Bore and stroke...
 

Hey guys heres one for ya, what is the better way bigger bore shorter stroke?, smaller bore bigger stroke?, or bigger bore bigger stroke?. Been looking around at this for awhile now and noticing some things.
Look at your engines of today small bore larger stroke 5.4 makes 365tq@3750rpm they have pretty good power but alot more compression 3V aluminum heads over the engines of the past and roughly same or lower fuel economy.
Then its to the bigger bore smaller stroke 351w 325tq@2800 with 8.8:1 compression heads that are a joke for flow from the factory tiny valves could go on but won't.
bigger bore bigger stroke, the 400 right out of the box basically was ran down by emissions 8:1 retarted timing sets flat cams and still produced decent tq.
Bigger bore shorter stroke, the 460 same way no where near the same compression still produces tons of tq easily.
What do you guys think? build the old with a set of aluminum heads that flow, up the compression to comparible numbers with roller cam and decent exhaust who would come out on top for torque, efficency, and reliability? I am a fan of pushrods but I like my fords all in all, drive all of them from 300, 302, 330, 351, 400, 460.
IMO my 400 just has 4bbl intake, stock heads, 9:1 pistons, custom ground cam thats under .500lift that is ticket, just needs efi it has great power needs OD for economy and I am set. C'mon lets hear what you guys have to say.

Curtis

Its all down to the cubic inches, stroke, and top end of the engine.

If ya want torque gains only then going with a longer stroke would be obvious.
If horsepower is whats wanted a shorter stroke and bigger bore is what is called for.

For example: A 460 is going to be a power house simply because of the cubes it houses long stroke and huge bore. Thats why HP is big and torque is way up there. The more cubes, the more power is achievable.

BUT if the intake and exhaust flow isnt up to the task it will not produce power on certain sides of the engine.

A 351 cleveland makes HUGE amounts of horsepower. But the ports are so big the velocities are way down. There for it is a high rev motor and is slow down low.

Engines now adays claim those HP numbers because thats the numbers it makes on premium fuel. If regular is used, it detunes the engine to prevent detonation from the high pressure levels, making less power.

Go ahead and rebuild the engine with aluminum heads! Only will improve the engines power.

Im not sure about this, as Ive never had aluminum heads. But it would seem to me the expansion rates would just tear the head gaskets. The aluminum would stretch out before the block and just rip them. Does that sound likely?

My 351 windsor I built. I punched .30 over and used a 383 stroker kit. I used a BIG cam in it and ported the stock heads. I still have lots of low end grunt but it screams past 5000rpm!

There just are to many engine combos to work with to really say which one is the best. But really any engine can be built to perform where its wanted. Just my 2cents

It's displacement, cam and tuning.

300 Ford, 4 x 3.98

305 GMC, 4.25 x 3.58

HP and Torque nearly the same, at the same low revs.

Hot Rod built two BBCs, differing the bore and stroke to max the engines to big bore/short stroke vs. small bore/long stroke. Same CID. Same power.

And yes, if you could do such a thing with a Ford it would act the same way.

Someone posted on another thread how a 400 would be better for torque than a 460 because of the longer stroke. Yea sure...

You compare new engines to the boat anchors of yore....apples vs. orangautans. Cams, efi, everything is different. Throw in variable valve timing and it gets farther away.

All the engines you listed can be built to make gobs of power. Better heads, manifolds and cams along with some compression and presto, even an old turd AMC 390 can make tire-shredding power.

So don't worry about the bore/stroke question. Just make it as big as you can and put the other goodies on there and drive it.

if two of the same size engines are compared, the longer stroke one will always produce more torque if all other things are equal, it has to do with leveage on the crankshat. If you put a bar on your rachet, its easier to turn. The same basic principles apply with engines. The longer the stoke, the further the rod journals are from the crank centerline, which increases the leverage on the crankshaft. A longer stroke also increases the amount of time that the forces of the expanding gasses have to act on the top of the piston.

This is a simplified explination that doesnt take into consideration piston speed, rod length and valve shrouding, but it should give you a general idea of why a long stroke engine produces more torque. The clasic example would be a 300 vs a 302.

But, a 300 vs 302 can't be directly compared. Different head vs heads, and different cams. And, also, the 300 doesn't have 'more' torque, it's peak torque is at a lower RPM than the 302. It is a smaller number, though. And, no, I'm not defending either engine.

Yea the 300 vs 302 wasn't ment as direct comperison, I just used it as a quick example that most people could relate to. If someone wanted something concrete, they would have to build two engines with the same top half and with the only difference being the rotating assemble, which wouldn't be very practical.

You don't know what the hell your talking about, 330 HP 390 AMC motors kicked azz in their day, body styles had a lot to desire.
AMC Scrambler here w/458", 69 AMX w/401, 69 Javelin w390-401-438- 458.

With the "turd 390" 12.59 at 108 mph quarters with over 40K street use miles between rebuilds back in 73 that spanked many so called performance FE powered Fords.

Been there done that just had to vent.

Ford 300 vs Ford 302---forget it. One's a 6, the other 8. One has 12 valves, the other 16. Compare the GMC V6 305 to the Ford 300. Nearly identical power at the same low revs.

http://www.6066gmcguy.org/EngineData.htm

As for the statement that the long stroke engine will "always" have more torque, it's not true. While the long stroke has a longer "arm" to lever with, the big bore has a bigger "hand" to push with. All things equal, with equal displacement, you get equal power, within reason, of course.

As for the AMC 390, well, I thought they was boat anchors but maybe they was runners. Anyway, if they ran good new, you can make 'em run better now and fix the oiling thing as well.

If head flow does not matter what about when GM took their trucks from TBI to vortec with the 305 and 350 that made a huge diffrence better efi yes, roller cam yes, but the tbi heads did not flow worth a crap to the 180cfm on the intake of the vortec heads.
Ford 302 4"x3" chevy 305 3.74"x3.48" stroke crank. The ford makes its peak tq in a truck at 280tq@2400rpm the chevy makes 270tq@2850rpm and thats within 3ci. of each other I have towed with both I like the 302 better.

Curtis

Just read through again something I noticed, one of the big reasons I said aluminum heads is you can run higher compression without the need for the higher octane due to most of todays aftermarket has better designed chambers and they handle it better. There are tons of guys out there with the mustangs that beat them and run them harder than 95% of us do our trucks and they don't have a issue with head gaskets. Look at the modulars iron block aluminum heads they don't have issues, heck there almost at 10:1!and burning 87octane. My 400 has the stock heads .010 shaved and 9:1 pistons and it likes 89+ octane.
EFI and cams thats all variables that can be done old engine cam tech. keeps improving well to a extent no varitalbe valve timing but for me being been to GM cert classes seeing all of this they can keep it. But efi is not bad to do on engines I am doing efi on my 400, I have a friend that has put eec-iv on big block chryslers small block chevys, eec-iv is very adaptible as long as you can tune it. My 92 f150 in my sig. is getting my 351W I just rebuilt with the addition of EEC-V from a 96 351w truck, why? SEFI MA and the V processor is much more efficent my 96 gets better economy that my 92 with a 5speed ever could.

Curtis

No replacement for displacment Big motor big cam big heads big power everywhere