|02-06-2011 09:06 PM|
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.
|02-06-2011 10:38 AM|
|jeffery wells||f-bird is hitting the nail on the head with having the cam grinded and custom fit for your application, however, if your looking for something with throttle response, acceleration, and not so bad at the pump in a daily driver, the lunati hydraulic 262 will give you a higher rpm range and set down you lifters a little easier for a quieter operation. this cam will give you that aggressive sound and performance of a classic rodder without breaking your bank account, but of course, these are all just suggestions, in the end it's up to you decide what you want out of your car.|
|02-06-2011 12:10 AM|
If you insist on using a dynamic cr calc to tell you what compression ratio can be used with a cam, you had best convert the Crane @.004" spec to a good estimate of the spec @.006" which is what the calc needs for an input.
A good estimate of the duration @ .006" will be 275° in and 283° ex.
Now redo the dynamic calc.
garbage in = garbage out
If you need this cam on a small base circle cam core for stroker rod clearance or want it on a different LSA like 108° call Crane Cams. They can custom grind.
If you need clarification on the difference between .004 and .006 advertized seat durations, and what that means
and what this cam actually measures at .006 ask Crane cams tech.
|02-05-2011 11:34 PM|
If you use the Crane advertized durations in the typical dynamic cr calcs you will get a false dynamic cr.
Crane measures their seat durations 288°-296° at a different spec (.004" instead of typcial .006" lifter rise. This makes the advertised seat numbers bigger they they are. (@.006")
The 11:1 mechanical compression ratio is a bit too high for daily street use on premium unleaded on a engine without computer engine management to keep it out of trouble under less than optimum operating/driving conditions. (like when things get hot in traffic etc). Build it with a real measured 10.5:1 or a bit less and it will be trouble free.
The Crane (HR) hydraulic and (SR) mechanical street roller cams are a premium product using a billet roller cam core with a pressed on cast distributor gear on the end to be compatible with standard distributor gears. (a bronze distributor gear is not required). thats why they cost a bit more than some other brand street rollers that are a cast cam core. (ya get what you pay for)
The one you have chosen is a good one for moderate street performance with a broad power range. Consider 1.6 intake rocker arms for increased intake valve lift to take full advantage of the good AFR cylinder heads.
a 3.55 to 4.10 gear rear gear will work very well. Can use a stock 12" "2100 stall" converter and really rocks with a 2800-3000 stall converter. use a 10" 3500 stall and 4.10's for max drag performance on drag slicks or ET streets.
|02-05-2011 08:48 PM|
Well, I haven't been here long, but I have read enough old posts, and been on enough forums to know it is best to give hopefully enough info to get some help, no point in wasting mine, and other's time with silly questions that could have all been put in the first post.
Thanks for the Lunati direction. I forgot about them, last time I build an engine, over 10 years ago, Crane and Comp cams were the big players, not to say they aren't now, but people seem to be looking other directions.
I will run a few of their cams through DTD2k and see what I come up with. Any particular one you think I should consider? Their prices seem to be less then Crane Cams.
|02-04-2011 06:00 PM|
|jeffery wells||wow, you've been here before huh, lol, and the only BAd experience i've had with those is when i pulled one out only to find that it hadn't been tightened down all the way, and it snapped. but still, not the cams fault, the guy just didn't know what he was doing, but i haven't had any problems with em, for the most part there a good choice, i would go with lunati, but that's just me.|
|02-03-2011 10:33 PM|
Cam opinions wanted.
Does anyone have experience with the Crane Cams Powermax hydraulic roller cams?
I am looking at this cam for my Chevy 383 build,
part number: 119701
Grind Number HR-222/345-2S-12.90 IG
Duration at 050 inch Lift
222 int./230 exh.
288 int./296 exh.
Valve Lift with Factory Rocker Arm Ratio
0.518 int./0.539 exh.
I am most likely going to be going with AFR 195cc heads, performer rpm air gap,750 cfm 4 bbl carb.
Engine is most likely going to go in an 81 Monte Carlo. the tranny needs rebuilt, so i can match the stall converter to what is needed.
here are the numbers fromDTD2k
RPM HP TQ
2000 189 495
2500 239 501
3000 289 507
3500 339 508
4000 381 501
4500 415 484
5000 435 457
5500 436 416
6000 418 365
6500 384 310
7000 343 257
7500 300 210
The engine will most likely not see the north side of 6000 rpm's.
Static comp ratio is 11.08 and dynamic comp ratio is 8.10
I have also been considering the 1 smaller cam in this line, the
Grind HR-216/339-2S-12.90 IG part #119671
RPM HP TQ
2000 192 504
2500 241 506
3000 291 509
3500 336 504
4000 375 493
4500 404 471
5000 417 437
5500 414 395
6000 385 337
6500 352 284
7000 306 229
7500 260 182
SCR = 10.95:1 DCR=8.16:1
had to drop SCR a little to get the DCR under 8.25:1
Not sure what my rear gear ratio is, probably what ever was stock in an 81 Monte.
your thoughts and opinions are welcome.