The Stovebolt Site Forums The Shop Area The HiPo Shop 250 cubic inch small block V8

With a little creative tinkering, it's possible to build a REALLY small Chevy V8 that might be interesting to experiment with. I did something similar on the round track back when we were running in a class that required using a 350 CFM Holley 2 barrel carburetor as a hedge against some competitors spending bushels of money. No point in using high-dollar heads and a monster camshaft if the carb won't let the engine breathe! By combining a 305 block with a 3.1" stroke crankshaft, I got a 272 cubic inch engine that would turn about 1,000 RPM faster on that carb than the 355 engines my competitors were running. The tech inspectors couldn't figure out what I was doing, because all the casting numbers they could see on my engine showed I was running a 305, and none of my competitors wanted to pony up the money to do a complete engine teardown.

By taking that concept a step further, plus a little (OK, a LOT) of custom machining, the CID can be reduced further, to 252 cubic inches by destroking a 283 crankshaft to a 2 7/8" stroke, using Honda-sized NASCAR connecting rods, and adapting the 305 main bearing bores to the 283 crankshaft with reducers. With a small Carter 4-barrel, and a roller cam with a rev kit, suddenly we've got an engine that lives very comfortably at a redline of 8,000 RPM, and will give 20+ MPG when driven sensibly. I drove a Porsche 928 with a 255 cubic inch V8 for a while, and that one saw 160 MPH a couple of times, with RPM to spare. No reason the engine I'm building on paper couldn't do something similar with the right transmission and rear axle ratio! Now, anybody want to drive a stovebolt that fast? LOL!
Jerry

Probably don't want to drive my old stovebolt that fast. Sounds interesting.

Count me in Jerry..... but wait, the 37 already gets wobbly about 130! That Porche is a lot more aeromatic than the 37. But I like to go fast!!

....I also enjoy reading about some of your "inventions". When my brother was building racing engines and we got pulled he would just laugh and say "cool her down boys and lets take some more money". To us that's what it was all about, coming up with "something" the rest knew nothing about. Those days are gone now but they were sure were exciting and the days in the dyno room with him are moments I'll cherish forever. RIP brother.

The fun part of racing is sneaking a modification past the tech inspectors! In the immortal words of Smokey Yunick "It ain't cheatin' if ya don't get caught!" I had a few tricks up my sleeve to make "stock appearing" parts perform way above their expected level, and most of the tech inspectors I was dealing with weren't sharp enough to figure out what I was doing. That small-displacement engine was right on the ragged edge of illegal because we weren't supposed to change the stroke, but most of the tech crew figured only a fool would build a smaller than "legal" engine. Of course, they never figured out that building a smaller engine would translate into more RPM when the carburetor was the limiting factor. My engines always sounded like a bumblebee on steroids, and if I we ever got out front, there was no catching us.
Jerry

So now we need to figure out an easy way to de-stroke a 235...

Then you'd have a 216- - - -or actually, about a 224- - - - -somehow I doubt that would be an improvement! All the stovebolts have going for them is low-end torque!

However- - - -reboring for a set of aluminum 235 pistons is a good way to pep up a 216 when you rebuild it. They have the same wrist pin size and compression distance as 216 pistons, just a bigger bore.
Jerry

You can also get a smaller SBC by using a 262 block which is 3.671" bore and destroking it with the 2-7/8" crank you mentioned and have 243-ish cubic inch.

Those 262's are awfully hard to find- - - -plenty of 305's out there! The smaller bore also limits the size of the intake valve pretty severely. I like to run a 1.75" intake and a 1.6" exhaust in a 58CC 305 head with a little pocket porting under the valves. That's the same combustion chamber size as the old 283 "Power Pack" heads, but they've got the tapped accessory holes on the ends of the heads.

It's heresy to mention it here, but the 62 Ford Fairlane had a 221 cubic inch OHV V8 on the same block as the 260, 289, and 302!

Jerry

Jerry;

Concerning your comment "All Stovebolts have going for them is low end torque." What is it about the Stovebolt motor that makes it so torquey? Is there anyway to specifically go after increased torque? I have often toyed with the idea of putting a 292 in my Burb for increased power and torque over my 250. As they say "horsepower sells cars but torque wins races." How do I get more torque in my motor???

The 216 has a 3 3/4" stroke, and the 235 bumps that up to 3 15/16". That's a lot of leverage on the trans input shaft, particularly when the compression ratio was increased on the 56-up 235's. Since the cylinder head port geometry restricts airflow pretty severely and porting and polishing doesn't help much to get the RPM up, all we're left to work with is torque. Going to the slightly oversized intake valves used on the early Powerglide engines, and using an 848 head with a little more head milling will help a little, but it's expensive, and requires some pretty involved machine work. Too much cam and/or carburetion actually reduces low-end torque, so the 2-carb setup with a lumpy camshaft makes the engine look and sound good, but it's wasted effort. Dual exhausts without the multiple carburetion can be helpful, however.

The same concept was used by Ford for a long time, with a 3 3/4" stroke on their V8's for almost 30 years, and a 4" stroke in the 49-53 Mercury engine. The Mercury crankshaft was a welcome change for the hotrodders- - - -it fit in the Ford blocks, and with some offset grinding and welding, the stroke could be increased to 4 1/4" without a great deal of effort. 4 1/8" was possible without welding, by using the small-diameter connecting rods that were used in the 85 HP V8's from the late 1930's. The round track engines my father ran in the early 1950's had a 3 7/16" bore (1/4" oversize) and a 4 1/8" stroke, with 11:1 compression and alcohol. Then he turned them up to about 6K RPM with only 3 main bearings! When one scattered, it really hand-grenaded!
Jerry

I know of a fellow that races a 56 Chev Sedan in a NHRA Super Stock class.Rules state the only a 60 thou over bore is allowed from the original factory cubic inch. [265] By the rules,he can use a 350 c.i. high nichel block. Then it is sleeved down to 272ci. What crank,pistons etc.is secrete

Smallblock V8's are very versatile, with a lot of options available to someone who is willing to mix and match parts and/or do some custom machining. I was fitting aftermarket 4-bolt main bearing caps to 305 blocks back when I was dealing with cubic inch and/or carburetor restrictions, changing connecting rod lengths, angle-milling cylinder heads for higher compression with heads with "legal" casting numbers, and doing a bunch of other quasi-legal stuff to get a hot-rodded engine through the tech line. It was a constant battle of wits with the tech inspectors, but a lot of them came to the game poorly-armed! LOL!
Jerry

I've heard of some Stock Eliminator Engine have all but one cylinder bored out.Then tested for volume the cylinder offered for testing proved legal.

The oldtimers used to bore one cylinder bank of a flathead V8 1/4" oversize, and leave the other side standard, or maybe .060" oversize, then they would pull one head for a bore/stroke measurement if there was a protest. That was long before pneumatic cylinder volume checkers were invented!
Jerry

NHRA Stock Eliminator classes must have a fuel drain valve at the induction system [carb or FI] for random testing after a run.

So, sounds like (for your average home builder) there isn't much you can do to significantly boost torque in a Stovebolt. Best to get it running up to its standard potential and be happy with it???

Good point, Larry- - - -dual carbs, dual exhausts, and a lot of the other popular modifications are just stovebolt eye candy- - - -once the carburetion is up to par (use a Carter carb) and the ignition is optimized with the proper timing advance curve and a good-working vacuum advance for fuel economy, just drive it. Electronic ignition is nice, but don't go overboard with an ultra high voltage coil. There's a reason the people who designed the HEI system went with BIG wires and a large-diameter distributor cap and rotor. Most of the purists who want a stock-looking system ignore the possibility of flashover and try to make a silk purse out of a sow's ear.

It takes a lot of very sophisticated modifying to hotrod a stovebolt, with a lot of money spent for a relatively modest high speed power gain and a huge loss of low-end torque.

However- - - -I am in the midst of gathering up the bits and pieces to build a 6K RPM 230 engine with 3 side draft carbs and a low-restriction exhaust to run in an Excalibur roadster I've got under construction. The valve gear, intake and exhaust ports, and 7 main bearing lower end of the 194-292 series of engines lends itself to hotrodding much better than the early stovebolt engines.
Jerry