BIG BORE VS BIG STROKE-372 VS 383-WHICH SBC STROKER DOES IT BEST? BONUS TEST-302 VS 347 FORD

WHICH ONE MAKES MORE POWER, BIG BORE OR BIG STROKE? DOES A 372/377 MAKE MORE POWER THAN A 383? DOES THE 4.125-INCH BORE ON THE 372 MAKE THE HEADS FLOW BETTER? WILL THE INCREASED HEAD FLOW TRANSLATE TO MORE POWER? DOES A BIGGER MOTOR MAKE MORE POWER? WHY IS THE 383 STROKER SO POPULAR? DO I NEED AN AFTER MARKET BLOCK TO MAKE A 377? CAN I USE A 400 BLOCK? BONUS TEST-302 VS 347 WITH THE STOCK HEADS, CAM AND INTAKE. WILL THE EXTRA CUBES STILL MAKE MORE TORQUE WHEN CHOKED OFF WITH THE STOCK INDUCTION SYSTEM? CHECK OUT THE VIDEO FOR FULL DYNO RESULTS.

[mrmiscast]

I've built both a 383 and a 372. Same cam in both, same World Products heads. Hey, I worked at a auto parts store at the time. Maybe more torque below the 4500 mark for the 383, but a fair amount more power above 4500 for the shorter stroke. The only explanation at the time was the bigger bore made better use of "average" heads with no issues with flow around the valves near the cylinder walls. I actually liked the 372 better, but when I did both engines the idea of the 383 was fairly new and some guys were having problems with side load on what you'd have to call crappy pistons. A friend built a 383 as well, and he came up with the most common sense outlook on both engines. Build a 383, put it in a truck... Build a 372, put it in a non heavy car with some decent rear end gear, and enjoy the top end. Or build an all out effort (read as All Your Money) of either and never notice the difference.

[whataboutbob]

Uncle swore by the 377(400block-350 crank) in the sprintcar. Did not need gobs of tq, but the extended rpm help with tractable tq for a very light car.
The tow/hauler ran a 383-more drivable tq. Both motors were very different tho. But who doesn't like a rooting tootin gross pollutin high revin sbc?

[mikegillam]

I think the 302/347 comparison was more helpful because it was a direct comparison with no variation between cam grinds, heads, intakes etc. Both the 383 and the 372 would be fun engines, but it wasn’t apples to apples enough to really gain any insight into differences between the two engines. Lift and cam timing at 050 were similar, but we don’t know much about the rest of the profile. The heads and intake may have flowed similarly, but at these power levels lots of little variables can stack up. The higher torque and better midrange for the 383 are classic benefits of a tighter LSA and more displacement, though

[PatandDoopypoopy]

A neat comparison for the bore/stroke comparison would be, cam and intake each combo for the inherent sweet spots. Go for 500+torque and 5700rpm redline on the 383. Go for 500hp and 6500+rpm on the377. Use formula for a car and see which is faster. Of course some like brute torque and others like banging gears at 7000rpm. It's really all about flavor, yes?? Im just a car dude. Thank you for videos and community interaction. Be well everybody.

[toxiclightning]

I’ve always thought of an experiment like this with the LS platform.
Comparing a 5.7L ls1 with an “LS7” based engine destroked to 5.7L with the 4.8 rotating assembly. Both of these engines displacements and compression ratios are both within 1%! With the same cylinder head / valvetrain it would be interesting to see how they compare!

[theshed]

Bore = potential valve area. Stroke = length of the lever.
Long stroke means more piston speed, which will help at lower rev's. The Ford numbers would have been very interesting from 1000 rpm lower, but unfortunately that's not how it happened. Good information Richard. Thanks very much

[ChristopherGaul]

This comparison is a great example of why we should be using area under the curve instead of just peak numbers.

[ChristopherGaul]

With regards to stroke vs. bore, it's all about use case.
I have a 3/4 Ton Suburban, and not long after I got it, I replaced the 350 with a GMPP HT383E. I have zero regrets about that choice. It didn't just give me more power, but it gave it to me where I especially wanted it, down low. It gets that heavy truck moving so much easier, and it's a tow beast a well. Plus, it will power through heavy snow and dirt with ease.
That said, back in my youth I had a buddy with a really lightweight Nova with a 327, and that high RPM power curve was perfect. I'd love to see it scream with a high revving 372 with 2.02/1.60 valved heads.

[Tchristman]

I have a 1963 Ford Falcon that came with 260. I now have 302 with 1969 351W heads. A 351 will not fit in the engine compartment without serious modifications. So a 347 might be good. But the 302 is sufficient.

[bobgyetvai]

On the SBCs the stroke swallowed the duration up on the 383 so it did better lower . The narrower lsa also helped the 383 more due to stroke . But truthfully both lsa were too wide .

[senseimarvin]

adding stroke not only increases some displacement, but it also increases the leverage of the crank. the pistons are now pushing down on a LONGER torque arm.
Also on a small block chevy, if you put a 3.75 stroke crank in a 4.125 bore block you will make more power than both the 383 and 377. I think they might have made an engine with that combo.

[jfseaman]

Re 372 4.125x3.48 vs 383 4.03x3.75

I tune lots of bike engines. I see both configurations in similar displacements.

Torque falls off more the more over square. Horsepower goes up from breathing and more esoteric things like sqirl and squish.

[craigmichels]

Second half of the video was great! I have a 305 and thinking about making it a 334 and leaving the heads, intake, and carb the same but wasn't sure if it would work. This pretty much confirms it would and would give the gains in low end power I am looking for. Most bolt on power only helps at the top end and hurts the low end. Spinning an engine over 5k rpm doesn't have much real world application.

[Paulster]

My thoughts on the 372 v 383: With the bigger bore, the 372 did better on the top end because the larger bore allowed for better airflow. The reason why the 383 had more torque was because of the displacement difference. I'd personally take either one of them, but there really is no replacement for displacement, so the 383 wins in my book. having better torque all the way down the graph in the area where you need it makes a lot of sense to me.

[joealbert]

I built a 372 back in '75 for my sprint car. It was the least expensive way to gain more cubic inches over a 350. It was a very good combination and won it's share of races. I later built a 400 using a stock 400 crank which I had balanced. I never thought it was that much better than the 372, but it did pull hard on the bottom end.

[SweatyFatGuy]

The 302 v 347 thing has been done before, Pontiac has been doing that from the factory since the V8 came out. You can put the same top end and cam in a 350, 400, 428, and 455 to see how much difference displacement makes. You can also see what happens when you increase airflow through the heads on those engines.

Only the 350 is small enough to move the torque band up with increased airflow. The 400, 428, and 455 all simply make more torque through the entire RPM range. Thats because the runners are the same length on every one of the, and that is where the torque comes from. The ports are kinda small for a 400 inch and larger engine, so the power band doesn't move much in the RPM range, it just gets bigger.

Pontiac is fun, because the main differences between the 400 and the 428 are main journal diameter and stroke, 3.75" vs 4" and the 400 vs 455 is .030" bore and a 4.21" stroke. You can get crank kits for the 400 block with 4, 4.21, 4.25, 4.35, and 4.5 inch strokes, that cost about the same as grinding a stock crank, adding forged rods, and new pistons. So why not make that 400 into a bigger engine?

The grunt from a 455 is addictive... especially with a 2.73 to 3.55 gear behind it. The 455 in my 65 GTO is pushing a 3.08 gear, and it pushes you into your seat far harder and longer than a car with a 4.56 gear does.... provided the tires don't go up in smoke. As long as you don't think more's better with gear like its a sbc, the Pontiac is an inexpensive way to the low 12s to high tens.

The problem is you aren't finding these engines in most junkyards, you have to find the entire car most of the time (usually 4 doors), and that is getting harder too.

If you weren't so far away Rich, I would bring stock and modified 400 and 455 engines for you to test. Might be fun finding out how much power my latest build with the tunnel ram makes. Its raining again today, otherwise some dragy runs would be happening. Maybe tomorrow morning, since its Sunday and the traffic will be lighter.. if its not moist.

[gothicpagan.]

That long/short stroke graph looks like every test I've ever done, though being in the UK our No's are on another scale.
90% of the motors we work with wouldn't make 500hp with boost, nitrous and race fuel. 🙂 Or if they did, the pistons would go down, and keep going . Our stuff is just so much smaller, a 2Ltr is now regarded as a big motor

[logwilky]

I’ve been requesting this for years. Thank you

[Harrybowles]

Thanks Richard. The charts tell me a stroker wouldn't be a waste of time with stock heads if just for a nice street driver. I learned something today 👍

[LeadStarDude]

I would really love to have my 5.7 Hemi stroked, some Edelbrock heads, and some headers for my 2005 Daytona edition RAM 1500. I don't want a different camshaft, and I don't want a different intake manifold. I just want more torque with a little more airflow on the exhaust side. Nothing super fancy. Just a stroker crankshaft with the appropriate connecting rods and pistons, new heads, and headers.