what would you rather do, for a mild street build...in general, not engine specific.

 

I said more rod, less stroke. The engine will rev higher and hold together longer.

 

When i got my 427 the crank was trash so i put in a 428 crank...long stroke..the motor was strong but i just was not happy with it..after a couple seasons i rebuilt it an installed a 391 crank shorter stroke..it really comes on stronger..i like a big bore and short stroke.. long stroke is great if you want tork..like mud running but for my drag racing i want to twist fast..that my 2-cents good luck

 

I voted more rod too...been concocting all kinds of different ideas for fun.
heres one, the 240 I6's rod is 6.795" long, same journal as a 302. Using a 351w with 347 stroker pistons (1.09" comp height), offset ground crank to 3.24" of stroke (with 4" bore) makes a 326 with a rod:stroke ratio of 2.15:1....I bet 9000 rpm would come nicely.
I know, but I enjoy crafting up crazy ideas.

 

Longer rod here- a longer rod dwells longer @ BDC, promoting more efficient cylinder filling, where more stroke just increases piston speed, and doesn't do much for your VE unless you're running forced induction and great flowing heads. He IS talking about a mild street motor, too. JMO
Pud, have you been junkyard parts-swap dreaming again?


Pete

 

hah yeah lol I remembered someone told me how to make a 317 out of a 302 using 2.3L rods (5.2") and offset grinding the crank/custom pistons....but I forgot how long they were so I made a post over at stangnet and someone gave me this link http://www.fordracingparts.com/download/charts/217.pdf
...and my wheels started turning again (too much free time maybe). I can picture the torque curve on a dyno graph with the destroked windsor tho ....long high and flat!
however...with the slower piston speeds and longer dwell times, what would that do to idle rpm and intake air velocity? Im sure the slower piston speeds would slow down the incoming air, creating a choppier idle...but would it really be noticeable?
edit: then you could put a turbo off a semi on it, and spin the engine to ungodly rpm, having it start boosting around 5000rpm
sounds fun to me!

 

That's where people run into trouble- they run too much head (valve) and carb (venturi size). That, coupled with say, a single plane manifold, and they get zip for intake velocity. That's another point where cam choice gets tougher- duration, not necessarily lift, plus oh yeah- this is a street motor, so you're not turning a whole lot of revs,

Pete

 

crazy car on the street is fun too...as long as it will move in the under 4500 rpm range, and not need a +3000rpm stall converter. Theres no drag tracks around here, either, just ovals.
Now I was just being a little crazy talking 9000rpm with a mack truck turbo haha, but with the proper head/cam/intake selection could end up with one hell of a smooth powerband with a monster torque curve.

 

Pud, I like your thoughts. I get tired of hearing so many people and their "more is better" ideas.

 

thanks, I like brewing up frankenstein-esque ideas. Most people are just happy to go spend the hundreds of dollars on new performance parts, not me I figure I'll do everything I can to stretch my dollar out, or at least get the knowledge to know what I can do without spending an arm and a leg. So when I actually decide to start spending money, I know if Im getting burnt or not....and to me, I cant justify thousands of dollars into an engine that I built because its a fun hobby.
edit: more is usually better, depending on how you got more. Nowadays you can get more out of less (cid) also. Look at those 7 second imports screaming 10000rpm down the track with a turbo larger than their engine. Now do the same things to a larger engine and you will go faster, but who needs their hobby car to run faster than 7 seconds down the 1/4, let alone 9s or 10s...once you get down into 9s IMO it goes from a casual hobby to a more serious competitive hobby....maybe now youre on a circuit racing for money...
beside, stick a 326 in a 5.0L mustang and you still get more

 

heres 2 pics I photochopped


they look pretty awsome IMO, and all I did was tuck the bumpers, make the wheel openings and wheels/tires larger along with the stripe. Just another peak into what kind of ideas I get....lol

 

There are many more articles mentioning rod length and valve timing at this site. I recall reading in HRM that they had "settled" the rod length thing. Perhaps, as this article shows. Perhaps not.

http://www.hotrod.com/tipstricks/34219/index30.html

And more in an index from the same site.

http://www.hotrod.com/tipstricks/34219/index.html

 

Concerning that first link. Their dyno tests may not show much of a difference, but there will be a big difference 100,000 miles down the road when the long rod motor is still running, and the short rod motor shucked out due to too much rod angularity! Although realistically, anything above about a 1.7 to 1 rod to stroke ratio is probably wasting your time, durability wise.

 

that first link also compared rod length differenes of 0.40" and under...what im talking about is a difference of 1.3947", providing someone built a 331 out of a 302 as a comparison. The 331 is an overbored 302 with 3.25" stroke, and 5.4" rods are the largest available to run in a 5.0L block. So when they are talking about minimal differences between rods, the comparison factors are close to the same. Now figure in my idea is just short of 3.5x the difference in length they measured (1.3947"/0.040"=3.48)...

measure extreme opposites and post results and I will be satisfied. However, I do agree, fractions of an inch in rod length diff is like splitting hairs.

Ive also read, many many times, that a 1.6-1.7:1 rod/stroke ratio is the desireable range, and 1.8:1 is optimal.

I do have to dispute the fact that anything over 1.7 is probably wasting time. If 1.7 is better than 1.6, and 1.8 is better than 1.7, then anything over 2:1 is way better...IMO! Go crank a nut tight with your stubby wrench, and then stick the long wrench on it and see how much more the leverage will spin it. More rod=less resistance=less power consumption....but like I said, no need to split hairs over decimal points in an inch.

I would just as soon run less rod for more stroke as long as it cleared, but that definately would not be my 1st choice, and is why I voted more rod.

 

The increased "dwell time" that is afforded by the longer rod makes for more efficient breathing.