How about a nice GM crate 383 stroker? They pull like a big block without the weight and come with a warranty.

 

If you intend to start with an 870 block, then the most important thing to do is to have it sonic checked for cylinder wall thickness. Old castings were subject to core shift, which resulted in variations in thicknesses. You need more thickness on the thrust side of the cylinder walls. Google for recommended thicknesses depending on your horsepower requirement. There are other things you can do to stiffen cylinder walls.

Torque breaks drivetrains. Besides, you can't install big enough tires to handle the torque of a large displacement engine without further modifications. I like my 480 HP 331. Lots of torque down low, and Z06 killing power.

 

Both Dave and Mark wanted to maintain original appearance, but improve top end power with little or no loss of low end torque. Dave's engine was a 65 L-79 and Mark's a '65 L-76. Dave reported no meaningful loss of low end torque and Mark reported a big improvement in low end torque. Power is a function of torque and revs, so if you want to maximize power on a short stroke engine you have to let them rev with free flowing heads and a suitable cam that doesn't choke flow at the top end while maintaining decent low end torque.

All other things equal a long stroke engine will make about the same peak power at the same mean piston speed as a short stroke engine. This is Taylor's Rule. The longer stroke engine will make more average power though the useable range, but I'm not in favor of grinding down large journal cranks to fit a small journal block. You lose crankshaft stiffness due to less journal overlap. It's just not an elegant solution.

I don't know how high Dave ever revved his engine on the road, but 6400 was max on the lab dyno, and it had barely achieved peak power. Mark revved his to 7250 on a chassis dyno, and I recommended he limit revs to about 7000. Back in the day a lot of 327s were lost due to high revving, but it was the weak OE rods that broke. With sufficiently strong rods, occasionally revving to 7000 will cause no harm

Dave achieved a NCRS Top Flight award and there was no question about whether or not his car had the right camshaft during ops check. The lash I recommended eliminated any mechanical lifter clatter and the judges didn't notice the slightly rougher idle.

SHP cams need aggressive spark advance maps and high compression - at least 10:1, NTE 10.5 to operate detonation-free on current premium pump gas. Too low compression or a lazy spark advance map can make the engine feel doggy. The configuration has to be "system engineered" so all systems are complimentary, which is what it takes to achieve maximum torque/HP across the entire rev range, but most guys don't understand that a bigger cam requires a different spark advance map and end up leaving a lot on the table with sometimes disappointing results.

Whether you are turning 6000 or 7000 I think most guys understand that it's downright stupid to do so within sight of a cop.

My current favorite config. for a sixties vintage SBC high performance road engine is a ...657 block with 3.75" stroke, 2.45/2.10" journal crank, L-88 flywheel, massaged OE heads, McCagh Special camshaft retarded four degrees, a big plenum FI system, and, of course, 2.5" exhaust manifolds with OE equivalent off-road exhaust. Expect about 350 honest SAE net HP at the flywheel in the 5000-5500 range with the maximum useable range extending to about 6000 and about 400 lb-ft net peak torque at 3500-4000 with close to 90 percent at 2000. Overall the engine will feel more like a 427/390 than what appears to be an OE '63-'65 FI engine, but without the extra mass.

Then I'd mate it to a Richmond wide ratio Super T-10 (2.88, 1.91, 1.33, 1.00:1) with a 2.73:1 axle. First gear overall would be the same as a 2.20 first gear CR with a 3.55 axle. You could do burnouts to your heart's content while only turning about 2500 at 70 on the freeway.

The only giveaway to a casual observer that it's not an OE configured FI engine is the smooth 500 RPM idle, but that can be "fixed" by increasing idle speed and leaning out he idle mixture to roughen the idle a bit.

Of course, it won't judge well because of the non-original block.

Duke

 

With respect to the OP, in the C2 era:

The 327 was the big displacement factory small block. GM, was no different than the tuners in knowing that there is no replacement for displacement in making power. The Gran Sport chassis cars ran as much a 377ci displacement engines, as tuners ran what they could build and remain compliant with the sanctioning body rules. The point is, for any configuration not restricted by rules, the largest displacement engine will make more torque easier than spinning a smaller displacement engine. A 327 will beat a 283 or 265 in this respect for easy power, and fall behind a 350, 383, 400, or modern 427+ ci small blocks for easy power.

Limiting the discussion to the factory 327 platform, limits the options.

The 870 castings are all similar small journal blocks (250 to 375hp). Any good Flint block can be machined to SHP specs.

The crankshafts are separated by normal forgings, and the tuffrided (casehardened) SHP cranks with drilled and tapped balancer snouts. Any 327 crank can be machined and balanced to SHP specs (with the exception of casehardening, and even that can be done it a cost but is not needed with modern bearing materials).

The factory 62 to 65 small journal connecting rods are the same, and considered weak for extended use above 6000 rpm. The later factory 67 rods are better, but much better aftermarket rods are available for less cost (or more, with a cost range from $400 Eagle rods to $2000 Oliver rods, depending on peak rpm and durability for extended use at high rpm).

The factory heads are different for each major jump in power, as are the cams and intake/exhaust manifolds. Porting and machine work can improve any head (250 to 375hp) to flow as good as raw SHP castings, but modern CNC ported aftermarket assembly line heads are less money and flow better too. Cams and manifolds are the same, with modern reproductions that perform better than factory pieces available at less cost.

The big improvements since the 60's have been materials and computer modeling to direct improved configurations for better power at a target rpm range. These two major improvements work to build a better small block, of any displacement. The computer modeling can match more modern cams and piston configurations to take the package beyond a guess of compression ratio and cam. The ability to plan and computer model the head chamber, piston dome, deck height, head gasket, and cam intake close point gives the modern engine builder/tuner a huge advantage over the educated guesswork and dyno exploration Engineering effort of the 1960's. This opens up options for a docile idling 327 displacement engine that makes a wider and more powerful powerband than the factory SHP engines, or a SHP style idling engine that makes 30%+ or more power over a wider powerband.

Taking the OP questions back to our modern reality of options, the direction is returned to what rules to follow. Factory assembly, factory look and sound (modern assembly, and/or largest displacement), deviations from factory NCRS ideals or the 20 foot inspection factory style appearance from SBC enthusiasts (or best power for ×$$$ and non-factory appearance, etc.).

​​​​​​​Identify the goal and rules, and then work around the defined limitations .

 

This thread reminds me of the old saying " Different strokes for different folks".......

 

All that from a 383!!!

This is from a .030" over 327:

Expect 437 honest SAE net HP at the flywheel @ 5500 RPM, peak power of 476.1 SAE net flywheel @ 6556 RPM with 90% power range extending from 5250 RPM to 7600 RPM, and 422 ft-lbs net peak torque @ 5600 RPM with 90% peak extending from 3200 to 6250 RPM and 345 net ft-lbs torque @ 2500 RPM.

I see no valid reason why any sane man would change both the transmission and axle ratio to end up with only 4 speeds when he could have simply replaced his trans with a 5 speed with overdrive,

 

Yup. I had a 3.36 axle and a CR Muncie. (2.20 1st and 1:1 4th)
I put in a Tremec TKO 500 - 3.27 1st and .67 5th - and left the axle alone.

It totally transformed the car - easier to drive around town, faster off the line, and much nicer on the highway - 2000 rpm at 70 mph now vs 3000 before.

That and the Borgeson power steering are two best things I've ever done to the car!

 

True.

I designed my 355 to be able to operate at a sprint car like 7000+ rpm for extend periods of time, and idle and drive like the original 340hp L76 off-idle, with an extra 100+ Hp over a wider powerband. It looks near stock for most enthusiasts at 20 feet, and delivers torque and power like a SHP 427. I do drive it at 4500+ rpm for miles at a stretch, with blasts to the rev limiter (currently at 7400). It is designed to run reliable at the rpm, even if peak power is at ~6500 and it idles smoother than an LT1.

​​​​​​​I can make more power at higher rpm with a different cam, intake, and headers, but it works for me (until I swap back to my improved original block 327 and move the 355 to another platform).

I do have a preference for the 7000+ rpm sound, and while bigger SBC displacement configurations may perform as well at a lower rpm for less cost, that sound and accompanying rush is hard to deny as a satisfying experience. Power from more displacement costs money and power from more RPM costs exponential money, but if you have the reliable high rpm parts make the most from what you have.

The best engine gets you there, and back, with a smile (even in the stock 250 Hp 327 configuration).

 

I understand and agree - with some wistful remembrance. Back in the day - 1972 - 1985ish - I ran a 350/370 hp LT1 with worked heads and long tube headers as the then second engine in the car. That thing was an absolute beast, and just screamed and howled up to the 7000 rpm limit I used. It was a little weak off the line what with the 3.36 axle and 2.20 1st I had then. I'd love to have tried that set up with the Tremec 5 spd I have now.............

 

AND

More cubes requires more gas. And a ratmotor upsets the beautiful balance of the car.

I'm mulling over whether to build a 355 using 4 1/8" bore aluminum block and 2.08" intakes, or a SBC 427 with 15 degree heads.

My rev limiter is set to 7750, but I shift at 7250 at the track. I use mine as a daily driver with occasional trips to the drags. The great thing about it is that I get 23 MPG on the highway if I obey the speed limit (very hard to do). Can a big cube engine duplicate that?

 

Hi Joe C:

Ever since building my 383, I have been toying with the idea of building a small block 427. This requires the larger 4.125" bore of a 400 block or an aftermarket block like the Dart Sportsman.

If you decide you want to pursue the 427 that you have been thinking about, I'd love to compare notes.

What I have figured out so far is that with an aftermarket 4.125" bore block, there is less problem with rod clearance at the pan rail because the aftermarket blocks have generous rod clearance and the water jacket area at the base of the cylinder is solid metal. So, the biggest challenge becomes cam clearance.

In my 383 with a good "stroker profile" rod and a roller cam, I had to grind just a tiny bit off the shoulder of the rod to get .050" clearance between the rod and cam. This tells me that I would need .125" MORE clearance to handle a 4.0" stroke.

An easy fix is to use a block with a raised cam, but then you lose the appearance of a stock timing cover. World products has a block that raises the cam just a little, and still uses the stock timing cover. However, it appears that the timing set has to be converted to a belt drive.

So, my current thought process is focused on coming up with a way to use a block that has the cam at the standard height. I think this may be possible with some rod trimming, a 2.0" rod journal, and possibly a small-base-circle cam.

I'm uneasy about small-base-circle cams because it seems like the dynamics might be harder on the cam/lifter interface, but I can't quite visualize how the dynamics change with small base circle. What are your thoughts on small-base-circle roller cams?

 

Hi Joe,

As long as you stay with fairly compliant springs you should be OK.

Because of the smaller lobe, there is more contact area between the lobe and the tappet. Because of this, they are subject to more torsional loads and more lobe/tappet wear if you use flat tappets, which I doubt that you will do. Even with a roller, they don't stand up to bending loads as well as a standard base circle cam would because the core diameter is smaller. Supposedly the difference in bending strength is on the order of 4%. Lighter valve springs minimize both types of loading.

If I ever do the 355 or 427 (I'm more prone to build the shorter stroke, high revving version), then I'd use a modern "foundation" for a number of reasons, the most important of which is the consistency of the bore thicknesses.

 

Hi Joe C:

Thanks for the explanation. I would definitely use a roller cam, and I think the spring pressure could be held to a reasonable level. Still, I'd like to figure out a way to use a standard base circle cam.

If you build the 4.125" 355, you will have no issues at all with cam clearance, which is a plus. Somehow I just like the idea of building a 427 that looks like a 327, but it's a tight fit for the rods.

 

Good luck Joe.

It won't look exactly like a 327 because the extra freeze-out plugs on the sides of the block are a dead giveaway. Besides, the 400 SBC uses an externally balanced damper. If you do this, I hope you go all-out this time. Headers with at least 1 7/8" primaries would be a MUST, and a 750 DP would be the smallest carb I'd use. With all those cubes there'd be no question that a single plane intake is the right way to go.........prolly an Edelbrock Victor.

I'll be going all aluminum. Not only is it a better foundation, but the country bumpkin hayseeds who save old junk will be looking to steal your drawers with the price of a GM block. That's the way a few guys here who have this block sound. They are salivating like Pavlov's dogs. Have you asked World, Dart and others about cam fitment? You MIGHT be able to shave the rod bolts and/or rod caps to squeeze a standard cam in. I'd look at that first. I don't like the strain aspect of a small base circle cam. Anything that would take away from valve lift sticks in my craw....................even if it's only a few thousandths of an inch.

 

Hi Joe:

When I say "looks like a 327," I'm only referring to the general appearance of the engine to a casual observer. For any block that has 4.125" bores (GM 400, GM Performance Bowtie, Dart, etc.), there will be several ways that a careful observer could detect that it is not a 327 block. Regarding freeze plugs, though, some of the 400 blocks had just two per side.

Based on what I have read so far, I think that an aftermarket block would have a better chance of maintaining a standard base circle cam in the OEM position. While an aftermarket block itself can not do anything directly about rod-to-cam clearance if the cam is at OEM height, there is an indirect benefit from the larger rod clearance at the base of the cylinder. This opens up more options for rod selection.

For example, the Callies Ultra HD has a novel offset rod cap that provides more cam clearance at the expense of less clearance at the base of the cylinder.

In any event, all of this is just a thought experiment at present, and it's interesting to think about. In the meantime, I still don't have my 383 in the car yet, but at least the original 327 is about ready to pull. There sure is a lot stuff to disconnect before you pull an engine, especially is the car has power steering and A/C!