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Old 05-29-2008, 08:42 AM

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The Sbc Legend, The 327 ?

Hi guys, Im not here to ask how much power I have or which ways I could Im just here to learn something about a motor that I kind of like. I just wanted to know facts about it, why it was was of the best small blocks ever made, How could it rev so High and hold it there for awhile, why did it die out ?. What would be its best at racing ?. How High can they rev ?. Which Is better for longer life the Large Journal or the small journal, why were these motors always put onto a powerglide transmission, Are they fairly good gas savers stock ?. People have told me they rev so fast you have to watch what out cause it will blow up so fast, is all this true ?. I know Ive been annoying in the past, but Im just wanting to learn about motors because i want to have a career in it. Thanks

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Old 05-29-2008, 09:52 AM
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Moving to the Basics Forum.
I'm the one your momma never told you about...

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Old 05-29-2008, 12:22 PM
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Ok good, since you're asking in this way........The 327 chevy was introduced due to the horse power wars heating up "back in the day". The cars were getting bigger/heavier and the 283 couldn't produce the needed torque. The same reason the 350 took the 327's place years later. The 327 is a great engine but it has it's limits like all engines.

Lot's of myths in "engine lore" but they were high revers due to the large bore, short stroke design, like the infamous 302 Z-28. To answer your question about "blowing up" can over rpm any engine to the point it will grenade after a while but whoever told you that they blow up quickly is just taking out their a--. The 327 came with 3 speeds, 4 speeds and of course the Powerglide because thats all chevy had back then for an automatic.

The small journal vs. large is a mute point for the street, use whichever you have. In all out racing the small journal would see a little less amount of parasitic loss due to the smaller bearing surface. You can build a mild 327 with a 2 bbl or small 4 bbl or better yet with a good fuel injection set up it ....and keep your foot out of it then you could get decent mileage, but remember it's still a 327 cubic inch engine so it needs to be fed more fuel/air than say a 283.

There's nothing magical or mysterious about the 327, it's just one of the well engineered sbc that were produced. If you have one then do your homework and build it to meet your*** NEEDED APPLICATION *** and you'll have an engine that will last a long time........Dave
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Old 05-29-2008, 01:31 PM
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Hats off to you Dave...that was a very good answer.

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Old 05-29-2008, 01:38 PM
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What was said is true. You can build one to rev a long way up there if you got a real fat wallet, but you wont do it on stock parts. while a 327 is my favorite small block, you can have all the revs you want, I'll take the torque of a 400 small block any day. Torque is what moves you, not horsepower.
The horsepower wars kicked off the in the 50s, the 283 reached a impression factory peak of 315 horsepower. In 1962, the demand for more horsepower made chevy engineers create a bigger small block with a bigger bore and longer stroke, 4.000 X 3.250 The 327. in 1964, it reached its zenith, the 375 horsepower version that came with a solid lifter duntov 30 30 cam, 11:1 forged pistons, 2.02 1.60 valve heads, mechanical fuel injection, dual exhaust. The highest horsepower rating of any small block, however, this is misleading. When 1967 rolled around, chevy again increased displacement by increasing the stroke to 3.480 to create 350 cubic inches. Chevy knew as everybody did, the more displacement the more power, leaving no future for the 327 and it was discontinued in 1969. In 1970, the LT1 350 was introduced, using many of the same parts the 327 did in its highest horsepower form, only it used a holley carb, it was rated at 370 horsepower, even so it had far more. the 350 became chevys flag ship small block.
many things you will hear from "small block genuises" as I call them, like it'll blow due to revving too high and etc. The valve train limits revability, the valves will float long before it'll come apart providing the bottom end is in good shape. The small journal had some issues, while they were good engines, the rods are somewhat weak, so if any real performance is planned with it, replace the rods with better aftermarket units. Remember also, shorter stroke engines somewhat rev fast, but, if you take a bigger engine with a light rotating assembly it'll rev faster, weight plays a big role. Many other things add to this also. For you I would suggest you read online about the small block chevy, all the answers are there is more written about it than any other engine in history.
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Old 05-29-2008, 04:03 PM
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The max power 327's were built in an era where very high octane fuel was available at the corner filling station, so operating an iron-headed motor at 11.0:1 on the street was no problem at all. Add a mechanical flat tappet cam of very long duration and either two 4-bbl carbs or Rochester mechanical fuel injection and you have a recipe for 365 hp with carbs or 375 hp with injection. The short 3.25" stroke, fairly light reciprocating parts and solid lifters allowed the motors to rev to the moon.

As you have more than likely learned from this board, any engine you screw together is no more than an air pump. You can move more air two ways. Increase displacement or rev higher.

Previously, I gave you the formula for determining static compression ratio. Now, I'll give you the formula for determining air flow through a motor in cubic feet per minute (CFM). A naturally-aspirated motor (meaning that the cylinders are filled by the push of atmospheric pressure only, without the aid of a supercharger or turbocharger) will not fill the cylinders fully on a run-of-the-mill grocery getter motor. Some specific-designed naturally aspirated racing motors will exceed 100% with tuned intake and exhaust runner lengths and diameters, but for the sake of determining the CFM of a naturally aspirated grocery getter, we use something less than 100%, usually based on common sense and the combination at hand. In other words, if you are using highly efficient cylinder heads, you might use a 90 or 95% figure in your calculations. If you're using junk smog heads and intake manifold from the 70's, you might use a 80 or 85% efficiency figure in your calculations.

First, to find cubic inches, you must know the bore and stroke and number of cylinders. In the case of a 327, that's 4.000" and 3.25" and 8.
So, 0.7854 times 4 times 4 times 3.25 times 8 equals 326.72 cubic inches, rounded off to 327.
Next, pick an rpm where you want to find the CFM. W'ell use 7000 in this exercise, because the little 327 had no problem revving to 7000.....and beyond. And we'll use an efficiency figure of 85%, because of the relatively old school heads and manifold architecture used on these motors originally.

There are 1,728 cubic inches in a cubic foot. If this motor were a 2-stroke where the cylinders are filled with every ONE revolution of the crankshaft, we would use the 1,728 figure. But it's not, it's a 4-stroke, where the cylinders are filled every TWO revolutions of the crankshaft or every 720 degrees of crankshaft rotation. Therefore, instead of 1,728, we'll use double that, or 3,456 in our equation.

7000 times 327 divided by 3456 equals 662 CFM. Multiplying that number times 0.85 (85% efficiency) equals 562 CFM.

On the flip side, using a motor with 400 cubic inches, but turning less rpm, we'll look at a comparison:
400 times 6000 divided by 3456 times 0.85 equals 590 CFM. So, you could theoretically make more power with a 400 turning 6000 than you could with a 327 turning 7000, all other things being equal.

Hope this helps with your education.
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Old 05-29-2008, 05:23 PM
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So you say the 1080 Holly three barrel I had on my 327 back in the late 60s was a little overkill? I still have the carb on the shelf in the garage. I guess thats where it belongs.
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Old 05-29-2008, 06:04 PM
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Originally Posted by cgates
So you say the 1080 Holly three barrel I had on my 327 back in the late 60s was a little overkill? I still have the carb on the shelf in the garage. I guess thats where it belongs.
Had one on a 454 LS6......Good times..............
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Old 05-29-2008, 11:56 PM
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Thanks Henry I appreciate the kudo's......speaking of the 3 bbl. Holley, back in '65 my brother bought a '63 split window as a theft recovery. I know this will sound like name dropping but he went to high school with Gale Banks and we were going to El Mirage with Gale and his '53 stude.....poor man's pit crew. I was 18 and they were 22, nobody had any money back then but man did we have a lot of fun.

So along with Gale in his little one car garage/shop we put together a nice 327 with the fuelie heads and 30-30 cam and for some unknown reason installed a 950 cfm Holley 3 bbl. carb. It was a major pig till about 4000 then the engine would start to catch up to that big Holley and it would start to SCREAM. Learned how to "row" that Muncie pretty well with that car. I think he sold that '63 for $1700 a couple of years later.
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