NPI cam choices....

[Outlaw97GT]

All these cam questions got me thinking..

To start off, I want to stay with the NPI heads.

Does anybody know what the HP and TQ differences would be between:
1. PI cams, not sure of the specs.
2. 262H- in.224, ex. 232 @ .500 lift
3. 268H- in.230, ex. 236 @ .500 lift

Can you use the PI comp-cams in a NPI, like the 262AH in.226, ex.230 @ .550 lift?

Thanks

 

[Pughman]

.550 lift is bad in npi, go the 268H and a tune...

 

[stangGT97]

I think you need to notch your pistons if you want to use any sort of high-lift cam. I can't comment on power gains with either of the aforementioned comp-cams but the 268s may need valve springs so keep that in mind.

 

[Pughman]

yes valve springs are always good...

 

[DropTopPony]

The PI cam is good for 15rwhp or so but i really like the Crower NPI cams...VT is having a sale $535 for the St 1 or 2 NPI's I bet with a tune you will gain 30-40rwhp over the stock npi's

 

[COramprat]

230HP 273TQ with my 262's on a Mustang Dyno.

kboy262 got 237HP 273TQ on his old 98 at Modular Powerhouse. He had 268's in his. Does anyone know if Tim has a Dynojet or Mustang Dyno?

 

[stangGT97]

The PI cam is good for 15rwhp or so but i really like the Crower NPI cams...VT is having a sale $535 for the St 1 or 2 NPI's I bet with a tune you will gain 30-40rwhp over the stock npi's

VT makes NPI cams? wow I have to look into that!

 

[DropTopPony]

VT makes NPI cams? wow I have to look into that!

no they sell the Crower NPI's

 

[TGJ]

Alright, I will take this one on. You need Crower Offset retainers and a good set of springs to run the PI Comp cams in NPI heads. You do not need to put valve reliefs into the pistons if using PI Comp cams and NPI heads. The PI Comp cams are really .545 lift, not the .550 lift as advertised. Now if you are going to run a cam with more than .545 lift, than you need to look at some other things to make those cams work in a NPI head.

 

[Outlaw97GT]

Thanks for the info....

Ive done some research and I think the 268H (NPI) cams would be my best choice. Im going to try and get some parts through out the winter for next summers build-up. Cams, PI intake, shorty headers and a custom tune.

Keep the info coming guys.....:SNSign:

 

[TGJ]

I researched Comp's cams quite a bit when I was planning my Big-Bore. I would go with the PI 262's over the NPI 268's, if it was my car. I have an excel file that compares all of Comp's cams to the Stock PI cam. All the cams were installed into the same car, so the only difference was the cams and the 262AH was a better performer than the 268.

 

[Outlaw97GT]

230HP 273TQ with my 262's on a Mustang Dyno.

kboy262 got 237HP 273TQ on his old 98 at Modular Powerhouse. He had 268's in his. Does anyone know if Tim has a Dynojet or Mustang Dyno?

Do you have the PI intake also?
Do you have before cam #'s?

Thanks

 

[stangGT97]

Do you have the PI intake also?
Do you have before cam #'s?

Thanks

I believe he is running the stock NPI intake.

Droptoppony, I thought by your post that VT had NPI cams, thanks for the clarification.

I have an excel file that compares all of Comp's cams to the Stock PI cam. All the cams were installed into the same car, so the only difference was the cams and the 262AH was a better performer than the 268.

do you think I could have a copy of that file? I'd be interested to look at it. The PI 262s wont have PTV issues in an NPI head?

 

[TGJ]

I will post that Excel file later on today.

It is not PTV to worry about with Comp's PI cams in NPI heads, it is coil bind. That will be taken care of with a good set of springs and Crower Offset Retainers.

 

[prsrizdgt]

My 2 cents is that if you are not going with a power adder to strongly consider the VT cams. I am running the Comp 268's with an Eaton blower mainly because the Comps are ground on a blower friendly 114* centerline. I think the VT's are ground at 113*. Now, I didn't dial them in (used the Andersen tool), and many people say you need to do this for another 5 horsepower, but I wasn't blown away(pardon the pun) by the difference in power. I personally would have sacrificed a little horsepower on the bottom end because of the roots blower, if they would have loped more than they do also. At least I don't think they lope very much. You hear a little more with a five speed because you a pushing in the clutch every time you come to a stop, but with an auto you don't. They act differently in the mod motors. When my car is in park you can get the lope and sound, but drop it in gear and it smooths out. Thats not how it is with a pushrod motor.

I'm not unhappy to the point of pulling them out because my cars runs real good, but everybody seems to rave about the VT cams though. Keep your options open and talk to alot of people.

 

[stangGT97]

It is not PTV to worry about with Comp's PI cams in NPI heads, it is coil bind. That will be taken care of with a good set of springs and Crower Offset Retainers.

could you explain coil bind?

 

[prsrizdgt]

could you explain coil bind?

Basically what it sounds like. The lift on the cam lobe gets to the point that it is opening the valve so far that the coils of the valve spring can't collapse anymore. Once you get metal to metal contact.........sumpin bads gonna happen. The springs can be engineered to allow more lift without bind, and still maintain seat pressure to a point.

Somebody can answer this I'm sure. I have heard that switching to aftermarket springs on the NPI head solves the problem and you can run the cams with .550 lift..........I have also heard that PI springs and NPI springs are the exact same spring, but the geometry differences between the heads still won't allow a .550 cam in the stock NPI head.

You can also get the straight scoop by calling VT Cams or Comp Cams I am sure.

 

[TGJ]

Stangnet won't let me upload the file but this is the data. I don't remember what the mods were done to the car so don't ask.

RPM PI-HP 262H-HP 268H-HP 274H-HP 262AH-HP 270AH-HP 278AH-HP

2500 146 141 136 135 139 136 131
2700 156 150 145 145 149 147 141
2900 168 163 160 160 162 159 159
3100 184 186 178 177 184 179 172
3300 205 208 206 205 210 207 203
3500 229 225 220 225 229 223 219
3700 243 240 236 240 244 236 235
3900 263 264 261 260 266 261 255
4100 281 280 278 276 283 278 270
4300 297 295 292 290 299 290 283
4500 312 311 308 311 321 314 306
4700 329 333 331 336 342 337 335
4900 336 349 349 354 356 357 353
5100 341 358 360 362 364 366 365
5300 342 363 366 369 369 372 372
5500 343 369 372 375 376 378 378
5700 344 374 379 382 383 385 384
5900 341 376 381 384 385 387 389
6100 333 374 377 382 378 385 393
6300 320 364 373 373 370 377 388
6500 315 354 364 369 361 366 383

RPM PI-TQ 262H-TQ 268H-TQ 274H-TQ 262AH-TQ 270AH-TQ 278AH-TQ
2500 307 297 285 284 293 285 276
2700 303 291 283 282 291 285 274
2900 305 295 289 290 294 287 280
3100 312 315 301 300 311 303 291
3300 326 331 329 327 334 330 324
3500 343 337 332 337 343 335 329
3700 345 340 334 341 346 335 334
3900 354 355 350 350 358 352 344
4100 359 358 354 353 362 356 346
4300 361 360 354 355 366 355 346
4500 363 363 360 363 374 367 357
4700 366 372 370 375 382 377 374
4900 361 374 374 379 382 383 378
5100 351 369 371 373 375 377 376
5300 339 360 363 366 366 368 369
5500 328 352 355 358 359 361 361
5700 317 345 349 352 353 355 354
5900 304 335 339 342 343 344 343
6100 287 322 325 329 325 332 338
6300 266 303 311 311 308 314 324
6500 247 286 294 299 292 296 310

 

[DropTopPony]

Stangnet won't let me upload the file but this is the data. I don't remember what the mods were done to the car so don't ask.

RPM PI-HP 262H-HP 268H-HP 274H-HP 262AH-HP 270AH-HP 278AH-HP

2500 146 141 136 135 139 136 131
2700 156 150 145 145 149 147 141
2900 168 163 160 160 162 159 159
3100 184 186 178 177 184 179 172
3300 205 208 206 205 210 207 203
3500 229 225 220 225 229 223 219
3700 243 240 236 240 244 236 235
3900 263 264 261 260 266 261 255
4100 281 280 278 276 283 278 270
4300 297 295 292 290 299 290 283
4500 312 311 308 311 321 314 306
4700 329 333 331 336 342 337 335
4900 336 349 349 354 356 357 353
5100 341 358 360 362 364 366 365
5300 342 363 366 369 369 372 372
5500 343 369 372 375 376 378 378
5700 344 374 379 382 383 385 384
5900 341 376 381 384 385 387 389
6100 333 374 377 382 378 385 393
6300 320 364 373 373 370 377 388
6500 315 354 364 369 361 366 383

RPM PI-TQ 262H-TQ 268H-TQ 274H-TQ 262AH-TQ 270AH-TQ 278AH-TQ
2500 307 297 285 284 293 285 276
2700 303 291 283 282 291 285 274
2900 305 295 289 290 294 287 280
3100 312 315 301 300 311 303 291
3300 326 331 329 327 334 330 324
3500 343 337 332 337 343 335 329
3700 345 340 334 341 346 335 334
3900 354 355 350 350 358 352 344
4100 359 358 354 353 362 356 346
4300 361 360 354 355 366 355 346
4500 363 363 360 363 374 367 357
4700 366 372 370 375 382 377 374
4900 361 374 374 379 382 383 378
5100 351 369 371 373 375 377 376
5300 339 360 363 366 366 368 369
5500 328 352 355 358 359 361 361
5700 317 345 349 352 353 355 354
5900 304 335 339 342 343 344 343
6100 287 322 325 329 325 332 338
6300 266 303 311 311 308 314 324
6500 247 286 294 299 292 296 310

was this from that test in mmff or 5.0 a couple years ago?

 

[prsrizdgt]

Yea, that looks like where it came from to me. Thats why I went with the 268 with my roots blower. I could give up a few numbers down in the lower rpms for what the 268 cam gives you back above 4500rpms.