OK, let me take a crack at this.

I’m going to use some very simple examples so bear with me. Say you have a big block that puts out 500 ft-lbs of torque at 2000 RPM. To get the car to the speed you desire, you choose a 2:1 rear end. Effectively the rear gears act like a torque multiplier, so you end up with 1000 ft-lbs of torque in the rear.

Now you decide to do the same thing with a small block. Your small block puts out 250 ft-lbs of torque at 4000 RPM. You now stuff in a 4:1 rear end. This gives you the same 1000 ft-lbs of torque at the rear wheels as the big block. It also gives you the same car speed.

You could also observe that the big block at 2000 RPM is putting out the same horsepower as the small block at 4000 RPM. Horsepower is merely torque multiplied by RPM (with the appropriate conversion factor).

The above simplified example gives identical performance; in the real world the problem is a lot more nebulous. The issue boils down to: Will the small block extend the RPM range far enough to compensate for its lower torque output? Start throwing in things like frictional losses and rotating mass and the problem gets really complex.

The best of both worlds???? A big cubic inch motor that can rev to 8000RPM.

 

I don't know that I'd try to run a blower on a production block at .060 over. They tend to have cooling issues at that bore and a blower will make it worse, IMHO.

 

Maybe rather than comparing a 383 to a 302, we should compare it to something along the the same lines (big bore/short stroke) with similar cubes. like a 377. This might be more of a matchup.

 

CHP actually did a 377 vs 383 comparison a few years back. Again, there wasn't enough difference between the two to say that one won out over the other, or at least that I can remember.

 

I read a few articles from hot rod and another magazine, that a guy on Chevelle Forum emailed to me. Its funny because I decided to inquire about the benefits of a high revving engine, as opposed to your standard power house that makes most of its torque under 4000 and most of its horsepower from 4000-6000. Yet, it doesn't apper that even the magazines are tackling high revving small and big block engines. Most of the articles I read, the engines power bands were in the same places they would be on a big block... down low....

I am still interested in the 8000RPM 383 Screamer you speak of though, just want to make sure its going to get me down the 1/4 mile faster then the guy with the low end 383 next to me (or in my case my neighbors BB). LOL

Dan

 

How much money do you have to spend on this 8000 rpm 383 motor?

Because I will build you one. In fact I have a 8000 rpm capable one in my Vette right now. but I set my rev limiter at 7500 to make it last longer. Longer is a relative term also. I've had to do a $2000 refresh before it even had two years on it. the little tiny rings on the light weight pistons ware pretty fast and you start to use oil. The valve guides were also in need of replacement because of over .600 lift and opening and closing at 300+ times per second just beats the crap out of them. I replace the springs every year or two at about $400 per set.

If your answer to my first question isn't $10,000 for a complete motor and cooling system to handle it. Then you might as well just forget about it. Or just go buy you one of these 600 hp small block crate motors for $12,000 and about another $10K in mods to get the power to the ground day after day.

 

Now there is a practical answer! Money is a great engineering decision tool.

-Mark.

 

Thanks but the reason for my building the engine and not buying one from summit is to save money. I managed my 454 from start to finsh for just over $3200. Not to mention wheres the fun in that. This is a project, I'm not looking to pay someone to build my car for me, that takes all the fun out of it.

Thanks for the offer though,

Right now I am just looking to learn from eveyones experience here on the forum.... Chances are I will stick with what I learned to begin with, but I just wanted to find out what all the hype was about.

Dan

 

I use the www.flatlanderracing.com rotating kits.

I think they are about $3200 for the crank, rods, pistons, rings , bearings

Heads with good springs and shaft rockers installed are about $3000

Then add all the ignition, intake, carb, headers, timing set, racing oil pan......... It's very easy to get $8000 - 10,000 just in parts and you do the labor.

but it will rev to over 8000 if your cam and heads are up to it.

 

I see where your coming from, which is part of the reason why I am taking the time now to research what the best bang for my buck is. I think I previously stated that I will more then likely build what I am familiar with, but what the intended purpose of this thread was to get information about High RPM engines. I was just interested in what the craze was; I've been noticing alot of emphasis on the old 302 chevys. I always went by the saying, theirs no replacement for displacement - more torque the better. I wanted to see if there were any benefits to making less power but being able to revs higher, or even for that matter, why you would need to revs an engine making the same power that high??

If you have knowledge you would like to contribute it would be appreciated, but other then that, theirs not much else up for discussion here. I can assure you I have no interest in, or funds to purchase a $10000 already built engine.

Dan

 

Until you've driven a car that shifts at 10,000 or above, you will never understand. It is kind of like a slot car, you squeeze the trigger and it just goes incredibly fast very, very quickly.


The question is what are you doing with it. If you are driving next to a tractor trailer some time, listen closely. The engine pulls up in RPM VERY slowly. Yes, it makes incredible horsepower, but at a very slow rate. And realize that it is revving from around 1000 rpm to maybe 2500 rpm. It is running very low rpm.

For a big truck pulling a load, that is fine.

Go to the drags. The fastest cars are those that get the engines up to the peak of the horsepower curve the fastest. In a 5 sec quarter, you can't wait 4 seconds for the engine to get to speed.

The issue not addressed (not that I saw) is how fast the engine accelerates. Not how fast the car does, but the engine. A long stroke tends to have more flywheel effect, so the engine revs at a slower rate than one with similar parts that has a shorter stroke.

So if you get the stroke short enough, the engine will rev (accelerate) much faster, and get to the peak power quicker. It can also rev higher due to piston speed.

Now this all comes at a cost. You can't take a standard 350 and just rev it to 8000 or 9000 rpm. First, the cam won't make it. Even if you get a cam profile that will work at that range, you discover the valve train, the rods, the crank, everything begins to show stresses that they never had at 5000 rpm. They will also develop vibration and balance issues that were insignificant at 5000 rpm.

You run into critical issues with piston speeds. There is a point pistons will either blow apart from the speed or stretch the rods until the pistons hit. This is not a cheap issue.

Now on the street, it will beat the long stroke high torque cars, but it becomes instantly noticable with the high scream that comes with it.

Look at the imports with the high revving engines vs most V8s today. A friend in HS had a 302 in a '65 Chevelle that would eat the '68-9 Chevelle SS 396s and '70 SS 454s all day long.

Now an alternative is to lighten the long stroke engine until it can rev (accelerate) faster by reducing the flywheel effect. This is what many do with the aluminum flywheels and the L88 did with its 12 lb. nodular iron flywheel. This is why so many race cars use small diameter flywheels and clutches (6 to 8 inch clutch diameter) to reduce the flywheel effect.

So this is what some were referring to as the best of both worlds, a high revving long stroke engine.

And of course, everything depends on longevity you are after. One 8 second run and rebuild? Easy.

A weekend of 8 second runs? Much harder.

A season of 8 second runs? Very hard.

This is why the rock solid, long stroke, moderate revving 502 has become so popular, as did the 383. You get a lot of power in a package that can last a long time.

The Chevy 302 could run 8000 rpm out of the crate. With work, you could do 9000 - 10,000 rpm. When engine sizes were limited to around 450 cid or so, the 302 had an advantage in engine acceleration and lightness. But even in the late '60s, the unlimited Can Am showed that unlimited cubic inches would beat outrageous revving small blocks.

The only drawback is the first time you shift a 302 at such speeds, you are just waiting for it to explode, as it is just unnatural to rev a small block that high.

The 302 also could produce good power from about 3000 to 9500 with the right cam. That is a 6500 rpm power band. The power band is longer than the range many engines can even turn, let alone make power.

 

The single most real beauty of a high rpm capable motor with a wide power band is:

You don't have to shift. shifting detracts from you paying attention to the road. Up or down shifting upsets the balance of the car and the grip of the tires.

Just think of your going to work favorite freeway on ramp. The high rpm motor never has to shift in the middle of the turn or when merging into traffic because each might be 50 mph wide. People that ride hot rice bikes really understand this. Modern bikes might have a 13,000 red line. You enter a turn knee draging at 7000 rpm and modulate the throttle and coming out of the turn right at max power. Trying to shift could just send the rear end out and crash

Modern metals and spring techology have erased the 30 year old mithes about the advantages to short stroke motors like the 302. The bottom end hardly ever fails these days. But valve train is where you really start to have problems in any motor that can exceed 7000 rpm