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Old 02-06-2011, 09:06 PM
mbaldwin mbaldwin is offline
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F-BIRD'88,
hi, thanks for the good info. I actually setup my own excel spreadsheet for all my calculations, I don't have to go back and forth between different websites to refigure stuff if I make one change. I got the formulas for DCR from http://www.empirenet.com/pkelley2/DynamicCR.html.
Granted I am not taking in to account the bore and piston clearance, or the space above the top ring to the top of the piston, but that should not change my ratios to much, not enough on a street engine at least.

Thanks for pointing out Cranes seat to seat of .004. I guess I read that, but didn't think much of it. Could that make a difference of more than a degree or to for the intake closing though? A call to Crane might be in order though, just to get the .006 info.

even with aluminum heads, and a DCR of less then 8.25, you think 11:1 is to high of a SCR for 91-93 octane? Well, if I go with the 70cc heads, that will get me 10.36 SCR which would be about 7.59 SCR with the HR-222/345-2S-12.90 IG cam, and the HR-216/339-2S-12.90 IG cam is 7.74 DCR, using Crane's seat to seat numbers.

Good quality is worth the extra in my mind. If I go with the Crane cam and roller lifters, that will cost more than my crank, rods, and pistons. Seems kind of weird. But, if I am not going to push out 800 poneys, I see no point buying an $800 crank.

I am glad to see what you recommended for rear gears, that was about the same range I was considering. at 65 MPH with 28 tires 3.73 gears I would be around 2900 RPM's. I will most likely stay with the TH350 or TH400 I already have, unless I can find a 700r4 for a good price. Not sure where the cruise RPM needs to be in relation to my torque curve though, but that is a little off from the cam discussion of this thread.

using the estimated 275/283, DTD2K calculated the intake closing at 64 degrees ABDC, which I guess is a huge difference from their advertised 75 degrees. But DTD2K figured the closing at 71 degrees with their advertised durations, so something is not quite on somewhere. if the 64 is about right, I will need to drop my SCR to about 10.15 to get a DCR of 8.16.

A custom ground cam is a possibility, I like what changing the LSA to 108 does on the estimated Hp and torque.
HR-222/345-2S-12.90 IG cam
with 108 LSA and 1.6 intake rocker ratio
2000 183 480
2500 230 483
3000 279 488
3500 326 489
4000 372 488
4500 410 479
5000 435 456
5500 446 426
6000 434 379
6500 413 334
7000 377 283
7500 344 241

HR-216/339-2S-12.90 IG cam
with 108 LSA and 1.6 intake rocker ratio
2000 188 493
2500 235 494
3000 283 496
3500 330 495
4000 370 486
4500 404 471
5000 426 448
5500 430 411
6000 415 363
6500 387 312
7000 348 261
7500 308 215

I will definitely be calling Crane to get the .006 specs and such.

Thanks,
Michael
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