I would not want a shorter stroke, and John Kasse seems to agree. He sleeved his cylinders down to allow the CI to be made with stroke.

I see the larger diameter swing of a longer stroke applying a smoother and slower action on the piston. I dont know if I am correct, but in my minds eye I see a long rod as well as a long stroke as allowing a slower pass thru TDC/BDC.

A shorter rod will be slower at 90 degress and fasterat 45/135 do to the moment whip of the angle. If you can picture it, the piston with a shorter rod starts moving faster, slows down mid way (80-100 deg) and whips again towards TDC. THats why I personally like the longest rod I can get. I will refute my own statement.....anytime the crank stroke grows the rod inclination sees itself as if you just shortened the rod......therefor causing more of the afformentioned whip at the TDC/BDC. Once more a tall deck/long rod/long stroke is the way to go IMHO. BTW I have DD2K. If you give flow numbers at ever .100, full cam specs with lobe sep, lobe type (roller drag race, street lobe, street/strip...) Carb CFM....put it in one post with whatever your current thinking is with bore and stroke...and I will run it to see the best guess dd2k output. I see a flaw in that program because if you design an engine and do what a pal told me to do...."Change the intake valve to 4"....you suddenly make more power! The flow numbers you input are still the same, but the 4" valve that would not even fit in RL makes a great performance gain in the software for no reason.

 

THe 2 kids would be percived as the exact same weight. Your wrong. If they moved thier positions one could appear to offer more resistance than the other. If they got off and you went over to knock them down....the bigger one would surely be harder to move :]

 

John's going to win again this year

 

fordtrkpuller,

3.59 stroke
4.500 bore
Mech. .640, .666, 260*, 270*@.050, 295*, 305* adv. 110 LSA
(drag race)
14.5:1 comp.
Al SCJ heads
352 cfm int. @.700
249 cfm exh. @.700
Weiand Stealth
1150 Dominator

 

OK, Here is what I get...
RPM HP TQ

2000 160 419
2500 218 458
3000 275 482
3500 350 525
4000 433 568
4500 514 600
5000 586 616
5500 649 619
6000 684 599
6500 708 572
7000 708 531
7500 695 486
8000 664 436
8500 623 385
9000 580 338

 

Torque is way down. HP range is too high for the EM challenge.

 

It doesn't gain HP, and loses TQ after 6500, the MAX for the EM Challenge. HP and TQ look really good to me.

 

Well it is average hp and average tq that matters. You want the fat part of both of those curves to be in the middle of the RPM range, not maxing out at 6500.

 

Avg HP from 3K to 7K is 545.22 HP
Avg TQ from 3K to 7K is 568.00 FT/LB

 

bigsnag, if you check the ave. betrween 3000 and 6500, which was spec for the challenge, this combo is good for an 8th place finish, and when you consider tune time, possibly higher. not bad for a combo that can be built for under $8000.00

 

fordtrkpuller,
How would it change if the compression was dropped to 14:1, and the header primaries were changed to 2", all else being equal? Thank you for running the numbers.

 

But here is with small tube primarys rather than large tube, and drop the compression 0.5 point to 14.0:1 from the original 14.5:1.

RPM HP TQ
3000 268 469
3500 342 514
4000 425 558
4500 505 589
5000 576 605
5500 636 607
6000 667 584
6500 687 555
7000 682 511
7500 663 464

The average for 3K to 6.5K is513.25 HP and 560.125 FT/LB
Remember I did the average on the one prior to this out of range (3K to 7K)

 

I changed the lobe sep angle to 114 and found that this is a better angle for your biuld.

RPM HP TQ
3000 271 474
3500 344 516
4000 425 558
4500 507 592
5000 581 610
5500 639 610
6000 675 590
6500 696 562
7000 694 520
7500 678 474

The new averages with same small tube primary and 14:1 comp with a 114 degree lobe sep are:
517.25 HP and 564 FT/LB

I am sure if I took the time to play with valve timing I could squeeze more out of it, but I'm on the clock at work :]

 

OK, Im going to a meeting all afternoon, then I'll be back in the office tomorow. So, I assigned my PC the task of running 750,000 possible cam configs on this engine to see if we can generate more torque in the 3K-6.5K rpm range. Tomorow it should be finished when I come in, and I'll post you the results if they are worth looking at. I already ran a quick test and was able gain about 40 ft/lb of tq but it lost a bit of HP. Lets see what turns up.

 

Well I ran some numbers on my DD2000 and used some number for head flow from ported Blue Thunders and came up with a combo that gave me 1178.5 total points. It took me all of about 5 minutes. That would be good enough for 2nd and only 0.3 points behind Kaase. I used a stock 460 crank and bored it out to give the largest CID allowed, 12.5:1 CR, 1100 carb, and even small tube headers with mufflers, and a roller cam measuring 280/290 with only .650/.670 lift. Obviously this is just a bunch of bench racing BS, but I think it shows that it is easier to make a flat meaty torque curve with a longer stroke. I'll work on it a bit more and see how much I can actually squeeze out of it.