I'll agree, but an engine will come to a point where there's a diminishing return. A small bore, short stroke motor will handle so much before the load stress takes its toll on internals. The 279 is a think walled beast, with lots of metal surrounding the internals. It is physically more suited to a torque house task. A 302 can absultely make a very respectable engine, creating plenty of power and torque, but for constant use in excess of 10,000 lbs, I think it will not be a very long lasting or reliable power plant. That's one of the many reasons the 239 Y finally died in dads 55. It really wasn't designed to handle 10K lb + loads on a regular basis, and it saw them, all the time. But, I'll take a 302 over a 350 any day. Can spin higher in stock trim, than a 350 can all day long. For the purpose of this thread, my opinion would be to replace the 279 with a big block, or a diesel.

 

I was WAAY off about manifolds, stock ones fit like a glove, no problem with steering box.

 

alot of people here will tell me i dont know my *** from a hole in the ground when I say this but Stroke does NOT affect torque output or affect an engines ability to pull. The GMC v6 engines were all short stroke design and built for truck duty. An engines output is determined by port volumn and camshaft design. Also keep in mind that a short stroke engines piston speed is slower at any given RPM and that reduces the load on the bottom end. If you build two engines of like displacment and are alike save for bore and stroke there will not be a significant diff. in output. Now there is no displacement for cubic inces but with the right camshaft and heads along with the proper gearing that 302 will work just fine. Stick a good oil cooler on it if you are gonna work it hard.

 

Stroke does affect torque and even rpm range of components. If you take a 302 and then put a bigger crank in it while keeping everything the same you will find that it will the torque output goes up but also at a lower peak rpm.

Port volume by itself doesn't mean a whole lot by itself. It's the port length and average cross section area of the port. For instance a 170cc Trick Flow Twisted Wedge flows just as much as a 185cc Air Flow Research head. Also small ports don't make torque. The bigger the head the less an engine has to work to make power.

As for bore and stroke. Big bores is pretty much hp and stroke is torque (simplified). Put both together and you got one sweet engine. As far as similar engines go, if you compare a 302 vs a 305. The Ford is big bore/small stroke and it walks all over the 305 small bore/big stroke. They have about the power output too. It's just harder to stuff air in a small cylinder compared to a big one. A 302 just accelerates faster than the 305 since it doesn't have to work as hard to fill the cylinders. There are tricks to stuff more air in but I think we are getting over the scope of this topic though.

 

for starters if you put a longer stroke crank in a 302 you are going to get more torque because you just increased the displacement of the engine. What joe is saying is that a short stroke motor does not make low end power which is not true. A 305 chevy is a turd and never intinded as a performance engine for starters the small bore cannot accomodate big valves but my point being if you take a 400 cid engine and build two of them with idintical heads and cams just diffrent bore and stroke combos there will not be a significant diff. in power. Period. To build a 302 for pulling and low end due to its small displacment the heads and cam need to be matched for low rpm potintal. there are alot of factors in flow but port volumn generally has alot to do with what rpm peak power accurs. a 302 will need a small port volumn to insure a high flow volocity at low rpm. If you put large port racing heads on any motor you will loose low end power you just pick it up at a higher RPM. Of course as you pointed out it is more than just the port volumn to take into account but usually a smaller port will have a narrower cross section. If anything a short stroke big bore combo will be capable of making more power potentially due to the higher rpm ability and the big bore will allow for bigger valves, but it is all in the engines intinded purpose.

 

A short stroke engine will produce its most taxable power in the upper RPM range. Take, for instance, destroking a 400 chevy. Taking a 400 block, using spacer mains, and installing a 350 crank. It decreases the stroke, and increases the RPM potential, sacrificing bottom end power. To compensate, you now need to install a shorter duration cam. To make up for the loss in cam duration, and in turn the loss in cam lobe lift, you would need to increase valve lift be using a higher ratio rocker. My employer is a former NHRA Pro pit chief. I am VERY familiar with the workings of an engine. It is what feeds my family every week. I build motors EVERY day. A short stroke motor will NOT produce as much torque in the hole that a longer stroke engine will. Take, for instance, a diesel. VERY, VERY long stroke engines. That is why they build sooooo much torque. Spin a merry-go-round. The center is spin faster than the out side edge. Same laws of physics as an engine crank shaft. The farther out you get from center, the slower it is. There for, the shorter the stroke, the faster it spins. The longer the stroke, the slower. A high revving engine will not make as much torque as a slow revving long stroke motor. Again, diesels. Slow speed motor, gobs of torque. Chevy 377 (destroked 400). Will turn upwards of 10,000 RPM, Safely, if the properly built. NASCAR engines are based on this law of physics. That is why they'll turn 9,000 RPM. NHRA motors do not. NASCAR is about staying at the top of the power band. NHRA is about using the bottom end to get you off the line quick, and staying in that band all the way down the track. They need as much in the bottom as they do in the top inorder to run consistently, at a lower E.T. I'm sorry, but your assesment is incorrect. This is why a 302 will rev higher, and outlast a 350 at those higher RPMs. Build a stock 350, and a stock 302, to with stand 8,000 RPM, and the 302 will last longer, and produce more peak horsepower, but the 350 will leave it behind in the torque range. It's basic engine dynamics, something I am VERY familiar with. If you would like, I can get numerous tech articles to back up my information, and can provide date from numerous NHRA, and NASCAR sources to cooberate it. What I may lack in certain areas, I more than make up for in the engine builder area.

 

This isn't really true anymore. Engine building has really changed in the last decade. I know a guy that has a 289 with 195 cc Canfield, 950 cfm carb. He spins this engine 7000 rpm at the track and is daily driven. This thing puts out more torque than the factory 87-93 Mustang 5.0L ever did at the same rpm and peaks at 5300 rpm.

 

If there are charts and articles online, I'd like to see them just to understand. (If it's not trouble.) The only benefits I can see with these variables is decrease in friction and fatigue failure. Because after all, he could install a wankle engine with no torque and still sacrifice top speed for acceleration with the right transmission... hehe well maybe.

 

The reason a diesel builds so much torque is because there is a turbo strapped to it number one, number two is the way the diesel fuel burns, it continues to build cylinder pressure after tdc the direct opposite of a gas engine. Also a diesel engines internals wiegh ALOT that is one of the reasons you cant spin them so fast the other is that diesel fuel burns slower than gas. If you were to put Boss 302 heads on that engine it would not be a good truck motor. It is all about head design and camshaft specs. Sure the outside diam. Off the crank is spinning slow but the pistons are hauling ***. That is why long stroke motors cannot rev as fast. A smaller motor motor might have to rev a little higher but the piston speed is slower so the engine is not in that big of a strain. but we can agree to disagree. I say stroke does not affect peak torque. unless the engines you build do not apply to the rules of physics the only thing that will affect what rpm an engine makes its peak power is air flow not stroke. Also last time I checked NASCAR is not in the habit of building pulling motors. Given most bigger engines have a longer stroke because there is no more room to expand the bore. It is all about volumnetric efficiancy not cid. Now back to dodges question he can make a 302 pull like a tugboat with the right combo and gears. Can he make more power with a bigger motor, yes because of the available CID not because they have a long stroke. To say a 302 cannot make good torque down low because it has a short stroke is wrong. It will make good power relative to its displacment.

 

dueller I assume we both agree that a 302 will make good torque? Any way joe here is my point a GMC 305 of 1965 vintage Bore 4.250X3.58 stroke 280 lbsft@ 1600 rpm. Ford 300 1965 vintage 4.00X3.98 213 lbsft@2000rpm. Chevy 292 3.875X4.125 275lbft@1600. still think a short stroke engine cant make power down low. If I am not mistaken the 460 is an undersquare motor making it a short stroke engine as well as a 454. my point is two engines of like displacement and diffrent bore and stroke combos can make very similar power at the same rpm levels. I am sure i can come up with some more numbers to support my opinion, can you?

 

interesting:
http://en.wikipedia.org/wiki/Power_band

To decrease the sideways pressure on the cylinder wall and extend engine life, it is best to use long rods for heavy duty applications, long rod to crank shaft total diameter/stroke.

 

I see the point. I guess, I erred in my vague description. Most notably, the lack of inclusion of deck height, rod length, piston pin location, etc., etc. My very vague generalization, is based on the reletively short stroke of the 302, which also has a short crank centerline to deck surface height. Using the stock rods, and assuming the piston pin is in the stock location, the 302 is not a good candidate for a torque producing engine. However, with the ample supply of todays aftermarket parts, yes, any engine can be made suitable. It would, however, require replacing most everything in the 302, in order to produce the low end torque of a naturally longer stroked, and taller decked engine. Then, topping it off with improved flow rates for the heads' intake and exhaust runners, using long tube headers, and a suitable short duration cam, and good dual plane intake, the 302 could be made to provide plenty of torque. I still, though, do not feel that a small displacement small block is a good choice for a very, very heavy 3 ton rated truck. I still feel that a large displacement small block, or small displacement big block would be a more reliable, and less costly choice to replace an orginal engine that was built for specifically for that purpose. It would still be like trying to get a roughly 400 CID engine to lug my 15,500 pound semi around, and not fart on itself when asked to actually work. The 302 will be fine for cruising that big truck, but I think it will be very gutless, no matter what is done to it, when asked to perform typical load hauling tasks. There are many better choices out there for that, and at a lesser cost to achieve the same end result.

 

Dont get me wrong joe, im not saying a 302 will build 500lbft@1400rpm but I dont think 300lbft below 2000rpm is unrealistic, and with the factory gears that I assume are 5.83:1 or lower that will be more than adaquate. I see why he wants to use the 302 as he already has it and if he wants to he can put a 351w and use his same mounts and trans and such. Hey Dodge, What transmission are you planning on using?

 

Believe it or not ( and I am sure this is going to really cause some laughs ) but I am using everyting that was in the 86. I still even left the 4 wheel drive transfer case under there. I made my own motor mounts of course and the same with the trans mount which caused me the greatest grief but it is all there done. I spent today hanging the power brake booster and running all new brake lines. I converted the entire brake pedal assy over also today. You would not believe how easy that was, it was almost as if the brake cage was made for the 52. Tommorrow I will start on fuel, as I mentioned the motor is late 86 so it is injected so I have to plumb in a return fuel line to my tank I guess. All in all it is going very well, I would post pict. here but I do not have them saved anywhere on line, only in my comp. If anyone wants to post them for me give me your e-mail address and I will send them to you.
BTW no matter what anyone says that 302 that I pulled out of my truck has more tourge and hauling capacity than I could ever use. I have hauled entire trees as big around as a 18 inch wheel in that truck and pulling my double axle trailer. Your right it is going to prob. go soon enough but only because it is worn out with over 200 plus on it but when it does I will just go thru it and stick it back in again.
I am also wondering what trans might be in there so if anyone can tell me that would be nice.

 

if it is a 4spd i would guess maybe a t-18 or t-19.