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As we mentioned, the LQ9 gets... As we mentioned, the LQ9 gets its compression boost over the more common LQ4 from a set of flat-top pistons. Given the lack of piston reliefs, and the fact that the slugs protrude 0.009-inch above the deck (thanks again, LS1Tech.com), a new cam must be chosen with care. Also, be sure to blow any water out of the block boltholes when swapping heads, or you’ll have problems with the new head bolts. For our final test, we bolted on a set of RHS’ new Pro Action cathedral-port heads for LS applications. These new lungs, which use Clean Cast Technology to maintain more precise tolerances than are normally found in an “as cast head”, bumped our engine’s compression ratio up to 11.41:1 (due to its 62cc combustion chamber) and added a 225cc intake runner. The extra air and bump in compression allowed our transformed truck engine to really take off, recording 521 hp at 6,300 rpm, along with 476 lb-ft of torque at 5,000 rpm. If the engine is turned on, it’s making more than 400 lb-ft. That’s a total increase of 105 hp more than the carbureted stock long-block version, along with an extra 37 lb-ft of torque at the peak of a much fatter torque band. It’s also a 16 lb-ft and 26hp improvement over the stock lungs. This rejuvenated truck lump makes lots of useful torque throughout the powerband, and it now has a great top end. It should make for one snappy, fun-to-drive Chevelle. We’ll let you know.
LQ9 Shopping List |
|
PN |
Description |
Price |
| ARP |
134-3609 |
High Performance Series cylinder head bolts |
$170 |
| 134-2001 |
carburetor studs |
18 |
| 130-2001 |
intake manifold bolts |
31 |
| COMP Cams |
26918-16 |
valvesprings |
188 |
| 7795-16 |
Hi-Tech pushrods, 7.375 inches |
136 |
| 54-428-11 |
XR281HR camshaft |
370 |
| Edelbrock |
41183 |
coil covers |
215 |
| 71187 |
LS1 Performer RPM |
266 |
| Fel-Pro |
1161L/1161R |
MLS head gaskets |
192 |
| 1312-3 |
intake manifold gaskets |
26 |
| Holley |
0-86770BK |
Ultra Street Avenger Carburetor |
500 |
| 302-1 |
LS Retro-Fit oil pan |
400 |
| MSD Ignition |
6010 |
LS6 Timing Control Module |
320 |
| RHS |
54302-05TS |
Pro Action 225cc cathedral port heads (assembled) |
1,470 |
| TCI |
399753 |
LS1 168-tooth flywheel |
215 |
| TOTAL |
$4,517 |
 You usually can’t see the...  You usually can’t see the difference in camshaft specs by looking, but the disparity between the stock cam and our COMP replacement is evident to the eyeball. The stocker specs in at 0.497/0.467-inch lift (intake/exhaust) and 196/207 degrees duration at 0.050 with an LSA of 116 degrees. The XR281HR we chose has more than 0.074-inch extra lift (it’s a whopping 0.106 inch on the exhaust side), along with more than 30 degrees extra duration on both sides. It isn’t the biggest LS cam in COMP’s catalog, but it positively transformed our pedestrian truck engine.  These heads use RHS’ Clean...  These heads use RHS’ Clean Cast Technology, which uses permanent-mold tooling to closely control manufacturing tolerances. This control goes a long way toward providing the tight tolerances you’ll find in a CNC’d head, without the expense of a full port job. As is typical with aluminum heads, you can see the cleanup work done inside the port.
Baseline |
| Holley 770-cfm Ultra Street Avenger |
| Jets: 73/81 primary/secondary |
| Headers: 13/4 Kooks long tubes with 18-inch extensions |
| Fuel: 91-octane unleaded |
| Advance: 33 degrees |
| RPM |
LB-FT |
HP |
| 3,100 |
421 |
248 |
| 3,200 |
419 |
256 |
| 3,300 |
422 |
265 |
| 3,400 |
426 |
276 |
| 3,500 |
429 |
286 |
| 3,600 |
431 |
295 |
| 3,700 |
433 |
305 |
| 3,800 |
435 |
314 |
| 3,900 |
436 |
324 |
| 4,000 |
438 |
334 |
| 4,100 |
439 |
343 |
| 4,200 |
438 |
351 |
| 4,300 |
437 |
358 |
| 4,400 |
437 |
366 |
| 4,500 |
436 |
374 |
| 4,600 |
434 |
380 |
| 4,700 |
431 |
386 |
| 4,800 |
429 |
392 |
| 4,900 |
425 |
397 |
| 5,000 |
422 |
402 |
| 5,100 |
418 |
406 |
| 5,200 |
413 |
409 |
| 5,300 |
408 |
412 |
| 5,400 |
402 |
414 |
| 5,500 |
396 |
414 |
| 5,600 |
390 |
416 |
| 5,700 |
384 |
416 |
| 5,800 |
377 |
416 |
| 5,900 |
370 |
416 |
| 6,000 |
363 |
415 |
| Average Torque |
418 |
| Average Power |
360 |
Looking ahead, we had many of the pieces that we’ll need when this mill takes up its new residence under the hood of a ’66 Chevelle. One of these is Holley’s new LS Retro-Fit oil pan. According to Holley, this slick casting provides maximum chassis clearance for GM rear-wheel-drive applications, small-block or big-block, as long as it came with a rear sump oil pan. It also comes with a sump baffle, pickup tube, sump plug, oil filter stud, and an oil passage cover.
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