|
Hypothetical 383in SBC engine....
Not really hypothetical, this engine exists it's just not mine.
Would this combination make a good motor for my 3500lbs Formula F206? What would be the max RPM range? GM 383 crate engine Compression...9.1:1 Heads...Stock Vortec iron with 1.94/1.50 valves Rockers...GM roller 1.6 Cam...GM Hot Cam P/N 24502586 Duration 218/228 Lift .525/.525 w/1.6 rocker Lobe separation 112 Intake...Edelbrock Performer RPM Air Gap Carb...750 Holley Ignition...stock HEI Dyno test RPM TQ HP 2500 412 196 2600 419 207 2700 425 218 2800 434 231 2900 442 244 3000 448 256 3100 425 266 3200 455 277 3300 460 289 3400 464 300 3500 466 310 3600 466 319 3700 465 327 3800 464 336 3900 462 343 4000 462 352 4100 463 362 4200 462 369 4300 459 376 4400 456 382 4500 453 388 4600 449 394 4700 446 399 4800 441 403 4900 436 406 5000 429 409 5100 423 411 5200 417 413 5300 410 414 5400 402 413 5500 396 415 5600 390 416 5700 376 409 |
Is that the 'LT4' hot cam? It seems to have a nice powerband! But maybe look at something with a slightly larger LSA, or maybe just something that isn't cut with a built in degreed baseline..
But dayum thats some nice numbers... IMHO 450ft-lb and 416hph from a 383 with only 9:1... --Adam (who would love a motor like that in hihs car, although prolly rather have bigger heads and a CC 304 cam ;) |
This same engine but with a Comp Cams XE282 HR and matching springs (230/236 dur, .544/555 lift (1.6 rocker) with a 110 LSA) pumped out 473 lbs/TQ at 4400 and 446 hp at 5400.
I thought this combo had a torque peak at too high an rpm for a boat. The other set up would be better. You are right it is the LT-4 cam. From GM Performance Hydraulic Roller (LT4 Hot Cam) This hydraulic roller cam is for service only for all V8 engines with roller camshafts. The duration at lash point in degrees (intake/exhaust) is 279/287; duration at .050" tappet lift (intake/exhaust) is 218/228; and maximum lift with 1.6 rocker ratio (intake/exhaust) is 525/525. Valve lash is zero/zero and lobe centerline is 112 degrees. Technical Notes: The LT4 camshaft P/N 24502586 was designed to be used in a number of different engines. Therefore, the following change may need to be made to allow for correct assembly of the engine: For LT1 and L98 engines 1995 and before, the dowel pin in the end of the camshaft must be pushed in so extension from end of cam is .30+/-.01", the same as the production part. For 1996 LT1 and LT4 engines, the dowel pin is in the correct position, extending .620" from the end of the camshaft. This camshaft has a fuel pump lobe. |
Yeah you can handle the tight LSA cuz you don't need idle vacuum, but a tighter LSA means a narrower torque band...
Is there something similar with like a 114? Either that or see if you can get then to dyno it with big rockers on the intake, but 1.5's on the exhaust, that might get you some more torque :) --Adam |
Arg, ok now I'd love for one of the real marine engine guys to jump in here, cuz I really have no marine engine building experience (even bench building ;)
But an LT4HOT on a 383 is a pretty mild cam, look for something with bigger duration, and keep in mind that you don't want a massive exhaust duration I wouldnt think. That HOT cam installed 'straight up' [which IIRC is 5 deg advanced in the grind] will make the motor idle without any real lope... On a 350, it lopes a bit however. Keep in mind also that you will quickly run out of heads, so perhaps the best thing to do would be call comp cams and discuss it with them. You probably need to be moreconcerned with the profile around the center of the valve lift, cuz I don't think you'll be able to flow much more than that. I might even say use a large duration but lower lift cam... Again YMMV, and I may be on crack here, it wouldnt be the first time.. hehe Ciao --Adam |
| All times are GMT -5. The time now is 01:27 PM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.