.....when you rebuild your engine? I know you have to use stiff springs to keep the valves from floating at high rpms...but how do you know it you can take it up to....lets say 7000 rpm???

I would hate to rebuild my engine and take it out to the strip and over rev it.

Thanks!

 

retainers make a big difference also, youll need Titanium ones to take it to 7K

 

When you have the motor rebuilt. tell the builder what you are looking to get out of the valvetrain as far as rpms go. If you are getting new heads, the manufacturer will know what works well for a particular setup. Other than that it is a litlle hard to say what your redline will be exactly, unless your setup is similar to another proven setup. The best idea is to go by the builder's recommendations, just make sure he knows what you are trying to achieve.

 

Just go with top quality components. High quality lightweight valves, awesome springs and good lifters will get you there.

If you go with a solid roller setup you can easily boost your redline even higher as you don't have to worry about the hydraulic lifters screwing you over.

 

Hey Ron, if you're still running a TPI, no matter how much you port it, its not doing you any good to turn it above 6K.

I have a friend with a completely stock bottom end/heads LT4 with a hot cam and a port matched intake that turns to 7300. Valve springs, push rods, lifters all are completely stock.

I saw 7000 in the numbers on my L98 one time when I missed a shift. The highest I've ever turn it is 6400. You should be okay with stock or better parts.

 

While the rods MIGHT be fine above 6500 RPM, the cast crank and 2-bolt main caps in the bottom-end won't hold up to that kind of abuse for very long.

If you are getting the motor rebuilt, make sure you have splayed caps installed for the main bearings. The cast crank is good for up to 6500 RPM, but I wouldn't push it past that very often. Forged steel cranks (properly balanced of course) will turn 7000+ all day long. Just look at those 302 Camaros they built in the late 60's...9000 RPM redline :eek:

Like the rest have said, if you stick with a stock TPI-style setup, you won't see any power above 5500 RPM. In that case, the splayed caps will just keep everything in place better. The use of "exotic metals" like titanium in the valvetrain will reduce the float potential and since it weighs less will free up a "little" horsepower.

What determines the top-end redline number is the quality of the components inside the engine. The head/intake package will directly affect the numbers as well. If the intake won't flow enough air to maintain the correct air/fuel ratios at higher rpm's, then the motor falls on its face.

Your shift-point/redline will be found on the chassis or engine dyno. Find where you make peak horsepower with the engine and that is where you'll want to shift. Spinning it any faster will not gain you anything, and only stress the motor out.

 

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 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!





[Modified by grumpyvette, 10:12 PM 3/5/2002]


[Modified by grumpyvette, 10:15 PM 3/5/2002]

 

True enough, everything is cumulative.

I know an engineering type who replaces his rods every 2-3 years based on his experience with metal stresses (It is his job...go figure). He doesn't turn the motor very high at all, just the fact that after 1 million cycles a rod is basically junk from the internal stress. His opinion is to use it as a paperweight or recycle it to make new rods. Better that than to see it from the wrong end dripping oil all over the highway...

This particular point is always a moving target in engines. Without going heavily into physics, everything is a crap-shoot to the lay-person trying to figure it out. And it is always a moving target, because the longer you run the engine, the more stress you accumulate, so the lower the red-line is on a sliding scale....my engineer friend has a logbook that tells him how high he can rev the motor over time. When he gets to a certain point he changes the pill in the MSD to a lower value and repeats as necessary.

That is a little more engineering than I personally want to do, but then again, he hasn't blown an engine in years....it costs a lot less to rebuild an engine than to have to possibly replace the whole thing due to catastrophic failure.

 

Just rev it until you have valve float or the actual piston to valve connection..This will be your redline :D


[Modified by JB'S LT4, 11:38 PM 3/5/2002]

 

I beg to differ. I have seen MANY SBC's over stretch and break their LT1 'pink' rods on 383's and 350's. I have never seen a cast crank break ( well, except for that even fire buick V6 I used to toy with...and that was a fluke. )

In fact, after running my last 383 for years on end reaching 7000 RPM's almost as a daily routine, one of the rods let loose at the big end ( LT1 pink rod too :( ). The crank was fine ( 400 cast crank turned down ), but the block was busted.

 

BBA,
Not to get off the subject but I forgot you needed the shims for the D36. E-mail me at work what you need and they will ship tomorrow.
Justin

 

Will do.

I put it on the back burner anyway...don't get much time for stuff like that anymore...well, not as much time as I would like to have. :D

 

Thanks Guys....alot of good info here...so what I take it is it isn't one thing that determines your redline, but the package as a whole. I guess it makes sense, the higher the quality of the parts, the higher you can safely rev it.

As for my intake, no..I don't plan on keeping the stock TPI.....I am either going with the new Holley Set up or a lowprofile dual card setup...