engine rpm

[austinjjesus]

How do you determine an engines max rpm or redline?

[andrewb70]

How do you determine an engines max rpm or redline?

Rev it up unit it blows and back off 500 RPM. :-)

In all seriousness there are a lot of factors. Most often the limiting factor is valve float and not related to the rotating assembly.

What engine are we talking about specifically?

Andrew

[austinjjesus]

Well I'm talking about three engines in particular. One was a 433 bbc that made around 600 horse and then there was a mast motorsports ls7 that they destroked that revved to 8500 rpm and made like 800hp I think and lastly the 364 sbc in hobaughs vette that revs to 7500 and makes 500 hp. I'd like to build a engine for my car that revs high and makes a ton of power but don't know how to determine an engines rpm tolerance. I'll post links to the 433 and the ls7

[austinjjesus]

http://www.hotrod.com/events/popular-hot-rodding-engine-masters/2014/433ci-big-block-chevy-by-performance-crankshaft-at-amsoil-engine-masters-challenge-2014/

433 bbc

http://www.superchevy.com/how-to/engines-drivetrain/1510-de-stroked-8000-rpm-ls-build-for-pro-touring-corvette/

Ls7

[Schwartz Performance]

High rpm = fast moving valve train = heavy valve springs = strong rocker arms and push rods.
Additionally you need a proper camshaft and heads that have the power range you're looking for.

They aren't cheap builds, but one of the biggest advantages is you get more mph out of each gear which can be ideal for autocross situations

-Dale

[austinjjesus]

Does a short stroke help the situation? Does the block have anything to do with it?

[1BADBET]

There's a few things to consider, first is what is your limit? By that I mean you can do almost anything these days but are you limited to a budget? Maximum gear your willing to live with? Maintaince you want to do? HP and RPM your want to turn. Figure the constraints of the build or the "box" your working in then plan the build.

What limits RPM is the induction system with the given cubic inches. For example X cylinder head makes 500hp with a 408 at 6400RPM same head makes the same 500hp with 350 inches at 7200rpm. If your being limited by the cam, spring, or valvetrain then your don't have the appropriate pieces for your build.

You ALWAYS want to turn as much RPM as you can. Doing this hurts bottom end power but that makes it easier to drive, you can pick up the throttle faster coming off a turn and not worry about tire spin and then you get to put more gear in the car so it accelerates faster. You win twice! That's what they did to the 427 in Danny Pop's vette and he said it was much easier to drive and put 2 full seconds on his lap time from the year before at the same track at USCA

[austinjjesus]

There's a few things to consider, first is what is your limit? By that I mean you can do almost anything these days but are you limited to a budget? Maximum gear your willing to live with? Maintaince you want to do? HP and RPM your want to turn. Figure the constraints of the build or the "box" your working in then plan the build.

What limits RPM is the induction system with the given cubic inches. For example X cylinder head makes 500hp with a 408 at 6400RPM same head makes the same 500hp with 350 inches at 7200rpm. If your being limited by the cam, spring, or valvetrain then your don't have the appropriate pieces for your build.

You ALWAYS want to turn as much RPM as you can. Doing this hurts bottom end power but that makes it easier to drive, you can pick up the throttle faster coming off a turn and not worry about tire spin and then you get to put more gear in the car so it accelerates faster. You win twice! That's what they did to the 427 in Danny Pop's vette and he said it was much easier to drive and put 2 full seconds on his lap time from the year before at the same track at USCA

budget i'd say 5k? and thats my father in law putting it together so no labor costs. I want atleast 500 horse and I want it to rev to 7000ish. I love danny's set up. I'm going to good guys scottsdale and I hope he brings the vette out. If I could afford his motor I'd have it

[uxojerry]

What engine do you have now?

[1BADBET]

And what car? Trans?

[austinjjesus]

It's a 79 trans am, 403 olds. Turbo 350. But I do have a 383 short block at my disposal as well

[chpr1972]

If you are going for street use, just remember that without a set of low gears 4:10's or lower it will be a REAL DOG. Also expect to run 55mph at 4000rpm or more. It also requires a very strong valve springs which will wear out the valve train real quick. Heavy springs wear out valve seats valves and heads real quick.On a High rpm car the cam will not pull good until 3500/4000 rpm. Your pix shows a pickup and that thing probably weighs in around 4500/5000 lbs. A 7000/plus motor in that truck off the line would be beat by an old lady in a Toyota. Find a 454/turbo 400 or od transmission with a mild cam and performance torque converter and it will pull like a tractor pull truck off the line! If it is a track use truck that see no street use then build your 383. Nothing is more fun with 3 pedals!

[chpr1972]

Sorry I forgot it was a Firebird, you pix was a chev pu. It will still weigh 3500 lbs but will not be so bad. Just do not forget that the chev 383 will require an adapter or diff transmission torque converter, and a rear gear change. 7000 rpm and a 336? rear gear it will be a dog. All that has to be considered in your $5000 and then frame connectors to help keep the body from twisting as it is a unibody.

[austinjjesus]

All good, the pickup is next that I want to do a mild big block and 5 speed mainly for street use. The Trans am I want to autocross so I want it to rev all the way to hell. It already has subframe connectors. Is it possible to get a 383 to rev really high and not be a dog? With a gear change and a manual? The adapter and all that I would consider extra above the 5k budget

[Ron Sutton]

All good, the pickup is next that I want to do a mild big block and 5 speed mainly for street use. The Trans am I want to autocross so I want it to rev all the way to hell. It already has subframe connectors. Is it possible to get a 383 to rev really high and not be a dog? With a gear change and a manual? The adapter and all that I would consider extra above the 5k budget

Austin, you've been given some good advice ... and some hilarious advice too. :)

The information I would like to share with you is, the 3 biggest mechanical factors to engine rpm are:
1. Mean piston speed
2. Valvetrain capability
3. Induction system airflow.

1. Mean Piston Speed (MPS) is calculated: Stroke x RPM ÷ 6 = MPS in Feet Per Minute (FPM)

Here are some examples:
A. SBC 327 w/3.25" stroke x 7000 RPM ÷ 6 = 3792 FPM
B. SBC 327 w/3.25" stroke x 8000 RPM ÷ 6 = 4333 FPM
C. SBC 327 w/3.25" stroke x 9000 RPM ÷ 6 = 4875 FPM
D. SBC 383 w/3.75" stroke x 6000 RPM ÷ 6 = 3750 FPM
E. SBC 383 w/3.75" stroke x 7000 RPM ÷ 6 = 4375 FPM
F. SBC 383 w/3.75" stroke x 7600 RPM ÷ 6 = 4750 FPM
G. Chevy LS 427 w/4.00" stroke x 7000 RPM ÷ 6 = 4667 FPM
H. Chevy LS 388/392 w/3.62" stroke x 8000 RPM ÷ 6 = 4827 FPM

As the MPS goes up the load on the rotating assembly (crank, rods, pistons, etc) goes up too. Above 3500 FPM requires good quality parts. Above 4000 FPM requires VERY good quality parts. Above 4500 FPM requires extreme quality parts. All of this costs LOTS more money to build ... and more money to maintain, as rebuilds are more frequent.

2. As the rpm goes up, so does the need for a lighter & stronger valvetrain. If the valvetrain isn't lighter, we'll have a valvetrain that can't follow the cam & makes the job of control harder on the springs ... and breakage. "Lighter" & "stronger" are enemies. With increased RPM, the camshaft profiles get meaner. So to build the valvetrain to handle & survive at 8000 rpm can cost twice as much as a valvetrain to handle 7000 rpm.

3. Just because an engine is built to survive higher RPM, doesn't mean it automatically has the power to pull hard to that rpm. That is a function of Airflow ... from the induction system ... meaning the heads, intake, throttle bottle, or carb, etc, as well as the exhaust. Of course, these to be a well matched combination for the rpm range being targeted. But ... higher flow induction systems cost mo' money.

So ... money is the key to rpm. You need ...
1. Higher quality ... and more costly ... rotating assembly to handle the higher MPS.
2. Higher quality ... and more costly ... valvetrain to handle the higher RPM.
3. Higher quality ... and more costly ... induction system to flow the air required to achieve the higher RPM.

Frankly, you need more money to maintain it, because even though the engine is built stronger, the "life" of all the components goes down with high rpms. So you would be wise to rebuild the engine more often ... hopefully on a well thought out plan based on the duty cycles & life expectancy of the engine components.

OR ...

You can build an engine with more cubic inches, rev it less & make similar power.

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A $5,000 engine budget is very modest. So the last thing I would do with that budget is attempt to build a rev'er. If you put quality parts in & on the 383 you have access to, you'll have a good powerplant. But IMHO, a better route would be to buy an aluminum LS engine pull-out ... change the cam ... and dial it in.


:cheers: