (longer dwell time as you said) but if a engine is spinning 5000rpm with either rod length the piston still needs to cover the entire stroke length in a set time frame 1/5000th of a minute or 166.66 times a second so the longer rod puts less stress on the piston,a better rod ratio, less ring drag and skirt to bore friction due to that better rod angle but the piston still covers the same total distance in the same amount of time and unless you match your cam timeing to take advantage of that longer or shorter rod ratio theres little power benefit to be gained other than some friction and engine stress benefits that the longer rod provides and because the piston pin location must be higher and the piston skirts tend to be shouter with the longer rod the pistons tend to be lighter. now if you read what ISKI says you will think theres not much advantage but hes tying on purpose to not match the correct parts and cam timeing to PROVE HIS point that without properly matched parts there really not enough differance to worry about.

[pparaska]

Grumpy, it's actually tech tip 2005. And I agree, both this argument of his AND the tech tip 2003 seem to have a flavor of lining parts combos up to prove his point.

 

I've played with DD2000 to see what was up with single and dual pattern cams (see tech tip 2003), and for a mufflered system, I have to say that a dual pattern cam will almost always get you more low end torque with more top end power, if you chose the durations correctly (optimize them for both areas). Very strange, I thought that I could learn something from Ed, but instead I seem to be seeing holes in his theories. I probably just don't understand what he's getting at.

[Guest needwaymorespeed]

Thanks grumpy makes sense-the final piston speed will still be the same regardless of rod length,but the piston acceleration rate will be slower

thanks

[Guest needwaymorespeed]

Grumpy

Does the rod ratio effect piston speed?

or does it only effect piston dwell time at tdc and bdc?

Curtis